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Sample records for repeated eccentric contractions

  1. Effects of repeated concentric and eccentric contractions on tendon blood circulation.

    Science.gov (United States)

    Kubo, K

    2015-06-01

    Previous studies demonstrated that treatment involving eccentric training was effective in the conservative management of chronic tendinosis. However, the mechanisms for these phenomena are unknown. The purpose of this study was to compare changes in blood circulation of the tendons after the repeated concentric and eccentric contractions. 11 healthy males volunteered for this study. Subjects performed the repeated concentric (CON) and eccentric (ECC) contractions (5 sets of 10 maximal voluntary contractions) of the plantar flexors. During and after repeated contractions, oxyhemoglobin (Oxy), deoxyhemoglobin (Deoxy), total hemoglobin (THb), and oxygen saturation (StO2) of the Achilles tendons were measured using red laser lights. Oxy and THb increased during and after ECC, but not CON. Deoxy decreased during both CON and ECC. Increase in StO2 during and after ECC was greater than that during and after CON. These results suggested that changes in blood circulation of the Achilles tendon during and after repeated eccentric contractions were more remarkable than those during and after repeated concentric contractions.

  2. Reduced muscle lengthening during eccentric contractions as a mechanism underpinning the repeated-bout effect.

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    Lau, Wing Yin; Blazevich, Anthony J; Newton, Michael J; Wu, Sam Shi Xuan; Nosaka, Kazunori

    2015-05-15

    This study investigated biceps brachii distal myotendinous junction (MTJ) displacement during maximal eccentric elbow flexor contractions to test the hypothesis that muscle length change would be smaller (less MTJ displacement) during the second than the first exercise bout. Ten untrained men performed two eccentric exercise bouts (ECC1 and ECC2) with the same arm consisting of 10 sets of six maximal isokinetic (60°/s) eccentric elbow flexor contractions separated by 4 wk. Biceps brachii distal MTJ displacement was assessed using B-mode ultrasonography, and changes in the displacement (muscle length change) from the start to the end of each contraction during each set and over 10 sets were compared between bouts by two-way repeated-measures ANOVA. Several indirect muscle damage markers were also measured and compared between bouts by two-way repeated-measures ANOVA. The magnitude of MTJ displacement (average of six contractions) increased from set 1 (8.2 ± 4.7 mm) to set 10 (16.4 ± 4.7 mm) during ECC1 (P < 0.05), but no significant changes over sets were evident during ECC2 (set 1: 8.5 ± 4.0 mm; set 10: 9.3 ± 3.1 mm). Changes in maximal voluntary isometric contraction strength, range of motion, muscle thickness, ultrasound echo intensity, serum creatine kinase activity, and muscle soreness (visual analog scale) were smaller (P < 0.05) following ECC2 than ECC1, showing less damage in the repeated bout. These results indicate that the magnitude of muscle lengthening was less during the second than the first eccentric exercise bout, which appears to be a mechanism underpinning the repeated-bout effect. Copyright © 2015 the American Physiological Society.

  3. Repeated bouts of fast velocity eccentric contractions induce atrophy of gastrocnemius muscle in rats.

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    Ochi, Eisuke; Nosaka, Kazunori; Tsutaki, Arata; Kouzaki, Karina; Nakazato, Koichi

    2015-10-01

    One bout of exercise consisting of fast velocity eccentric contractions has been shown to increase muscle protein degradation in rats. The present study tested the hypothesis that muscle atrophy would be induced after four bouts of fast velocity eccentric contractions, but not after four bouts of slow velocity eccentric contractions. Male Wistar rats were randomly placed into 3 groups; fast (180°/s) velocity (180EC, n = 7), slow (30°/s) velocity eccentric exercise (30EC, n = 7), or sham-treatment group (control, n = 7). The 180EC and 30EC groups received 4 sessions of 4 sets of 5 eccentric contractions of triceps surae muscles by extending the ankle joint during evoked electrical stimulation of the muscles, and the control group had torque measures, every 2 days, and all rats were sacrificed 1 day after the fourth session. Medial and lateral gastrocnemius wet mass were 4-6 % smaller, cross-sectional area of medial gastrocnemius was 6-7% smaller, and isometric tetanic torque of triceps surae muscles was 36 % smaller (p contractions.

  4. Eccentric Contraction-Induced Muscle Fibre Adaptation

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    Arabadzhiev T. I.

    2009-12-01

    Full Text Available Hard-strength training induces strength increasing and muscle damage, especially after eccentric contractions. Eccentric contractions also lead to muscle adaptation. Symptoms of damage after repeated bout of the same or similar eccentrically biased exercises are markedly reduced. The mechanism of this repeated bout effect is unknown. Since electromyographic (EMG power spectra scale to lower frequencies, the adaptation is related to neural adaptation of the central nervous system (CNS presuming activation of slow-non-fatigable motor units or synchronization of motor unit firing. However, the repeated bout effect is also observed under repeated stimulation, i.e. without participation of the CNS. The aim of this study was to compare the possible effects of changes in intracellular action potential shape and in synchronization of motor units firing on EMG power spectra. To estimate possible degree of the effects of central and peripheral changes, interferent EMG was simulated under different intracellular action potential shapes and different degrees of synchronization of motor unit firing. It was shown that the effect of changes in intracellular action potential shape and muscle fibre propagation velocity (i.e. peripheral factors on spectral characteristics of EMG signals could be stronger than the effect of synchronization of firing of different motor units (i.e. central factors.

  5. Insights into the neural control of eccentric contractions.

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    Duchateau, Jacques; Baudry, Stéphane

    2014-06-01

    The purpose of this brief review is to examine our current knowledge of the neural control of eccentric contractions. The review focuses on three main issues. The first issue considers the ability of individuals to activate muscles maximally during eccentric contractions. Most studies indicate that, regardless of the experimental approach (surface EMG amplitude, twitch superimposition, and motor unit recordings), it is usually more difficult to achieve full activation of a muscle by voluntary command during eccentric contractions than during concentric and isometric contractions. The second issue is related to the specificity of the control strategy used by the central nervous system during submaximal eccentric contractions. This part underscores that although the central nervous system appears to employ a single size-related strategy to activate motoneurons during the different types of contractions, the discharge rate of motor units is less during eccentric contractions across different loading conditions. The last issue addresses the mechanisms that produce this specific neural activation. This section indicates that neural adjustments at both supraspinal and spinal levels contribute to the specific modulation of voluntary activation during eccentric contractions. Although the available information on the control of eccentric contractions has increased during the last two decades, this review indicates that the exact mechanisms underlying the unique neural modulation observed in this type of contraction at spinal and supraspinal levels remains unknown and their understanding represents, therefore, a major challenge for future research on this topic.

  6. Effects of recovery modes after knee extensor muscles eccentric contractions

    National Research Council Canada - National Science Library

    Martin, Vincent; Millet, Guillaume Y; Lattier, Grégory; Perrod, Loïc

    2004-01-01

    ...) to hasten the recovery process from eccentric-contraction-induced injury. Before and 30 min, 24 h, 48 h, and 96 h after a one-legged downhill run, electrical stimulations were applied to the femoral nerve of healthy volunteers...

  7. Unilateral eccentric contraction of the plantarflexors leads to bilateral alterations in leg dexterity

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    Akira Nagamori

    2016-11-01

    Full Text Available Eccentric contractions can affect musculotendon mechanical properties and disrupt muscle proprioception, but their behavioral consequences are poorly understood. We tested whether repeated eccentric contractions of plantarflexor muscles of one leg affected the dexterity of either leg. Twenty healthy male subjects (27.3+/-4.0 yrs compressed a compliant and slender spring prone to buckling with each isolated leg. The maximal instability they could control (i.e., the maximal average sustained compression force, or lower extremity dexterity force, LEDForce quantified the dexterity of each leg. We found that eccentric contractions did not affect LEDForce, but reduced force variability (LEDSD. Surprisingly, LEDForce increased in the non-exposed, contralateral leg. These effects were specific to exposure to eccentric contractions because an effort-matched exposure to walking did not affect leg dexterity. In the exposed leg, eccentric contractions (i reduced voluntary error corrections during spring compressions (i.e., reduced 0.5-4 Hz power of LEDForce; (ii did not change spinal excitability (i.e., unaffected H-reflexes; and (iii changed the structure of the neural drive to the alpha-motoneuron pool (i.e., reduced EMG power within the 4-8 Hz physiological tremor band. These results suggest that repeated eccentric contractions alter the feedback control for dexterity in the exposed leg by reducing muscle spindle sensitivity. Moreover, the unexpected improvement in LEDForce in the non-exposed contralateral leg was likely a consequence of crossed-effects on its spinal and supraspinal feedback control. We discuss the implications of these bilateral effects of unilateral eccentric contractions, their effect on spinal and supraspinal control of dynamic foot-ground interactions, and their potential to facilitate rehabilitation from musculoskeletal and neuromotor impairments.

  8. Eccentric contractions lead to myofibrillar dysfunction in muscular dystrophy.

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    Blaauw, Bert; Agatea, Lisa; Toniolo, Luana; Canato, Marta; Quarta, Marco; Dyar, Kenneth A; Danieli-Betto, Daniela; Betto, Romeo; Schiaffino, Stefano; Reggiani, Carlo

    2010-01-01

    It is commonly accepted that skeletal muscles from dystrophin-deficient mdx mice are more susceptible than those from wild-type mice to damage from eccentric contractions. However, the downstream mechanisms involved in this enhanced force drop remain controversial. We studied the reduction of contractile force induced by eccentric contractions elicited in vivo in the gastrocnemius muscle of wild-type mice and three distinct models of muscle dystrophy: mdx, alpha-sarcoglycan (Sgca)-null, and collagen 6A1 (Col6a1)-null mice. In mdx and Sgca-null mice, force decreased 35% compared with 14% in wild-type mice. Drop of force in Col6a1-null mice was comparable to that in wild-type mice. To identify the determinants of the force drop, we measured force generation in permeabilized fibers dissected from gastrocnemius muscle that had been exposed in vivo to eccentric contractions and from the contralateral unstimulated muscle. A force loss in skinned fibers after in vivo eccentric contractions was detectable in fibers from mdx and Sgca-null, but not wild-type and Col6a1-null, mice. The enhanced force reduction in mdx and Sgca-null mice was observed only when eccentric contractions were elicited in vivo, since eccentric contractions elicited in vitro had identical effects in wild-type and dystrophic skinned fibers. These results suggest that 1) the enhanced force loss is due to a myofibrillar impairment that is present in all fibers, and not to individual fiber degeneration, and 2) the mechanism causing the enhanced force reduction is active in vivo and is lost after fiber permeabilization.

  9. Effectiveness of daily eccentric contractions induced via kilohertz frequency transcutaneous electrical stimulation on muscle atrophy.

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    Tanaka, Minoru; Nakanishi, Ryosuke; Murakami, Shinichiro; Fujita, Naoto; Kondo, Hiroyo; Ishihara, Akihiko; Roy, Roland R; Fujino, Hidemi

    2016-01-01

    The effects of daily repeated bouts of concentric, isometric, or eccentric contractions induced by high frequency (kilohertz) transcutaneous electrical stimulation in ameliorating atrophy of the soleus muscle in hindlimb unloaded rats were determined. Five groups of male rats were studied: control, hindlimb unloaded for 2 weeks (HU), or HU plus two daily bouts of concentric, isometric, or eccentric high-frequency electrical stimulation-induced contractions of the calf musculature. Soleus mass and fiber size were smaller, the levels of phosphorylated Akt1 and FoxO3a lower, and atrogin-1 and ubiquitinated proteins higher in the HU, and the HU plus concentric or isometric contraction groups than in the control group. In contrast, daily bouts of eccentric contractions maintained these values at near control levels and all measures were significantly different from all other HU groups. These results indicate that daily bouts of eccentric contractions induced by high-frequency stimulation inhibited the ubiquitin-proteasome catabolic pathway and enhanced the Akt1/FoxO3a anabolic pathway that resulted in a prevention of the atrophic response of the soleus muscle to chronic unloading.

  10. The repeated bout effect of eccentric exercise is not associated with changes in voluntary activation.

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    Kamandulis, Sigitas; Skurvydas, Albertas; Brazaitis, Marius; Skikas, Laimutis; Duchateau, Jacques

    2010-04-01

    The aim of this study was to compare the possible changes in muscle activation level between a first and second bout of damaging eccentric exercise performed at 2 weeks interval (i.e. repeated bout effect). To that purpose, ten physically active males took part in this study. The eccentric exercise consisted of 10 sets of 12 maximal voluntary contractions (MVC) produced by the knee extensors during movements performed at a constant speed of 160 degrees s(-1). Changes in voluntary and electrically evoked torque in concentric and/or isometric conditions were assessed at the following time points: pre-exercise, and 2 min, 1 and 24 h after each eccentric exercise. At the same time points, voluntary activation was quantified by the superimposed electrical stimulation technique. Muscle soreness and plasma CK activity were measured within 48 h after the eccentric exercise. The results showed that the decrease in eccentric peak torque was linear throughout the exercise protocol. At the end of bouts 1 and 2, torque was significantly reduced by 27.7 +/- 9.1 and 23.4 +/- 11.2, respectively, with no difference between bouts (P > 0.05). At 24 h post-exercise, a lower reduction (P eccentric exercise appears to reduce muscle damage, but does not influence the level of voluntary activation.

  11. Decreased muscle GLUT-4 and contraction-induced glucose transport after eccentric contractions

    DEFF Research Database (Denmark)

    Kristiansen, S; Asp, Svend; Richter, Erik

    1996-01-01

    Eccentric exercise causes muscle damage and decreased muscle glycogen and glucose transporter isoform (GLUT-4) protein content. We investigated whether the contraction-induced increase in skeletal muscle glucose transport and muscle performance is affected by prior eccentric contractions. The calf...... than in CT rats. In the GW and GR muscle, prior eccentric exercise decreased contraction-induced stimulation of glucose transport compared with CT, ST, and CC rats despite no difference in tension development and oxygen uptake among the groups. There was no change in total GLUT-4 content and glucose...... muscles from rats were stimulated for eccentric (EC) or concentric (CC) contractions or were passively stretched (ST). Muscles from unstimulated control (CT) rats were also studied. Two days later, all rats had their isolated hindlimbs perfused either at rest or during 15 min of isometric muscle...

  12. Eccentric contraction-induced myofiber growth in tumor-bearing mice.

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    Hardee, Justin P; Mangum, Joshua E; Gao, Song; Sato, Shuichi; Hetzler, Kimbell L; Puppa, Melissa J; Fix, Dennis K; Carson, James A

    2016-01-01

    Cancer cachexia is characterized by the progressive loss of skeletal muscle mass. While mouse skeletal muscle's response to an acute bout of stimulated low-frequency concentric muscle contractions is disrupted by cachexia, gaps remain in our understanding of cachexia's effects on eccentric contraction-induced muscle growth. The purpose of this study was to determine whether repeated bouts of stimulated high-frequency eccentric muscle contractions [high-frequency electrical muscle stimulation (HFES)] could stimulate myofiber growth during cancer cachexia progression, and whether this training disrupted muscle signaling associated with wasting. Male Apc(Min/+) mice initiating cachexia (N = 9) performed seven bouts of HFES-induced eccentric contractions of the left tibialis anterior muscle over 2 wk. The right tibialis anterior served as the control, and mice were killed 48 h after the last stimulation. Age-matched C57BL/6 mice (N = 9) served as wild-type controls. Apc(Min/+) mice lost body weight, muscle mass, and type IIA, IIX, and IIB myofiber cross-sectional area. HFES increased myofiber cross-sectional area of all fiber types, regardless of cachexia. Cachexia increased muscle noncontractile tissue, which was attenuated by HFES. Cachexia decreased the percentage of high succinate dehydrogenase activity myofibers, which was increased by HFES, regardless of cachexia. While cachexia activated AMP kinase, STAT3, and ERK1/2 signaling, HFES decreased AMP kinase phosphorylation, independent of the suppression of STAT3. These results demonstrate that cachectic skeletal muscle can initiate a growth response to repeated eccentric muscle contractions, despite the presence of a systemic cachectic environment.

  13. Unaccustomed Eccentric Contractions Impair Plasma K+ Regulation in the Absence of Changes in Muscle Na+,K+-ATPase Content

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    Goodman, Craig A.; Bennie, Jason A.; Leikis, Murray J.; McKenna, Michael J.

    2014-01-01

    The Na+,K+-ATPase (NKA) plays a fundamental role in the regulation of skeletal muscle membrane Na+ and K+ gradients, excitability and fatigue during repeated intense contractions. Many studies have investigated the effects of acute concentric exercise on K+ regulation and skeletal muscle NKA, but almost nothing is known about the effects of repeated eccentric contractions. We therefore investigated the effects of unaccustomed maximal eccentric knee extensor contractions on K+ regulation during exercise, peak knee extensor muscle torque, and vastus lateralis muscle NKA content and 3-O-MFPase activity. Torque measurements, muscle biopsies, and venous blood samples were taken before, during and up to 7 days following the contractions in six healthy adults. Eccentric contractions reduced peak isometric muscle torque immediately post-exercise by 26±11% and serum creatine kinase concentration peaked 24 h post-exercise at 339±90 IU/L. During eccentric contractions, plasma [K+] rose during Set 1 and remained elevated at ∼4.9 mM during sets 4–10; this was despite a decline in work output by Set 4, which fell by 18.9% at set 10. The rise in plasma [K+].work−1 ratio was elevated over Set 2 from Set 4– Set 10. Eccentric contractions had no effect on muscle NKA content or maximal in-vitro 3-O-MFPase activity immediately post- or up to 7 d post-exercise. The sustained elevation in plasma [K+] despite a decrease in work performed by the knee extensor muscles suggests an impairment in K+ regulation during maximal eccentric contractions, possibly due to increased plasma membrane permeability or to excitation-contraction uncoupling. PMID:24959836

  14. Unaccustomed eccentric contractions impair plasma K+ regulation in the absence of changes in muscle Na+,K+-ATPase content.

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    Craig A Goodman

    Full Text Available The Na+,K+-ATPase (NKA plays a fundamental role in the regulation of skeletal muscle membrane Na+ and K+ gradients, excitability and fatigue during repeated intense contractions. Many studies have investigated the effects of acute concentric exercise on K+ regulation and skeletal muscle NKA, but almost nothing is known about the effects of repeated eccentric contractions. We therefore investigated the effects of unaccustomed maximal eccentric knee extensor contractions on K+ regulation during exercise, peak knee extensor muscle torque, and vastus lateralis muscle NKA content and 3-O-MFPase activity. Torque measurements, muscle biopsies, and venous blood samples were taken before, during and up to 7 days following the contractions in six healthy adults. Eccentric contractions reduced peak isometric muscle torque immediately post-exercise by 26±11% and serum creatine kinase concentration peaked 24 h post-exercise at 339±90 IU/L. During eccentric contractions, plasma [K+] rose during Set 1 and remained elevated at ∼4.9 mM during sets 4-10; this was despite a decline in work output by Set 4, which fell by 18.9% at set 10. The rise in plasma [K+] x work(-1 ratio was elevated over Set 2 from Set 4- Set 10. Eccentric contractions had no effect on muscle NKA content or maximal in-vitro 3-O-MFPase activity immediately post- or up to 7 d post-exercise. The sustained elevation in plasma [K+] despite a decrease in work performed by the knee extensor muscles suggests an impairment in K+ regulation during maximal eccentric contractions, possibly due to increased plasma membrane permeability or to excitation-contraction uncoupling.

  15. Unaccustomed eccentric contractions impair plasma K+ regulation in the absence of changes in muscle Na+,K+-ATPase content.

    Science.gov (United States)

    Goodman, Craig A; Bennie, Jason A; Leikis, Murray J; McKenna, Michael J

    2014-01-01

    The Na+,K+-ATPase (NKA) plays a fundamental role in the regulation of skeletal muscle membrane Na+ and K+ gradients, excitability and fatigue during repeated intense contractions. Many studies have investigated the effects of acute concentric exercise on K+ regulation and skeletal muscle NKA, but almost nothing is known about the effects of repeated eccentric contractions. We therefore investigated the effects of unaccustomed maximal eccentric knee extensor contractions on K+ regulation during exercise, peak knee extensor muscle torque, and vastus lateralis muscle NKA content and 3-O-MFPase activity. Torque measurements, muscle biopsies, and venous blood samples were taken before, during and up to 7 days following the contractions in six healthy adults. Eccentric contractions reduced peak isometric muscle torque immediately post-exercise by 26±11% and serum creatine kinase concentration peaked 24 h post-exercise at 339±90 IU/L. During eccentric contractions, plasma [K+] rose during Set 1 and remained elevated at ∼4.9 mM during sets 4-10; this was despite a decline in work output by Set 4, which fell by 18.9% at set 10. The rise in plasma [K+] x work(-1) ratio was elevated over Set 2 from Set 4- Set 10. Eccentric contractions had no effect on muscle NKA content or maximal in-vitro 3-O-MFPase activity immediately post- or up to 7 d post-exercise. The sustained elevation in plasma [K+] despite a decrease in work performed by the knee extensor muscles suggests an impairment in K+ regulation during maximal eccentric contractions, possibly due to increased plasma membrane permeability or to excitation-contraction uncoupling.

  16. FKBP12 deficiency reduces strength deficits after eccentric contraction-induced muscle injury

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    Corona, Benjamin T.; Rouviere, Clement; Hamilton, Susan L.; Ingalls, Christopher P.

    2008-01-01

    Strength deficits associated with eccentric contraction-induced muscle injury stem, in part, from excitation-contraction uncoupling. FKBP12 is a 12-kDa binding protein known to bind to the skeletal muscle sarcoplasmic reticulum Ca2+ release channel [ryanodine receptor (RyR1)] and plays an important role in excitation-contraction coupling. To assess the effects of FKBP12 deficiency on muscle injury and recovery, we measured anterior crural muscle (tibialis anterior and extensor digitorum longus muscles) strength in skeletal muscle-specific FKBP12-deficient and wild-type (WT) mice before and after a single bout of 150 eccentric contractions, as well as before and after the performance of six injury bouts. Histological damage of the tibialis anterior muscle was assessed after injury. Body weight and peak isometric and eccentric torques were lower in FKBP12-deficient mice compared with WT mice. There were no differences between FKBP12-deficient and WT mice in preinjury peak isometric and eccentric torques when normalized to body weight, and no differences in the relative decreases in eccentric torque with a single or multiple injury bouts. After a single injury bout, FKBP12-deficient mice had less initial strength deficits and recovered faster (especially females) than WT mice, despite no differences in the degree of histological damage. After multiple injury bouts, FKBP12-deficient mice recovered muscle strength faster than WT mice and exhibited significantly less histological muscle damage than WT mice. In summary, FKBP12 deficiency results in less initial strength deficits and enhanced recovery from single (especially females) and repeated bouts of injury than WT mice. PMID:18511525

  17. Blood flow after contraction and cuff occlusion is reduced in subjects with muscle soreness after eccentric exercise.

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    Souza-Silva, E; Christensen, S W; Hirata, R P; Larsen, R G; Graven-Nielsen, T

    2017-04-28

    Delayed onset muscle soreness (DOMS) occurs within 1-2 days after eccentric exercise, but the mechanism mediating hypersensitivity is unclear. This study hypothesized that eccentric exercise reduces the blood flow response following muscle contractions and cuff occlusion, which may result in accumulated algesic substances being a part of the sensitization in DOMS. Twelve healthy subjects (five women) performed dorsiflexion exercise (five sets of 10 repeated eccentric contractions) in one leg, while the contralateral leg was the control. The maximal voluntary contraction (MVC) of the tibialis anterior muscle was recorded. Blood flow was assessed by ultrasound Doppler on the anterior tibialis artery (ATA) and within the anterior tibialis muscle tissue before and immediately after 1-second MVC, 5-seconds MVC, and 5-minutes thigh cuff occlusion. Pressure pain thresholds (PPTs) were recorded on the tibialis anterior muscle. All measures were done bilaterally at day 0 (pre-exercise), day 2, and day 6 (post-exercise). Subjects scored the muscle soreness on a Likert scale for 6 days. Eccentric exercise increased Likert scores at day 1 and day 2 compared with day 0 (Pexercise (day 0), reduced PPT (~25%, Peccentric contractions decreased vessel diameter, impaired the blood flow response, and promoted hyperalgesia. Thus, the results suggest that the blood flow reduction may be involved in the increased pain response after eccentric exercise. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  18. Variability in Muscle Damage after Eccentric Exercise and the Repeated Bout Effect

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    Chen, Trevor C.

    2006-01-01

    The first purpose of this study was to determine a possible explanation for the variability in the response to eccentric exercise by having participants repeat the same exercise 1 year apart. The second purpose was to examine whether initial injury in response to eccentric exercise was associated with the extent of the repeated bout effect (RBE).…

  19. Variability in Muscle Damage after Eccentric Exercise and the Repeated Bout Effect

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    Chen, Trevor C.

    2006-01-01

    The first purpose of this study was to determine a possible explanation for the variability in the response to eccentric exercise by having participants repeat the same exercise 1 year apart. The second purpose was to examine whether initial injury in response to eccentric exercise was associated with the extent of the repeated bout effect (RBE).…

  20. The effects of K+ channel blockade on eccentric and isotonic twitch and fatiguing contractions in situ

    OpenAIRE

    Michelle eMoyer; Erik evan Lunteren

    2012-01-01

    K+ channel blockers like 3,4-diaminopyridine (DAP) can double isometric muscle force. Functional movements require more complex concentric and eccentric contractions, however the effects of K+ channel blockade on these types of contractions in situ are unknown. Extensor digitorum longus (EDL) muscles were stimulated in situ with and without DAP in anesthetized rats and fatigability was addressed using a series of either concentric or eccentric contractions. During isotonic protocols (5-100...

  1. The Effects of K+ Channel Blockade on Eccentric and Isotonic Twitch and Fatiguing Contractions in situ

    OpenAIRE

    van Lunteren, Erik; Moyer, Michelle

    2012-01-01

    K+ channel blockers like 3,4-diaminopyridine (DAP) can double isometric muscle force. Functional movements require more complex concentric and eccentric contractions, however the effects of K+ channel blockade on these types of contractions in situ are unknown. Extensor digitorum longus (EDL) muscles were stimulated in situ with and without DAP in anesthetized rats and fatigability was addressed using a series of either concentric or eccentric contractions. During isotonic protocols (5–100% l...

  2. Physiological Mechanisms of Eccentric Contraction and Its Applications: A Role for the Giant Titin Protein

    OpenAIRE

    Hessel, Anthony L.; Lindstedt, Stan L.; Nishikawa, Kiisa C.

    2017-01-01

    When active muscles are stretched, our understanding of muscle function is stretched as well. Our understanding of the molecular mechanisms of concentric contraction has advanced considerably since the advent of the sliding filament theory, whereas mechanisms for increased force production during eccentric contraction are only now becoming clearer. Eccentric contractions play an important role in everyday human movements, including mobility, stability, and muscle strength. Shortly after the s...

  3. EFFECTS OF A 4-WEEK ECCENTRIC TRAINING PROGRAM ON THE REPEATED BOUT EFFECT IN YOUNG ACTIVE WOMEN

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    Rodrigo Fernandez-Gonzalo

    2011-12-01

    Full Text Available The aim of this study was to analyze the responses of women to the repeated bout effect (RBE and to a short eccentric training program. Twenty-four young females were randomly assigned to a training group (TG, n = 14 or a control group (CG, n = 10. They performed two identical acute eccentric bouts (120 repetitions at 70% of 1RM in a leg-press device in an 8 weeks interval. TG followed a 4-week-eccentric-training program between the bouts. Maximal isometric contraction, range of motion, peak power and quadriceps muscle soreness were compared between and within groups before and after the two acute eccentric bouts. TG and CG presented significant losses of isometric strength and peak power, and an increment in soreness after the first bout. Isometric strength and peak power were recovered faster in CG after the second bout (p < 0.05 compared with TG, which showed a similar recovery of these parameters after the second bout compared with the first one. A decrease in soreness and a faster recovery of range of motion were found in TG (p < 0.05 following the second bout compared with the first one, but not in CG. Data indicate that a 4-week eccentric training program may prevent the RBE over those adaptations related with muscle damage (e.g. strength loss, but it may increase RBE impact on inflammatory processes (e.g. soreness.

  4. Isometric contractions combined with eccentric contractions and stretching exercises on patient with subacromial impingement syndrome

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    Efstratiadis Anastasios

    2015-10-01

    Full Text Available Many people with shoulder pain and disability have signs of subacromial impingement syndrome. The subacromial impingement syndrome of the shoulder is a general term, which is often used to describe pain and dysfunction in the area around the shoulder. The aim of the present report is to find the effect of isometric contractions combined with eccentric contractions and stretching exercises on a patient with subacromial impingement syndrome. A patient with subacromial impingement syndrome for 1 year was included in the case report. The patient followed an exercise program consisted of stretching exercises of shoulder muscles extensors, isometric contractions of shoulder extensors and eccentric exercises of shoulder extensors, 4 times per week. The exercise program was individualized according to pain and symptoms of the patient. Outcome measures were pain, pain rest, pain activity, pain night measured on a visual analogue scale (VAS, disability index (DASH score and range of motion (Goniometer. The patient was evaluated at baseline and after 4 weeks. At the end of the program, there was a significant improvement pain, disability and range of motion. In this clinical case the patient was improved significantly in all outcome measures. Further studies based on better design, are needed to investigate the effect of those methods on a random population group with subacromial impingement syndrome.

  5. Muscle damage and inflammation after eccentric exercise: can the repeated bout effect be removed?

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    Margaritelis, Nikos V; Theodorou, Anastasios A; Baltzopoulos, Vasilios; Maganaris, Constantinos N; Paschalis, Vassilis; Kyparos, Antonios; Nikolaidis, Michalis G

    2015-12-01

    The current consensus in exercise physiology is that the repeated bout effect always appears after few eccentric exercise sessions. This is the first attempt to challenge this tenet, by exploiting specificity in muscle plasticity. More specifically, we examined whether the opposing adaptations in muscle induced after concentric and eccentric exercise can attenuate and/or remove the repeated bout effect. Seventeen young men were randomly assigned into one of the following groups: (1) the alternating eccentric-concentric exercise group; and (2) the eccentric-only exercise group. Both groups performed 8 weeks of resistance exercise using the knee extensors of both legs on an isokinetic dynamometer. The alternating eccentric-concentric exercise group performed an alternating exercise protocol, switching between eccentric-only and concentric-only exercise every 4 weeks, while the eccentric-only group performed eccentric exercise. Evaluation of muscle damage using physiological (isometric torque, delayed onset muscle soreness, and range of movement) and biochemical (creatine kinase) markers and inflammation (C-reactive protein) was performed at weeks 1, 5, and 10. Baseline isometric peak torque was also evaluated at week 14 after another cycle (4 weeks) of alternating or eccentric-only exercise training. In the alternating eccentric-concentric exercise group, the concentric exercise training performed prior to eccentric exercise reduced dramatically the repeated bout effect by reversing muscle back to its unaccustomed state. On the contrary, the eccentric-only exercise group exhibited a typical manifestation of the repeated bout effect. Interestingly, muscle strength was elevated similarly for both alternating and eccentric-only exercise groups after 13 weeks of training. The alternating eccentric-concentric exercise scheme, implemented in the present study, has for the first time successfully overcame the repeated bout effect. The similarity in muscle strength

  6. Eccentric exercise slows in vivo microvascular reactivity during brief contractions in human skeletal muscle.

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    Larsen, Ryan G; Hirata, Rogerio P; Madzak, Adnan; Frøkjær, Jens B; Graven-Nielsen, Thomas

    2015-12-01

    Unaccustomed exercise involving eccentric contractions results in muscle soreness and an overall decline in muscle function, however, little is known about the effects of eccentric exercise on microvascular reactivity in human skeletal muscle. Fourteen healthy men and women performed eccentric contractions of the dorsiflexor muscles in one leg, while the contralateral leg served as a control. At baseline, and 24 and 48 h after eccentric exercise, the following were acquired bilaterally in the tibialis anterior muscle: 1) transverse relaxation time (T2)-weighted magnetic resonance images to determine muscle cross-sectional area (mCSA) and T2; 2) blood oxygen level-dependent (BOLD) images during and following brief, maximal voluntary contractions (MVC) to monitor the hyperemic responses with participants positioned supine in a 3T magnet; 3) muscle strength; and 4) pain pressure threshold. Compared with the control leg, eccentric exercise resulted in soreness, decline in strength (∼20%), increased mCSA (∼7%), and prolonged T2 (∼7%) at 24 and 48 h (P eccentric exercise, such that time-to-peak (∼35%, P eccentric exercise may impede rapid adjustments in muscle blood flow at exercise onset and during activities involving brief bursts of muscle activation, which may impair O2 delivery and contribute to reduced muscle function after eccentric exercise. Copyright © 2015 the American Physiological Society.

  7. Eccentric wrist extensor contractions and the force velocity relationship in muscle.

    Science.gov (United States)

    Walmsley, R P; Pearson, N; Stymiest, P

    1986-01-01

    The torque produced by the wrist extensors during maximal isometric and isokinetic eccentric contractions has been investigated. The torque produced by eccentric contractions was measured at three different velocities: 0.36, 0.93, and 1.64 cmlsec. The speeds of contraction were generated by a specially designed apparatus, consisting of a gear drive and an electric motor that would maintain its speed irrespective of the load applied. Tenison produced by the wrist extensors was measured using a load cell. The results indicated that eccentric contractions of the wrist extensors exceed those produced by isometric contractions. The force-velocity relationship during eccentric contractions was determined to be different from that during concentric contractions. Force values were found to increase as the velocity of eccentric contraction increased. No signficant effect of wrist joint angle on torque values was found, nor was there an interaction effect of velocity and joint angle. The implications for rehabilitation of these findings are outlined. J Orthop Sports Phys Ther 1986;8(6):288-293.

  8. The effects of K+ channel blockade on eccentric and isotonic twitch and fatiguing contractions in situ

    Directory of Open Access Journals (Sweden)

    Michelle eMoyer

    2012-09-01

    Full Text Available K+ channel blockers like 3,4-diaminopyridine (DAP can double isometric muscle force. Functional movements require more complex concentric and eccentric contractions, however the effects of K+ channel blockade on these types of contractions in situ are unknown. Extensor digitorum longus (EDL muscles were stimulated in situ with and without DAP in anesthetized rats and fatigability was addressed using a series of either concentric or eccentric contractions. During isotonic protocols (5-100% load, DAP significantly shifted shortening- and maximum shortening velocity-load curves upward and to the right and increased power and work. Maximum shortening, maximum shortening velocity and power doubled while work increased by approximately 250% during isotonic contraction at 50% load. During isotonic fatigue, DAP significantly augmented maximum shortening, work, shortening velocity and power. During constant velocity eccentric protocols (2-12 mm/s, DAP increased muscle force during eccentric contractions at 6, 8, 10 and 12 mm/s. During eccentric contraction at a constant velocity of 6mm/s while varying the stimulation frequency, DAP significantly increased muscle force during 20, 40 and 70 Hz . The effects of DAP on muscle contractile performance during eccentric fatigue varied with level of fatigue. DAP-induced contractile increases during isotonic contractions were similar to those produced during previously studied isometric contractions, while the DAP effect during eccentric contractions was more modest. These findings are especially important in attempting to optimize functional electrical stimulation parameters for spinal cord injury patients while also preventing rapid fatigue of those muscles.

  9. The Effects of K(+) Channel Blockade on Eccentric and Isotonic Twitch and Fatiguing Contractions in situ.

    Science.gov (United States)

    van Lunteren, Erik; Moyer, Michelle

    2012-01-01

    K(+) channel blockers like 3,4-diaminopyridine (DAP) can double isometric muscle force. Functional movements require more complex concentric and eccentric contractions, however the effects of K(+) channel blockade on these types of contractions in situ are unknown. Extensor digitorum longus (EDL) muscles were stimulated in situ with and without DAP in anesthetized rats and fatigability was addressed using a series of either concentric or eccentric contractions. During isotonic protocols (5-100% load), DAP significantly shifted shortening- and maximum shortening velocity-load curves upward and to the right and increased power and work. Maximum shortening, maximum shortening velocity, and power doubled while work increased by ∼250% during isotonic contraction at 50% load. During isotonic fatigue, DAP significantly augmented maximum shortening, work, shortening velocity, and power. During constant velocity eccentric protocols (2-12 mm/s), DAP increased muscle force during eccentric contractions at 6, 8, 10, and 12 mm/s. During eccentric contraction at a constant velocity of 6 mm/s while varying the stimulation frequency, DAP significantly increased muscle force during 20, 40, and 70 Hz. The effects of DAP on muscle contractile performance during eccentric fatigue varied with level of fatigue. DAP-induced contractile increases during isotonic contractions were similar to those produced during previously studied isometric contractions, while the DAP effect during eccentric contractions was more modest. These findings are especially important in attempting to optimize functional electrical stimulation parameters for spinal cord injury patients while also preventing rapid fatigue of those muscles.

  10. The Effects of K+ Channel Blockade on Eccentric and Isotonic Twitch and Fatiguing Contractions in situ

    Science.gov (United States)

    van Lunteren, Erik; Moyer, Michelle

    2012-01-01

    K+ channel blockers like 3,4-diaminopyridine (DAP) can double isometric muscle force. Functional movements require more complex concentric and eccentric contractions, however the effects of K+ channel blockade on these types of contractions in situ are unknown. Extensor digitorum longus (EDL) muscles were stimulated in situ with and without DAP in anesthetized rats and fatigability was addressed using a series of either concentric or eccentric contractions. During isotonic protocols (5–100% load), DAP significantly shifted shortening- and maximum shortening velocity-load curves upward and to the right and increased power and work. Maximum shortening, maximum shortening velocity, and power doubled while work increased by ∼250% during isotonic contraction at 50% load. During isotonic fatigue, DAP significantly augmented maximum shortening, work, shortening velocity, and power. During constant velocity eccentric protocols (2–12 mm/s), DAP increased muscle force during eccentric contractions at 6, 8, 10, and 12 mm/s. During eccentric contraction at a constant velocity of 6 mm/s while varying the stimulation frequency, DAP significantly increased muscle force during 20, 40, and 70 Hz. The effects of DAP on muscle contractile performance during eccentric fatigue varied with level of fatigue. DAP-induced contractile increases during isotonic contractions were similar to those produced during previously studied isometric contractions, while the DAP effect during eccentric contractions was more modest. These findings are especially important in attempting to optimize functional electrical stimulation parameters for spinal cord injury patients while also preventing rapid fatigue of those muscles. PMID:23060809

  11. Effect of eccentric contraction on satellite cell activation in human vastus lateralis muscle.

    Science.gov (United States)

    Imaoka, Yoko; Kawai, Minako; Mori, Futoshi; Miyata, Hirofumi

    2015-09-01

    We compared the time-course of satellite cell (SC) activation between eccentric and concentric contractions in the vastus lateralis (VL) muscle after step exercise. Young adults participated in a 30-min step up/down exercise which mainly involved concentric contractions with the right VL muscle and eccentric contractions with the left VL muscle. The concentric and eccentric contraction phases of the VL muscles were identified by changes in the electromyogram (EMG) and knee joint angle. Biopsy samples were taken from both VL muscles at three time periods: before the exercise and 2 and 5 days after the exercise. We found that the numbers of SCs were significantly increased in the type IIa fibers of the left VL at 2 and 5 days after the exercise. The expression of both hepatocyte growth factor (HGF) and myogenic differentiation 1 (MyoD) mRNA had significantly increased in the left VL at 2 and 5 days after the exercise and in the right VL at 5 days after the exercise. The expression of transient receptor potential canonical (TRPC) 1 mRNA also increased in the left VL at 2 days after exercise. These results indicate that eccentric contraction can effectively activate SC proliferation for up to 5 days after exercise. Similar changes in HGF, MyoD and TRPC1 mRNA expression suggest that HGF/c-Met signal activation through cation influx has a major impact on skeletal muscle SC activation in response to eccentric exercise.

  12. The effect of temperature on eccentric contraction-induced isometric force loss in isolated perfused rat medial gastrocnemius muscle

    Directory of Open Access Journals (Sweden)

    Vasaghi Gharamaleki B

    2008-09-01

    Full Text Available "nBackground: The typical features of eccentric exercise-induced muscle damage are delayed-onset muscle soreness (DOMS and prolonged loss of muscle strength. It has been shown that passive warmth is effective in reducing muscle injury. Due to the interaction of different systems in vivo, we used isolated perfused medial gastrocnemius skeletal muscle to study the direct effect of temperature on the eccentric contraction-induced force loss. "nMethods: After femoral artery cannulation of a rat, the left medial gastrocnemius muscle was separated and then the entire lower limb was transferred into a prewarmed (35oC chamber. With the chamber temperature at 31, 35 and 39oC before and during eccentric contraction. Isometric force loss was measured after 15 eccentric contractions (N=7-9. "nResults: Maximum contraction force reduction has been used as an index for eccentric contraction-induced force loss. In this study eccentric contraction caused a significant reduction in maximum isometric tension (p<0.01, but no significant difference was seen in isometric force loss at 31oC and 39oC compared with that at 35oC. "nConclusions: Our results suggest that temperature changes before or during eccentric contractions have no effect on eccentric contraction-induced force loss. "nKeywords: Isolated perfused muscle, skeletal muscle, eccentric contractions, isometric force, gastrocnemius muscle, temperature.

  13. The Effects of Eccentric Contraction Duration on Muscle Strength, Power Production, Vertical Jump, and Soreness.

    Science.gov (United States)

    Mike, Jonathan N; Cole, Nathan; Herrera, Chris; VanDusseldorp, Trisha; Kravitz, Len; Kerksick, Chad M

    2017-03-01

    Mike, JN, Cole, N, Herrera, C, VanDusseldorp, T, Kravitz, L, and Kerksick, CM. The effects of eccentric contraction duration on muscle strength, power production, vertical jump, and soreness. J Strength Cond Res 31(3): 773-786, 2017-Previous research has investigated the effects of either eccentric-only training or comparing eccentric and concentric exercise on changes related to strength and power expression, but no research to date has investigated the impact of altering the duration of either the concentric or the eccentric component on these parameters. Therefore, the purpose of this study was to assess the duration of eccentric (i.e., 2-second, 4-second vs. 6-second) muscle contractions and their effect on muscle strength, power production, vertical jump, and soreness using a plate-loaded barbell Smith squat exercise. Thirty college-aged men (23 ± 3.5 years, 178 ± 6.8 cm, 82 ± 12 kg, and 11.6 ± 5.1% fat) with 3.0 ± 1.0 years of resistance training experience and training frequency of 4.3 ± 0.9 days per week were randomized and assigned to 1 of 3 eccentric training groups that incorporated different patterns of contraction. For every repetition, all 3 groups used 2-second concentric contractions and paused for 1 second between the concentric and eccentric phases. The control group (2S) used 2-second eccentric contractions, whereas the 4S group performed 4-second eccentric contractions and the 6S group performed 6-second eccentric contractions. All repetitions were completed using the barbell Smith squat exercise. All participants completed a 4-week training protocol that required them to complete 2 workouts per week using their prescribed contraction routine for 4 sets of 6 repetitions at an intensity of 80-85% one repetition maximum (1RM). For all performance data, significant group × time (G × T) interaction effects were found for average power production across all 3 sets of a squat jump protocol (p = 0.04) while vertical jump did not reach

  14. Physiological Mechanisms of Eccentric Contraction and Its Applications: A Role for the Giant Titin Protein

    Science.gov (United States)

    Hessel, Anthony L.; Lindstedt, Stan L.; Nishikawa, Kiisa C.

    2017-01-01

    When active muscles are stretched, our understanding of muscle function is stretched as well. Our understanding of the molecular mechanisms of concentric contraction has advanced considerably since the advent of the sliding filament theory, whereas mechanisms for increased force production during eccentric contraction are only now becoming clearer. Eccentric contractions play an important role in everyday human movements, including mobility, stability, and muscle strength. Shortly after the sliding filament theory of muscle contraction was introduced, there was a reluctant recognition that muscle behaved as if it contained an “elastic” filament. Jean Hanson and Hugh Huxley referred to this structure as the “S-filament,” though their concept gained little traction. This additional filament, the giant titin protein, was identified several decades later, and its roles in muscle contraction are still being discovered. Recent research has demonstrated that, like activation of thin filaments by calcium, titin is also activated in muscle sarcomeres by mechanisms only now being elucidated. The mdm mutation in mice appears to prevent activation of titin, and is a promising model system for investigating mechanisms of titin activation. Titin stiffness appears to increase with muscle force production, providing a mechanism that explains two fundamental properties of eccentric contractions: their high force and low energetic cost. The high force and low energy cost of eccentric contractions makes them particularly well suited for athletic training and rehabilitation. Eccentric exercise is commonly prescribed for treatment of a variety of conditions including sarcopenia, osteoporosis, and tendinosis. Use of eccentric exercise in rehabilitation and athletic training has exploded to include treatment for the elderly, as well as muscle and bone density maintenance for astronauts during long-term space travel. For exercise intolerance and many types of sports injuries

  15. Physiological Mechanisms of Eccentric Contraction and Its Applications: A Role for the Giant Titin Protein.

    Science.gov (United States)

    Hessel, Anthony L; Lindstedt, Stan L; Nishikawa, Kiisa C

    2017-01-01

    When active muscles are stretched, our understanding of muscle function is stretched as well. Our understanding of the molecular mechanisms of concentric contraction has advanced considerably since the advent of the sliding filament theory, whereas mechanisms for increased force production during eccentric contraction are only now becoming clearer. Eccentric contractions play an important role in everyday human movements, including mobility, stability, and muscle strength. Shortly after the sliding filament theory of muscle contraction was introduced, there was a reluctant recognition that muscle behaved as if it contained an "elastic" filament. Jean Hanson and Hugh Huxley referred to this structure as the "S-filament," though their concept gained little traction. This additional filament, the giant titin protein, was identified several decades later, and its roles in muscle contraction are still being discovered. Recent research has demonstrated that, like activation of thin filaments by calcium, titin is also activated in muscle sarcomeres by mechanisms only now being elucidated. The mdm mutation in mice appears to prevent activation of titin, and is a promising model system for investigating mechanisms of titin activation. Titin stiffness appears to increase with muscle force production, providing a mechanism that explains two fundamental properties of eccentric contractions: their high force and low energetic cost. The high force and low energy cost of eccentric contractions makes them particularly well suited for athletic training and rehabilitation. Eccentric exercise is commonly prescribed for treatment of a variety of conditions including sarcopenia, osteoporosis, and tendinosis. Use of eccentric exercise in rehabilitation and athletic training has exploded to include treatment for the elderly, as well as muscle and bone density maintenance for astronauts during long-term space travel. For exercise intolerance and many types of sports injuries, experimental

  16. Eccentric contractions affect muscle membrane phospholipid fatty acid composition in rats

    DEFF Research Database (Denmark)

    Helge, Jørn Wulff; Therkildsen, K J; Jørgensen, T B

    2001-01-01

    This study investigated if prior eccentric contractions, and thus mechanical strain and muscle damage, exert an effect on the muscle membrane phospholipid fatty acid composition in rats, and whether a possible effect could be attenuated by dietary supplements. Twenty-three rats were randomised...... to three groups who received chow with added fish oil (n = 8), vitamin C (n = 8) or no supplement (n = 7). After 3 weeks of feeding, calf muscles on one side were stimulated electrically during anaesthesia causing eccentric contractions. Two days later the white gastrocnemius, a part of the stimulated calf...... muscle, was excised from both legs. In the muscles stimulated to contract eccentrically, compared to the control muscles, the proportion of arachidonic acid, C20:4,n-6 (17.7 +/- 0.6; 16.4 +/- 0.4% of total fatty acids, respectively) and docosapentanoeic acid, C22:5,n-3 (2.9 +/- 0.1 and 2.7 +/- 0...

  17. Decreased insulin action on muscle glucose transport after eccentric contractions in rats

    DEFF Research Database (Denmark)

    Asp, S; Richter, Erik

    1996-01-01

    We have recently shown that eccentric contractions (Ecc) of rat calf muscles cause muscle damage and decreased glycogen and glucose transporter GLUT-4 protein content in the white (WG) and red gastrocnemius (RG) but not in the soleus (S) (S. Asp, S. Kristiansen, and E. A. Richter. J. Appl. Physiol....... 79: 1338-1345, 1995). To study whether these changes affect insulin action, hindlimbs were perfused at three different insulin concentrations (0, 200, and 20,000 microU/ml) 2 days after one-legged eccentric contractions of the calf muscles. Compared with control, basal glucose transport was slightly...... velocity of glycogen synthase increased similarly with increasing insulin concentrations in Ecc- and control WG and RG. We conclude that insulin action on glucose transport but not glycogen synthase activity is impaired in perfused muscle exposed to prior eccentric contractions....

  18. Gender differences in fascicular lengthening during eccentric contractions: the role of the patella tendon stiffness.

    Science.gov (United States)

    Hicks, K M; Onambele-Pearson, G L; Winwood, K; Morse, C I

    2013-11-01

    Elastic tendons have been suggested to attenuate fascicle lengthening during eccentric contractions; however, there is no in vivo evidence to support this hypothesis. Therefore, the aim of this study was to determine whether patella tendon stiffness modulates vastus lateralis (VL) fascicle lengthening during eccentric contractions in males and females. Vastus lateralis and patella tendon properties were measured in males and females owing to previously reported intrinsic gender differences in tendon properties. During maximal voluntary eccentric knee extensions, VL fascicle lengthening and torque were recorded at every 10° (range of motion 20-90°). A significant correlation between maximal patella tendon stiffness and change in fascicle length (r=0.476, P=0.023) was observed. Similarly, there was a significant correlation between maximal Young's modulus and change in fascicle length (r=0.470, P=0.049). As expected, patella tendon stiffness and Young's modulus were significantly higher in males compared with females (Pmuscle-tendon unit elongation was estimated to be significantly greater in males compared with females (5.24 and 4.84 cm respectively). The significant difference in fascicle lengthening during eccentric contractions may be partly explained by the significantly higher patella tendon moment arm, patella tendon stiffness and Young's modulus found in males compared with females. The current study provides in vivo evidence to support the hypothesis that the tendon acts as a 'mechanical buffer' during eccentric contractions. © 2013 Scandinavian Physiological Society. Published by John Wiley & Sons Ltd.

  19. Time-Course of Neuromuscular Changes during and after Maximal Eccentric Contractions.

    Science.gov (United States)

    Doguet, Valentin; Jubeau, Marc; Dorel, Sylvain; Couturier, Antoine; Lacourpaille, Lilian; Guével, Arnaud; Guilhem, Gaël

    2016-01-01

    This study tested the relationship between the magnitude of muscle damage and both central and peripheral modulations during and after eccentric contractions of plantar flexors. Eleven participants performed 10 sets of 30 maximal eccentric contractions of the plantar flexors at 45°·s(-1). Maximal voluntary torque, evoked torque (peripheral component) and voluntary activation (central component) were assessed before, during, immediately after (POST) and 48 h after (48 h) the eccentric exercise. Voluntary eccentric torque progressively decreased (up to -36%) concomitantly to a significant alteration of evoked torque (up to -34%) and voluntary activation (up to -13%) during the exercise. Voluntary isometric torque (-48 ± 7%), evoked torque (-41 ± 14%) and voluntary activation (-13 ± 11%) decreased at POST, but only voluntary isometric torque (-19 ± 6%) and evoked torque (-10 ± 18%) remained depressed at 48 h. Neither changes in voluntary activation nor evoked torque during the exercise were related to the magnitude of muscle damage markers, but the evoked torque decrement at 48 h was significantly correlated with the changes in voluntary activation (r = -0.71) and evoked torque (r = 0.77) at POST. Our findings show that neuromuscular responses observed during eccentric contractions were not associated with muscle damage. Conversely, central and peripheral impairments observed immediately after the exercise reflect the long-lasting reduction in force-generating capacity.

  20. The impact of altered task mechanics on timing and duration of eccentric bi-articular muscle contractions during cycling.

    Science.gov (United States)

    Connick, Mark J; Li, François-Xavier

    2013-02-01

    In order to understand muscle adaptations to altered task mechanics during cycling, this study investigated the impact of altered seat height and cadence on timing and duration of gastrocnemius (GAST), biceps femoris (BF) and vastus lateralis (VL) eccentric contractions and muscle activation patterns, and cycling economy. Ten male cyclists completed 9 × 5 min of cycling at 3 seat heights and 3 cadences. Three-dimensional leg kinematics and muscle activation patterns were recorded to estimate timing of eccentric muscle contractions. Onset, offset and duration of eccentric contractions and, onset, offset and duration of muscle activation were calculated, along with cycling economy. Duration of GAST and VL eccentric contractions decreased with increasing seat height due to earlier offset of eccentric muscle contractions. Duration of BF eccentric contractions significantly increased with seat height due to a later eccentric contraction offset. Offset of GAST and BF muscle activation occurred earlier with increasing cadence. Cycling economy was significantly affected by cadence but not seat height. The results suggest that as a consequence of altered seat height, proprioceptive feedback is used to fine-tune the timing of bi-articular eccentric muscle contractions. These results may have implications for seat height self-selection.

  1. Reduced sarcoplasmic reticulum content of releasable Ca2+ in rat soleus muscle fibres after eccentric contractions

    DEFF Research Database (Denmark)

    Nielsen, J S; Sahlin, K; Ørtenblad, N

    2007-01-01

    AIM: The purpose was to evaluate the effects of fatiguing eccentric contractions (EC) on calcium (Ca2+) handling properties in mammalian type I muscles. We hypothesized that EC reduces both endogenous sarcoplasmic reticulum (SR) content of releasable Ca2+ (eSRCa2+) and myofibrillar Ca2+ sensitivity...

  2. Relationship Between Erectores Spinae Voltage and Back-Lift Strength for Isometric, Concentric, and Eccentric Contractions

    Science.gov (United States)

    Ashton, T. Edwin J.; Singh, Mohan

    1975-01-01

    This study determined the maximal mean values for concentric and eccentric back-lift strength as well as isometric, and examined and compared the relationships between the mean peak voltage of the erectores spinae muscle(s) and maximal force exerted for the three types of muscle contractions. (RC)

  3. Skeletal muscle collagen content in humans after high-force eccentric contractions

    DEFF Research Database (Denmark)

    Mackey, Abigail; Donnelly, Alan E; Turpeenniemi-Hujanen, Taina

    2004-01-01

    4) yr] each performed a bout of 100 maximum voluntary eccentric contractions of the knee extensors. Muscle biopsies were taken before exercise and on days 4 and 22 afterward. Image analysis of stained tissue sections was used to quantify endomysial collagen staining intensity. Maximum voluntary...

  4. Position sense and reaction angle after eccentric exercise: the repeated bout effect.

    Science.gov (United States)

    Paschalis, V; Nikolaidis, M G; Giakas, G; Jamurtas, A Z; Owolabi, E O; Koutedakis, Y

    2008-05-01

    The purpose of the present investigation was to examine the effects of a repeated eccentric exercise on position sense and muscle reaction angle. Fourteen healthy women underwent an isokinetic exercise session on their knee flexors, which was repeated after 4 weeks. Muscle damage indices, position sense and joint reaction angle of the knee were examined before, immediately after, as well as at 1, 2, 3, 4 and 7 days after exercise. The second exercise bout induced significantly lesser effects in all muscle damage indices as well as lesser disturbances in position sense and reaction angle when compared to the first one. The main finding of this study is that position sense and joint reaction angle to release of the lower limbs may adapt in response to a repeated bout of eccentric exercise, leading to less disturbances in position sense and reaction angle after the second bout of exercise.

  5. Differences in activation patterns in elbow flexor muscles during isometric, concentric and eccentric contractions.

    Science.gov (United States)

    Nakazawa, K; Kawakami, Y; Fukunaga, T; Yano, H; Miyashita, M

    1993-01-01

    To investigate the relative activation of the synergistic muscles during three different types of muscle contraction, the electromyograms (EMG) of two elbow flexor muscles, the biceps brachii (BB) and the brachioradialis (BR), have been compared. To accomplish this eight healthy human subjects performed the following elbow flexions against the same load--concentric, eccentric and isometric contractions. The isometric contractions were performed at three elbow angles: 10, 45 and 90 degrees (0 degree equal to full extension). The EMG were recorded by bipolar surface electrodes, and the relative activation between the two muscles was evaluated as the quotient of mean EMG activities (BR/BB). For the isotonic elbow flexions, BR/BB were calculated at three angle divisions: 0-30 degrees, 30-60 degrees and 60-90 degrees. Results indicated that the relative activation of the BR during the concentric contractions was higher than that of the eccentric contraction, particularly at the extended elbow angles, i.e. the BR/BB of the concentric contractions for the elbow joint angles ranging from 0-30 degrees and 30-60 degrees were significantly greater (P contractions. During the isometric and eccentric contractions, the BR/BB at the flexed joint angles tended to be greater than those at the extended angles. In contrast, there were no angle-dependent BR/BB variations during the concentric elbow flexions. Further, changing patterns in the EMG power spectra due to the type of contraction were different between BB and BR. These results indicated that the activation pattern in the two elbow flexor muscles varied with the muscle contraction pattern.

  6. The effect of eccentric exercise with blood flow restriction on neuromuscular activation, microvascular oxygenation, and the repeated bout effect.

    Science.gov (United States)

    Lauver, Jakob D; Cayot, Trent E; Rotarius, Timothy; Scheuermann, Barry W

    2017-05-01

    To examine the effect of low-intensity eccentric contractions with and without blood flow restriction (BFR) on microvascular oxygenation, neuromuscular activation, and the repeated bout effect (RBE). Participants were randomly assigned to either low-intensity (LI), low-intensity with BFR (LI-BFR), or a control (CON) group. Participants in LI and LI-BFR performed a preconditioning bout of low-intensity eccentric exercise prior to about of maximal eccentric exercise. Participants reported 24, 48, 72, and 96 h later to assess muscle damage and function. Surface electromyography (sEMG) and near-infrared spectroscopy (NIRS) were used to measure neuromuscular activation and microvascular deoxygenation (deoxy-[Hb + Mb]) and [total hemoglobin] ([THC]) during the preconditioning bout, respectively. During set-2, LI-BFR resulted in greater activation of the VM-RMS (47.7 ± 11.5% MVIC) compared to LI (67.0 ± 20.0% MVIC), as well as during set-3 (p exercise (LI 74.2 ± 14.1%, LI-BFR 75 ± 5.1%, CON 53 ± 18.6%). At 24, 48, 72, and 96 h post maximal eccentric exercise, LI and LI-BFR force deficit was not different from baseline. This study suggests that the neuromuscular and deoxygenation (i.e., metabolic stress) responses were considerably different between LI and LI-BFR groups; however, these differences did not lead to improvements in the RBE inferred by performing LI and LI-BFR.

  7. Aging is not a barrier to muscle and redox adaptations: applying the repeated eccentric exercise model.

    Science.gov (United States)

    Nikolaidis, Michalis G; Kyparos, Antonios; Spanou, Chrysa; Paschalis, Vassilis; Theodorou, Anastasios A; Panayiotou, George; Grivas, Gerasimos V; Zafeiridis, Andreas; Dipla, Konstantina; Vrabas, Ioannis S

    2013-08-01

    Despite the progress of analytic techniques and the refinement of study designs, striking disagreement exists among studies regarding the influence of exercise on muscle function and redox homeostasis in the elderly. The repeated eccentric exercise model was applied to produce long-lasting and extensive changes in redox biomarkers and to reveal more effectively the potential effects of aging on redox homeostasis. Ten young (20.6±0.5 years) and ten elderly men (64.6±1.1 years) underwent an isokinetic eccentric exercise session, which was repeated after three weeks. Muscle function/damage indices (torque, range of movement, muscle soreness and creatine kinase) and redox biomarkers (F2-isoprostanes, protein carbonyls, glutathione, catalase, superoxide dismutase, glutathione peroxidase, glucose-6-phosphate dehydrogenase, uric acid, bilirubin and albumin) were assessed in plasma, erythrocytes or urine pre-exercise, immediately post-exercise and at 2 and 4 days post-exercise. As expected, the elderly group exhibited oxidative stress in baseline compared to the young group. Extensive muscle damage and extensive alterations in redox homeostasis appeared after the first bout of eccentric exercise. Noteworthy, the redox responses were similar between the age groups despite their differences in baseline values. Likewise, both age groups demonstrated blunted alterations in muscle damage and redox homeostasis after the second bout of eccentric exercise indicating adaptations from the first bout of exercise. Elderly individuals seem to be well fitted to participate in demanding physical activities without suffering detrimental effects on skeletal muscle and/or disturbances on redox homeostasis. The repeated eccentric exercise model may be a useful and practical physiological tool to study redox biology in humans. Copyright © 2013 Elsevier Inc. All rights reserved.

  8. Pain sensitivity is normalized after a repeated bout of eccentric exercise.

    Science.gov (United States)

    Hosseinzadeh, Mahdi; Andersen, Ole K; Arendt-Nielsen, Lars; Madeleine, Pascal

    2013-10-01

    The purpose of this study was to investigate the effect of repeated bouts of eccentric exercise on the nociceptive withdrawal reflex (NWR) threshold, a measure of sensitivity in the spinal nociceptive system. Sixteen healthy students (age 25.7 ± 0.6 years, BMI 24.8 ± 1 kg m(-2)) participated in this randomized, controlled, crossover study. Two identical bouts of high-intensity eccentric exercises were performed on the tibialis anterior muscle 7 days apart. Control sessions involving no exercise were performed 4 weeks apart the exercise sessions. Pressure pain thresholds (PPT) and the NWR threshold were recorded before, immediately after, and 1 day after both bouts of exercise. Pressure pain thresholds decreased significantly at two of the muscle belly sites on the day after initial bout compared with baseline. NWR threshold decreased by 25 ± 4 % immediately after initial bout and by 30 ± 5 % the next day (p eccentric exercise indicating that both localized and generalized pain sensitivity were normalized. In conclusion, this study for the first time documented that an initial bout of unaccustomed high-intensity eccentric exercise, which results in muscle soreness can induce central sensitization. A repeated bout of exercise, however, facilitates inherent protective spinal mechanisms against the development of muscle soreness.

  9. Eccentric contractions do not induce rhabdomyolysis in malignant hyperthermia susceptible mice

    Science.gov (United States)

    Corona, Benjamin T.; Rouviere, Clement; Hamilton, Susan L.; Ingalls, Christopher P.

    2008-01-01

    Recent studies suggest a link between exercise-induced rhabdomyolysis and mutations of the ryanodine receptor (RYR1) associated with malignant hyperthermia (MH). We hypothesized that MH-susceptible mice (RYR1Y522S/wt) would exhibit greater anterior crural muscle [tibialis anterior (TA) and extensor digitorum longus (EDL) muscles] damage and strength deficits following the performance of a single or repeated bouts of eccentric contractions compared with wild-type (WT) mice. After a single injury bout, RYR1Y522S/wt mice produced more isometric torque than WT mice immediately and 3 and 7 days postinjury. Moreover, EDL muscle isometric specific force deficits were fully recovered for RYR1Y522S/wt but not WT mice 14 days postinjury. The percentage of fibers in TA muscle exhibiting signs of muscle damage 7 and 14 days postinjury were at least three times less in RYR1Y522S/wt than in WT mice. Uninjured and injured EDL muscle from RYR1Y522S/wt mice also displayed greater S-glutathionylation of RYR1 than that from WT mice. During the weekly injury bouts, torque production by RYR1Y522S/wt mice was fully recovered before the third and fourth injury bouts, whereas torque was still reduced for WT mice. Three days after multiple injury bouts, there were ∼50% fewer fibers exhibiting signs of muscle damage in RYR1Y522S/wt than in WT TA muscle. These findings indicate that the RYR1Y522S/wt mutation protects skeletal muscle from exercise-induced muscle injury and do not support a direct association between MH susceptibility and contraction-induced rhabdomyolysis when core temperature is maintained at lower physiological temperatures during exercise. PMID:18787086

  10. Analysis of concentric and eccentric contractions in biceps brachii muscles using surface electromyography signals and multifractal analysis.

    Science.gov (United States)

    Marri, Kiran; Swaminathan, Ramakrishnan

    2016-06-23

    Muscle contractions can be categorized into isometric, isotonic (concentric and eccentric) and isokinetic contractions. The eccentric contractions are very effective for promoting muscle hypertrophy and produce larger forces when compared to the concentric or isometric contractions. Surface electromyography signals are widely used for analyzing muscle activities. These signals are nonstationary, nonlinear and exhibit self-similar multifractal behavior. The research on surface electromyography signals using multifractal analysis is not well established for concentric and eccentric contractions. In this study, an attempt has been made to analyze the concentric and eccentric contractions associated with biceps brachii muscles using surface electromyography signals and multifractal detrended moving average algorithm. Surface electromyography signals were recorded from 20 healthy individuals while performing a single curl exercise. The preprocessed signals were divided into concentric and eccentric cycles and in turn divided into phases based on range of motion: lower (0°-90°) and upper (>90°). The segments of surface electromyography signal were subjected to multifractal detrended moving average algorithm, and multifractal features such as strength of multifractality, peak exponent value, maximum exponent and exponent index were extracted in addition to conventional linear features such as root mean square and median frequency. The results show that surface electromyography signals exhibit multifractal behavior in both concentric and eccentric cycles. The mean strength of multifractality increased by 15% in eccentric contraction compared to concentric contraction. The lowest and highest exponent index values are observed in the upper concentric and lower eccentric contractions, respectively. The multifractal features are observed to be helpful in differentiating surface electromyography signals along the range of motion as compared to root mean square and median

  11. Pressure pain mapping of the wrist extensors after repeated eccentric exercise at high intensity.

    Science.gov (United States)

    Delfa de la Morena, José M; Samani, Afshin; Fernández-Carnero, Josué; Hansen, Ernst A; Madeleine, Pascal

    2013-11-01

    The purpose of this study was to investigate adaptation mechanisms after 2 test rounds consisting of eccentric exercise using pressure pain imaging of the wrist extensors. Pressure pain thresholds (PPTs) were assessed over 12 points forming a 3 × 4 matrix over the dominant elbow in 12 participants. From the PPT assessments, pressure pain maps were computed. Delayed onset muscle soreness was induced in an initial test round of high-intensity eccentric exercise. The second test round performed 7 days later aimed at resulting in adaptation. The PPTs were assessed before, immediately after, and 24 hours after the 2 test rounds of eccentric exercise. For the first test round, the mean PPT was significantly lower 24 hours after exercise compared with before exercise (389.5 ± 64.1 vs. 500.5 ± 66.4 kPa, respectively; p = 0.02). For the second test round, the PPT was similar before and 24 hours after (447.7 ± 51.3 vs. 458.0 ± 73.1 kPa, respectively; p = 1.0). This study demonstrated adaptive effects of the wrist extensors monitored by pain imaging technique in healthy untrained humans. A lack of hyperalgesia, i.e., no decrease in PPT underlined adaptation after the second test round of eccentric exercise performed 7 days after the initial test round. The present findings showed for the first time that repeated eccentric exercise performed twice over 2 weeks protects the wrist extensor muscles from developing exacerbated pressure pain sensitivity. Thus, the addition of eccentric components to training regimens should be considered to induce protective adaptation.

  12. Temporal Pattern of the Repeated Bout Effect of Eccentric Exercise on Delayed-Onset Muscle Soreness

    Science.gov (United States)

    Cleary, Michelle A.; Kimura, Iris F.; Sitler, Michael R.; Kendrick, Zebulon V.

    2002-01-01

    Objective: To determine the temporal pattern of the repeated bout effect of eccentric exercise on perceived pain and muscular tenderness associated with delayed-onset muscle soreness (DOMS). Design and Setting: Subjects completed 2 identical eccentric exercise bouts separated by 6, 7, 8, or 9 weeks. The experiment was conducted in a biokinetics research laboratory. Subjects: Sixteen male and 15 female untrained subjects (age = 24.59 ± 4.42 years, height = 171.71 ± 7.81 cm, weight = 73.00 ± 11.20 kg). Measurements: Two physiologic characteristics of DOMS were measured immediately before and 0, 24, 48, and 72 hours after each eccentric exercise bout. Perceived pain was measured using a visual analog scale (VAS), and muscular tenderness was measured using a punctate tenderness gauge (PTG). Results: Two 4 × 2 × 5 (group × bout × time) analyses of variance with repeated measures on the bout and time factors were performed on the VAS and PTG data. Significant (P < .05) main effects were found for group, bout, and time for the VAS and the PTG data. No significant interactions were detected. Post hoc analysis revealed significantly less perceived pain for the 9-week group than the 8-week group. The 7-week group had significantly less and the 8-week group had significantly more muscular tenderness than any other group. Perceived pain and muscular tenderness were significantly less after exercise bout 2 than after exercise bout 1. All subjects had significantly less perceived pain and muscular tenderness pre-exercise than 0 and 24 hours after the eccentric exercise bouts. Conclusions: An effective prophylaxis for perceived pain and muscular tenderness associated with DOMS is the performance of an eccentric exercise bout 6 to 9 weeks before a similar exercise bout. PMID:12937441

  13. Two maximal isometric contractions attenuate the magnitude of eccentric exercise-induced muscle damage.

    Science.gov (United States)

    Chen, Hsin-Lian; Nosaka, Kazunori; Pearce, Alan J; Chen, Trevor C

    2012-08-01

    This study investigated whether maximal voluntary isometric contractions (MVC-ISO) would attenuate the magnitude of eccentric exercise-induced muscle damage. Young untrained men were placed into one of the two experimental groups or one control group (n = 13 per group). Subjects in the experimental groups performed either two or 10 MVC-ISO of the elbow flexors at a long muscle length (20° flexion) 2 days prior to 30 maximal isokinetic eccentric contractions of the elbow flexors. Subjects in the control group performed the eccentric contractions without MVC-ISO. No significant changes in maximal voluntary concentric contraction peak torque, peak torque angle, range of motion, upper arm circumference, plasma creatine kinase (CK) activity and myoglobin concentration, muscle soreness, and ultrasound echo intensity were evident after MVC-ISO. Changes in the variables following eccentric contractions were smaller (P MVC-ISO group (e.g., peak torque loss at 5 days after exercise, 23% ± 3%; peak CK activity, 1964 ± 452 IU·L(-1); peak muscle soreness, 46 ± 4 mm) or the 10 MVC-ISO group (13% ± 3%, 877 ± 198 IU·L(-1), 30 ± 4 mm) compared with the control (34% ± 4%, 6192 ± 1747 IU·L(-1), 66 ± 5 mm). The 10 MVC-ISO group showed smaller (P MVC-ISO group. Therefore, two MVC-ISO conferred potent protective effects against muscle damage, whereas greater protective effect was induced by 10 MVC-ISO, which can be used as a strategy to minimize muscle damage.

  14. Low-intensity eccentric contractions attenuate muscle damage induced by subsequent maximal eccentric exercise of the knee extensors in the elderly.

    Science.gov (United States)

    Chen, Trevor C; Tseng, Wei-Chin; Huang, Guan-Ling; Chen, Hsin-Lian; Tseng, Kou-Wei; Nosaka, Kazunori

    2013-04-01

    This study investigated whether low-intensity eccentric contractions of the knee extensors would attenuate the magnitude of muscle damage induced by maximal eccentric exercise of the same muscle performed 7 days later using elderly individuals. Healthy older men (66.4 ± 4.6 years) were assigned to control or experimental (Exp) group (n = 13 per group). The control group performed six sets of ten maximal eccentric contractions (MaxECC) of the knee extensors of non-dominant leg. The Exp group performed six sets of ten low-intensity eccentric contractions of the knee extensors on a leg extension machine by lowering a weight of 10 % maximal voluntary isometric knee extension strength (10 %ECC) 7 days prior to MaxECC. Changes in maximal voluntary isokinetic concentric torque (MVC-CON), angle at peak torque, range of motion (ROM), upper thigh circumference, muscle soreness, plasma creatine kinase activity and myoglobin (Mb) concentration and B-mode ultrasound echo-intensity before and for 5 days after MaxECC were compared between groups by a mixed factor ANOVA. No significant changes in any variables were observed following 10 %ECC. Following MaxECC, all variables changed significantly, and changes in all variables except for angle at peak torque were significantly different between groups. MVC-CON and ROM decreased smaller and recovered faster (P eccentric contractions was effective for attenuating muscle damage induced by subsequent MaxECC of the knee extensors for elderly individuals.

  15. Effects of set-repetition configuration in eccentric exercise on muscle damage and the repeated bout effect.

    Science.gov (United States)

    Chan, R; Newton, M; Nosaka, K

    2012-07-01

    The number of eccentric contractions is a factor affecting the magnitude of muscle damage; however, it is unknown whether set-repetition configurations for the same total number of eccentric contractions affect the muscle damage. The present study investigated whether different set-repetition configurations would result in different force output during eccentric exercise and different magnitude of muscle damage following the first and second exercise bouts. Ten non-resistance-trained men (26.1 ± 4.1 years) performed two bouts of eccentric exercise of the elbow flexors of each arm (4 bouts in total). One arm performed 3 sets of 10 maximal eccentric contractions (3 × 10) and the contralateral arm performed 10 sets of 3 maximal eccentric contractions (10 × 3), and each arm performed 20 sets of 3 maximal eccentric contractions (20 × 3) 4 weeks after the first bout. The order of the exercise (3 × 10, 10 × 3) and the use of arm (dominant, non-dominant) were counterbalanced amongst subjects. The torque produced over 30 eccentric contractions was similar between 3 × 10 and 10 × 3, and the changes in torque during 20 × 3 were similar between arms. Maximal voluntary contraction strength, range of motion, biceps brachii cross-sectional area and muscle soreness changed significantly (P exercise without significant differences between 3 × 10 and 10 × 3, and changes in the measures following 20 × 3 were similar between arms, except for range of motion (ROM). No significant difference in the changes in any measures except ROM was evident when compared between the first and second bouts. These results showed that changing the set-repetition configuration had little effect on muscle damage.

  16. Effects of concentric and repeated eccentric exercise on muscle damage and calpain-calpastatin gene expression in human skeletal muscle

    DEFF Research Database (Denmark)

    Vissing, K.; Overgaard, K.; Nedergaard, A.

    2008-01-01

    The purpose of this study was to compare the responsiveness of changes in Ca2+-content and calpain-calpastatin gene expression to concentric and eccentric single-bout and repeated exercise. An exercise group (n = 14) performed two bouts of bench-stepping exercise with 8 weeks between exercise bouts...... for muscle Ca2+-content and mRNA levels for calpain isoforms and calpastatin. Exercise reduced muscle strength and increased muscle soreness predominantly in the eccentric leg (P ... eccentric exercise bout (P eccentric exercise 24 h post-exercise (P

  17. Plyometric training improves voluntary activation and strength during isometric, concentric and eccentric contractions.

    Science.gov (United States)

    Behrens, Martin; Mau-Moeller, Anett; Mueller, Karoline; Heise, Sandra; Gube, Martin; Beuster, Nico; Herlyn, Philipp K E; Fischer, Dagmar-C; Bruhn, Sven

    2016-02-01

    This study investigated effects of plyometric training (6 weeks, 3 sessions/week) on maximum voluntary contraction (MVC) strength and neural activation of the knee extensors during isometric, concentric and eccentric contractions. Twenty-seven participants were randomly assigned to the intervention or control group. Maximum voluntary torques (MVT) during the different types of contraction were measured at 110° knee flexion (180°=full extension). The interpolated twitch technique was applied at the same knee joint angle during isometric, concentric and eccentric contractions to measure voluntary activation. In addition, normalized root mean square of the EMG signal at MVT was calculated. The twitch torque signal induced by electrical nerve stimulation at rest was used to evaluate training-related changes at the muscle level. In addition, jump height in countermovement jump was measured. After training, MVT increased by 20Nm (95% CI: 5-36Nm, P=0.012), 24Nm (95% CI: 9-40Nm, P=0.004) and 27Nm (95% CI: 7-48Nm, P=0.013) for isometric, concentric and eccentric MVCs compared to controls, respectively. The strength enhancements were associated with increases in voluntary activation during isometric, concentric and eccentric MVCs by 7.8% (95% CI: 1.8-13.9%, P=0.013), 7.0% (95% CI: 0.4-13.5%, P=0.039) and 8.6% (95% CI: 3.0-14.2%, P=0.005), respectively. Changes in the twitch torque signal of the resting muscle, induced by supramaximal electrical stimulation of the femoral nerve, were not observed, indicating no alterations at the muscle level, whereas jump height was increased. Given the fact that the training exercises consisted of eccentric muscle actions followed by concentric contractions, it is in particular relevant that the plyometric training increased MVC strength and neural activation of the quadriceps muscle regardless of the contraction mode. Copyright © 2015 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

  18. Influence of repeated bouts of eccentric exercise on high-intensity aerobic performance.

    Science.gov (United States)

    Higino, Wonder Passoni; Aparecido de Souza, Renato; Cavalcanti, Fabio de Sousa; Cardoso, Anderlei Dos Santos; Vasconcelos, Murilo Victor; Fernandes da Silva, Fabiano; Leme, José Alexandre C A

    2016-08-01

    [Purpose] It is believed that eccentric high-intensity exercise can decrease performance in subsequent exercise. However, with repetition, the deleterious effects can be minimized. Thus, this study evaluated the influence of repeated bouts of eccentric exercise on subsequent high-intensity aerobic performance. [Subjects and Methods] Seven healthy and sedentary male volunteers were recruited. a) Visit 1: determination of maximum oxygen uptake (VO2max) and speed associated with maximum oxygen uptake (vVO2max) in incremental treadmill testing; b) Visit 2: run to exhaustion at vVO2max (Tlim control); c) Visit 3: 10 sets of 10 depth jumps, followed by a run to exhaustion at vVO2max (Tlim 1); d) Visit 4: after 6 weeks without any physical training, the volunteers carried out the same procedures as on the third visit (Tlim 2). Data were analyzed using one-way analysis of variance (ANOVA) with the post-hoc Tukey test. [Results] Significant differences were found between Tlim control and Tlim 1 (283.4 ± 47.7 s vs. 125.2 ± 64.1 s, respectively), these were not different from Tlim 2. [Conclusion] Eccentric exercise showed deleterious effects on subsequent high-intensity aerobic performance. These effects were minimized after the exercise protocol was repeated 6 weeks after the first event.

  19. A novel three-filament model of force generation in eccentric contraction of skeletal muscles.

    Directory of Open Access Journals (Sweden)

    Gudrun Schappacher-Tilp

    Full Text Available We propose and examine a three filament model of skeletal muscle force generation, thereby extending classical cross-bridge models by involving titin-actin interaction upon active force production. In regions with optimal actin-myosin overlap, the model does not alter energy and force predictions of cross-bridge models for isometric contractions. However, in contrast to cross-bridge models, the three filament model accurately predicts history-dependent force generation in half sarcomeres for eccentric and concentric contractions, and predicts the activation-dependent forces for stretches beyond actin-myosin filament overlap.

  20. Alterations in Whole-Body Insulin Sensitivity Resulting From Repeated Eccentric Exercise of a Single Muscle Group: A Pilot Investigation.

    Science.gov (United States)

    Gonzalez, Javier T; Barwood, Martin J; Goodall, Stuart; Thomas, Kevin; Howatson, Glyn

    2015-08-01

    Unaccustomed eccentric exercise using large muscle groups elicits soreness, decrements in physical function and impairs markers of whole-body insulin sensitivity; although these effects are attenuated with a repeated exposure. Eccentric exercise of a small muscle group (elbow flexors) displays similar soreness and damage profiles in response to repeated exposure. However, it is unknown whether damage to small muscle groups impacts upon whole-body insulin sensitivity. This pilot investigation aimed to characterize whole-body insulin sensitivity in response to repeated bouts of eccentric exercise of the elbow flexors. Nine healthy males completed two bouts of eccentric exercise separated by 2 weeks. Insulin resistance (updated homeostasis model of insulin resistance, HOMA2-IR) and muscle damage profiles (soreness and physical function) were assessed before, and 48 h after exercise. Matsuda insulin sensitivity indices (ISI Matsuda) were also determined in 6 participants at the same time points as HOMA2-IR. Soreness was elevated, and physical function impaired, by both bouts of exercise (both p Eccentric exercise decreased ISI Matsuda after the first but not the second bout of eccentric exercise (time x bout interaction p Eccentric exercise performed with an isolated upper limb impairs whole-body insulin sensitivity after the first, but not the second, bout.

  1. Regulatory light chain phosphorylation increases eccentric contraction-induced injury in skinned fast-twitch fibers.

    Science.gov (United States)

    Childers, Martin K; McDonald, Kerry S

    2004-02-01

    During contraction, activation of Ca(2+)/calmodulin-dependent myosin light chain kinase (MLCK) results in phosphorylation of myosin's regulatory light chain (RLC), which potentiates force and increases speed of force development over a wide range of [Ca(2+)]. We tested the hypothesis that RLC phosphorylation by MLCK mediates the extent of eccentric contraction-induced injury as measured by force deficit in skinned fast-twitch skeletal muscle fibers. Results indicated that RLC phosphorylation in single skinned rat psoas fibers significantly increased Ca(2+) sensitivity of isometric force; isometric force from 50 +/- 16 to 59 +/- 18 kN/m(2) during maximal Ca(2+) activation; peak absolute power output from 38 +/- 15 to 48 +/- 14 nW during maximal Ca(2+) activation; and the magnitude of contraction-induced force deficit during maximal (pCa 4.5) activation from 26 +/- 9.8 to 35 +/- 9.6%. We conclude that RLC phosphorylation increases force deficits following eccentric contractions, perhaps by increasing the number of force-generating cross-bridges.

  2. Enhanced Glycogen Storage of a Subcellular Hot Spot in Human Skeletal Muscle during Early Recovery from Eccentric Contractions

    DEFF Research Database (Denmark)

    Nielsen, Joachim; Farup, Jean; Rahbek, Stine Klejs

    2015-01-01

    Unaccustomed eccentric exercise is accompanied by muscle damage and impaired glucose uptake and glycogen synthesis during subsequent recovery. Recently, it was shown that the role and regulation of glycogen in skeletal muscle are dependent on its subcellular localization, and that glycogen...... content during post-exercise recovery from eccentric contractions. Analysis was completed on five male subjects performing an exercise bout consisting of 15 x 10 maximal eccentric contractions. Carbohydrate-rich drinks were subsequently ingested throughout a 48 h recovery period and muscle biopsies...... in both type I and II fibers were lower in the exercise leg compared with the control leg, and this was associated with a smaller size of the glycogen particles. We conclude that in the carbohydrate-supplemented state, the effect of eccentric contractions on glycogen metabolism depends on the subcellular...

  3. Induction of Muscle Hypertrophy in Rats through Low Intensity Eccentric Contraction

    OpenAIRE

    Tsumiyama, Wakako; Oki, Sadaaki; Takamiya, Naomi; Umei, Namiko; Shimizu, Michele Eisemann; Ono, Takeya; Otsuka, Akira

    2014-01-01

    [Purpose] The purpose of this study was to examine whether a low intensity exercise using an eccentric contraction would result in skeletal muscle hypertrophy in rats. [Subjects and Methods] Eighteen female Wistar rats were used in this study. The rats were randomly divided into three groups. The control group performed no exercise. The level group ran on a treadmill on a 0° incline. The downhill group ran on a treadmill on a −16° incline. The two exercise groups ran on a treadmill at 16 m/mi...

  4. Pathways of Ca²⁺ entry and cytoskeletal damage following eccentric contractions in mouse skeletal muscle.

    Science.gov (United States)

    Zhang, Bao-Ting; Whitehead, Nicholas P; Gervasio, Othon L; Reardon, Trent F; Vale, Molly; Fatkin, Diane; Dietrich, Alexander; Yeung, Ella W; Allen, David G

    2012-06-01

    Muscles that are stretched during contraction (eccentric contractions) show deficits in force production and a variety of structural changes, including loss of antibody staining of cytoskeletal proteins. Extracellular Ca(2+) entry and activation of calpains have been proposed as mechanisms involved in these changes. The present study used isolated mouse extensor digitorum longus (EDL) muscles subjected to 10 eccentric contractions and monitored force production, immunostaining of cytoskeletal proteins, and resting stiffness. Possible pathways for Ca(2+) entry were tested with streptomycin (200 μM), a blocker of stretch-activated channels, and with muscles from mice deficient in the transient receptor potential canonical 1 gene (TRPC1 KO), a candidate gene for stretch-activated channels. At 30 min after the eccentric contractions, the isometric force was decreased to 75 ± 3% of initial control and this force loss was reduced by streptomycin but not in the TRPC1 KO. Desmin, titin, and dystrophin all showed patchy loss of immunostaining 30 min after the eccentric contractions, which was substantially reduced by streptomycin and in the TRPC1 KO muscles. Muscles showed a reduction of resting stiffness following eccentric contractions, and this reduction was eliminated by streptomycin and absent in the TRPC1 KO muscles. Calpain activation was determined by the appearance of a lower molecular weight autolysis product and μ-calpain was activated at 30 min, whereas the muscle-specific calpain-3 was not. To test whether the loss of stiffness was caused by titin cleavage, protein gels were used but no significant titin cleavage was detected. These results suggest that Ca(2+) entry following eccentric contractions is through a stretch-activated channel that is blocked by streptomycin and encoded or modulated by TRPC1.

  5. Induction of Muscle Hypertrophy in Rats through Low Intensity Eccentric Contraction.

    Science.gov (United States)

    Tsumiyama, Wakako; Oki, Sadaaki; Takamiya, Naomi; Umei, Namiko; Shimizu, Michele Eisemann; Ono, Takeya; Otsuka, Akira

    2014-10-01

    [Purpose] The purpose of this study was to examine whether a low intensity exercise using an eccentric contraction would result in skeletal muscle hypertrophy in rats. [Subjects and Methods] Eighteen female Wistar rats were used in this study. The rats were randomly divided into three groups. The control group performed no exercise. The level group ran on a treadmill on a 0° incline. The downhill group ran on a treadmill on a -16° incline. The two exercise groups ran on a treadmill at 16 m/min for 90 minutes, once every three days for a total of twenty sessions. [Results] The muscle wet weights, the relative weight ratios, and the muscle fiber cross-section minor axes of the downhill group were significantly larger than those of the control and level groups. There were no differences in the muscle wet weights, the relative weight ratios, and the muscle fiber cross-section minor axes between the control group and the level group. [Conclusion] The stimulation from the low intensity eccentric contraction may have produced enough mechanical stress to induce muscle hypertrophy without the over-stressing that might have produced muscle fiber damage. These results indicate that this technique may be an effective method of inducing hypertrophy in skeletal muscle.

  6. Electromechanical delay in human skeletal muscle under concentric and eccentric contractions.

    Science.gov (United States)

    Cavanagh, P R; Komi, P V

    1979-11-01

    In contraction of skeletal muscle a delay exists between the onset of electrical activity and measurable tension. This delay in electromechanical coupling has been stated to be between 30 and 100 ms. Thus, in rapid movements it may be possible for electromyographic (EMG) activity to have terminated before force can be detected. This study was designed to determine the dependence of the EMG-tension delay upon selected initial conditions at the time of muscle activation. The right forearms of 14 subjects were passively oscillated by a motor-driven dynamometer through flexion-extension cycles of 135 deg at an angular velocity of approximately equal to 0.5 rad/s. Upon presentation of a visual stimulus the subjects maximally contracted the relaxed elbow flexors during flexion, extension, and under isometric conditions. The muscle length at the time of the stimulus was the same in all three conditions. An on-line computer monitoring surface EMG (Biceps and Brachioradialis) and force calculated the electromechanical delay. The mean value for the delay under eccentric condition, 49.5 ms, was significantly different (p less than 0.05) from the delays during isometric (53.9 ms) and concentric activity (55.5 ms). It is suggested that the time required to stretch the series elastic component (SEC) represents the major portion of the measured delay and that during eccentric muscle activity the SEC is in a more favorable condition for rapid force development.

  7. Nociceptor interleukin 10 receptor 1 is critical for muscle analgesia induced by repeated bouts of eccentric exercise in the rat.

    Science.gov (United States)

    Alvarez, Pedro; Bogen, Oliver; Green, Paul G; Levine, Jon D

    2017-08-01

    Delayed-onset muscle soreness is typically observed after strenuous or unaccustomed eccentric exercise. Soon after recovery, blunted muscle soreness is observed on repeated eccentric exercise, a phenomenon known as repeated bout effect (RBE). Although regular physical activity decreases muscle hyperalgesia, likely because of increased production of the anti-inflammatory cytokine interleukin-10 (IL-10) in the skeletal muscle, whether IL-10 also contributes to the antinociceptive effect of RBE is unknown. Furthermore, whether IL-10 attenuates muscle hyperalgesia by acting on muscle nociceptors remains to be established. Here, we explored the hypothesis that blunted muscle nociception observed in RBE depends on a local effect of IL-10, acting on IL-10 receptor 1 (IL-10R1) expressed by muscle nociceptors. Results show that after a second bout of eccentric exercise, rats exhibited decreased muscle hyperalgesia, indicative of RBE, and increased expression of IL-10 in the exercised gastrocnemius muscle. Although knockdown of IL-10R1 protein in nociceptors innervating the gastrocnemius muscle by intrathecal antisense oligodeoxynucleotide did not change nociceptive threshold in naive rats, it unveiled latent muscle hyperalgesia in rats submitted to eccentric exercise 12 days ago. Furthermore, antisense also prevented the reduction of muscle hyperalgesia observed after a second bout of eccentric exercise. These data indicate that recovery of nociceptive threshold after eccentric exercise and RBE-induced analgesia depend on a local effect of IL-10, acting on its canonical receptor in muscle nociceptors.

  8. Torque loss induced by repetitive maximal eccentric contractions is marginally influenced by work-to-rest ratio.

    Science.gov (United States)

    McNeil, Chris J; Allman, Brian L; Symons, T Brock; Vandervoort, Anthony A; Rice, Charles L

    2004-05-01

    The influence of different work-to-rest (W:R) ratios during fatigue induced by maximal eccentric contractions is unknown. The present study sought to expand the understanding of the task-dependent nature of eccentric contractions, and the associated fatigue, during exercise and acute as well as extended recovery periods. Using a Biodex multi-joint dynamometer, the ankle dorsiflexors of eight men [26 (4) years] were fatigued with 150 maximal eccentric contractions. Set structure was manipulated such that one leg performed 3 sets of 50 repetitions (short rest protocol, SRP), and the other leg performed 15 sets of 10 repetitions (long rest protocol, LRP). A 1-min rest interval separated each set, which resulted in 2 and 14 min of total rest for the SRP and the LRP, respectively. At fatigue, the SRP demonstrated a marginally greater loss of average peak eccentric torque than the LRP ( Ptorque loss and the degree of low-frequency fatigue (LFF) were not recovered ( Ptorque was persistent and equal for each protocol at 96 h of recovery ( Pratio has a modest influence on the fatigue (torque loss) induced by maximal eccentric contractions, but maximal isometric torque during recovery and LFF are insensitive to changes in total rest time.

  9. Low-intensity eccentric contractions of the knee extensors and flexors protect against muscle damage.

    Science.gov (United States)

    Lin, Min-Ju; Chen, Trevor Chung-Ching; Chen, Hsin-Lian; Wu, Bo-Han; Nosaka, Kazunori

    2015-10-01

    This study investigated the magnitude and duration of the protective effect of low-intensity eccentric contractions (LowEC) against damage induced by maximal eccentric contractions (MaxEC) of the knee flexors (KF) and extensors (KE). Young men were assigned to 8 experimental groups and 2 control groups (n = 13/group); the experimental groups performed LowEC of KF or KE 2 days (2d), 1 week (1wk), 2 weeks (2wk), or 3 weeks (3wk) before MaxEC, while the control groups performed MaxEC of KF or KE without LowEC. The 2d, 1wk, 2wk, and 3wk groups performed 30 LowEC of KF or 60 LowEC of KE with a load of 10% of maximal voluntary isometric contraction strength on a resistance-training machine, and all groups performed 30 MaxEC of KF or 60 MaxEC of KE on an isokinetic dynamometer. Several muscle damage markers were measured from before to 2 days after exercise (LowEC) or from before to 5 days after exercise (MaxEC). No significant changes in any variables were evident after LowEC. The changes in all variables after MaxEC were smaller (P < 0.05) for the 2d and 1wk groups (e.g., peak creatine kinase activity: 1002 ± 501 IU/L; peak muscle soreness: 13 ± 5 mm) than for the control group (peak creatine kinase activity: 3005 ± 983 IU/L; peak muscle soreness 28 ± 6 mm) for both KE and KF. There were no significant differences between the 2d and 1wk groups or among the 2wk, 3wk, and control groups. These results show that LowEC provided 30%-66% protection against damage induced by MaxEC of KF and KE, and the protective effect lasted 1 week.

  10. Brain Functional Connectivity is Different during VoluntaryConcentric and Eccentric Muscle Contraction

    Directory of Open Access Journals (Sweden)

    Wan X Yao

    2016-11-01

    Full Text Available Previous studies report greater activation in the cortical motor network in controlling eccentric contraction (EC than concentric contraction (CC of human skeletal muscles despite lower activation level of the muscle associated with EC. It is unknown, however, whether the strength of functional coupling between the primary motor cortex (M1 and other involved areas in the brain differs as voluntary movements are controlled by a network of regions in the primary, secondary and association cortices. Examining fMRI-based functional connectivity (FC offers an opportunity to measure strength of such coupling. To address the question, we examined functional MRI (fMRI data acquired during EC and CC (20 contractions each with similar movement distance and speed of the right first dorsal interosseous (FDI muscle in 11 young (20-32 years and healthy individuals and estimated FC between the M1 and a number of cortical regions in the motor control network. The major findings from the behavioral and fMRI-based FC analysis were that (1 no significant differences were seen in movement distance, speed and stability between the EC and CC; (2 significantly stronger mean FC was found for CC than EC. Our finding provides novel insights for a better understanding of the control mechanisms underlying voluntary movements produced by EC and CC. The finding is potentially helpful for guiding the development of targeted sport training and/or therapeutic programs for performance enhancement and injury prevention.

  11. Age-related functional changes and susceptibility to eccentric contraction-induced damage in skeletal muscle cell

    Directory of Open Access Journals (Sweden)

    Seung-Jun Choi

    2016-09-01

    Full Text Available Depending upon external loading conditions, skeletal muscles can either shorten, lengthen, or remain at a fixed length as they produce force. Fixed-end or isometric contractions stabilize joints and allow muscles to act as active struts during locomotion. Active muscles dissipate energy when they are lengthened by an external force that exceeds their current force producing capacity. These unaccustomed eccentric activities often lead to muscle weakness, soreness, and inflammation. During aging, the ability to produce force under these conditions is reduced and appears to be due to not only reductions in muscle mass but also to alterations in the basic mechanisms of contraction. These alterations include impairments in the excitation–contraction process, and the action of the cross-bridges. Also, it is well known that age-related skeletal muscle atrophy is characterized by a preferential atrophy of fast fibers, and increased susceptibility to fast muscle fiber when aged muscles are exposed to eccentric contraction followed by the impaired recovery process has been reported. Taken together, the selective loss of fast muscle fiber in aged muscle could be affected by eccentric-induced muscle damage, which has significant implication to identify the etiology of the age-related functional changes. Therefore, in this review the alteration of age-related muscle function and its impact to/of eccentric induced muscle damage and recovery will be addressed in detail.

  12. Effect of Contraction Velocity on Selected Muscle Damage Indices Following Acute Eccentric Exercise-Induced Muscle Damage: A Review

    Directory of Open Access Journals (Sweden)

    Farzaneh Movaseghi

    2016-12-01

    Full Text Available Background & Objective: Eccentric muscle action is mechanically more efficient but employs a unique activation strategy which predisposes the muscle to damage. Type II muscle fibers are more susceptible than type I fibers to muscle damage; hence, velocity probably interferes with mechanical stress and thus may modulate muscle damage. The purpose of this review study was to investigate the effect of contraction velocity on selected muscle damage indices following acute eccentric exercise-induced muscle damage. Material & Method: Looking up related articles published in valid scientific databases such as PubMed, Springer, Elsevier, Science Direct, and SID with standard keywords and according to the research criteria, 16 studies (1980 to 2015 were selected. Results: Ten studies showed that high velocity eccentric exercise induced greater muscle damage. Five studies showed no differences between velocities, and a single study indicated a greater magnitude of muscle damage following slow eccentric exercise. Conclusion: Thus, greater magnitude of damage is induced by contractions performed at a higher velocity. However, considering differences during tension in the majority of studies, focusing on elbow flexor muscles and muscle damage profile variety in various muscle groups, and more animal and human studies in other muscular groups are necessary to confirm how the velocity of acute eccentric exercise would affect the muscle damage.

  13. A contralateral repeated bout effect attenuates induction of NF-κB DNA binding following eccentric exercise.

    Science.gov (United States)

    Xin, Ling; Hyldahl, Robert D; Chipkin, Stuart R; Clarkson, Priscilla M

    2014-06-01

    We investigated the existence of contralateral repeated bout effect and tested if the attenuation of nuclear factor-kappa B (NF-κB; an important regulator of muscle inflammation) induction following eccentric exercise is a potential mechanism. Thirty-one healthy men performed two bouts of knee extension eccentric exercise, initially with one leg and then with the opposite leg 4 wk later. Vastus lateralis muscle biopsies of both exercised and control legs were taken 3 h postexercise. Knee extension isometric and isokinetic strength (60°/sec and 180°/sec) were measured at baseline, pre-exercise, immediately postexercise, and 1/day for 5 days postexercise. Serum creatine kinase (CK) activity and muscle soreness were assessed at baseline and 1/day for 5 days postexercise. NF-κB (p65) DNA-binding activity was measured in the muscle biopsies. Isometric strength loss was lower in bout 2 than in bout 1 at 24, 72, and 96 h postexercise (P eccentric exercise (compared with the control leg) in bout 1 (122.9% ± 2.6%; P eccentric exercise results in a contralateral repeated bout effect, which could be due to the attenuated increase in NF-κB activity postexercise. Copyright © 2014 the American Physiological Society.

  14. The impact of a repeated bout of eccentric exercise on muscular strength, muscle soreness and creatine kinase.

    Science.gov (United States)

    Smith, L L; Fulmer, M G; Holbert, D; McCammon, M R; Houmard, J A; Frazer, D D; Nsien, E; Israel, R G

    1994-01-01

    The purpose of this study was to determine if there were any beneficial or detrimental effects regarding delayed onset muscle soreness (DOMS), serum creatine kinase (CK), and maximum concentric strength at 80% of 1-RMconc, if a bout of eccentric exercise was repeated at 48 h after an initial bout. A secondary purpose was to determine whether unaccustomed eccentrics might affect plasma cholesterol (TC). Twenty-six men were randomly assigned to a control (Group 1) or experimental group (Group 2). Both groups performed three sets (12 repetitions per set) of the eccentric phase of a chest press, at 80% of one repetition maximum (1-RMconc); Group 2 repeated this exercise 48 h later. DOMS and CK were measured before, and every 24 h for 8 days after; TC was measured before, and every 24 h for 4 days. Maximum strength during the concentric phase of a chest press (1-RMconc) was measured before and at 48-h intervals after. A repeated measures analysis of variance revealed a significant time effect (P < 0.05) for DOMS, CK and strength, but no significant difference between groups (P < 0.05). An interesting finding was the significant (P < 0.05) reduction in TC at 24, 48 and 72 h, after exercise in both groups, which we hypothesized was associated with cellular repair. From these results we concluded that when a bout of eccentrics is repeated 48 h after an initial bout, there is no change in the characteristic time-course and/or intensity of DOMS, CK or 1-RMconc. PMID:7894959

  15. Motor unit activity during isometric and concentric-eccentric contractions of the human first dorsal interosseus muscle.

    Science.gov (United States)

    Howell, J N; Fuglevand, A J; Walsh, M L; Bigland-Ritchie, B

    1995-08-01

    1. Motor unit activity was recorded with intramuscular fine wire electrodes during isometric, concentric, and eccentric activity in the human first dorsal interosseus muscle. Twenty-one units from 11 subjects were sampled. 2. During isotonic cycles of shortening and lengthening, 18 of 21 units were recruited during the concentric phase, increased their discharge rates as the concentric movement progressed, then decreased their discharge rate during the eccentric phase, and were derecruited. 3. A different pattern of recruitment was observed in recordings from three units. These units were recruited during the eccentric phase, at a time when other units were decreasing their discharge rate or being derecruited. In two of the units selectively recruited during the eccentric phase, it was possible to determine their isometric thresholds, which were higher than those of units exhibiting the more common pattern of recruitment. 4. For two of the three units exhibiting selective recruitment during eccentric contraction, the unit was recorded simultaneously with different pairs of recording wires separated by 5-10 mm. Each discharge of these units was detected by both electrodes, making it unlikely that movement artifact was responsible for the initiation or cessation of discharge. 5. The recruitment patterns observed suggest that changes in the type or distribution of synaptic inputs to motoneurons during movement can, in some instances, override pre- and postsynaptic factors that shape recruitment order in isometric conditions.

  16. Attenuation of eccentric exercise-induced muscle damage conferred by maximal isometric contractions: a mini review

    Directory of Open Access Journals (Sweden)

    Leonardo Coelho Rabello Lima

    2015-10-01

    Full Text Available Although beneficial in determined contexts, eccentric exercise-induced muscle damage (EIMD might be unwanted during training regimens, competitions and daily activities. There are a vast number of studies investigating strategies to attenuate EIMD response after damaging exercise bouts. Many of them consist of performing exercises that induce EIMD, consuming supplements or using equipment that are not accessible for most people. It appears that performing maximal isometric contractions (ISOs 2-4 days prior to damaging bouts promotes significant attenuation of EIMD symptoms that are not related to muscle function. It has been shown that the volume of ISOs, muscle length in which they are performed, and interval between them and the damaging bout influence the magnitude of this protection. Additionally, it appears that this protection is not long-lived, lasting no longer than 4 days. Although no particular mechanisms for these adaptations were identified, professionals should consider applying this non-damaging stimulus before submitting their patients to unaccustomed exercised. However, it seems not to be the best option for athletes or relatively trained individuals. Future studies should focus on establishing if ISOs protect other populations (i.e., trained individuals or muscle groups (i.e., knee extensors against EIMD, as well as investigate different mechanisms for ISO-induced protection.

  17. Aerobic interval exercise with an eccentric contraction induces muscular hypertrophy and augmentation of muscular strength in rats

    OpenAIRE

    Tsumiyama, Wakako; Oki, Sadaaki; Takamiya, Naomi; Umei, Namiko; Shimizu, Michele Eisemann; Ono, Takeya; Otsuka, Akira

    2015-01-01

    [Purpose] The purpose of this study was to examine whether an aerobic interval exercise using an eccentric contraction would result in skeletal muscular hypertrophy and augmentation of muscular strength in rats. [Subjects and Methods] Twenty-one female Wistar rats were used in this study. The rats were randomly divided into three groups. The control group performed no exercise. The aerobic endurance exercise group ran for 90 min. The aerobic interval exercise group ran for a total of 90 minut...

  18. Changes in power and force generation during coupled eccentric-concentric versus concentric muscle contraction with training and aging

    DEFF Research Database (Denmark)

    Caserotti, Paolo; Aagaard, Per; Puggaard, Lis

    2008-01-01

    center of mass were measured in two standardised vertical jumps (squatting jump, SQJ; countermovement jump, CMJ). Pre-stretch enhancement during CMJ did not improve performance [i.e., no enhanced maximal muscle power (P (peak)) and jump height (JH)] compared to concentric-alone muscle contraction (SQJ......-alone and coupled eccentric-concentric contraction and selected functional motor performances before and after 36-week multicomponent training including aerobic, strength, balance, flexibility and coordination components in elderly males. Vertical force, excursion, velocity, power and acceleration of the body...

  19. Leucine-enriched essential amino acids attenuate inflammation in rat muscle and enhance muscle repair after eccentric contraction.

    Science.gov (United States)

    Kato, Hiroyuki; Miura, Kyoko; Nakano, Sayako; Suzuki, Katsuya; Bannai, Makoto; Inoue, Yoshiko

    2016-09-01

    Eccentric exercise results in prolonged muscle damage that may lead to muscle dysfunction. Although inflammation is essential to recover from muscle damage, excessive inflammation may also induce secondary damage, and should thus be suppressed. In this study, we investigated the effect of leucine-enriched essential amino acids on muscle inflammation and recovery after eccentric contraction. These amino acids are known to stimulate muscle protein synthesis via mammalian target of rapamycin (mTOR), which, is also considered to alleviate inflammation. Five sets of 10 eccentric contractions were induced by electrical stimulation in the tibialis anterior muscle of male SpragueDawley rats (8-9 weeks old) under anesthesia. Animals received a 1 g/kg dose of a mixture containing 40 % leucine and 60 % other essential amino acids or distilled water once a day throughout the experiment. Muscle dysfunction was assessed based on isometric dorsiflexion torque, while inflammation was evaluated by histochemistry. Gene expression of inflammatory cytokines and myogenic regulatory factors was also measured. We found that leucine-enriched essential amino acids restored full muscle function within 14 days, at which point rats treated with distilled water had not fully recovered. Indeed, muscle function was stronger 3 days after eccentric contraction in rats treated with amino acids than in those treated with distilled water. The amino acid mix also alleviated expression of interleukin-6 and impeded infiltration of inflammatory cells into muscle, but did not suppress expression of myogenic regulatory factors. These results suggest that leucine-enriched amino acids accelerate recovery from muscle damage by preventing excessive inflammation.

  20. Blood flow restriction prevents muscle damage but not protein synthesis signaling following eccentric contractions.

    Science.gov (United States)

    Sudo, Mizuki; Ando, Soichi; Poole, David C; Kano, Yutaka

    2015-07-01

    There is a growing body of evidence to suggest that resistance training exercise combined with blood flow restriction (BFR) increases muscle size and strength in humans. Eccentric contraction (ECC) frequently induces severe muscle damage. However, it is not known whether and to what extent muscle damage occurs following ECC + BFR due to the difficulty of conducting definitive invasive studies. The purpose of this study was to examine muscle fiber damage following ECC + BFR at the cellular level. High-intensity ECC was purposefully selected to maximize the opportunity for muscle damage and hypertrophic signaling in our novel in vivo animal model. Male Wistar rats were assigned randomly to the following groups: ECC and ECC + BFR at varying levels of occlusion pressure (140, 160, and 200 Torr). In all conditions, electrical stimulation was applied to the dorsiflexor muscles simultaneously with electromotor-induced plantar flexion. We observed severe histochemical muscle fiber damage (area of damaged fibers/total fiber area analyzed) following ECC (26.4 ± 4.0%). Surprisingly, however, muscle damage was negligible following ECC + BFR140 (2.6 ± 1.2%), ECC+BFR160 (3.0 ± 0.5%), and ECC + BFR200 (0.2 ± 0.1%). Ribosomal S6 kinase 1 (S6K1) phosphorylation, a downstream target of rapamycin (mTOR)-phosphorylation kinase, increased following ECC + BFR200 as well as ECC. In contrast, S6K1 phosphorylation was not altered by BFR alone. The present findings suggest that ECC combined with BFR, even at high exercise intensities, may enhance muscle protein synthesis without appreciable muscle fiber damage.

  1. Effects of delayed NSAID administration after experimental eccentric contraction injury – A cellular and proteomics study

    Science.gov (United States)

    Aldape, Michael J.; Bayer, Clifford R.; Katahira, Eva J.; Bond, Laura; Nicora, Carrie D.; Fillmore, Thomas L.; Clauss, Therese R. W.; Metz, Thomas O.; Webb-Robertson, Bobbie-Jo; Stevens, Dennis L.

    2017-01-01

    Background Acute muscle injuries are exceedingly common and non-steroidal anti-inflammatory drugs (NSAIDs) are widely consumed to reduce the associated inflammation, swelling and pain that peak 1–2 days post-injury. While prophylactic use or early administration of NSAIDs has been shown to delay muscle regeneration and contribute to loss of muscle strength after healing, little is known about the effects of delayed NSAID use. Further, NSAID use following non-penetrating injury has been associated with increased risk and severity of infection, including that due to group A streptococcus, though the mechanisms remain to be elucidated. The present study investigated the effects of delayed NSAID administration on muscle repair and sought mechanisms supporting an injury/NSAID/infection axis. Methods A murine model of eccentric contraction (EC)-induced injury of the tibialis anterior muscle was used to profile the cellular and molecular changes induced by ketorolac tromethamine administered 47 hr post injury. Results NSAID administration inhibited several important muscle regeneration processes and down-regulated multiple cytoprotective proteins known to inhibit the intrinsic pathway of programmed cell death. These activities were associated with increased caspase activity in injured muscles but were independent of any NSAID effect on macrophage influx or phenotype switching. Conclusions These findings provide new molecular evidence supporting the notion that NSAIDs have a direct negative influence on muscle repair after acute strain injury in mice and thus add to renewed concern about the safety and benefits of NSAIDS in both children and adults, in those with progressive loss of muscle mass such as the elderly or patients with cancer or AIDS, and those at risk of secondary infection after trauma or surgery. PMID:28245256

  2. Fiber-type susceptibility to eccentric contraction-induced damage of hindlimb-unloaded rat AL muscles

    Science.gov (United States)

    Vijayan, K.; Thompson, J. L.; Norenberg, K. M.; Fitts, R. H.; Riley, D. A.

    2001-01-01

    Slow oxidative (SO) fibers of the adductor longus (AL) were predominantly damaged during voluntary reloading of hindlimb unloaded (HU) rats and appeared explainable by preferential SO fiber recruitment. The present study assessed damage after eliminating the variable of voluntary recruitment by tetanically activating all fibers in situ through the motor nerve while applying eccentric (lengthening) or isometric contractions. Muscles were aldehyde fixed and resin embedded, and semithin sections were cut. Sarcomere lesions were quantified in toluidine blue-stained sections. Fibers were typed in serial sections immunostained with antifast myosin and antitotal myosin (which highlights slow fibers). Both isometric and eccentric paradigms caused fatigue. Lesions occurred only in eccentrically contracted control and HU muscles. Fatigue did not cause lesions. HU increased damage because lesioned- fiber percentages within fiber types and lesion sizes were greater than control. Fast oxidative glycolytic (FOG) fibers were predominantly damaged. In no case did damaged SO fibers predominate. Thus, when FOG, SO, and hybrid fibers are actively lengthened in chronically unloaded muscle, FOG fibers are intrinsically more susceptible to damage than SO fibers. Damaged hybrid-fiber proportions ranged between these extremes.

  3. ESTRADIOL IN FEMALES MAY NEGATE SKELETAL MUSCLE MYOSTATIN MRNA EXPRESSION AND SERUM MYOSTATIN PROPEPTIDE LEVELS AFTER ECCENTRIC MUSCLE CONTRACTIONS

    Directory of Open Access Journals (Sweden)

    Darryn S. Willoughby

    2006-12-01

    Full Text Available Eccentric contractions produce a significant degree of inflammation and muscle injury that may increase the expression of myostatin. Due to its anti- oxidant and anti-flammatory effects, circulating 17-β estradiol (E2 may attenuate myostatin expression. Eight males and eight females performed 7 sets of 10 reps of eccentric contractions of the knee extensors at 150% 1-RM. Each female performed the eccentric exercise bout on a day that fell within her mid-luteal phase (d 21-23 of her 28-d cycle. Blood and muscle samples were obtained before and 6 and 24 h after exercise, while additional blood samples were obtained at 48 and 72 h after exercise. Serum E2 and myostatin LAP/propeptide (LAP/pro levels were determined with ELISA, and myostatin mRNA expression determined using RT-PCR. Data were analyzed with two-way ANOVA and bivariate correlations (p 0.05. Compared to pre-exercise, males had significant increases (p < 0.05 in LAP/propetide and mRNA of 78% and 28%, respectively, at 24 h post-exercise, whereas females underwent respective decreases of 10% and 21%. E2 and LAP/propeptide were correlated at 6 h (r = -0.804, p = 0.016 and 24 h post- exercise (r = -0.841, p = 0.009 in males, whereas in females E2 levels were correlated to myostatin mRNA at 6 h (r =0.739, p = 0.036 and 24 h (r = 0.813, p = 0.014 post-exercise and LAP/propeptide at 6 h (r = 0.713, p = 0.047 and 24 h (r = 0.735, p = 0.038. In females, myostatin mRNA expression and serum LAP/propeptide levels do not appear to be significantly up-regulated following eccentric exercise, and may be due to higher levels of circulating E2

  4. Heat shock protein translocation and expression response is attenuated in response to repeated eccentric exercise

    DEFF Research Database (Denmark)

    Vissing, K.; Bayer, M.L.; Overgaard, K.

    2009-01-01

    and cytoskeletal protein fractions. The first bout of exercise reduced muscle strength and increased muscle soreness predominantly in the eccentric leg (P ... weeks between bouts, and were compared with a control group (n = 6). Muscle biopsies collected from m. vastus lateralis of both legs prior to and at 3 h, 24 h and 7 days after exercise were quantified for mRNA levels and/or for HSP27, alpha beta-crystallin and inducible HSP70 content in cytosolic...... eccentric exercise bout. Our results show that HSP translocation and expression responses are induced by muscle damaging exercise, and suggest that such HSP responses are closely related to the extent of muscle damage Udgivelsesdato: 2009/7...

  5. Eccentric exercise

    DEFF Research Database (Denmark)

    Kjaer, Michael; Heinemeier, Katja Maria

    2014-01-01

    Eccentric exercise can influence tendon mechanical properties and matrix protein synthesis. mRNA for collagen and regulatory factors thereof are upregulated in animal tendons, independent of muscular contraction type, supporting the view that tendon, compared with skeletal muscle, is less sensitive...

  6. Leucine-enriched essential amino acids attenuate muscle soreness and improve muscle protein synthesis after eccentric contractions in rats.

    Science.gov (United States)

    Kato, Hiroyuki; Suzuki, Hiromi; Mimura, Masako; Inoue, Yoshiko; Sugita, Mayu; Suzuki, Katsuya; Kobayashi, Hisamine

    2015-06-01

    Eccentric exercise results in prolonged muscle weakness and muscle soreness, which are typical symptoms of muscle damage. Recovery from muscle damage is related to mammalian target of rapamycin (mTOR) activity. Leucine-enriched essential amino acids (LEAAs) stimulate muscle protein synthesis via activation of the mTOR pathway. Therefore, we investigated the effect of LEAAs on muscle protein synthesis and muscle soreness after eccentric contractions (EC). Male Sprague-Dawley rats (9-11 weeks old) were administered an LEAA solution (AminoL40; containing 40 % leucine and 60 % other essential amino acids) at 1 g/kg body weight or distilled water (control) 30 min before and 10 min after EC. Tibialis anterior (TA) muscle was exposed to 500 EC by electrical stimulation under anesthesia. The fractional synthesis rate (FSR; %/h) in the TA muscle was measured by incorporating L-[ring-(2)H5] phenylalanine into skeletal muscle protein. Muscle soreness was evaluated by the paw withdrawal threshold using the Randal-Selitto test with some modifications from 1 to 3 days after EC. The FSR in the EC-control group (0.147 ± 0.016 %/h) was significantly lower than in the sedentary group (0.188 ± 0.016 %/h, p < 0.05). AminoL40 administration significantly mitigated the EC-induced impairment of the FSR (0.172 ± 0.018 %/h). EC decreased the paw withdrawal threshold at 1 and 2 days after EC, which indicated that EC induced muscle soreness. Furthermore, AminoL40 administration alleviated the decreased paw withdrawal threshold. These findings suggest that LEAA supplementation improves the rate of muscle protein synthesis and ameliorates muscle soreness after eccentric exercise.

  7. Protective effect by maximal isometric contractions against maximal eccentric exercise-induced muscle damage of the knee extensors.

    Science.gov (United States)

    Tseng, Kuo-Wei; Tseng, Wei-Chin; Lin, Ming-Ju; Chen, Hsin-Lian; Nosaka, Kazunori; Chen, Trevor C

    2016-01-01

    This study investigated whether maximal voluntary isometric contractions (MVIC) performed before maximal eccentric contractions (MaxEC) would attenuate muscle damage of the knee extensors. Untrained men were placed to an experimental group that performed 6 sets of 10 MVIC at 90° knee flexion 2 weeks before 6 sets of 10 MaxEC or a control group that performed MaxEC only (n = 13/group). Changes in muscle damage markers were assessed before to 5 days after each exercise. Small but significant changes in maximal voluntary concentric contraction torque, range of motion (ROM) and plasma creatine kinase (CK) activity were evident at immediately to 2 days post-MVIC (p < 0.05), but other variables (e.g. thigh girth, myoglobin concentration, B-mode echo intensity) did not change significantly. Changes in all variables after MaxEC were smaller (p < 0.05) by 45% (soreness)-67% (CK) for the experimental than the control group. These results suggest that MVIC conferred potent protective effect against MaxEC-induced muscle damage.

  8. The role of phosphoinositide 3-kinase and phosphatidic acid in the regulation of mammalian target of rapamycin following eccentric contractions.

    Science.gov (United States)

    O'Neil, T K; Duffy, L R; Frey, J W; Hornberger, T A

    2009-07-15

    Resistance exercise induces a hypertrophic response in skeletal muscle and recent studies have begun to shed light on the molecular mechanisms involved in this process. For example, several studies indicate that signalling by the mammalian target of rapamycin (mTOR) is necessary for a hypertrophic response. Furthermore, resistance exercise has been proposed to activate mTOR signalling through an upstream pathway involving the phosphoinositide 3-kinase (PI3K) and protein kinase B (PKB); however, this hypothesis has not been thoroughly tested. To test this hypothesis, we first evaluated the temporal pattern of signalling through PI3K-PKB and mTOR following a bout of resistance exercise with eccentric contractions (EC). Our results indicated that the activation of signalling through PI3K-PKB is a transient event (12 h). Furthermore, inhibition of PI3K-PKB activity did not prevent the activation of mTOR signalling by ECs, indicating that PI3K-PKB is not part of the upstream regulatory pathway. These observations led us to investigate an alternative pathway for the activation of mTOR signalling involving the synthesis of phosphatidic acid (PA) by phospholipase D (PLD). Our results demonstrate that ECs induce a sustained elevation in [PA] and inhibiting the synthesis of PA by PLD prevented the activation of mTOR. Furthermore, we determined that similar to ECs, PA activates mTOR signalling through a PI3K-PKB-independent mechanism. Combined, the results of this study indicate that the activation of mTOR following eccentric contractions occurs through a PI3K-PKB-independent mechanism that requires PLD and PA.

  9. Surface Electromyography Assessments of the Vastus medialis and Rectus femoris Muscles and Creatine Kinase after Eccentric Contraction Following Glutamine Supplementation.

    Science.gov (United States)

    Rahmani-Nia, Farhad; Farzaneh, Esmail; Damirchi, Arsalan; Majlan, Ali Shamsi; Tadibi, Vahid

    2014-03-01

    L-glutamine is the most abundant amino acid found in human muscle and plays an important role in protein synthesis and can reduce the levels of inflammation biomarkers and creatine kinase (CK) after training sessions. Delayed onset muscle soreness (DOMS) develops after intense exercise and is associated with an inflammatory response. The purpose of this study was to investigate the effect of glutamine supplementation on surface electromyography activity of the vastus medialis muscle (VMM) and rectus femoris muscle (RFM) and levels of creatine kinase after an eccentric contraction. SEVENTEEN HEALTHY MEN (AGE: 22.35±2.27yr; body mass: 69.91± 9.78kg; height: 177.08±4.32cm) were randomly assigned to experimental (n=9) and control groups (n=8) in a double-blind manner. In both groups, subjects were given L-glutamine supplementation (0.1g.kg(-1)) or placebo three times a week for 4 weeks. Median frequency (MDF) and mean power frequency (MPF) for VMM and RFM muscles and also CK measurements were performed before, 24h and 48 h after a resistance training session. The resistance training included 6 sets of eccentric leg extensions to exhaustion with 75% of 1RM. There was no significant difference between groups for MDF or MPF in VMM and RFM. The difference of CK level between the groups was also not significant. The results of this study indicate that glutamine supplementation has no positive effect on muscle injury markers after a resistance training session.

  10. The influence of resistance exercise with emphasis on specific contractions (concentric vs. eccentric on muscle strength and post-exercise autonomic modulation: a randomized clinical trial

    Directory of Open Access Journals (Sweden)

    Mariana O. Gois

    2014-01-01

    Full Text Available Background: Compared to eccentric contractions, concentric contractions result in higher cardiovascular stress. However, we do not know how these two types of contractions influence cardiac autonomic modulation during the post-exercise recovery period. Objective: to compare the effect of resistance training that is performed with concentric vs. eccentric emphasis on muscle strength and on post-exercise recovery which was assessed by examining heart rate variability (HRV, for the knee extensor muscle group in young healthy adults. Methods: For this study, 105 men between 18 and 30 years of age were randomized into 4 groups: concentric control (CONCC, eccentric control (ECCC, concentric training (CONCT and eccentric training (ECCT. The CONCC and ECCC groups underwent one session of resistance exercise (RE using the knee extensor muscle group (3 sets of 1 repetition at 100% of the maximal repetition [1MR] and the CONCT and ECCT groups performed 10 training sessions. The HRV was analyzed at baseline and across four recovery periods (T1, T2, T3 and T4. Results: The ECCT group exhibited increased muscle strength at the end of the study. Regarding cardiac autonomic modulation, the CONCC and ECCC groups exhibited increases in overall variability (SDNN and SD2 at T1 compared to baseline, and the ECCT group demonstrated increases in variables reflecting vagal modulation and the recovery process (RMSSD, SD1 and HF [ms2] at T1, T2 and T4 compared to baseline. Conclusions: Resistance training with emphasis on eccentric contractions promoted strength gain and an increase in cardiac vagal modulation during recovery compared to baseline.

  11. Aerobic interval exercise with an eccentric contraction induces muscular hypertrophy and augmentation of muscular strength in rats.

    Science.gov (United States)

    Tsumiyama, Wakako; Oki, Sadaaki; Takamiya, Naomi; Umei, Namiko; Shimizu, Michele Eisemann; Ono, Takeya; Otsuka, Akira

    2015-04-01

    [Purpose] The purpose of this study was to examine whether an aerobic interval exercise using an eccentric contraction would result in skeletal muscular hypertrophy and augmentation of muscular strength in rats. [Subjects and Methods] Twenty-one female Wistar rats were used in this study. The rats were randomly divided into three groups. The control group performed no exercise. The aerobic endurance exercise group ran for 90 min. The aerobic interval exercise group ran for a total of 90 minutes in 5 minute bouts separated by 2 minute rest periods. The exercise groups ran on a downhill treadmill incline, once every three days, for a total of twenty sessions. [Results] The muscle wet weights, the muscle fiber cross-section minor axes, and the tetanus tension results of the aerobic endurance and aerobic interval exercise groups were significantly larger than those of the control group. [Conclusion] These results indicate that aerobic interval exercise may be an effective method of inducing hypertrophy and augmenting muscular strength in skeletal muscle.

  12. Elevation of myostatin and FOXOs in prolonged muscular impairment induced by eccentric contractions in rat medial gastrocnemius muscle.

    Science.gov (United States)

    Ochi, Eisuke; Hirose, Tatsuro; Hiranuma, Kenji; Min, Seok-Ki; Ishii, Naokata; Nakazato, Koichi

    2010-02-01

    This study aimed to investigate torque deficit and activation of protein synthesis and/or protein degradation signaling pathways during the early and recovery phase after high- and low-velocity eccentric contractions (ECs). Male Wistar rats (n = 36) were randomly divided into fast angular velocity ECs group (FAST; 180 degrees/s; n = 12), slow ECs group (SLOW; 30 degrees/s; n = 12), and control group (control; n = 12). ECs comprised four sets of five forced dorsiflexions combined with electrical stimulation of the plantar flexors. Isometric tetanic torque was measured before and after ECs. Tissue contents of Akt(P) (P, phosphorylated), mammalian target of rapamycin (mTOR)(P), 70-kDa ribosomal protein S6 kinase (P70S6k), P70S6k(P), forkhead transcription factor 1 of the O class (FOXO1), FOXO1(P), FOXO3, FOXO3(P), myostatin, and activin receptor type IIB (ActRIIB) were measured. The isometric tetanic torque after ECs was significantly lower in FAST than in SLOW (days 1, 3, and 5, P muscular function and activation of protein synthesis and/or protein degradation signaling pathways.

  13. Efficacy of epicutaneous Diractin® (ketoprofen in Transfersome® gel for the treatment of pain related to eccentric muscle contractions

    Directory of Open Access Journals (Sweden)

    Matthias Rother

    2009-05-01

    Full Text Available Matthias Rother1,2, Egbert J Seidel3, Priscilla M Clarkson4, Stefan Mazgareanu1, Ulrich Vierl1, ilka Rother21IDEA AG, Muenchen, Germany; 2X-pert Med GmbH, Graefelfing, Germany; 3Department Physical and Rehabilitation Medicine, Sophien- and Hufeland-Clinic Centre, Weimar, Germany; 4Department of Kinesiology, School of Public Health and Health Sciences, University of Massachusetts, Amherst, MA, USAObjective: To investigate the effect of epicutaneously applied Diractin® (ketoprofen in Transfersome® gel on pain induced by eccentric muscle contractions. Methods: Three pilot studies which were subsequently pooled for a meta-analysis compared the efficacy of a single application of 25 mg ketoprofen in Diractin® to 25 mg oral ketoprofen and placebo for the treatment of pain induced by 50 eccentric contractions of the elbow flexor muscles. In addition, the effect of multiple usage of up to 100 mg ketoprofen in Diractin® bid over seven days on pain induced by walking down stairs with a total altitude of 200 meters was investigated.Results: A single dose of 25 mg ketoprofen in Diractin® after the elbow flexion exercise was significantly superior to placebo from 5 to 12 hours after treatment and also to oral ketoprofen at some time points after treatment. In contrast, oral ketoprofen was not different to placebo at any time after treatment. Multiple doses of up to 100 mg ketoprofen Diractin® provided significant more pain relief than placebo on muscle pain induced by walking down stairs. Conclusions: Eccentric exercise-induced muscle soreness was shown to be an appropriate acute pain model to evaluate the efficacy of nonsteroidal anti-inflammatory drugs applied epicutaneously with Transfersome® carriers. Diractin® proved to be efficacious in relieving pain from eccentric muscle contractions and muscle overexercise, respectively. The effect needs to be confirmed in a larger prospective clinical trial.Keywords: ketoprofen, Transfersome

  14. Repeated static contractions increase mitochondrial vulnerability toward oxidative stress in human skeletal muscle

    DEFF Research Database (Denmark)

    Sahlin, Kent; Nielsen, Jens Steen; Mogensen, Martin

    2006-01-01

    Repeated static contractions (RSC) induce large fluctuations in tissue oxygen tension and increase the generation of reactive oxygen species (ROS). This study investigated the effect of RSC on muscle contractility, mitochondrial respiratory function, and in vitro sarcoplasmic reticulum (SR) Ca(2+...

  15. Mechanical compression during repeated sustained isometric muscle contractions and hyperemic recovery in healthy young males

    DEFF Research Database (Denmark)

    Osada, Takuya; Mortensen, Stefan P; Rådegran, Göran

    2015-01-01

    BACKGROUND: An elevated intramuscular pressure during a single forearm isometric muscle contraction may restrict muscle hyperemia. However, during repeated isometric exercise, it is unclear to what extent mechanical compression and muscle vasodilatation contribute to the magnitude and time course...... of beat-to-beat limb hemodynamics, due to alterations in leg vascular conductance (LVC). METHODS: In eight healthy male subjects, the time course of both beat-to-beat leg blood flow (LBF) and LVC in the femoral artery was determined between repeated 10-s isometric thigh muscle contractions and 10-s muscle...... (%). RESULTS: The exercise protocol was performed completely by all subjects (≤50 % MVC), seven subjects (≤70 % MVC), and two subjects (≤90 % MVC). During a 10-s isometric muscle contraction, the time course in both beat-to-beat LBF and LVC displayed a fitting curve with an exponential increase (P 

  16. The Effect of Exercise-Induced Muscle Damage After a Bout of Accentuated Eccentric Load Drop Jumps and the Repeated Bout Effect.

    Science.gov (United States)

    Bridgeman, Lee A; Gill, Nicholas D; Dulson, Deborah K; McGuigan, Michael R

    2017-02-01

    Bridgeman, LA, Gill, ND, Dulson, DK, and McGuigan, MR. The effect of exercise induced muscle damage after a bout of accentuated eccentric load drop jumps and the repeated bout effect. J Strength Cond Res 31(2): 386-394, 2017-Although previous studies have investigated exercise-induced muscle damage (EIMD) after a bout of unloaded drop jumps (DJs), none have investigated the effects of accentuated eccentric load (AEL) DJs on EIMD. The purpose of this study was to investigate the effects of 30 and 50 AEL DJs on strength, jump performance, muscle soreness, and blood markers. Eight resistance trained athletes participated in this study. In week 1, baseline countermovement jump (CMJ), squat jump (SJ), concentric and eccentric peak force (PF), creatine kinase, and muscle soreness were assessed. Subjects then completed 30 AEL DJs and baseline measures were retested immediately postintervention, 1, 24, and 48 hours later. Two weeks later, the subjects completed the same protocol with an increase in AEL DJ volume (50). Subjects' SJ height was reduced in week 1 compared with week 3, postintervention, 1, 24, and 48 hours later (ES = -0.34, -0.44, -0.38, and -0.40). Subjects' CMJ height was reduced in week 1 compared with week 3, postintervention, 1, and 24 hours later (ES = -0.37, -0.29, and -0.39). Concentric PF was reduced in week 1 compared with week 3, postintervention and 24 and 48 hours later (ES = -0.02, -0.23, and -0.32). Eccentric PF was reduced in week 1 compared with week 3, postintervention, 24, and 48 hours later (ES = -0.24, -0.16, and -0.50). In this sample, 30 AEL DJs attenuated the effects of EIMD following which 50 AEL DJs completed 2 weeks later.

  17. Overexpression of Galgt2 in skeletal muscle prevents injury resulting from eccentric contractions in both mdx and wild-type mice.

    Science.gov (United States)

    Martin, Paul T; Xu, Rui; Rodino-Klapac, Louise R; Oglesbay, Elaine; Camboni, Marybeth; Montgomery, Chrystal L; Shontz, Kim; Chicoine, Louis G; Clark, K Reed; Sahenk, Zarife; Mendell, Jerry R; Janssen, Paul M L

    2009-03-01

    The cytotoxic T cell (CT) GalNAc transferase, or Galgt2, is a UDP-GalNAc:beta1,4-N-acetylgalactosaminyltransferase that is localized to the neuromuscular synapse in adult skeletal muscle, where it creates the synaptic CT carbohydrate antigen {GalNAcbeta1,4[NeuAc(orGc)alpha2, 3]Galbeta1,4GlcNAcbeta-}. Overexpression of Galgt2 in the skeletal muscles of transgenic mice inhibits the development of muscular dystrophy in mdx mice, a model for Duchenne muscular dystrophy. Here, we provide physiological evidence as to how Galgt2 may inhibit the development of muscle pathology in mdx animals. Both Galgt2 transgenic wild-type and mdx skeletal muscles showed a marked improvement in normalized isometric force during repetitive eccentric contractions relative to nontransgenic littermates, even using a paradigm where nontransgenic muscles had force reductions of 95% or more. Muscles from Galgt2 transgenic mice, however, showed a significant decrement in normalized specific force and in hindlimb and forelimb grip strength at some ages. Overexpression of Galgt2 in muscles of young adult mdx mice, where Galgt2 has no effect on muscle size, also caused a significant decrease in force drop during eccentric contractions and increased normalized specific force. A comparison of Galgt2 and microdystrophin overexpression using a therapeutically relevant intravascular gene delivery protocol showed Galgt2 was as effective as microdystrophin at preventing loss of force during eccentric contractions. These experiments provide a mechanism to explain why Galgt2 overexpression inhibits muscular dystrophy in mdx muscles. That overexpression also prevents loss of force in nondystrophic muscles suggests that Galgt2 is a therapeutic target with broad potential applications.

  18. Blood flow after contraction and cuff occlusion is reduced in subjects with muscle soreness after eccentric exercise

    DEFF Research Database (Denmark)

    Souza-Silva, Eduardo; Wittrup Christensen, Steffan; Hirata, Rogerio Pessoto

    2017-01-01

    anterior muscle. All measures were done bilaterally at day-0 (pre-exercise), day-2 and day-6 (post-exercise). Subjects scored the muscle soreness on a Likert scale for 6 days. Results: Eccentric exercise increased Likert scores at day-1 and day-2 compared with day-0 (P

  19. Eccentric contraction-induced injury to type I, IIa, and IIa/IIx muscle fibers of elderly adults

    Science.gov (United States)

    Muscles of old laboratory rodents experience exaggerated force losses after eccentric contractile activity. We extended this line of inquiry to humans and investigated the influence of fiber myosin heavy chain (MHC) isoform content on the injury process. Skinned muscle fiber segments, prepared from ...

  20. Numerical calculation of viscoelastic flows through eccentric abrupt contraction; Henshin kyushuku shoryuro ni okeru nendansei ryutai no nagare no suchi kaiseki

    Energy Technology Data Exchange (ETDEWEB)

    Nakamura, K.; Mori, N.; Matsumura, K. [Osaka University, Osaka (Japan). Faculty of Engineering

    1997-04-25

    Numerical simulations of viscoelastic flows through an eccentric four-to-one abrupt contraction are carried out using the Giesekus model. The SMAC (Simplified-Marker-and-Cell) method is used to analyze the three-dimensional flows. The velocity profiles along the path line passing through the center of the exit exhibit an overshoot near the entry section, and at high Weissenberg numbers an undershoot follows the overshoot. The magnitude of the stress along the same path line has a peak near the entry, section, and its slow relaxation process indicates that a large downstream length is necessary for fully developed stress conditions to exist. The peak is lower than that for the flow through the concentric four-to-one abrupt contraction ; the decrease in the peak amplitude is understood to be due to the distortion of the path line in the eccentric geometry. A corner vortex, the height of which is a maximum at the widest corner, grows as the Weissenberg number increases. Furthermore, the tangential flow toward the widest section inside the vortex is determined. 19 refs., 10 figs.

  1. Diapocynin, a dimer of the NADPH oxidase inhibitor apocynin, reduces ROS production and prevents force loss in eccentrically contracting dystrophic muscle.

    Directory of Open Access Journals (Sweden)

    Hesham M Ismail

    Full Text Available Elevation of intracellular Ca2+, excessive ROS production and increased phospholipase A2 activity contribute to the pathology in dystrophin-deficient muscle. Moreover, Ca2+, ROS and phospholipase A2, in particular iPLA2, are thought to potentiate each other in positive feedback loops. NADPH oxidases (NOX have been considered as a major source of ROS in muscle and have been reported to be overexpressed in muscles of mdx mice. We report here on our investigations regarding the effect of diapocynin, a dimer of the commonly used NOX inhibitor apocynin, on the activity of iPLA2, Ca2+ handling and ROS generation in dystrophic myotubes. We also examined the effects of diapocynin on force production and recovery ability of isolated EDL muscles exposed to eccentric contractions in vitro, a damaging procedure to which dystrophic muscle is extremely sensitive. In dystrophic myotubes, diapocynin inhibited ROS production, abolished iPLA2 activity and reduced Ca2+ influx through stretch-activated and store-operated channels, two major pathways responsible for excessive Ca2+ entry in dystrophic muscle. Diapocynin also prevented force loss induced by eccentric contractions of mdx muscle close to the value of wild-type muscle and reduced membrane damage as seen by Procion orange dye uptake. These findings support the central role played by NOX-ROS in the pathogenic cascade leading to muscular dystrophy and suggest diapocynin as an effective NOX inhibitor that might be helpful for future therapeutic approaches.

  2. Gender and contraction mode on perceived exertion.

    Science.gov (United States)

    Pincivero, D M; Polen, R R; Byrd, B N

    2010-05-01

    The purpose of this study was to examine perceived exertion responses during concentric and eccentric elbow flexor contractions between young adult men and women. Thirty healthy young adults participated in two experimental sessions. During the first session, subjects performed five concentric isokinetic maximal voluntary contractions (MVC) of elbow flexion, followed by nine, randomly-ordered sub-maximal contractions (10-90% MVC). The same procedures were repeated during the second session, with the exception that eccentric contractions were performed. Subjects rated their perceived exertion following the sub-maximal contractions with the Borg category-ratio scale. Perceived exertion was significantly (pMVC. A three-factor interaction between 30-40% MVC indicated that perceived exertion increased more during the eccentric, than concentric, contractions in women, while the opposite pattern was evident for the men. There were no significant contraction mode or gender differences. Power function modeling revealed that perceived exertion increased in a negatively accelerating manner, except for the men performing eccentric exercise. Perceived exertion increases in a similar non-linear manner between men and women during concentric contractions, while men exhibited a statistically linear pattern during eccentric contractions.

  3. Fatigue-induced dissociation between rate of force development and maximal force across repeated rapid contractions.

    Science.gov (United States)

    Boccia, Gennaro; Dardanello, Davide; Tarperi, Cantor; Festa, Luca; La Torre, Antonio; Pellegrini, Barbara; Schena, Federico; Rainoldi, Alberto

    2017-08-01

    We examined whether the presence of fatigue induced by prolonged running influenced the time courses of force generating capacities throughout a series of intermittent rapid contractions. Thirteen male amateur runners performed a set of 15 intermittent isometric rapid contractions of the knee extensor muscles, (3s/5s on/off) the day before (PRE) and immediately after (POST) a half marathon. The maximal voluntary contraction force, rate of force development (RFDpeak), and their ratio (relative RFDpeak) were calculated. At POST, considering the first (out of 15) repetition, the maximal force and RFDpeak decreased (p<0.0001) at the same extent (by 22±6% and 24±22%, respectively), resulting in unchanged relative RFDpeak (p=0.6). Conversely, the decline of RFDpeak throughout the repetitions was more pronounced at POST (p=0.02), thus the decline of relative RFDpeak was more pronounced (p=0.007) at POST (-25±13%) than at PRE (-3±13%). The main finding of this study was that the fatigue induced by a half-marathon caused a more pronounced impairment of rapid compared to maximal force in the subsequent intermittent protocol. Thus, the fatigue-induced impairment in rapid muscle contractions may have a greater effect on repeated, rather than on single, attempts of maximal force production. Copyright © 2017 Elsevier B.V. All rights reserved.

  4. Black Currant Nectar Reduces Muscle Damage and Inflammation Following a Bout of High-Intensity Eccentric Contractions.

    Science.gov (United States)

    Hutchison, Alexander T; Flieller, Emily B; Dillon, Kimber J; Leverett, Betsy D

    2016-01-01

    This investigation determined the efficacy of black currant nectar (BCN) in reducing symptoms of exercise-induced muscle damage (EIMD). Sixteen college students were randomly assigned to drink either 16 oz of BCN or a placebo (PLA) twice a day for eight consecutive days. A bout of eccentric knee extensions (3 × 10 sets @ 115% of 1RM) was performed on the fourth day. Outcome measures included muscle soreness (subjective scale from 0 to 10) and blood markers of muscle damage (creatine kinase, CK), inflammation (interleukin-6, IL-6), and oxygen radical absorbance capacity (ORAC). Although there were no differences in reported soreness between groups, consumption of BCN reduced CK levels at both 48 (PLA = 82.13% vs. BCN = -6.71%, p = .042) and 96 h post exercise (PLA = 74.96% vs. BCN = -12.11%, p = .030). The change in IL-6 was higher in the PLA group (PLA = 8.84% vs. BCN = -6.54%, p = .023) at 24 h post exercise. The change in ORAC levels was higher in the treatment group (BCN = 2.68% vs. PLA = -6.02%, p = .039) at 48 h post exercise. Our results demonstrate that consumption of BCN prior to and after a bout of eccentric exercise attenuates muscle damage and inflammation.

  5. Eccentric exercise testing and training

    Science.gov (United States)

    Clarkson, Priscilla M.

    1994-01-01

    Some researchers and practitioners have touted the benefits of including eccentric exercise in strength training programs. However, others have challenged its use because they believe that eccentric actions are dangerous and lead to injuries. Much of the controversy may be based on a lack of understanding of the physiology of eccentric actions. This review will present data concerning eccentric exercise in strength training, the physiological characteristics of eccentric exercise, and the possible stimulus for strength development. Also a discussion of strength needs for extended exposure to microgravity will be presented. Not only is the use of eccentric exercise controversial, but the name itself is fraught with problems. The correct pronunciation is with a hard 'c' so that the word sounds like ekscentric. The confusion in pronunciation may have been prevented if the spelling that Asmussen used in 1953, excentric, had been adopted. Another problem concerns the expressions used to describe eccentric exercise. Commonly used expressions are negatives, eccentric contractions, lengthening contractions, resisted muscle lengthenings, muscle lengthening actions, and eccentric actions. Some of these terms are cumbersome (i.e., resisted muscle lengthenings), one is slang (negatives), and another is an oxymoron (lengthening contractions). Only eccentric action is appropriate and adoption of this term has been recommended by Cavanagh. Despite the controversy that surrounds eccentric exercise, it is important to note that these types of actions play an integral role in normal daily activities. Eccentric actions are used during most forms of movement, for example, in walking when the foot touches the ground and the center of mass is decelerated and in lowering objects, such as placing a bag of groceries in the car.

  6. EFFECT OF HEAT PRECONDITIONING BY MICROWAVE HYPERTHERMIA ON HUMAN SKELETAL MUSCLE AFTER ECCENTRIC EXERCISE

    Directory of Open Access Journals (Sweden)

    Norio Saga

    2008-03-01

    Full Text Available The purpose of this study was to clarify whether heat preconditioning results in less eccentric exercise-induced muscle damage and muscle soreness, and whether the repeated bout effect is enhanced by heat preconditioning prior to eccentric exercise. Nine untrained male volunteers aged 23 ± 3 years participated in this study. Heat preconditioning included treatment with a microwave hyperthermia unit (150 W, 20 min that was randomly applied to one of the subject's arms (MW; the other arm was used as a control (CON. One day after heat preconditioning, the subjects performed 24 maximal isokinetic eccentric contractions of the elbow flexors at 30°·s-1 (ECC1. One week after ECC1, the subjects repeated the procedure (ECC2. After each bout of exercise, maximal voluntary contraction (MVC, range of motion (ROM of the elbow joint, upper arm circumference, blood creatine kinase (CK activity and muscle soreness were measured. The subjects experienced both conditions at an interval of 3 weeks. MVC and ROM in the MW were significantly higher than those in the CON (p < 0.05 for ECC1; however, the heat preconditioning had no significant effect on upper arm circumference, blood CK activity, or muscle soreness following ECC1 and ECC2. Heat preconditioning may protect human skeletal muscle from eccentric exercise-induced muscle damage after a single bout of eccentric exercise but does not appear to promote the repeated bout effect after a second bout of eccentric exercise

  7. Repeatability study of mechanomyography in submaximal isometric contractions using coefficient of variation and intraclass correlation coefficient.

    Science.gov (United States)

    Akataki, K; Mita, K; Itoh, Y

    1999-01-01

    The within-day and between-day repeatability of the mechanomyogram (MMG) was assessed using the coefficient of variation (CV) and the intraclass correlation coefficient (ICC) and was compared with that of the electromyogram (EMG). The MMG and EMG were recorded simultaneously during isometric elbow flexion trials at different submaximal levels of 10% to 90% MVC. The testing session consisting of 9 submaximal trials was repeated 8 times on the same day for estimation of the within-day variation. In order to examine the between-day variation, the same testing session was also performed 8 times over 3 weeks with a 2-day rest interval between each session. The CVs within-day and between-day in both the MMG and EMG did not demonstrate any significant differences relating to the magnitude of force exerted. The CVs combined over all the force levels were approximately 10% within the same day and 25% between days for both the MMG and EMG. These corresponded to the within-day ICC of approximately 0.95 and the between-day ICC of 0.80. The repeatability of the MMG during submaximal isometric contractions of biceps brachii muscles is considered to be similar to that of the more established EMG.

  8. Reliability of near-infrared spectroscopy for measuring biceps brachii oxygenation during sustained and repeated isometric contractions

    Science.gov (United States)

    Muthalib, Makii; Millet, Guillaume Y.; Quaresima, Valentina; Nosaka, Kazunori

    2010-01-01

    We examine the test-retest reliability of biceps brachii tissue oxygenation index (TOI) parameters measured by near-infrared spectroscopy during a 10-s sustained and a 30-repeated (1-s contraction, 1-s relaxation) isometric contraction task at 30% of maximal voluntary contraction (30% MVC) and maximal (100% MVC) intensities. Eight healthy men (23 to 33 yr) were tested on three sessions separated by 3 h and 24 h, and the within-subject reliability of torque and each TOI parameter were determined by Bland-Altman+/-2 SD limits of agreement plots and coefficient of variation (CV). No significant (P>0.05) differences between the three sessions were found for mean values of torque and TOI parameters during the sustained and repeated tasks at both contraction intensities. All TOI parameters were within+/-2 SD limits of agreement. The CVs for torque integral were similar between the sustained and repeated task at both intensities (4 to 7%) however, the CVs for TOI parameters during the sustained and repeated task were lower for 100% MVC (7 to 11%) than for 30% MVC (22 to 36%). It is concluded that the reliability of the biceps brachii NIRS parameters during both sustained and repeated isometric contraction tasks is acceptable.

  9. Eccentric Exercise: Physiological Characteristics and Acute Responses.

    Science.gov (United States)

    Douglas, Jamie; Pearson, Simon; Ross, Angus; McGuigan, Mike

    2017-04-01

    An eccentric contraction involves the active lengthening of muscle under an external load. The molecular and neural mechanisms underpinning eccentric contractions differ from those of concentric and isometric contractions and remain less understood. A number of molecular theories have been put forth to explain the unexplained observations during eccentric contractions that deviate from the predictions of the established theories of muscle contraction. Postulated mechanisms include a strain-induced modulation of actin-myosin interactions at the level of the cross-bridge, the activation of the structural protein titin, and the winding of titin on actin. Accordingly, neural strategies controlling eccentric contractions also differ with a greater, and possibly distinct, cortical activation observed despite an apparently lower activation at the level of the motor unit. The characteristics of eccentric contractions are associated with several acute physiological responses to eccentrically-emphasised exercise. Differences in neuromuscular, metabolic, hormonal and anabolic signalling responses during, and following, an eccentric exercise bout have frequently been observed in comparison to concentric exercise. Subsequently, the high levels of muscular strain with such exercise can induce muscle damage which is rarely observed with other contraction types. The net result of these eccentric contraction characteristics and responses appears to be a novel adaptive signal within the neuromuscular system.

  10. Homogeneity of fascicle architecture following repeated contractions in the human gastrocnemius medialis.

    Science.gov (United States)

    Thomas, Neil M; Dewhurst, Susan; Bampouras, Theodoros M

    2015-12-01

    This investigation sought to determine the effects of fatigue on fascicle architecture across the length of the human gastrocnemius medialis (GM). With institutional ethical approval, fifteen healthy males performed repeated isometric plantar flexion maximal voluntary contractions (MVC) until peak force fell 30% below baseline. Brightness-mode ultrasound was used to determine fascicle length and pennation angle at rest and during MVC prior to and following the fatiguing contractions. The results show a significant increase in fascicle length during MVC in the distal (2.8 mm, 8.1%) middle, (4.9 mm, 14.1%), and proximal (5.2 mm, 14.7%) regions post-fatigue compared to pre-fatigue (p MVC in the distal (3.3°, 8.8%), middle (3.9°, 9.4%), and proximal (2.9°, 6.9%) regions post-fatigue compared to pre-fatigue (p < 0.05). These changes, however, were not region specific. These are the first results to show that fascicle shortening within the GM remains homogeneous following fatigue, suggesting that the fascicles were fatigued in a similar pattern throughout the muscle. The significant reduction of fascicle shortening may reflect an additional strategy to maintain an optimal force output in fatigued conditions, although future work is needed to confirm this notion.

  11. IGF-1 response to arm exercise with eccentric and concentric muscle contractions in resistance-trained athletes with left ventricular hypertrophy.

    Science.gov (United States)

    Żebrowska, A; Waśkiewicz, Z; Zając, A; Gąsior, Z; Galbo, H; Langfort, J

    2013-02-01

    The study aimed at evaluating changes in plasma levels of insulin-like growth factor 1 (IGF-1), insulin-like growth factor binding protein-3 (IGFBP-3), testosterone, growth hormone (GH), cortisol, and insulin in resistance-trained male athletes with (n=9) and without (n=9) left ventricular hypertrophy (LVH) in response to eccentric (ECC) and concentric (CON) arm exercise. 10 age-matched healthy non-trained subjects served as controls. M-mode and 2D Doppler echocardiography were used to estimate LV mass.Resting IGF-1 concentration was higher in LVH athletes compared to controls (52 ± 5 nM vs. 46 ± 7 nM, pexercise resulted in higher (pexercise resulted in higher serum IGFBP-3 levels in LVH athletes compared to controls (242 ± 57 and 274 ± 58, athletes, vs. 215 ± 63 and 244 ± 67, controls, nM, pexercise, GH concentrations were lower in LVH than in non-LVH athletes (4.7 ± 2.1 vs. 6.1 ± 1.8 ng  mL(-1), peccentric arm exercise. These findings suggest a role of IGF-1, possibly released from contracting muscle, in stimulating LV hypertrophy in resistance training.

  12. Transcription-induced CAG repeat contraction in human cells is mediated in part by transcription-coupled nucleotide excision repair.

    Science.gov (United States)

    Lin, Yunfu; Wilson, John H

    2007-09-01

    Expansions of CAG repeat tracts in the germ line underlie several neurological diseases. In human patients and mouse models, CAG repeat tracts display an ongoing instability in neurons, which may exacerbate disease symptoms. It is unclear how repeats are destabilized in nondividing cells, but it cannot involve DNA replication. We showed previously that transcription through CAG repeats induces their instability (Y. Lin, V. Dion, and J. H. Wilson, Nat. Struct. Mol. Biol. 13:179-180). Here, we present a genetic analysis of the link between transcription-induced repeat instability and nucleotide excision repair (NER) in human cells. We show that short interfering RNA-mediated knockdown of CSB, a component specifically required for transcription-coupled NER (TC-NER), and knockdowns of ERCC1 and XPG, which incise DNA adjacent to damage, stabilize CAG repeat tracts. These results suggest that TC-NER is involved in the pathway for transcription-induced CAG repeat instability. In contrast, knockdowns of OGG1 and APEX1, key components involved in base excision repair, did not affect repeat instability. In addition, repeats are stabilized by knockdown of transcription factor IIS, consistent with a requirement for RNA polymerase II (RNAPII) to backtrack from a transcription block. Repeats also are stabilized by knockdown of either BRCA1 or BARD1, which together function as an E3 ligase that can ubiquitinate arrested RNAPII. Treatment with the proteasome inhibitor MG132, which stabilizes repeats, confirms proteasome involvement. We integrate these observations into a tentative pathway for transcription-induced CAG repeat instability that can account for the contractions observed here and potentially for the contractions and expansions seen with human diseases.

  13. 一次和重复大强度离心运动前后大鼠骨骼肌超微结构变化%The Ultrastructural Changes in Skeletal Muscle of Rat after Acute and Repeated Eccentric Exercise

    Institute of Scientific and Technical Information of China (English)

    董贵俊; 吕晨曦; 葛新发; 李可峰; 潘卫东

    2013-01-01

    Objective To study the ultrastructural changes in skeletal muscle of rat after acute and repeated eccentric exercise. Methods 72 rats were randomly assigned to normal control group,acute eccentric exercise group and repeated eccentric exercise group. Rats in acute eccentric exercise group ran on a downhill treadmill(-16° slope) twice at a speed of 18m/min for 30 minutes with an interval of 5 minutes. Rats in repeated eccentric exercise group underwent the protocol as rats in acute eccentric exercise group twice with an interval of 1 week. The ultrastructural changes in skeletal muscle were observed 24 hours,48 hours,72 hours and 168 hours after the acute or repeated exercises. Results Disordered or disappeared sarcomere,fractured Z-line,and decomposed myofilament occurred 48 hours after acute exercise,and partially restored within 72 hours. Mitochondria was severely damaged 24 hours after repeated exercise,and restored within 72 hours,whereas mitochondrial number,structure and function did not completely recovered. Conclusions Compared to the acute eccentric exercise, repeated eccentric exercise causes less ultrastructural changes in skeletal muscle.%目的:探讨一次和重复离心运动后大鼠骨骼肌超微结构的改变.方法:72只Wistar大鼠分为正常对照组、一次离心运动组和重复离心运动组.一次大强度运动组采用速度18 m/min、坡度-16°的下坡跑运动,大鼠先运动30 min休息5 min,再运动30 min.重复运动在一次运动结束一周后进行(运动2次),观察一次和重复运动后即刻、24 h、48 h、72 h和168 h大鼠股四头肌超微结构变化.结果:一次运动后48 h肌节损伤情况最严重,肌节紊乱甚至消失,Z线断裂,肌丝溶解,72 h出现部分恢复.重复运动后24 h,线粒体严重破坏,48 h线粒体结构逐渐恢复,72 h肌纤维已经重建,但线粒体数量、结构和功能尚未完全恢复.结论:重复运动较一次大强度离心运动促进肌纤维再生及骨骼

  14. Repeatability of maximal voluntary force and of surface EMG variables during voluntary isometric contraction of quadriceps muscles in healthy subjects.

    Science.gov (United States)

    Rainoldi, A; Bullock-Saxton, J E; Cavarretta, F; Hogan, N

    2001-12-01

    The repeatability of initial values and rate of change of EMG signal mean spectral frequency (MNF), average rectified values (ARV), muscle fiber conduction velocity (CV) and maximal voluntary contraction (MVC) was investigated in the vastus medialis obliquus (VMO) and vastus lateralis (VL) muscles of both legs of nine healthy male subjects during voluntary, isometric contractions sustained for 50 s at 50% MVC. The values of MVC were recorded for both legs three times on each day and for three subsequent days, while the EMG signals have been recorded twice a day for three subsequent days. The degree of repeatability was investigated using the Fisher test based upon the ANalysis Of VAriance (ANOVA), the Standard Error of the Mean (SEM) and the Intraclass Correlation Coefficient (ICC). Data collected showed a high level of repeatability of MVC measurement (normalized SEM from 1.1% to 6.4% of the mean). MNF and ARV initial values also showed a high level of repeatability (ICC>70% for all muscles and legs except right VMO). At 50% MVC level no relevant pattern of fatigue was observed for the VMO and VL muscles, suggesting that other portions of the quadriceps might have contributed to the generated effort. These observations seem to suggest that in the investigation of muscles belonging to a multi-muscular group at submaximal level, the more selective electrically elicited contractions should be preferred to voluntary contractions.

  15. Skeletal muscle fiber type composition and performance during repeated bouts of maximal, concentric contractions

    Science.gov (United States)

    Colliander, E. B.; Dudley, G. A.; Tesch, P. A.

    1988-01-01

    Force output and fatigue and recovery patterns were studied during intermittent short-term exercise. 27 men performed three bouts of 30 maximal unilateral knee extensions on 2 different occasions. Blood flow was maintained or occluded during recovery periods (60 s). Blood flow was restricted by inflating a pneumatic cuff placed around the proximal thigh. Muscle biopsies from vastus lateralis were analyzed for identification of fast twitch (FT) and slow twitch (ST) fibers and relative FT area. Peak torque decreased during each bout of exercise and more when blood flow was restricted during recovery. Initial peak torque (IPT) and average peak torque (APT) decreased over the three exercise bouts. This response was 3 fold greater without than with blood flow during recovery. IPT and APT decreased more in individuals with mainly FT fibers than in those with mainly ST fibers. It is suggested that performance during repeated bouts of maximal concentric contractions differs between individuals with different fiber type composition. Specifically, in high intensity, intermittent exercise with emphasis on anaerobic energy release a high FT composition may not necessarily be advantageous for performance.

  16. Loss of nNOS inhibits compensatory muscle hypertrophy and exacerbates inflammation and eccentric contraction-induced damage in mdx mice

    Science.gov (United States)

    Froehner, Stanley C.; Reed, Sarah M.; Anderson, Kendra N.; Huang, Paul L.; Percival, Justin M.

    2015-01-01

    Approaches targeting nitric oxide (NO) signaling show promise as therapies for Duchenne and Becker muscular dystrophies. However, the mechanisms by which NO benefits dystrophin-deficient muscle remain unclear, but may involve nNOSβ, a newly discovered enzymatic source of NO in skeletal muscle. Here we investigate the impact of dystrophin deficiency on nNOSβ and use mdx mice engineered to lack nNOSμ and nNOSβ to discern how the loss of nNOS impacts dystrophic skeletal muscle pathology. In mdx muscle, nNOSβ was mislocalized and its association with the Golgi complex was reduced. nNOS depletion from mdx mice prevented compensatory skeletal muscle cell hypertrophy, decreased myofiber central nucleation and increased focal macrophage cell infiltration, indicating exacerbated dystrophic muscle damage. Reductions in muscle integrity in nNOS-null mdx mice were accompanied by decreases in specific force and increased susceptibility to eccentric contraction-induced muscle damage compared with mdx controls. Unexpectedly, muscle fatigue was unaffected by nNOS depletion, revealing a novel latent compensatory mechanism for the loss of nNOS in mdx mice. Together with previous studies, these data suggest that localization of both nNOSμ and nNOSβ is disrupted by dystrophin deficiency. They also indicate that nNOS has a more complex role as a modifier of dystrophic pathology and broader therapeutic potential than previously recognized. Importantly, these findings also suggest nNOSβ as a new drug target and provide a new conceptual framework for understanding nNOS signaling and the benefits of NO therapies in dystrophinopathies. PMID:25214536

  17. Time Course Change of IGF1/Akt/mTOR/p70s6k Pathway Activation in Rat Gastrocnemius Muscle During Repeated Bouts of Eccentric Exercise

    OpenAIRE

    Eisuke Ochi; Naokata Ishii; Koichi Nakazato

    2010-01-01

    The purpose of this study was to examine whether insulin-like growth factor (IGF-1) and Akt/mTOR/p70S6K pathway activity is altered by chronic eccentric exercise in rat medial gastrocnemius muscle. Male Wistar rats (n = 24) were randomly assigned to 1 of the 2 groups: eccentric exercise (ECC) group or sham-operated control (CON) group. Rats in the ECC group were trained every second day for 10 days (5 sessions in total) or 20 days (10 sessions in total). After either 5 or 10 exercise sessions...

  18. Residual force enhancement following eccentric induced muscle damage.

    Science.gov (United States)

    Power, Geoffrey A; Rice, Charles L; Vandervoort, Anthony A

    2012-06-26

    During lengthening of an activated skeletal muscle, the force maintained following the stretch is greater than the isometric force at the same muscle length. This is termed residual force enhancement (RFE), but it is unknown how muscle damage following repeated eccentric contractions affects RFE. Using the dorsiflexors, we hypothesised muscle damage will impair the force generating sarcomeric structures leading to a reduction in RFE. Following reference maximal voluntary isometric contractions (MVC) in 8 young men (26.5±2.8y) a stretch was performed at 30°/s over a 30° ankle excursion ending at the same muscle length as the reference MVCs (30° plantar flexion). Surface electromyography (EMG) of the tibialis anterior and soleus muscles was recorded during all tasks. The damage protocol involved 4 sets of 25 isokinetic (30°/s) lengthening contractions. The same measures were collected at baseline and immediately post lengthening contractions, and for up to 10min recovery. Following the lengthening contraction task, there was a 30.3±6.4% decrease in eccentric torque (Pmuscle damage (Pmuscle function compared to isometric actions succeeding damage. Thus, active force of cross-bridges is decreased because of impaired excitation-contraction coupling but force generated during stretch remains intact because force contribution from stretched sarcomeric structures is less impaired.

  19. Residual force depression following muscle shortening is exaggerated by prior eccentric drop jump exercise.

    Science.gov (United States)

    Dargeviciute, Gintare; Masiulis, Nerijus; Kamandulis, Sigitas; Skurvydas, Albertas; Westerblad, Håkan

    2013-10-15

    We studied the relation between two common force modifications in skeletal muscle: the prolonged force depression induced by unaccustomed eccentric contractions, and the residual force depression (rFD) observed immediately after active shortening. We hypothesized that rFD originates from distortion within the sarcomeres and the extent of rFD: 1) correlates to the force and work performed during the shortening steps, which depend on sarcomeric integrity; and 2) is increased by sarcomeric disorganization induced by eccentric contractions. Nine healthy untrained men (mean age 26 yr) participated in the study. rFD was studied in electrically stimulated knee extensor muscles. rFD was defined as the reduction in isometric torque after active shortening compared with the torque in a purely isometric contraction. Eccentric contractions were performed as 50 repeated drop jumps with active deceleration to 90° knee angle, immediately followed by a maximal upward jump. rFD was assessed before and 5 min to 72 h after drop jumps. The series of drop jumps caused a prolonged force depression, which was about two times larger at 20-Hz than at 50-Hz stimulation. There was a significant correlation between increasing rFD and increasing mechanical work performed during active shortening both before and after drop jumps. In addition, a given rFD was obtained at a markedly lower mechanical work after drop jumps. In conclusion, the extent of rFD correlates to the mechanical work performed during active shortening. A series of eccentric contractions causes a prolonged reduction of isometric force. In addition, eccentric contractions exaggerate rFD, which further decreases muscle performance during dynamic contractions.

  20. Contraction-specific differences in maximal muscle power during stretch-shortening cycle movements in elderly males and females

    DEFF Research Database (Denmark)

    Caserotti, Paolo; Aagaard, Per; Simonsen, Erik Bruun

    2001-01-01

    Aging, muscle power, stretch-shortening cycle, eccentric muscle actions, concentric contractions......Aging, muscle power, stretch-shortening cycle, eccentric muscle actions, concentric contractions...

  1. Contractions

    Science.gov (United States)

    ... the opening to the uterus through which the baby passes during delivery). The contractions tend to increase in the weeks ... experience cramps, contractions and discomfort for weeks before delivery. ... The feeling that the baby has settled lower in your belly. This can ...

  2. Chronic Eccentric Exercise and the Older Adult.

    Science.gov (United States)

    Gluchowski, Ashley; Harris, Nigel; Dulson, Deborah; Cronin, John

    2015-10-01

    Eccentric exercise has gained increasing attention as a suitable and promising intervention to delay or mitigate the known physical and physiological declines associated with aging. Determining the relative efficacy of eccentric exercise when compared with the more conventionally prescribed traditional resistance exercise will support evidence-based prescribing for the aging population. Thus, original research studies incorporating chronic eccentric exercise interventions in the older adult population were included in this review. The effects of a range of eccentric exercise modalities on muscular strength, functional capacity, body composition, muscle architecture, markers of muscle damage, the immune system, cardiovascular system, endocrine system, and rating of perceived exertion were all reviewed as outcomes of particular interest in the older adult. Muscular strength was found to increase most consistently compared with results from traditional resistance exercise. Functional capacity and body composition showed significant improvements with eccentric endurance protocols, especially in older, frail or sedentary cohorts. Muscle damage was avoided with the gradual progression of novel eccentric exercise, while muscle damage from intense acute bouts was significantly attenuated with repeated sessions. Eccentric exercise causes little cardiovascular stress; thus, it may not generate the overload required to elicit cardiovascular adaptations. An anabolic state may be achievable following eccentric exercise, while improvements to insulin sensitivity have not been found. Finally, rating of perceived exertion during eccentric exercise was often significantly lower than during traditional resistance exercise. Overall, evidence supports the prescription of eccentric exercise for the majority of outcomes of interest in the diverse cohorts of the older adult population.

  3. Muscle oxygenation of superficial and deep regions in knee extensor and plantar flexor muscles during repeated isometric contractions.

    Science.gov (United States)

    Kubo, K

    2015-04-01

    The purpose of this study was to investigate changes in muscle oxygenation of knee extensor and plantar flexor muscles during repeated muscle contractions under the same condition. In addition, we compared changes in muscle oxygenation between superficial and deep regions of both muscles. Eleven healthy males participated in this study. During repeated knee extensions and plantar flexions (50 repetitions at 50% of the isometric maximum voluntary contraction for 3 s with 3 s relaxations), blood volume and oxygen saturation (StO₂) of the vastus lateralis and medial gastrocnemius muscles (superficial and deep region of each muscle) were measured using near infrared spectroscopy. The decrement of StO₂at the end of exercises was greater in plantar flexor muscle than in knee extensor muscle (Pmuscles, the decrement of StO₂at the end of exercises was greater in the deep region than in the superficial one (both Pmuscle and deep regions of each muscle were higher than that of knee extensor muscle and superficial regions of each muscle.

  4. Repeatability of corticospinal and spinal measures during lengthening and shortening contractions in the human tibialis anterior muscle.

    Directory of Open Access Journals (Sweden)

    Jamie Tallent

    Full Text Available UNLABELLED: Elements of the human central nervous system (CNS constantly oscillate. In addition, there are also methodological factors and changes in muscle mechanics during dynamic muscle contractions that threaten the stability and consistency of transcranial magnetic stimulation (TMS and perpherial nerve stimulation (PNS measures. PURPOSE: To determine the repeatability of TMS and PNS measures during lengthening and shortening muscle actions in the intact human tibialis anterior. METHODS: On three consecutive days, 20 males performed lengthening and shortening muscle actions at 15, 25, 50 and 80% of maximal voluntary contraction (MVC. The amplitude of the Motor Evoked Potentials (MEPs produced by TMS was measured at rest and during muscle contraction at 90° of ankle joint position. MEPs were normalised to Mmax determined with PNS. The corticospinal silent period was recorded at 80% MVC. Hoffman reflex (H-reflex at 10% isometric and 25% shortening and lengthening MVCs, and V-waves during MVCs were also evoked on each of the three days. RESULTS: With the exception of MEPs evoked at 80% shortening MVC, all TMS-derived measures showed good reliability (ICC = 0.81-0.94 from days 2 to 3. Confidence intervals (CI, 95% were lower between days 2 and 3 when compared to days 1 and 2. MEPs significantly increased at rest from days 1 to 2 (P = 0.016 and days 1 to 3 (P = 0.046. The H-reflex during dynamic muscle contraction was reliable across the three days (ICC = 0.76-0.84. V-waves (shortening, ICC = 0.77, lengthening ICC = 0.54 and the H-reflex at 10% isometric MVC (ICC = 0.66 was generally less reliable over the three days. CONCLUSION: Although it is well known that measures of the intact human CNS exhibit moment-to-moment fluctuations, careful experimental arrangements make it possible to obtain consistent and repeatable measurements of corticospinal and spinal excitability in the actively lengthening and shortening human

  5. Time Course Change of IGF1/Akt/mTOR/p70s6k Pathway Activation in Rat Gastrocnemius Muscle During Repeated Bouts of Eccentric Exercise.

    Science.gov (United States)

    Ochi, Eisuke; Ishii, Naokata; Nakazato, Koichi

    2010-01-01

    The purpose of this study was to examine whether insulin-like growth factor (IGF-1) and Akt/mTOR/p70S6K pathway activity is altered by chronic eccentric exercise in rat medial gastrocnemius muscle. Male Wistar rats (n = 24) were randomly assigned to 1 of the 2 groups: eccentric exercise (ECC) group or sham-operated control (CON) group. Rats in the ECC group were trained every second day for 10 days (5 sessions in total) or 20 days (10 sessions in total). After either 5 or 10 exercise sessions, muscle specimens were dissected and weighed. The mRNA expression of IGF-1 and its variant, mechano growth factor (MGF), was evaluated using real time reverse transcriptase-polymerase chain reaction (RT-PCR). Tissue concentrations of Akt (P), mTOR (P), and p70S6K (P) were measured by using western blot analysis. The medial gastrocnemius muscle mass of the ECC group did not show any significant difference after 5 exercise sessions, whereas the muscle mass increased significantly after 10 exercise sessions with a concomitant increase in the cross-sectional area of muscle fibers (p exercise sessions was significantly higher than those of the age-matched controls and the rats that received 5 exercise sessions. The expression of MGF mRNA in both ECC5S and ECC10S were significantly higher than that in each period-matched control (p exercise, when significant muscular hypertrophy is observed. Key pointsWe confirmed that the rat muscular exercise model using originally-developed equipment increased the wet mass of the medial gastrocnemius muscle and cross-sectional areas of muscle fibres in 10 sessions (20 days) but not in 5 sessions (10days).We clarified that the increases of muscle mass and CSA of muscle fibers were accompanied by IGF-1 mRNA expression, the phosphorylated Akt, mTOR, and p70S6K.These results suggest that muscular hypertrophy in our model was achieved after 10 sessions of exercise and associated with the activation of IGF-1/Akt/mTOR/p70S6K signal pathway.

  6. TIME COURSE CHANGE OF IGF1/AKT/MTOR/P70S6K PATHWAY ACTIVATION IN RAT GASTROCNEMIUS MUSCLE DURING REPEATED BOUTS OF ECCENTRIC EXERCISE

    Directory of Open Access Journals (Sweden)

    Eisuke Ochi

    2010-06-01

    Full Text Available The purpose of this study was to examine whether insulin-like growth factor (IGF-1 and Akt/mTOR/p70S6K pathway activity is altered by chronic eccentric exercise in rat medial gastrocnemius muscle. Male Wistar rats (n = 24 were randomly assigned to 1 of the 2 groups: eccentric exercise (ECC group or sham-operated control (CON group. Rats in the ECC group were trained every second day for 10 days (5 sessions in total or 20 days (10 sessions in total. After either 5 or 10 exercise sessions, muscle specimens were dissected and weighed. The mRNA expression of IGF-1 and its variant, mechano growth factor (MGF, was evaluated using real time reverse transcriptase-polymerase chain reaction (RT-PCR. Tissue concentrations of Akt (P, mTOR (P, and p70S6K (P were measured by using western blot analysis. The medial gastrocnemius muscle mass of the ECC group did not show any significant difference after 5 exercise sessions, whereas the muscle mass increased significantly after 10 exercise sessions with a concomitant increase in the cross-sectional area of muscle fibers (p < 0.05. The expression of IGF-1 mRNA and the tissue concentrations of Akt (P and p70S6K (P after 10 exercise sessions was significantly higher than those of the age-matched controls and the rats that received 5 exercise sessions. The expression of MGF mRNA in both ECC5S and ECC10S were significantly higher than that in each period-matched control (p < 0.01. The tissue concentration of mTOR (P after 10 sessions showed a significant increase when compared with period-matched controls (p < 0.01. These results suggest that activation of the IGF-1/Akt/mTOR/p70S6K signaling pathway becomes dominant in the later phase of chronic exercise, when significant muscular hypertrophy is observed

  7. Electromyographic analysis of an eccentric calf muscle exercise in persons with and without Achilles tendinopathy.

    Science.gov (United States)

    Reid, Duncan; McNair, Peter J; Johnson, Shelley; Potts, Geoff; Witvrouw, Erik; Mahieu, Nele

    2012-08-01

    To compare surface electromyographic (EMG) activity of the gastrocnemius and soleus muscles between persons with and without Achilles tendinopathy (AT) during an eccentric muscle exercise in different knee joint positions. Repeated measures design. Research laboratory. Participants (n = 18) diagnosed with AT and 18 control subjects were recruited. Gastrocnemius and soleus muscle activity was examined by surface (EMG) during extended and flexed knee joint conditions while performing the eccentric training technique. The EMG data were expressed as a percentage of a maximum voluntary contraction (MVC). EMG activity was notably higher (mean difference: 10%, effect size: 0.59) in those subjects with AT. Irrespective of the presence of AT, there was a significant interaction effect between muscle and joint position. The gastrocnemius muscle was significantly more active in the extended knee condition and soleus muscle activity was unchanged across joint positions. The results indicated that the presence of AT influenced calf muscle activity levels during performance of the eccentric exercise. There were differences in muscle activity during the extended and flexed knee conditions. This result does support performing Alfredson, Pietila, Jonsson, and Lorentzon (1998) eccentric exercise in an extended knee position but the specific effects of the knee flexed position on the Achilles tendon during eccentric exercise have yet to be determined, particularly in those with AT. Copyright © 2011 Elsevier Ltd. All rights reserved.

  8. Attenuation of indirect markers of eccentric exercise-induced muscle damage by curcumin.

    Science.gov (United States)

    Tanabe, Yoko; Maeda, Seiji; Akazawa, Nobuhiko; Zempo-Miyaki, Asako; Choi, Youngju; Ra, Song-Gyu; Imaizumi, Atsushi; Otsuka, Yoshihiko; Nosaka, Kazunori

    2015-09-01

    Polyphenolic curcumin is known to have potent anti-inflammatory effects; thus the present study investigated the hypothesis that curcumin ingestion would attenuate muscle damage after eccentric exercise. Fourteen untrained young men (24 ± 1 years) performed 50 maximal isokinetic (120°/s) eccentric contractions of the elbow flexors of one arm on an isokinetic dynamometer and the same exercise with the other arm 4 weeks later. They took 150 mg of curcumin (theracurmin) or placebo (starch) orally before and 12 h after each eccentric exercise bout in a randomised, crossover design. Maximal voluntary contraction (MVC) torque of the elbow flexors, range of motion of the elbow joint, upper-arm circumference, muscle soreness, serum creatine kinase (CK) activity, and plasma interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) concentration were measured before, immediately after, and 24, 48, 72 and 96 h after each eccentric exercise. Changes in these variables over time were compared between curcumin and placebo conditions by two-way repeated measures ANOVA. MVC torque decreased smaller and recovered faster (e.g., 4 days post-exercise: -31 ± 13 % vs. -15 ± 15 %), and peak serum CK activity was smaller (peak: 7684 ± 8959 IU/L vs. 3398 ± 3562 IU/L) for curcumin than placebo condition (P exercise. It is concluded that theracurmin ingestion attenuates some aspects of muscle damage such as MVC loss and CK activity increase.

  9. Inferring the eccentricity distribution

    CERN Document Server

    Hogg, David W; Bovy, Jo

    2010-01-01

    Standard maximum-likelihood estimators for binary-star and exoplanet eccentricities are biased high, in the sense that the estimated eccentricity tends to be larger than the true eccentricity. As with most non-trivial observables, a simple histogram of estimated eccentricities is not a good estimate of the true eccentricity distribution. Here we develop and test a hierarchical probabilistic method for performing the relevant meta-analysis, that is, inferring the true eccentricity distribution, taking as input the likelihood functions for the individual-star eccentricities, or samplings of the posterior probability distributions for the eccentricities (under a given, uninformative prior). The method is a simple implementation of a hierarchical Bayesian model; it can also be seen as a kind of heteroscedastic deconvolution. It can be applied to any quantity measured with finite precision--other orbital parameters, or indeed any astronomical measurements of any kind, including magnitudes, parallaxes, or photometr...

  10. A New Look at the Old Problem of a Reasonable Expectation: The Reasonableness of Repeated Renewals of Fixed Term Contracts as Opposed to Indefinite Employment

    Directory of Open Access Journals (Sweden)

    E Gericke

    2011-04-01

    Full Text Available In South Africa, the Labour Relations Act 66 of 1995 (LRA regulates and protects the position of the employee who reasonably expects that a fixed-term contract will be renewed on the same or similar terms while the employer only offered to renew the contract on less favourable terms or in some instances was not prepared torenew the fixed-term contract at all. The LRA regards the latter conduct as a dismissal, as long as the employee can prove that the employer was responsible for creating the reasonable expectation of contractual renewal. In contrast to this position, the LRA does not regulate or protect the position of the employee whose fixed-term contract was repeatedly renewed on the same, similar or even improved terms, while the employer was in a position to offer the employee indefinite employment. The employer may even have created a reasonable expectation that repeated renewals would result in permanent employment. The exploitation and abuse of the fixed-term contract to the extent that an employee is deprived of employment security and the benefits linked to an employment relationship of indefinite duration have prompted a comparative investigation into this particular field of law.

  11. Effectiveness of a Home-Based Eccentric-Exercise Program on the Torque-Angle Relationship of the Shoulder External Rotators: A Pilot Study.

    Science.gov (United States)

    Uhl, Timothy L; Rice, Thomas; Papotto, Brianna; Butterfield, Timothy A

    2017-04-01

    The role of the rotator cuff is to provide dynamic stability to the glenohumeral joint. Human and animal studies have identified sarcomerogenesis as an outcome of eccentric training indicated by more torque generation with the muscle in a lengthened position. The authors hypothesized that a home-based eccentric-exercise program could increase the shoulder external rotators' eccentric strength at terminal internal rotation (IR). Prospective case series. Clinical laboratory and home exercising. 10 healthy subjects (age 30 ± 10 y). All participants performed 2 eccentric exercises targeting the posterior shoulder for 6 wk using a home-based intervention program using side-lying external rotation (ER) and horizontal abduction. Dynamic eccentric shoulder strength measured at 60°/s through a 100° arc divided into 4 equal 25° arcs (ER 50-25°, ER 25-0°, IR 0-25°, IR 25-50°) to measure angular impulse to represent the work performed. In addition, isometric shoulder ER was measured at 5 points throughout the arc of motion (45° IR, 30° IR, 15° IR, 0°, and 15° ER). Comparison of isometric and dynamic strength from pre- to posttesting was evaluated with a repeated-measure ANOVA using time and arc or positions as within factors. The isometric force measures revealed no significant differences between the 5 positions (P = .56). Analysis of the dynamic eccentric data revealed a significant difference between arcs (P = .02). The percentage-change score of the arc of IR 25-50° was found to be significantly greater than that of the arc of IR 0-25° (P = .007). After eccentric training the only arc of motion that had a positive improvement in the capacity to absorb eccentric loads was the arc of motion that represented eccentric contractions at the longest muscle length.

  12. Eccentric connectivity index

    CERN Document Server

    Ilić, Aleksandar

    2011-01-01

    The eccentric connectivity index $\\xi^c$ is a novel distance--based molecular structure descriptor that was recently used for mathematical modeling of biological activities of diverse nature. It is defined as $\\xi^c (G) = \\sum_{v \\in V (G)} deg (v) \\cdot \\epsilon (v)$\\,, where $deg (v)$ and $\\epsilon (v)$ denote the vertex degree and eccentricity of $v$\\,, respectively. We survey some mathematical properties of this index and furthermore support the use of eccentric connectivity index as topological structure descriptor. We present the extremal trees and unicyclic graphs with maximum and minimum eccentric connectivity index subject to the certain graph constraints. Sharp lower and asymptotic upper bound for all graphs are given and various connections with other important graph invariants are established. In addition, we present explicit formulae for the values of eccentric connectivity index for several families of composite graphs and designed a linear algorithm for calculating the eccentric connectivity in...

  13. On eccentric connectivity index

    CERN Document Server

    Zhou, Bo

    2010-01-01

    The eccentric connectivity index, proposed by Sharma, Goswami and Madan, has been employed successfully for the development of numerous mathematical models for the prediction of biological activities of diverse nature. We now report mathematical properties of the eccentric connectivity index. We establish various lower and upper bounds for the eccentric connectivity index in terms of other graph invariants including the number of vertices, the number of edges, the degree distance and the first Zagreb index. We determine the n-vertex trees of diameter with the minimum eccentric connectivity index, and the n-vertex trees of pendent vertices, with the maximum eccentric connectivity index. We also determine the n-vertex trees with respectively the minimum, second-minimum and third-minimum, and the maximum, second-maximum and third-maximum eccentric connectivity indices for

  14. Changes in electrical pain threshold of fascia and muscle after initial and secondary bouts of elbow flexor eccentric exercise.

    Science.gov (United States)

    Lau, Wing Yin; Blazevich, Anthony J; Newton, Michael J; Wu, Sam Shi Xuan; Nosaka, Kazunori

    2015-05-01

    This study investigated changes in electrical pain threshold (EPT) after repeated eccentric exercise bouts to test the hypothesis that fascia would become more sensitive than muscle when greater delayed onset muscle soreness (DOMS) is induced. Ten young men performed two eccentric exercise bouts (ECC1, ECC2) consisting of ten sets of six maximal isokinetic eccentric contractions of the elbow flexors with the same arm separated by 4 weeks. Maximal voluntary isometric contraction torque, range of motion, muscle soreness assessed by a visual analogue scale (VAS) and pressure pain threshold (PPT) were measured before, immediately after and 1-5 days after exercise. EPT was assessed in the biceps brachii fascia (BBF), biceps brachii muscle, and brachialis fascia (BF) 1 day before, immediately after, and 1, 2 and 4 days after exercise. All measures showed smaller changes (P fascia becomes more sensitive than muscle to electrical stimulation after the initial eccentric exercise, suggesting that damage inflammation to fascia than muscle fibres is more associated with DOMS.

  15. Effects of eccentric cycle ergometry in alpine skiers.

    Science.gov (United States)

    Gross, M; Lüthy, F; Kroell, J; Müller, E; Hoppeler, H; Vogt, M

    2010-08-01

    Eccentric cycling, where the goal is to resist the pedals, which are driven by a motor, increases muscle strength and size in untrained subjects. We hypothesized that it could also be beneficial for athletes, particularly in alpine skiing, which involves predominantly eccentric contractions at longer muscle lengths. We investigated the effects of replacing part of regular weight training with eccentric cycling in junior male alpine skiers using a matched-pair design. Control subjects ( N=7) executed 1-h weight sessions 3 times per week, which included 4-5 sets of 4 leg exercises. The eccentric group ( N=8) performed only 3 sets, followed by continuous sessions on the eccentric ergometer for the remaining 20 min. After 6 weeks, lean thigh mass increased significantly only in the eccentric group. There was a groupxtime effect on squat-jump height favouring the eccentric group, which also experienced a 6.5% improvement in countermovement-jump height. The ability to finely modulate muscle force during variable eccentric cycling improved 50% (p=0.004) only in the eccentric group. Although eccentric cycling did not significantly enhance isometric leg strength, we believe it is beneficial for alpine skiers because it provides an efficient means for hypertrophy while closely mimicking the type of muscle actions encountered while skiing.

  16. The Eccentric Torque Production Capacity of the Ankle, Knee, and Hip Muscle Groups in Patients with Unilateral Chronic Ankle Instability

    Science.gov (United States)

    Negahban, Hossein; Moradi-Bousari, Aida; Naghibi, Saeed; Sarrafzadeh, Javad; Shaterzadeh-Yazdi, Mohammad-Jafar; Goharpey, Shahin; Etemadi, Malihe; Mazaheri, Masood; Feizi, Awat

    2013-01-01

    Purpose The aim of this study was to investigate eccentric torque production capacity of the ankle, knee and hip muscle groups in patients with unilateral chronic ankle instability (CAI) as compared to healthy matched controls. Methods In this case-control study, 40 participants (20 with CAI and 20 controls) were recruited based on convenient non-probability sampling. The average peak torque to body weight (APT/BW) ratio of reciprocal eccentric contraction of ankle dorsi flexor/plantar flexor, ankle evertor/invertor, knee flexor/extensor, hip flexor/extensor and hip abductor/adductor was determined using an isokinetic dynamometer. All subjects participated in two separate sessions with a rest interval of 48 to 72 hours. In each testing session, the torque production capacity of the ankle, knee, and hip muscle groups of only one lower limb was measured. At first, 3 repetitions of maximal eccentric-eccentric contraction were performed for the reciprocal muscles of a joint in a given movement direction. Then, the same procedure of practice and testing trials was repeated for the next randomly-ordered muscle group or joint of the same limb. Results There was no significant interaction of group (CAI and healthy controls) by limb (injured and non-injured) for any muscle groups. Main effect of limb was not significant. Main effect of group was only significant for eccentric torque production capacity of ankle dorsi flexor and hip flexor muscle groups. The APT/BW ratio of these muscles was significantly lower in the CAI group than the healthy controls (P<0.05). Conclusion CAI is associated with eccentric strength deficit of ankle dorsi flexor and hip flexor muscles as indicated by reduction in torque production capacity of these muscles compared to healthy controls. This strength deficit appeared to exist in both the injured and non-injured limbs of the patients. PMID:23802057

  17. The susceptibility of the knee extensors to eccentric exercise-induced muscle damage is not affected by leg dominance but by exercise order.

    Science.gov (United States)

    Hody, S; Rogister, B; Leprince, P; Laglaine, T; Croisier, J-L

    2013-09-01

    The aims of this study were first to compare the response of dominant and non-dominant legs to eccentric exercise and second, to examine whether there is an effect of exercise order on the magnitude of symptoms associated with intense eccentric protocols. Eighteen young men performed three sets of 30 maximal eccentric isokinetic (60° s(-1)) contractions of the knee extensors (range of motion, ROM: 0°-100°, 0 = full extension) using either dominant or non-dominant leg. They repeated a similar eccentric bout using the contralateral leg 6 weeks later. The sequence of leg's use was allocated to create equally balanced groups. Four indirect markers of muscle damage including subjective pain intensity, maximal isometric strength, muscle stiffness and plasma creatine kinase (CK) activity were measured before and 24 h after exercise. All markers changed significantly following the eccentric bout performed either by dominant or non-dominant legs, but no significant difference was observed between legs. Interestingly, the comparison between the first and second eccentric bouts revealed that muscle soreness (-42%, Pexercise-induced muscle damage and supports for the first time the existence of a contralateral protection against exercise-induced muscle damage in the lower limbs.

  18. Small heat shock proteins translocate to the cytoskeleton in human skeletal muscle following eccentric exercise independently of phosphorylation.

    Science.gov (United States)

    Frankenberg, Noni T; Lamb, Graham D; Overgaard, Kristian; Murphy, Robyn M; Vissing, Kristian

    2014-06-01

    Small heat shock proteins (sHSPs) are a subgroup of the highly conserved family of HSPs that are stress inducible and confer resistance to cellular stress and injury. This study aimed to quantitatively examine whether type of contraction (concentric or eccentric) affects sHSPs, HSP27 and αB-crystallin, localization, and phosphorylation in human muscle. Vastus lateralis muscle biopsies from 11 healthy male volunteers were obtained pre- and 3 h, 24 h, and 7 days following concentric (CONC), eccentric (ECC1), and repeated bout eccentric (ECC2) exercise. No changes were apparent in a control group (n = 5) who performed no exercise. Eccentric exercise induced muscle damage, as evidenced by increased muscle force loss, perceived muscle soreness, and elevated plasma creatine kinase and myoglobin levels. Total HSP27 and αB-crystallin amounts did not change following any type of exercise. Following eccentric exercise (ECC1 and ECC2) phosphorylation of HSP27 at serine 15 (pHSP27-Ser15) was increased approximately 3- to 6-fold at 3 h, and pαB-crystallin-Ser59 increased ~10-fold at 3 h. Prior to exercise most of the sHSP and psHSP pools were present in the cytosolic compartment. Eccentric exercise resulted in partial redistribution of HSP27 (~23%) from the cytosol to the cytoskeletal fraction (~28% for pHSP27-Ser15 and ~7% for pHSP27-Ser82), with subsequent full reversal within 24 h. αB-crystallin also showed partial redistribution from the cytosolic to cytoskeletal fraction (~18% of total) 3 h post-ECC1, but not after ECC2. There was no redistribution or phosphorylation of sHSPs with CONC. Eccentric exercise results in increased sHSP phosphorylation and translocation to the cytoskeletal fraction, but the sHSP translocation is not dependent on their phosphorylation. Copyright © 2014 the American Physiological Society.

  19. Low-frequency fatigue at maximal and submaximal muscle contractions

    Directory of Open Access Journals (Sweden)

    R.R. Baptista

    2009-04-01

    Full Text Available Skeletal muscle force production following repetitive contractions is preferentially reduced when muscle is evaluated with low-frequency stimulation. This selective impairment in force generation is called low-frequency fatigue (LFF and could be dependent on the contraction type. The purpose of this study was to compare LFF after concentric and eccentric maximal and submaximal contractions of knee extensor muscles. Ten healthy male subjects (age: 23.6 ± 4.2 years; weight: 73.8 ± 7.7 kg; height: 1.79 ± 0.05 m executed maximal voluntary contractions that were measured before a fatigue test (pre-exercise, immediately after (after-exercise and after 1 h of recovery (after-recovery. The fatigue test consisted of 60 maximal (100% or submaximal (40% dynamic concentric or eccentric knee extensions at an angular velocity of 60°/s. The isometric torque produced by low- (20 Hz and high- (100 Hz frequency stimulation was also measured at these times and the 20:100 Hz ratio was calculated to assess LFF. One-way ANOVA for repeated measures followed by the Newman-Keuls post hoc test was used to determine significant (P < 0.05 differences. LFF was evident after-recovery in all trials except following submaximal eccentric contractions. LFF was not evident after-exercise, regardless of exercise intensity or contraction type. Our results suggest that low-frequency fatigue was evident after submaximal concentric but not submaximal eccentric contractions and was more pronounced after 1-h of recovery.

  20. Low-Frequency Fatigue Assessed as Double to Single Twitch Ratio after Two Bouts of Eccentric Exercise of the Elbow Flexors

    Directory of Open Access Journals (Sweden)

    Damian Janecki, Anna Jaskólska, Jarosław Marusiak, Artur Jaskólski

    2016-12-01

    Full Text Available The aim of this study was to assess low-frequency fatigue as a double to single twitch ratio after repeated eccentric exercise of the elbow flexors. Maximal isometric torque, single and double twitch responses and low-frequency fatigue were assessed on the elbow flexors in 16 untrained male volunteers before, immediately after, 24 and 48 hours following two bouts of eccentric exercise consisted of 30 repetitions of lowering a dumbbell adjusted to ~75% of each individual’s maximal isometric torque. Maximal isometric torque and electrically evoked responses decreased significantly in all measurements after the first bout of eccentric exercise (p < 0.05. In measurements performed at 24 and 48 hours after the second bout both maximal voluntary isometric torque and electrically evoked contractions were significantly higher than in measurements performed after the first bout (p < 0.05. Although low-frequency fatigue significantly increased up to 48 hours after each bout of eccentric exercise, its values at 24 and 48 hours after the second bout were significantly lower than at respective time points after the first bout (p < 0.05. Double to single twitch ratio could be used as a sensitive tool in the evaluation of muscle recovery and adaptation to repeated eccentric exercise.

  1. Introducing Earth's Orbital Eccentricity

    Science.gov (United States)

    Oostra, Benjamin

    2015-01-01

    Most students know that planetary orbits, including Earth's, are elliptical; that is Kepler's first law, and it is found in many science textbooks. But quite a few are mistaken about the details, thinking that the orbit is very eccentric, or that this effect is somehow responsible for the seasons. In fact, the Earth's orbital eccentricity is…

  2. Oscillations of Eccentric Pulsons

    DEFF Research Database (Denmark)

    Christiansen, Peter Leth; Groenbech-Jensen, Niels; Lomdahl, Peter;

    1997-01-01

    Perturbation theory for elliptic pulsons is developed and predicts pulson and eccentricity oscillations. The pulson oscillation period is predicted qualitatively correct.......Perturbation theory for elliptic pulsons is developed and predicts pulson and eccentricity oscillations. The pulson oscillation period is predicted qualitatively correct....

  3. Strength gain through eccentric isotonic training without changes in clinical signs or blood markers

    OpenAIRE

    Alves, Thamara [UNESP; Guarnier, Flavia A.; Campoy,Fernanda A. S.; Gois, Mariana O.; Albuquerque, Maira C. [UNESP; Seraphim, Patricia M.; Netto Junior, Jayme; Marques Vanderlei, Luiz Carlos; Padovani, Carlos R; Cecchini, Rubens; Pastre, Carlos Marcelo

    2013-01-01

    Background Localized exercises are widely used in rehabilitation processes. The predominant options are exercises with an emphasis on either concentric or eccentric contractions. Eccentric exercises promote greater strength gains compared to classical concentric stimuli, but can cause muscle damage. The aim of present study was to compare strength training composed of 10 sessions with progressive loads between groups with a predominance of concentric versus eccentric contraction through an an...

  4. Neuromuscular factors contributing to in vivo eccentric moment generation.

    Science.gov (United States)

    Webber, S; Kriellaars, D

    1997-07-01

    Muscle series elasticity and its contribution to eccentric moment generation was examined in humans. While subjects [male, n = 30; age 26.3 +/- 4.8 (SD) yr; body mass 78.8 +/- 13.1 kg] performed an isometric contraction of the knee extensors at 60 degrees of knee flexion, a quick stretch was imposed with a 12 degrees -step displacement at 100 degrees /s. The test was performed at 10 isometric activation levels ranging from 1.7 to 95.2% of maximal voluntary contraction (MVC). A strong linear relationship was observed between the peak imposed eccentric moment derived from quick stretch and the isometric activation level (y = 1.44x + 7.08; r = 0.99). This increase in the eccentric moment is consistent with an actomyosin-dependent elasticity located in series with the contractile element of muscle. By extrapolating the linear relationship to 100% MVC, the predicted maximum eccentric moment was found to be 151% MVC, consistent with in vitro data. A maximal voluntary, knee extensor strength test was also performed (5-95 degrees, 3 repetitions, +/-50, 100, 150, 200, and 250 degrees/s). The predicted maximum eccentric moment was 206% of the angle- and velocity-matched, maximal voluntary eccentric moments. This was attributed to a potent neural regulatory mechanism that limits the recruitment and/or discharge of motor units during maximal voluntary eccentric contractions.

  5. THE ROLE OF THE REPEATED CONTRACTIONS AND OF THE ACTIVE RELAXATION-OPPOSITION MOVEMENT IN FACILITATING THE MOTOR RESPONSE IN THE CASE OF PATIENTS WITH MIXED PARESIS ON THE LEVEL OF THE MEDIAL AND CUBITAL NERVE

    National Research Council Canada - National Science Library

    Gabriela Ochiana; Maria Mindirigiu; Nicolae Ochiana

    2011-01-01

    ... of the proprioceptive and neuromuscular facilitation techniques, more exactly the repeated contractions and the active relaxation-opposition movement in facilitating the motor response on the level of the paretic muscles...

  6. Repeatability of Corticospinal and Spinal Measures during Lengthening and Shortening Contractions in the Human Tibialis Anterior Muscle

    NARCIS (Netherlands)

    Tallent, Jamie; Goodall, Stuart; Hortobagyi, Tibor; Gibson, Alan St Clair; French, Duncan N.; Howatson, Glyn

    2012-01-01

    Elements of the human central nervous system (CNS) constantly oscillate. In addition, there are also methodological factors and changes in muscle mechanics during dynamic muscle contractions that threaten the stability and consistency of transcranial magnetic stimulation (TMS) and perpherial nerve s

  7. Aging, Functional Capacity and Eccentric Exercise Training

    Science.gov (United States)

    Gault, Mandy L.; Willems, Mark E.T.

    2013-01-01

    Aging is a multi-factorial process that ultimately induces a decline in our physiological functioning, causing a decreased health-span, quality of life and independence for older adults. Exercise participation is seen as a way to reduce the impact of aging through maintenance of physiological parameters. Eccentric exercise is a model that can be employed with older adults, due to the muscle’s ability to combine high muscle force production with a low energy cost. There may however be a risk of muscle damage before the muscle is able to adapt. The first part of this review describes the process of aging and how it reduces aerobic capacity, muscle strength and therefore functional mobility. The second part highlights eccentric exercise and the associated muscle damage, in addition to the repeated bout effect. The final section reviews eccentric exercise interventions that have been completed by older adults with a focus on the changes in functional mobility. In conclusion, eccentric endurance exercise is a potential training modality that can be applied to older adults for improving muscle strength, aerobic capacity and functional ability. However, further research is needed to assess the effects on aerobic capacity and the ideal prescription for eccentric endurance exercise. PMID:24307968

  8. Vibration of an eccentrically clamped annular plate

    Science.gov (United States)

    Tseng, J.-G.; Wickert, J. A.

    1994-04-01

    Small amplitude vibration of an eccentric annular plate, which is free along its outer edge and clamped along the interior, is investigated through experimental and analytical methods. A disk with this geometry, or a stacked array in which the clamping and symmetry axes of each disk are nominally coincident, is common in data storage and brake systems applications. In the present case, the geometric imperfections on the boundary can have important implications for the disk's dynamic response. Changes that occur in the natural frequency spectrum, the mode shapes, and the free response under eccentric mounting are studied through laboratory measurements and an approximate discrete model of the plate. The natural frequencies and modes are found through global discretization of the Kamke quotient for a classical thin plate. For the axisymmetric geometry, the natural frequencies of the sine and cosine vibration modes for a specified number of nodal diameters are repeated. With increasing eccentricity, on the other hand, each pair of repeated frequencies splits at a rate that depends on the number of nodal diameters. Over a range of clamping and eccentricity ratios, the model's predictions are compared to the measured results.

  9. Effect of vibration treatment on symptoms associated with eccentric exercise-induced muscle damage.

    Science.gov (United States)

    Lau, Wing Yin; Nosaka, Kazunori

    2011-08-01

    : The aim of this study was to test the hypothesis that vibration treatment reduces delayed-onset muscle soreness and swelling and enhances recovery of muscle function after eccentric exercise. : A randomized crossover design was used. Fifteen young men performed ten sets of six maximal eccentric contractions of the elbow flexors with the right arm for one occasion and the left arm for the other occasion separated by 4 wks. One arm received a 30-min vibration treatment at 30 mins after and 1, 2, 3, and 4 days after the exercise (treatment group), and the other arm did not receive any treatment (control group). The order of the treatment and control conditions and the use of the dominant and nondominant arms were counterbalanced among subjects. Changes in indirect markers of muscle damage were compared between arms by a two-way repeated-measures analysis of variance. : Compared with the control group, the treatment group showed significantly (P reduction in delayed-onset muscle soreness at 2 to 5 days after exercise. The recovery of range of motion was significantly (P control group. However, no significant effects on the recovery of muscle strength and serum creatine kinase activity were evident. Immediately after the vibration treatment, a significant (P motion were found. : These results showed that the vibration treatment was effective for attenuation of delayed-onset muscle soreness and recovery of range of motion after strenuous eccentric exercise but did not affect swelling, recovery of muscle strength, and serum creatine kinase activity.

  10. Eccentricity from transit photometry

    DEFF Research Database (Denmark)

    Van Eylen, Vincent; Albrecht, Simon

    2015-01-01

    Solar system planets move on almost circular orbits. In strong contrast, many massive gas giant exoplanets travel on highly elliptical orbits, whereas the shape of the orbits of smaller, more terrestrial, exoplanets remained largely elusive. Knowing the eccentricity distribution in systems of small...... and can be described by a Rayleigh distribution with $\\sigma$ = 0.049 $\\pm$ 0.013. This is in full agreement with solar system eccentricities, but in contrast to the eccentricity distributions previously derived for exoplanets from radial velocity studies. Our findings are helpful in identifying which...... (TTVs), and we present some previously unreported TTVs. Finally transit durations help distinguish between false positives and true planets and we use our measurements to confirm six new exoplanets....

  11. Persistent attenuation and enhancement of the earthworm main muscle contraction generator response induced by repeated stimulation of a peripheral neuron

    Directory of Open Access Journals (Sweden)

    Y.C. Chang

    1998-10-01

    Full Text Available Responses evoked in the earthworm, Amynthas hawayanus, main muscle contraction generator M-2 (postsynaptic mechanical-stimulus-sensitive neuron by threshold mechanical stimuli in 2-s intertrial intervals (ITI were used as the control or unconditioned responses (UR. Their attenuation induced by decreasing these intervals in non-associative conditioning and their enhancement induced by associating the unconditioned stimuli (US to a train of short (0.1 s hyperpolarizing electrical substitutive conditioning stimuli (SCS in the Peri-Kästchen (PK neuron were measured in four parameters, i.e., peak numbers (N and amplitude (averaged from 120 responses, sum of these amplitudes (SAMP and the highest peak amplitude (V over a period of 4 min. Persistent attenuation similar to habituation was induced by decreasing the control ITI to 0.5 s and 2.0 s in non-associative conditioning within less than 4 min. Dishabituation was induced by randomly pairing one of these habituated US to an electrical stimulus in the PK neuron. All four parameters of the UR were enhanced by forward (SCS-US, but not backward (US-SCS, association of the US with 25, 100 and 250-Hz trains of SCS with 40-ms interstimulus intervals (ISI for 4 min and persisted for another 4 min after turning off the SCS. The enhancement of these parameters was proportional to the SCS frequencies in the train. No UR was evoked by the SCS when the US was turned off after 4 min of classical conditioning.

  12. Physiological and Neural Adaptations to Eccentric Exercise: Mechanisms and Considerations for Training

    OpenAIRE

    Nosratollah Hedayatpour; Deborah Falla

    2015-01-01

    Eccentric exercise is characterized by initial unfavorable effects such as subcellular muscle damage, pain, reduced fiber excitability, and initial muscle weakness. However, stretch combined with overload, as in eccentric contractions, is an effective stimulus for inducing physiological and neural adaptations to training. Eccentric exercise-induced adaptations include muscle hypertrophy, increased cortical activity, and changes in motor unit behavior, all of which contribute to improved muscl...

  13. Whey protein isolate attenuates strength decline after eccentrically-induced muscle damage in healthy individuals

    Directory of Open Access Journals (Sweden)

    Cribb Paul J

    2010-09-01

    Full Text Available Abstract Background We examined the effects of short-term consumption of whey protein isolate on muscle proteins and force recovery after eccentrically-induced muscle damage in healthy individuals. Methods Seventeen untrained male participants (23 ± 5 yr, 180 ± 6 cm, 80 ± 11 kg were randomly separated into two supplement groups: i whey protein isolate (WPH; n = 9; or ii carbohydrate (CHO; n = 8. Participants consumed 1.5 g/kg.bw/day supplement (~30 g consumed immediately, and then once with breakfast, lunch, in the afternoon and after the evening meal for a period of 14 days following a unilateral eccentric contraction-based resistance exercise session, consisting of 4 sets of 10 repetitions at 120% of maximum voluntary contraction on the leg press, leg extension and leg flexion exercise machine. Plasma creatine kinase and lactate dehydrogenase (LDH levels were assessed as blood markers of muscle damage. Muscle strength was examined by voluntary isokinetic knee extension using a Cybex dynamometer. Data were analyzed using repeated measures ANOVA with an alpha of 0.05. Results Isometric knee extension strength was significantly higher following WPH supplementation 3 (P Conclusions The major finding of this investigation was that whey protein isolate supplementation attenuated the impairment in isometric and isokinetic muscle forces during recovery from exercise-induced muscle injury.

  14. A contracted DNA repeat in LHX3 intron 5 is associated with aberrant splicing and pituitary dwarfism in German shepherd dogs.

    Directory of Open Access Journals (Sweden)

    Annemarie M W Y Voorbij

    Full Text Available Dwarfism in German shepherd dogs is due to combined pituitary hormone deficiency of unknown genetic cause. We localized the recessively inherited defect by a genome wide approach to a region on chromosome 9 with a lod score of 9.8. The region contains LHX3, which codes for a transcription factor essential for pituitary development. Dwarfs have a deletion of one of six 7 bp repeats in intron 5 of LHX3, reducing the intron size to 68 bp. One dwarf was compound heterozygous for the deletion and an insertion of an asparagine residue in the DNA-binding homeodomain of LHX3, suggesting involvement of the gene in the disorder. An exon trapping assay indicated that the shortened intron is not spliced efficiently, probably because it is too small. We applied bisulfite conversion of cytosine to uracil in RNA followed by RT-PCR to analyze the splicing products. The aberrantly spliced RNA molecules resulted from either skipping of exon 5 or retention of intron 5. The same splicing defects were observed in cDNA derived from the pituitary of dwarfs. A survey of similarly mutated introns suggests that there is a minimal distance requirement between the splice donor and branch site of 50 nucleotides. In conclusion, a contraction of a DNA repeat in intron 5 of canine LHX3 leads to deficient splicing and is associated with pituitary dwarfism.

  15. A Contracted DNA Repeat in LHX3 Intron 5 Is Associated with Aberrant Splicing and Pituitary Dwarfism in German Shepherd Dogs

    Science.gov (United States)

    Voorbij, Annemarie M. W. Y.; van Steenbeek, Frank G.; Vos-Loohuis, Manon; Martens, Ellen E. C. P.; Hanson-Nilsson, Jeanette M.; van Oost, Bernard A.; Kooistra, Hans S.; Leegwater, Peter A.

    2011-01-01

    Dwarfism in German shepherd dogs is due to combined pituitary hormone deficiency of unknown genetic cause. We localized the recessively inherited defect by a genome wide approach to a region on chromosome 9 with a lod score of 9.8. The region contains LHX3, which codes for a transcription factor essential for pituitary development. Dwarfs have a deletion of one of six 7 bp repeats in intron 5 of LHX3, reducing the intron size to 68 bp. One dwarf was compound heterozygous for the deletion and an insertion of an asparagine residue in the DNA-binding homeodomain of LHX3, suggesting involvement of the gene in the disorder. An exon trapping assay indicated that the shortened intron is not spliced efficiently, probably because it is too small. We applied bisulfite conversion of cytosine to uracil in RNA followed by RT-PCR to analyze the splicing products. The aberrantly spliced RNA molecules resulted from either skipping of exon 5 or retention of intron 5. The same splicing defects were observed in cDNA derived from the pituitary of dwarfs. A survey of similarly mutated introns suggests that there is a minimal distance requirement between the splice donor and branch site of 50 nucleotides. In conclusion, a contraction of a DNA repeat in intron 5 of canine LHX3 leads to deficient splicing and is associated with pituitary dwarfism. PMID:22132174

  16. Cross-education strength and activation after eccentric exercise.

    Science.gov (United States)

    Lepley, Lindsey K; Palmieri-Smith, Riann M

    2014-01-01

    After injury, eccentric exercise of the injured limb is often contraindicated. Cross-education training, whereby the uninvolved limb is exercised, is an alternative that may improve quadriceps muscle strength and activation in the unexercised limb. To determine the effect of eccentric exercise on quadriceps strength and activation gains in the unexercised limb. Eighteen healthy individuals were randomly assigned to an eccentric training group or a control group. Quadriceps strength and activation measures were collected at preintervention, midintervention, and postintervention. Eccentric training participants exercised their dominant limb with a dynamometer in eccentric mode at 60°/s, 3 times per week for 8 weeks. Quadriceps strength was quantified at 30° and 60°/s in concentric and eccentric modes. Quadriceps activation was assessed using the burst superimposition technique and quantified via the central activation ratio. A 2 × 3 repeated-measures analysis of variance was used to detect the effects of group and testing session on quadriceps strength and activation. Where appropriate, post hoc Bonferroni multiple-comparisons procedures were used. We found greater eccentric strength in the unexercised limbs of eccentric training participants between preintervention and midintervention and between preintervention and postintervention (preintervention to midintervention: 30°/s P = .05; preintervention to postintervention: 30°/s P = .02, 60°/s P = .02). No differences were noted in concentric strength (P > .05). An overall trend toward greater quadriceps activation in the unexercised knee was detected between preintervention and postintervention (P = .063), with the eccentric training group demonstrating a strong effect (Cohen d = 0.83). Control strength did not change (P > .05). Exercising with eccentric actions resulted in mode-specific and velocity-specific gains in quadriceps strength in the unexercised limb. A trend toward greater quadriceps activation in

  17. Origin of Prometheus Eccentricity

    Science.gov (United States)

    Rappaport, N. J.; Longaretti, P.

    2006-12-01

    A number of Saturn's small satellites, from Atlas to the coorbital satellites Janus and Epimetheus, move on orbits just outside the main rings of the planet. These satellites undergo extremely rapid resonant interaction with the rings and outward motion, strongly suggesting that they originated in Saturn's A ring. However, their eccentricities, of the order of 1/1000 are several orders of magnitude larger than what could be expected if the small satellites formed in the ring. This paper represents a first step to providing an explanation for this phenomenon, by focusing on the dynamical processes that have affected the eccentricity of Prometheus. The explanation invokes past resonances with the coorbital satellites combined with chaos due to overlapping of these resonances.

  18. Physiological and Neural Adaptations to Eccentric Exercise: Mechanisms and Considerations for Training.

    Science.gov (United States)

    Hedayatpour, Nosratollah; Falla, Deborah

    2015-01-01

    Eccentric exercise is characterized by initial unfavorable effects such as subcellular muscle damage, pain, reduced fiber excitability, and initial muscle weakness. However, stretch combined with overload, as in eccentric contractions, is an effective stimulus for inducing physiological and neural adaptations to training. Eccentric exercise-induced adaptations include muscle hypertrophy, increased cortical activity, and changes in motor unit behavior, all of which contribute to improved muscle function. In this brief review, neuromuscular adaptations to different forms of exercise are reviewed, the positive training effects of eccentric exercise are presented, and the implications for training are considered.

  19. Physiological and Neural Adaptations to Eccentric Exercise: Mechanisms and Considerations for Training

    Directory of Open Access Journals (Sweden)

    Nosratollah Hedayatpour

    2015-01-01

    Full Text Available Eccentric exercise is characterized by initial unfavorable effects such as subcellular muscle damage, pain, reduced fiber excitability, and initial muscle weakness. However, stretch combined with overload, as in eccentric contractions, is an effective stimulus for inducing physiological and neural adaptations to training. Eccentric exercise-induced adaptations include muscle hypertrophy, increased cortical activity, and changes in motor unit behavior, all of which contribute to improved muscle function. In this brief review, neuromuscular adaptations to different forms of exercise are reviewed, the positive training effects of eccentric exercise are presented, and the implications for training are considered.

  20. Preconditioning by light-load eccentric exercise is equally effective as low-level laser therapy in attenuating exercise-induced muscle damage in collegiate men

    Directory of Open Access Journals (Sweden)

    Nausheen S

    2017-09-01

    Full Text Available Samar Nausheen,1 Jamal Ali Moiz,1 Shahid Raza,1 Mohammad Yakub Shareef,2 Shahnawaz Anwer,3,4 Ahmad H Alghadir3 1Centre for Physiotherapy and Rehabilitation Sciences, Jamia Millia Islamia, New Delhi, India; 2Faculty of Dentistry, Jamia Millia Islamia, New Delhi, India; 3Rehabilitation Research Chair, College of Applied Medical Sciences, King Saud University, Riyadh, Saudi Arabia; 4Dr. D. Y. Patil College of Physiotherapy, Dr. D. Y. Patil Vidyapeeth, Pune, India Background/objective: Previous studies have already reported an independent effect of light-load eccentric exercise (10% eccentric exercise contraction [EEC] and low-level laser therapy (LLLT as a protective measure against more strenuous eccentric exercise. However, the difference between these two interventions is largely unknown. Therefore, the present study aimed to compare the preconditioning effect of 10% EEC vs. LLLT on subjective, physiological, and biochemical markers of muscle damage in elbow flexors in collegiate men.Methods: All 36 enrolled subjects were randomly assigned to either 10% EEC or LLLT group. Subjects in 10% EEC group performed 30 repetitions of an eccentric exercise with 10% maximal voluntary contraction strength 2 days prior to maximal eccentric exercise bout, whereas subjects in LLLT group were given LLLT. All the indirect markers of muscle damage were measured pre-exercise and at 24, 48, and 72 hours after the exercise-induced muscle damage protocol.Results: The muscle soreness was reduced in both groups (p = 0.024; however, soreness was attenuated more in LLLT group at 48 hours (33.5 vs. 42.7, p = 0.004. There was no significant difference between the effect of 10% EEC and LLLT groups on other markers of muscle damage like a maximum voluntary isometric contraction (p = 0.47, range of motion (p = 0.16, upper arm circumference (p = 0.70, creatine kinase (p = 0.42, and lactate dehydrogenase (p = 0.08. Within-group analysis showed both interventions provided

  1. Muscle-Tendon Unit Properties during Eccentric Exercise Correlate with the Creatine Kinase Response

    Directory of Open Access Journals (Sweden)

    Kirsty M. Hicks

    2017-09-01

    Full Text Available Aim: The aim of this paper was to determine whether; (1 patella tendon stiffness, (2 the magnitude of vastus lateralis fascicle lengthening, and (3 eccentric torque correlate with markers of exercise induced muscle damage.Method: Combining dynamometry and ultrasonography, patella tendon properties and vastus lateralis architectural properties were measured pre and during the first of six sets of 12 maximal voluntary eccentric knee extensions. Maximal isometric torque loss and creatine kinase activity were measured pre-damage (−48 h, 48, 96, and 168 h post-damage as markers of exercise-induced muscle damage.Results: A significant increase in creatine kinase (883 ± 667 UL and a significant reduction in maximal isometric torque loss (21% was reported post-eccentric contractions. Change in creatine kinase from pre to peak significantly correlated with the relative change in vastus lateralis fascicle length during eccentric contractions (r = 0.53, p = 0.02 and with eccentric torque (r = 0.50, p = 0.02. Additionally, creatine kinase tended to correlate with estimated patella tendon lengthening during eccentric contractions (p < 0.10. However, creatine kinase did not correlate with resting measures of patella tendon properties or vastus lateralis properties. Similarly, torque loss did not correlate with any patella tendon or vastus lateralis properties at rest or during eccentric contractions.Conclusion: The current study demonstrates that the extent of fascicle strain during eccentric contractions correlates with the magnitude of the creatine kinase response. Although at rest, there is no relationship between patella tendon properties and markers of muscle damage; during eccentric contractions however, the patella tendon may play a role in the creatine kinase response following EIMD.

  2. Decomposition of surface EMG signals from cyclic dynamic contractions.

    Science.gov (United States)

    De Luca, Carlo J; Chang, Shey-Sheen; Roy, Serge H; Kline, Joshua C; Nawab, S Hamid

    2015-03-15

    Over the past 3 decades, various algorithms used to decompose the electromyographic (EMG) signal into its constituent motor unit action potentials (MUAPs) have been reported. All are limited to decomposing EMG signals from isometric contraction. In this report, we describe a successful approach to decomposing the surface EMG (sEMG) signal collected from cyclic (repeated concentric and eccentric) dynamic contractions during flexion/extension of the elbow and during gait. The increased signal complexity introduced by the changing shapes of the MUAPs due to relative movement of the electrodes and the lengthening/shortening of muscle fibers was managed by an incremental approach to enhancing our established algorithm for decomposing sEMG signals obtained from isometric contractions. We used machine-learning algorithms and time-varying MUAP shape discrimination to decompose the sEMG signal from an increasingly challenging sequence of pseudostatic and dynamic contractions. The accuracy of the decomposition results was assessed by two verification methods that have been independently evaluated. The firing instances of the motor units had an accuracy of ∼90% with a MUAP train yield as high as 25. Preliminary observations from the performance of motor units during cyclic contractions indicate that during repetitive dynamic contractions, the control of motor units is governed by the same rules as those evidenced during isometric contractions. Modifications in the control properties of motoneuron firings reported by previous studies were not confirmed. Instead, our data demonstrate that the common drive and hierarchical recruitment of motor units are preserved during concentric and eccentric contractions.

  3. Supplementation with a whey protein hydrolysate enhances recovery of muscle force-generating capacity following eccentric exercise.

    Science.gov (United States)

    Buckley, Jonathan D; Thomson, Rebecca L; Coates, Alison M; Howe, Peter R C; DeNichilo, Mark O; Rowney, Michelle K

    2010-01-01

    There is evidence that protein hydrolysates can speed tissue repair following damage and may therefore be useful for accelerating recovery from exercise induced muscle damage. The potential for a hydrolysate (WPI(HD)) of whey protein isolate (WPI) to speed recovery following eccentric exercise was evaluated by assessing effects on recovery of peak isometric torque (PIT). In a double-blind randomised parallel trial, 28 sedentary males had muscle soreness (MS), serum creatine kinase (CK) activity, plasma TNFalpha, and PIT assessed at baseline and after 100 maximal eccentric contractions (ECC) of their knee extensors. Participants then consumed 250 ml of flavoured water (FW; n=11), or FW containing 25 g WPI (n=11) or 25 g WPI(HD) (n=6) and the assessments were repeated 1, 2, 6 and 24h later. PIT decreased approximately 23% following ECC, remained suppressed in FW and WPI, but recovered fully in WPI(HD) by 6h (P=0.006, treatment x time interaction). MS increased following ECC (P0.45). WPI(HD) may be a useful supplement for assisting athletes to recover from fatiguing eccentric exercise. Copyright (c) 2008 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

  4. Changes in the mechanical properties of human and amphibian muscle after eccentric exercise.

    Science.gov (United States)

    Jones, C; Allen, T; Talbot, J; Morgan, D L; Proske, U

    1997-01-01

    Following a series of eccentric contractions, that is stretching of the muscle while generating active tension, the length-tension relationship of isolated amphibian muscle has been shown to shift towards longer muscle length (Katz 1939; Wood et al. 1993). Here we report observations of electrically stimulated ankle extensor muscles of nine human subjects, demonstrating a similar shift in optimum angle for torque generation [3.9 (1.5) degrees] following exercise on an inclined treadmill that involved eccentric contractions in one leg. (All values are means with the SEMs in parentheses). The shift in the unexercised, control leg was significantly less [mean 0.4 (0.7) degree P post-exercise, while torque took a week to recover. A similar shift in optimum length [12 (1.3)% of rest length] was obtained for five toad (Bufo marinus) sartorius muscles subjected to 25 eccentric contractions. Isometrically contracted control muscles showed a smaller shift [3.5 (1.6)%, n = 5]. Accompanying the shift was a drop in tension of 46 (3)% after the eccentric contractions [control isometric, 23 (6)%, P < 0.0001]. By 5 h after the eccentric contractions the shift had returned to control values, while tension had not recovered. When viewed with an electron microscope, sartorius muscles fixed immediately after the eccentric contractions exhibited many small, and a few larger, regions of myofilament disruption. In muscles fixed 5 h after the contractions, no small regions of disruption were visible, and the number of large regions was no greater than in those muscles fixed immediately after the eccentric contractions. These disruptions are interpreted as the cause of the shift in length-tension relationship.

  5. Eccentric exercise: mechanisms and effects when used as training regime or training adjunct.

    Science.gov (United States)

    Vogt, Michael; Hoppeler, Hans H

    2014-06-01

    The aim of the current review is to discuss applications and mechanism of eccentric exercise in training regimes of competitive sports. Eccentric muscle work is important in most sports. Eccentric muscle contractions enhance the performance during the concentric phase of stretch-shortening cycles, which is important in disciplines like sprinting, jumping, throwing, and running. Muscles activated during lengthening movements can also function as shock absorbers, to decelerate during landing tasks or to precisely deal with high external loading in sports like alpine skiing. The few studies available on trained subjects reveal that eccentric training can further enhance maximal muscle strength and power. It can further optimize muscle length for maximal tension development at a greater degree of extension, and has potential to improve muscle coordination during eccentric tasks. In skeletal muscles, these functional adaptations are based on increases in muscle mass, fascicle length, number of sarcomeres, and cross-sectional area of type II fibers. Identified modalities for eccentric loading in athletic populations involve classical isotonic exercises, accentuated jumping exercises, eccentric overloading exercises, and eccentric cycle ergometry. We conclude that eccentric exercise offers a promising training modality to enhance performance and to prevent injuries in athletes. However, further research is necessary to better understand how the neuromuscular system adapts to eccentric loading in athletes. Copyright © 2014 the American Physiological Society.

  6. 整复手法结合抗阻离心收缩治疗脊神经后支源性腰痛的临床研究%Clinical study of manipulation and resistance eccentric contraction in the treatment of low back pain

    Institute of Scientific and Technical Information of China (English)

    张横滔; 王金叶; 肖洪波

    2013-01-01

    Objective To study the method of manipulation combined with resistance eccentric contraction of the posterior branch of spi -nal nerve origin low back pain patients. Methods With back muscle resistance of eccentric exercise at the same time ,29 cases of posterior branch of spinal nerve source lumbago patients were treated by adjusting the manipulation of vertebrae . Before treatment ,4 weeks and 3 months after the treatment we respectively used the visual analogue scale (VAS)and Oswestry disability index (ODI) to evaluate the degree of pain and dysfunction. Results Compared with the condition before treatment , at the end of 4 weeks after treatment and follow -up, pain degree of patients significantly reduced (P <0.05) ;patients with dysfunction was significantly improved (P <0.05). Conclusion The method of manipulation combined with lumbar muscle resistance eccentric contraction training is a safe and effective treatment for spinal nerve damage of posterior ramus of spinal nerve posterior branch of lumbar .%目的 研究整复手法结合抗阻离心收缩对脊神经后支源性腰痛患者的治疗效果.方法 对29例脊神经后支源性腰痛患者运用整复手法调整脊椎关节的同时进行腰背肌抗阻离心收缩训练,治疗前、治疗4周末以及治疗结束3个月后分别用目测类比评分(VAS)和Oswestry功能障碍指数(ODI)评价其疼痛程度和功能障碍程度.结果 与治疗前相比,治疗4周末及治疗结束3个月后随访时,患者疼痛程度明显减轻(P<0.05);患者功能障碍得到明显改善(P<0.05).结论 整复手法结合腰背肌抗阻离心收缩训练是一种不损害脊神经后支的治疗脊神经后支源性腰痛的安全有效的疗法.

  7. Facilitation of quadriceps activation is impaired following eccentric exercise.

    Science.gov (United States)

    Hedayatpour, N; Arendt-Nielsen, L; Falla, D

    2014-04-01

    Contracting the knee flexor muscles immediately before a maximum voluntary contraction (MVC) of knee extension increases the maximal force that the extensor muscles can exert. It is hypothesized that this phenomenon can be impaired by muscle fiber damage following eccentric exercise [delayed onset muscle soreness (DOMS)]. This study investigates the effect of eccentric exercise and DOMS on knee extension MVC immediately following a reciprocal-resisted knee flexion contraction. Electromyography (EMG) was recorded from the knee extensors and flexors of 12 healthy men during knee extension MVCs performed in a reciprocal (maximal knee extension preceded by resisted knee flexion), and nonreciprocal condition (preceded by relaxation of the knee flexors). At baseline, knee extension MVC force was greater during the reciprocal condition (P eccentric exercise, the MVC force was not different between conditions. Similarly, at baseline, the EMG amplitude of the quadriceps during the MVC was larger for the reciprocal condition (P eccentric exercise abolished the facilitation of force production for the knee extensors, which normally occurs when maximum knee extension is preceded by activation of the knee flexors.

  8. Neuromuscular responses to mild-muscle damaging eccentric exercise in a low glycogen state.

    Science.gov (United States)

    Gavin, James P; Myers, Stephen D; Willems, Mark E T

    2015-02-01

    The aim of this study was to examine the effect of low muscle glycogen on the neuromuscular responses to maximal eccentric contractions. Fourteen healthy men (22 ± 3 years) performed single-leg cycling (20 min at ~75% maximal oxygen uptake (V̇O2 max); eight 90 s sprints at a 1:1 work-to-rest ratio (5% decrements from 90% to 55% V̇O2 max until exhaustion) the evening before 100 eccentric (1.57 rads(-1)) with reduced (RED) and normal glycogen (NORM). Neuromuscular responses were measured during and up to 48 h after with maximal voluntary and involuntary (twitch, 20 Hz and 50 Hz) isometric contractions. During eccentric contractions, peak torque decreased (RED: -16.1 ± 2.5%; NORM: -6.2 ± 5.1%) and EMG frequency increased according to muscle length. EMG activity decreased for RED only. After eccentric contractions, maximal isometric force was reduced up to 24h for NORM (-13.5 ± 5.8%) and 48 h for RED (-7.4 ± 10.9%). Twelve hours after eccentric contractions, twitch force and the 20:50 Hz ratio were decreased for RED but not for NORM. Immediate involuntary with prolonged voluntary force loss suggests that reduced glycogen is associated with increased susceptibility to mild muscle-damaging eccentric exercise with contributions of peripheral and central mechanisms to be different during recovery. Copyright © 2014 Elsevier Ltd. All rights reserved.

  9. Eccentric Binary Millisecond Pulsars

    CERN Document Server

    Freire, Paulo C C

    2009-01-01

    In this paper we review the recent discovery of several millisecond pulsars (MSPs) in eccentric binary systems. Timing these MSPs we were able to estimate (and in one case precisely measure) their masses. These results suggest that, as a class, MSPs have a much wider range of masses (1.3 to > 2 solar masses) than the normal and mildly recycled pulsars found in double neutron star (DNS) systems (1.25 < Mp < 1.44 solar masses). This is very likely to be due to the prolonged accretion episode that is thought to be required to form a MSP. The likely existence of massive MSPs makes them a powerful probe for understanding the behavior of matter at densities larger than that of the atomic nucleus; in particular, the precise measurement of the mass of PSR J1903+0327 ($1.67 +/- 0.01 solar masses) excludes several "soft" equations of state for dense matter.

  10. Quadriceps femoris electromyogram during concentric, isometric and eccentric phases of fatiguing dynamic knee extensions.

    Science.gov (United States)

    Pincivero, Danny M; Gandhi, Varsha; Timmons, Mark K; Coelho, Alan J

    2006-01-01

    The objective of this study was to examine the superficial quadriceps femoris (QF) muscle electromyogram (EMG) during fatiguing knee extensions. Thirty young adults were evaluated for their one-repetition maximum (1RM) during a seated, right-leg, inertial knee extension. All subjects then completed a single set of repeated knee extensions at 50% 1RM, to failure. Subjects performed a knee extension (concentric phase), held the weight with the knee extended for 2s (isometric phase), and lowered the weight in a controlled manner (eccentric phase). Raw EMG of the vastus medialis (VM), vastus lateralis (VL) and rectus femoris (RF) muscles were full-wave rectified, integrated and normalized to the 1RM EMG, for each respective phase and repetition. The EMG median frequency (f(med)) was computed during the isometric phase. An increase in QF muscle EMG was observed during the concentric phase across the exercise duration. VL EMG was greater than the VM and RF muscles during the isometric phase, in which no significant changes occurred in any of the muscles across the exercise duration. A significant decrease in EMG across the exercise duration was observed during the eccentric phase, with the VL EMG greater than the VM and RF muscles. A greater decrease in VL and RF muscle f(med) during the isometric phase, than the VM muscle, was observed with no gender differences. The findings demonstrated differential recruitment of the superficial QF muscle, depending on the contraction mode during dynamic knee extension exercise, where VL muscle dominance appears to manifest across the concentric-isometric-eccentric transition.

  11. The acute effects of flotation restricted environmental stimulation technique on recovery from maximal eccentric exercise.

    Science.gov (United States)

    Morgan, Paul M; Salacinski, Amanda J; Stults-Kolehmainen, Matthew A

    2013-12-01

    Flotation restricted environmental stimulation technique (REST) involves compromising senses of sound, sight, and touch by creating a quiet dark environment. The individual lies supine in a tank of Epsom salt and water heated to roughly skin temperature (34-35° C). This study was performed to determine if a 1-hour flotation REST session would aid in the recovery process after maximal eccentric knee extensions and flexions. Twenty-four untrained male students (23.29 ± 2.1 years, 184.17 ± 6.85 cm, 85.16 ± 11.54 kg) participated in a randomized, repeated measures crossover study. The participants completed 2 exercise and recovery protocols: a 1-hour flotation REST session and a 1-hour seated control (passive recovery). After isometric muscle strength testing, participants were fatigued with eccentric isokinetic muscle contractions (50 repetitions at 60°·s) of the nondominant knee extensors and flexors. Blood lactate, blood glucose, heart rate, OMNI-rating of perceived exertion for resistance exercise (OMNI-RPE), perceived pain, muscle soreness, and isometric strength were collected before exercise, after treatment, and 24 and 48 hours later. A multivariate analysis of covariance found that treatment had a significant main effect on blood lactate, whereas subsequent univariate analyses of variance found statistical significance with the immediate posttreatment blood lactate measures. The results indicate that flotation REST appears to have a significant impact on blood lactate and perceived pain compared with a 1-hour passive recovery session in untrained healthy men. No difference was found between conditions for muscle strength, blood glucose, muscle soreness, heart rate, or OMNI-RPE. Flotation REST may be used for recreational and professional athletes to help reduce blood lactate levels after eccentric exercise.

  12. Muscle changes with eccentric exercise: Implications on earth and in space

    Science.gov (United States)

    Hargens, Alan R.; Parazynski, Scott; Aratow, Michael; Friden, Jan

    1989-01-01

    Recent investigations of fluid pressure, morpholo gy, and enzyme activities of skeletal muscle exercised eccentrically or concentrically in normal human subjects are reviewed. Intramuscular pressures were measured before, during, and after submaximal exercise and correlated with subjective muscle soreness, fiber size, water content, and blood indices of muscle enzymes. High intensity eccentric exercise is characterized by post exercise pain, elevated intramuscular pressures, and swelling of both type 1 and 2 fibers as compared to concentric exercise. Thus, long periods of unaccustomed, high level eccentric contraction may cause muscle injury, fiber swelling, fluid accumulation, elevated intramuscular pressure, and delayed muscle soreness. Training regimens of progressively increasing eccentric exercise, however, cause less soreness and are extremely efficacious in increasing muscle mass and strength. It is proposed that on Earth, postural muscles are uniquely adapted to low levels of prolonged eccentric contraction that are absent during weightlessness. The almost complete absence of eccentric exercise in space may be an important contributor to muscle atrophy and therefore equipment should be designed to integrate eccentric contractions into exercise protocols for long-term spaceflight.

  13. Eccentricity distribution of wide binaries

    CERN Document Server

    Tokovinin, Andrei

    2015-01-01

    A sample of 477 solar-type binaries within 67pc with projected separations larger than 50AU is studied by a new statistical method. Speed and direction of the relative motion are determined from the short observed arcs or known orbits, and their joint distribution is compared to the numerical simulations. By inverting the observed distribution with the help of simulations, we find that average eccentricity of wide binaries is 0.59+-0.02 and the eccentricity distribution can be modeled as f(e) ~= 1.2 e + 0.4. However, wide binaries containing inner subsystems, i.e. triple or higher-order multiples, have significantly smaller eccentricities with the average e = 0.52+-0.05 and the peak at e ~ 0.5. We find that the catalog of visual orbits is strongly biased against large eccentricities. A marginal evidence of eccentricity increasing with separation (or period) is found for this sample. Comparison with spectroscopic binaries proves the reality of the controversial period-eccentricity relation. The average eccentr...

  14. Eccentric exercise in aging and diseased skeletal muscle: good or bad?

    Science.gov (United States)

    Lovering, Richard M; Brooks, Susan V

    2014-06-01

    Evidence is accumulating regarding the benefits of exercise in people who are more susceptible to injury, such as the elderly, or those with a neuromuscular disease, for example Duchenne muscular dystrophy (DMD). There appears to be a consensus that exercise can be safely performed in aging and diseased muscles, but the role of eccentric exercise is not as clear. Eccentric (lengthening) contractions have risks and benefits. Eccentric contractions are commonly performed on a daily basis, and high-force voluntary eccentric contractions are often employed in strength training paradigms with excellent results; however, high-force eccentric contractions are also linked to muscle damage. This minireview examines the benefits and safety issues of using eccentric exercise in at-risk populations. A common recommendation for all individuals is difficult to achieve, and guidelines are still being established. Some form of exercise is generally recommended with aging and even with diseased muscles, but the prescription (frequency, intensity, and duration) and type (resistance vs. aerobic) of exercise requires personal attention, as there is great diversity in the functional level and comorbidities in the elderly and those with neuromuscular disease. Copyright © 2014 the American Physiological Society.

  15. Serial assessment of local peripheral vascular function after eccentric exercise.

    Science.gov (United States)

    Stacy, Mitchel R; Bladon, Kallie J; Lawrence, Jennifer L; McGlinchy, Sarah A; Scheuermann, Barry W

    2013-12-01

    Muscle damage is a common response to unaccustomed eccentric exercise; however, the effects of skeletal muscle damage on local vascular function and blood flow are poorly understood. This study examined serial local vascular responses to flow-mediated (endothelial-dependent) and nitroglycerin-mediated (endothelial-independent) dilation in the brachial artery after strenuous eccentric exercise and serially assessed resting blood flow. Ten healthy males performed 50 maximal eccentric unilateral arm contractions to induce muscle damage to the biceps brachii. Changes in maximal isometric strength and vascular responses were assessed 1, 24, 48, and 96 h after exercise. Mean blood velocities and arterial diameters, measured with Doppler ultrasound, were used to calculate blood flow and shear stress (expressed as area under the curve). Eccentric exercise resulted in impaired maximal isometric strength for up to 96 h (p exercise, 9.4% ± 2.6%; 1 h after exercise, 5.1% ± 2.2%) and nitroglycerin responses (before exercise, 26.3% ± 6.5%; 1 h after exercise, 20.7% ± 4.7%) were observed in the 1 h after exercise and remained lower for 96 h (p exercise and remained impaired for 48 h (p eccentric exercise leads to impaired local endothelial and vascular smooth muscle function. Lower shear stress after exercise might contribute to the observed reduction in flow-mediated dilation responses, but the mechanism responsible for the attenuated endothelial-independent vasodilation remains unclear.

  16. Specific training improves skeletal muscle mitochondrial calcium homeostasis after eccentric exercise.

    Science.gov (United States)

    Rattray, Ben; Thompson, Martin; Ruell, Patricia; Caillaud, Corinne

    2013-02-01

    There is limited understanding of the mitochondrial adaptation following repeated eccentric exercise bouts, a model resulting in muscle adaptation known as the repeat bout effect. It was hypothesized that downhill training would reduce mitochondrial calcium content (MCC) post an acute eccentric bout with concurrent improvements in mitochondrial respiratory function. Thirty-four Sprague-Dawley rats were divided into four groups: control (N), control with acute eccentric exercise (N (ecc)), trained control (X) and trained with acute eccentric exercise (X (ecc)). Training for X and X (ecc) consisted of 30 min per day for five consecutive days of downhill treadmill running. The acute eccentric exercise bout was a -14° treadmill exercise for 90 min performed 2 weeks after the training period. Animals were killed 48 h post-exercise. Isolated mitochondria from the red quadriceps allowed for the measure of mitochondrial respiratory indices and MCC. Calpain activity and heat shock protein 72 expression (HSP72) were also measured. MCC dramatically increased following the acute bout of eccentric exercise in N (ecc) (p eccentric exercise. The results suggest that downhill exercise training improves mitochondrial calcium homeostasis following an acute bout of prolonged eccentric exercise and may stabilize mitochondrial respiratory function. These improvements coincide with a reduction in calpain activity and heat shock protein upregulation.

  17. Eccentric exercise training as a countermeasure to non-weight-bearing soleus muscle atrophy

    Science.gov (United States)

    Kirby, Christopher R.; Ryan, Mirelle J.; Booth, Frank W.

    1992-01-01

    This investigation tested whether eccentric resistance training could prevent soleus muscle atrophy during non-weight bearing. Adult female rats were randomly assigned to either weight bearing +/- intramuscular electrodes or non-weight bearing +/- intramuscular electrodes groups. Electrically stimulated maximal eccentric contractions were performed on anesthetized animals at 48-h intervals during the 10-day experiment. Non-weight bearing significantly reduced soleus muscle wet weight (28-31 percent) and noncollagenous protein content (30-31 percent) compared with controls. Eccentric exercise training during non-weight bearing attenuated but did not prevent the loss of soleus muscle wet weight and noncollagenous protein by 77 and 44 percent, respectively. The potential of eccentric exercise training as an effective and highly efficient counter-measure to non-weight-bearing atrophy is demonstrated in the 44 percent attenuation of soleus muscle noncollagenous protein loss by eccentric exercise during only 0.035 percent of the total non-weight-bearing time period.

  18. Eccentric exercise training as a countermeasure to non-weight-bearing soleus muscle atrophy

    Science.gov (United States)

    Kirby, Christopher R.; Ryan, Mirelle J.; Booth, Frank W.

    1992-01-01

    This investigation tested whether eccentric resistance training could prevent soleus muscle atrophy during non-weight bearing. Adult female rats were randomly assigned to either weight bearing +/- intramuscular electrodes or non-weight bearing +/- intramuscular electrodes groups. Electrically stimulated maximal eccentric contractions were performed on anesthetized animals at 48-h intervals during the 10-day experiment. Non-weight bearing significantly reduced soleus muscle wet weight (28-31 percent) and noncollagenous protein content (30-31 percent) compared with controls. Eccentric exercise training during non-weight bearing attenuated but did not prevent the loss of soleus muscle wet weight and noncollagenous protein by 77 and 44 percent, respectively. The potential of eccentric exercise training as an effective and highly efficient counter-measure to non-weight-bearing atrophy is demonstrated in the 44 percent attenuation of soleus muscle noncollagenous protein loss by eccentric exercise during only 0.035 percent of the total non-weight-bearing time period.

  19. Strength gain through eccentric isotonic training without changes in clinical signs or blood markers.

    Science.gov (United States)

    Alves, Thâmara; Guarnier, Flávia A; Campoy, Fernanda A S; Gois, Mariana O; Albuquerque, Maíra C; Seraphim, Patrícia M; Netto, Jayme; Vanderlei, Luiz Carlos Marques; Padovani, Carlos R; Cecchini, Rubens; Pastre, Carlos Marcelo

    2013-11-21

    Localized exercises are widely used in rehabilitation processes. The predominant options are exercises with an emphasis on either concentric or eccentric contractions. Eccentric exercises promote greater strength gains compared to classical concentric stimuli, but can cause muscle damage. The aim of present study was to compare strength training composed of 10 sessions with progressive loads between groups with a predominance of concentric versus eccentric contraction through an analysis of isotonic strength, pressure pain threshold, creatine kinase, tumor necrosis factor-alpha and cortisol. One hundred twenty male subjects were divided into four groups: C1 and E1--single session of maximum strength with emphasis on concentric and eccentric contraction, respectively; C10 and E10--10 sessions with progressive loads from 80% to maximum strength with emphasis on concentric and eccentric contraction, respectively. Isotonic strength increased by 10% in E10 following the ten training sessions. C1 and E1 exhibited a lower pressure pain threshold 48 hours after the sessions in comparison to C10 and E10, respectively. Creatine kinase was increased in C1 in comparison to baseline, with significant differences (p ≤ 0.05) in comparison to E1 at 48 and 96 hours as well as C10 at 48, 72 and 96 hours. No significant differences were found in TNF-α or cortisol among the groups or evaluation times. Eccentric contraction training promotes functional adaptation. Moreover, both concentric and eccentric contraction training have a protective effect on the muscle in relation to a single session of maximum strength exercise. RBR-75scwh.

  20. The role of eccentric regime of leg muscle work in alpine skiing

    Directory of Open Access Journals (Sweden)

    Ropret Robert

    2017-01-01

    Full Text Available Alpine skiing is characterized by a great number of leg movements with muscle contractions in eccentric regime. The role of these movements is to absorb gravitation and inertial forces, manage skis more precisely and maintain balance. Recent studies have determined the volume, duration and intenisty of eccentric contractions as well as the basic characteristics of movement amplitudes and velocities. Based on the previous findings the experiments involving eccentric training using a bicycle ergometer confirmed a positive impact that this kind of training has on increasing maximum power, strength, endurance, coordination, injury prevention, metabolic work efficiency, more efficient work with longer muscle length and its role in miming skiers' movements. This paper is an review of the studies so far in the field of kinematics, skiing dynamics and the effect of eccentric training on the development of athletes' performances.

  1. Impact of the pay-for-performance contract and the management of hypertension in Scottish primary care: a 6-year population-based repeated cross-sectional study.

    LENUS (Irish Health Repository)

    Simpson, Colin R

    2011-07-01

    The 2004 introduction of the pay-for-performance contract has increased the proportion of income that GPs are able to earn by targeting quality care to patients with chronic diseases such as hypertension.

  2. Motor unit activity after eccentric exercise and muscle damage in humans.

    Science.gov (United States)

    Semmler, J G

    2014-04-01

    It is well known that unaccustomed eccentric exercise leads to muscle damage and soreness, which can produce long-lasting effects on muscle function. How this muscle damage influences muscle activation is poorly understood. The purpose of this brief review is to highlight the effect of eccentric exercise on the activation of muscle by the nervous system, by examining the change in motor unit activity obtained from surface electromyography (EMG) and intramuscular recordings. Previous research shows that eccentric exercise produces unusual changes in the EMG–force relation that influences motor performance during isometric, shortening and lengthening muscle contractions and during fatiguing tasks. When examining the effect of eccentric exercise at the single motor unit level, there are substantial changes in recruitment thresholds, discharge rates, motor unit conduction velocities and synchronization, which can last for up to 1 week after eccentric exercise. Examining the time course of these changes suggests that the increased submaximal EMG after eccentric exercise most likely occurs through a decrease in motor unit conduction velocity and an increase in motor unit activity related to antagonist muscle coactivation and low-frequency fatigue. Furthermore, there is a commonly held view that eccentric exercise produces preferential damage to high-threshold motor units, but the evidence for this in humans is limited. Further research is needed to establish whether there is preferential damage to high-threshold motor units after eccentric exercise in humans, preferably by linking changes in motor unit activity with estimates of motor unit size using selective intramuscular recording techniques.

  3. Eccentricity distribution in the main asteroid belt

    CERN Document Server

    Malhotra, Renu

    2016-01-01

    The observationally complete sample of the main belt asteroids now spans more than two orders of magnitude in size and numbers more than 64,000 (excluding collisional family members). We undertook an analysis of asteroids' eccentricities and their interpretation with simple physical models. We find that Plummer's (1916) conclusion that the asteroids' eccentricities follow a Rayleigh distribution holds for the osculating eccentricities of large asteroids, but the proper eccentricities deviate from a Rayleigh distribution: there is a deficit of eccentricities smaller than $\\sim0.1$ and an excess of larger eccentricities. We further find that the proper eccentricities do not depend significantly on asteroid size but have strong dependence on heliocentric distance: the outer asteroid belt follows a Rayleigh distribution, but the inner belt is strikingly different. Eccentricities in the inner belt can be modeled as a vector sum of a primordial eccentricity vector of random orientation and magnitude drawn from a Ra...

  4. Eccentric exercise as an adjuvant to influenza vaccination in humans.

    Science.gov (United States)

    Edwards, Kate M; Burns, Victoria E; Allen, Louise M; McPhee, Jamie S; Bosch, Jos A; Carroll, Douglas; Drayson, Mark; Ring, Christopher

    2007-02-01

    The immune response to vaccination in animals can be enhanced by exposure to acute stress at the time of vaccination. The efficacy of this adjuvant strategy for vaccination in humans requires investigation. The current study employed a randomised controlled trial design to examine the effects of eccentric exercise prior to influenza vaccination on the antibody and cell-mediated responses. Sixty young healthy adults (29 men, 31 women) performed eccentric contractions of the deltoid and biceps brachii muscles of the non-dominant arm (exercise group) or rested quietly (control group), and were vaccinated 6h later in the non-dominant arm. Change in arm circumference and pain were measured to assess the physiological response to exercise. Antibody titres were measured pre-vaccination and at 6- and 20-week follow-ups. Interferon-gamma in response to in vitro stimulation by the whole vaccine, an index of the cell-mediated response, was measured 8 weeks post-vaccination. Interferon-gamma responses were enhanced by exercise in men, whereas antibody titres were enhanced by eccentric exercise in women but not in men. Men showed greater increase in arm circumference after eccentric exercise than women but there was no difference in reported pain. The interferon-gamma response was positively associated with the percentage increase in arm circumference among the exercise group. Eccentric exercise exerted differential effects on the response to vaccination in men and women, with enhancement of the antibody response in women, but enhancement of the cell-mediated response in men. Eccentric exercise of the muscle at the site of vaccine administration should be explored further as a possible behavioural adjuvant to vaccination.

  5. Super-Eccentric Migrating Jupiters

    CERN Document Server

    Socrates, Aristotle; Dong, Subo; Tremaine, Scott

    2011-01-01

    An important class of formation theories for hot Jupiters involves the excitation of extreme orbital eccentricity (e=0.99 or even larger) followed by tidal dissipation at periastron passage that eventually circularizes the planetary orbit at a period less than 10 days. In a steady state, this mechanism requires the existence of a significant population of super-eccentric (e>0.9) migrating Jupiters with long orbital periods and periastron distances of only a few stellar radii. For these super-eccentric planets, the periastron is fixed due to conservation of orbital angular momentum and the energy dissipated per orbit is constant, implying that the rate of change in semi-major axis a is \\dot a \\propto a^0.5 and consequently the number distribution satisfies dN/dlog a\\propto a^0.5. If this formation process produces most hot Jupiters, Kepler should detect several super-eccentric migrating progenitors of hot Jupiters, allowing for a test of high-eccentricity migration scenarios.

  6. SUPER-ECCENTRIC MIGRATING JUPITERS

    Energy Technology Data Exchange (ETDEWEB)

    Socrates, Aristotle; Katz, Boaz; Dong Subo; Tremaine, Scott [Institute for Advanced Study, Princeton, NJ 08540 (United States)

    2012-05-10

    An important class of formation theories for hot Jupiters involves the excitation of extreme orbital eccentricity (e = 0.99 or even larger) followed by tidal dissipation at periastron passage that eventually circularizes the planetary orbit at a period less than 10 days. In a steady state, this mechanism requires the existence of a significant population of super-eccentric (e > 0.9) migrating Jupiters with long orbital periods and periastron distances of only a few stellar radii. For these super-eccentric planets, the periastron is fixed due to conservation of orbital angular momentum and the energy dissipated per orbit is constant, implying that the rate of change in semi-major axis a is a-dot {proportional_to}a{sup 1/2} and consequently the number distribution satisfies dN/d log a{proportional_to}a{sup 1/2}. If this formation process produces most hot Jupiters, Kepler should detect several super-eccentric migrating progenitors of hot Jupiters, allowing for a test of high-eccentricity migration scenarios.

  7. Velocity-specific strength recovery after a second bout of eccentric exercise.

    Science.gov (United States)

    Barss, Trevor S; Magnus, Charlene R A; Clarke, Nick; Lanovaz, Joel L; Chilibeck, Philip D; Kontulainen, Saija A; Arnold, Bart E; Farthing, Jonathan P

    2014-02-01

    A bout of eccentric exercise (ECC) has the protective effect of reducing muscle damage during a subsequent bout of ECC known as the "repeated bout effect" (RBE). The purpose of this study was to determine if the RBE is greater when both bouts of ECC are performed using the same vs. different velocity of contraction. Thirty-one right-handed participants were randomly assigned to perform an initial bout of either fast (3.14 rad·s [180°·s]) or slow (0.52 rad·s [30°·s]) maximal isokinetic ECCs of the elbow flexors. Three weeks later, the participants completed another bout of ECC at the same velocity (n = 16), or at a different velocity (n = 15). Indirect muscle damage markers were measured before, immediately after, and at 24, 48, and 72 hours postexercise. Measures included maximal voluntary isometric contraction (MVC) strength (dynamometer), muscle thickness (MT; ultrasound), delayed onset muscle soreness (DOMS; visual analog scale), biceps and triceps muscle activation amplitude (electromyography), voluntary activation (interpolated twitch), and twitch torque. After the repeated bout, MVC strength recovered faster compared with the same time points after the initial bout for only the same velocity group (p = 0.017), with no differences for all the other variables. Irrespective of velocity, MT and DOMS were reduced after the repeated bout compared with that of the initial bout at 24, 48, and 72 hours with a corresponding increase in TT at 72 hours (p effects contribute to the RBE. The current findings support the idea of multiple mechanisms contributing to the RBE.

  8. Eccentricity evolution in hierarchical triple systems with eccentric outer binaries

    CERN Document Server

    Georgakarakos, Nikolaos

    2014-01-01

    We develop a technique for estimating the inner eccentricity in hierarchical triple systems, with the inner orbit being initially circular, while the outer one is eccentric. We consider coplanar systems with well separated components and comparable masses. The derivation of short period terms is based on an expansion of the rate of change of the Runge-Lenz vector. Then, the short period terms are combined with secular terms, obtained by means of canonical perturbation theory. The validity of the theoretical equations is tested by numerical integrations of the full equations of motion.

  9. EFFECTIVENESS OF CONCENTRIC AND ECCENTRIC RESISTANCE TRAINING OF QUADRICEPS AND HAMSTRINGS ON MUSCLE STRENGTH, ROM, AND PAIN IN ACL RECONSTRUCTED SUBJECTS

    Directory of Open Access Journals (Sweden)

    G. Hari Babu

    2014-10-01

    Full Text Available Background: Ligament injury accounts for nearly 40% of all injury problems in anterior cruciate ligament injury constitute nearly 50% of all knee ligament injuries. Anterior cruciate ligament deficiency affects not only the mobility, self-confidence and lifestyle of the affected persons in short term but also causes arithmetic changes in the affected knee in the long run. Purpose of study to find the effectiveness of concentric and eccentric for post anterior cruciate ligament reconstruction subjects on muscle strength, joint range of motion and pain. Methods: 24 samples with age group of 35 years were randomly assigned to two groups Concentric and Eccentric groups. The Concentric group, performed 9 (3sets concentric contractions for knee extensors and 9 concentric contractions for knee flexor muscles. The eccentric group done 9 (3 sets eccentric contractions for knee extensors and 9 eccentric contractions for knee flexors. Results: Pain is significantly decreased in concentric group. But not significantly decreased in eccentric group (t = 2.85, P = 0.009; and t = 1.40; P = 0.17. The range of motion is significantly increased in both concentric knee extension and flexion and eccentric knee extension and flexion (t = 3.53, P = 0.0023; and t = 4.55; P < 0.001. The quadriceps muscle strength is significantly improved in both concentric and eccentric groups at 60° / sec and 90° / sec. Conclusion: The eccentric exercises are better than concentric exercises in improving the strength of hamstring and quadriceps muscles.

  10. Titan's Eccentricity Tides

    Science.gov (United States)

    Iess, L.; Jacobson, R.; Ducci, M.; Stevenson, D. J.; Lunine, J. I.; Armstrong, J. W.; Asmar, S.; Racioppa, P.; Rappaport, N. J.; Tortora, P.

    2011-12-01

    The large eccentricity (e=0.03) of Titan's orbit causes significant variations in the tidal field from Saturn and induces periodic stresses in the satellite body at the orbital period (about 16 days). Peak-to-peak variations of the tidal field (from pericenter to apocenter) are about 18% (6e). If Titan hosts a liquid layer (such as an internal ocean), the gravity field would exhibit significant periodic variations. The response of the body to fast variations of the external, perturbing field is controlled by the Love numbers, defined for each spherical harmonic as the ratio between the perturbed and perturbing potential. For Titan the largest effect is by far on the quadrupole field, and the corresponding Love number is indicated by k2 (assumed to be identical for all degree 2 harmonics). Models of Titan's interior generally envisage a core made up of silicates, surrounded by a layer of high pressure ice, possibly a liquid water or water-ammonia ocean, and an ice-I outer shell, with variations associated with the dehydration state of the core or the presence of mixed rock-ice layers. Previous analysis of Titan's tidal response [1] shows that k2 depends crucially on the presence or absence of an internal ocean. k2 was found to vary from about 0.03 for a purely rocky interior to 0.48 for a rigid rocky core surrounded by an ocean and a thin (20 km) ice shell. A large k2 entails changes in the satellite's quadrupole coefficients by a few percent, enough to be detected by accurate range rate measurements of the Cassini spacecraft. So far, of the many Cassini's flybys of Titan, six were used for gravity measurements. During gravity flybys the spacecraft is tracked from the antennas of NASA's Deep Space Network using microwave links at X- and Ka-band frequencies. A state-of-the-art instrumentation enables range rate measurements accurate to 10-50 micron/s at integration times of 60 s. The first four flybys provided the static gravity field and the moment of inertia factor

  11. A new kinematical definition of orbital eccentricity

    Directory of Open Access Journals (Sweden)

    Ninković S.

    2009-01-01

    Full Text Available A new concept of orbital eccentricity is given. The dimensionless quantities proposed in the present paper to serve as orbital eccentricities have a kinematical nature. The purpose is to use them in describing the motion for the case of three-dimensional orbits. A comparison done for nearly planar orbits shows that the values of the eccentricities proposed here do not differ significantly from those corresponding to the eccentricities of geometric nature usually applied.

  12. Repeated blood flow restriction induces muscle fiber hypertrophy.

    Science.gov (United States)

    Sudo, Mizuki; Ando, Soichi; Kano, Yutaka

    2017-02-01

    We recently developed an animal model to investigate the effects of eccentric contraction (ECC) and blood flow restriction (BFR) on muscle tissue at the cellular level. This study clarified the effects of repeated BFR, ECC, and BFR combined with ECC (BFR+ECC) on muscle fiber hypertrophy. Male Wistar rats were assigned to 3 groups: BFR, ECC, and BFR+ECC. The contralateral leg in the BFR group served as a control (CONT). Muscle fiber cross-sectional area (CSA) of the tibialis anterior was determined after the respective treatments for 6 weeks. CSA was greater in the BFR+ECC group than in the CONT (P muscle fiber hypertrophy at the cellular level. Muscle Nerve 55: 274-276, 2017. © 2016 Wiley Periodicals, Inc.

  13. Plasma Actin, Gelsolin and Orosomucoid Levels after Eccentric Exercise.

    Science.gov (United States)

    Tékus, Éva; Váczi, Márk; Horváth-Szalai, Zoltán; Ludány, Andrea; Kőszegi, Tamás; Wilhelm, Márta

    2017-02-01

    The present study investigated the acute effect of eccentric exercise on blood plasma actin, gelsolin (GSN) and orosomucoid (AGP) levels in untrained and moderately trained individuals, and their correlation with exercise induced muscle damage (EIMD) markers (CK, intensity of muscle soreness and maximal voluntary contraction torque deficit). Healthy physical education students (6 untrained, 12 moderately trained) participated in this research. Actin, GSN, AGP and CK levels were measured in blood plasma at baseline, immediately, 1 h, 6 h and 24 h post-exercise comprising 90 eccentric quadriceps contractions performed on a dynamometer. There was significant time main effect for GSN, AGP, CK and significant difference was found between baseline and the lowest value of post-exercise GSN (p exercise AGP (p exercise and CK activity at 6 h, p exercise, p eccentric exercise do not seem sensitive to training status. The plasma actin level is used as an indicator of injury, however, our results suggest that it is not an accurate marker of EIMD, while plasma GSN concentrations show a better relationship with EIMD and the post-exercise inflammatory process. The elevated plasma AGP and the correlation between GSN and AGP seem to be promising for assessment of exercise-induced muscle injury.

  14. ECCENTRIC JUPITERS VIA DISK–PLANET INTERACTIONS

    Energy Technology Data Exchange (ETDEWEB)

    Duffell, Paul C.; Chiang, Eugene, E-mail: duffell@berkeley.edu, E-mail: echiang@astro.berkeley.edu [Department of Astronomy and Theoretical Astrophysics Center, University of California, Berkeley (United States)

    2015-10-20

    Numerical hydrodynamics calculations are performed to determine the conditions under which giant planet eccentricities can be excited by parent gas disks. Unlike in other studies, Jupiter-mass planets are found to have their eccentricities amplified—provided their orbits start off as eccentric. We disentangle the web of co-rotation, co-orbital, and external resonances to show that this finite-amplitude instability is consistent with that predicted analytically. Ellipticities can grow until they reach of order of the disk's aspect ratio, beyond which the external Lindblad resonances that excite eccentricity are weakened by the planet's increasingly supersonic epicyclic motion. Forcing the planet to still larger eccentricities causes catastrophic eccentricity damping as the planet collides into gap walls. For standard parameters, the range of eccentricities for instability is modest; the threshold eccentricity for growth (∼0.04) is not much smaller than the final eccentricity to which orbits grow (∼0.07). If this threshold eccentricity can be lowered (perhaps by non-barotropic effects), and if the eccentricity driving documented here survives in 3D, it may robustly explain the low-to-moderate eccentricities ≲0.1 exhibited by many giant planets (including Jupiter and Saturn), especially those without planetary or stellar companions.

  15. Effect of eccentric exercise-induced muscle damage on electromyographyic activity of quadriceps in untrained healthy females.

    Science.gov (United States)

    Rezaei, Mandana; Ebrahimi-Takamjani, Ismael; Jamshidi, Ali A; Vassaghi-Gharamaleki, Behnoush; Hedayatpour, Nosratollah; Havaei, Naser

    2014-01-01

    The aim of this study was to investigate muscle damage indicators and electromyography activities of quadriceps muscles at 25° of hip flexion in untrained healthy females after an eccentric exercise induced muscle fiber damage. A total of 14 healthy females participated in this pre-experimental study. The subjects performed maximal eccentric quadriceps contractions at 25˚ of hip flexion. Maximum voluntary extensor isometric and concentric moments, angle of maximum moment for concentric contractions, perceived pain intensity, and pain pressure threshold were examined before, immediately, 48 hours, 120 hours and 14 days after eccentric exercise. Additionally, electromyography of three parts of quadriceps muscle, knee flexion range of motion and thigh circumference were measured before and after eccentric exercise. Significant reductions in maximum isometric moment and maximum concentric moment were observed at angular velocity of 60˚ per sec immediately after eccentric exercise (peccentric exercise. Increased pain intensity and decreased knee joint range of motion manifested 48 hours after eccentric exercise. Pain pressure threshold for the quadriceps was higher 14 days after exercise as compared to 48 and 120 hours (p0.05). Eccentric exercise performed at 25˚ of hip flexion resulted in muscle fiber injuries within the quadriceps muscle. However, electromyography of quadriceps muscle was not significantly different than the baseline. The result indicates that hip joint position may modify the effect of eccentric exercise on muscle activation.

  16. Subcellular fractionation reveals HSP72 does not associate with SERCA in human skeletal muscle following damaging eccentric and concentric exercise.

    Science.gov (United States)

    Frankenberg, Noni T; Lamb, Graham D; Vissing, Kristian; Murphy, Robyn M

    2014-06-01

    Through its upregulation and/or translocation, heat shock protein 72 (HSP72) is involved in protection and repair of key proteins after physiological stress. In human skeletal muscle we investigated HSP72 protein after eccentric (ECC1) and concentric (CONC) exercise and repeated eccentric exercise (ECC2; 8 wk later) and whether it translocated from its normal cytosolic location to membranes/myofibrils. HSP72 protein increased ~2-fold 24 h after ECC1, with no apparent change after CONC or ECC2. In resting (nonstressed) human skeletal muscle the total pool of HSP72 protein was present almost exclusively in the cytosolic fraction, and after each exercise protocol the distribution of HSP72 protein remained unaltered. Overall, the amount of HSP72 protein in the cytosol increased 24 h after ECC1, matching the fold increase that was measured in total HSP72 protein. To better ascertain the capabilities and limitations of HSP72, using quantitative Western blotting we determined the HSP72 protein content to be 11.4 μmol/kg wet weight in resting human vastus lateralis muscle, which is comprised of Type I (slow-twitch) and Type II (fast-twitch) fibers. HSP72 protein content was similar in individual Type I or II fiber segments. After physiological stress, HSP72 content can increase and, although the functional consequences of increased amounts of HSP72 protein are poorly understood, it has been shown to bind to and protect protein pumps like SERCA and Na(+)-K(+)-ATPase. Given no translocation of cytosolic HSP72, these findings suggest eccentric contractions, unlike other forms of stress such as heat, do not trigger tight binding of HSP72 to its primary membrane-bound target proteins, in particular SERCA. Copyright © 2014 the American Physiological Society.

  17. Neuromuscular and muscle-tendon system adaptations to isotonic and isokinetic eccentric exercise.

    Science.gov (United States)

    Guilhem, G; Cornu, C; Guével, A

    2010-06-01

    To present the properties of an eccentric contraction and compare neuromuscular and muscle-tendon system adaptations induced by isotonic and isokinetic eccentric trainings. An eccentric muscle contraction is characterized by the production of muscle force associated to a lengthening of the muscle-tendon system. This muscle solicitation can cause micro lesions followed by a regeneration process of the muscle-tendon system. Eccentric exercise is commonly used in functional rehabilitation for its positive effect on collagen synthesis but also for resistance training to increase muscle strength and muscle mass in athletes. Indeed, eccentric training stimulates muscle hypertrophy, increases the fascicle pennation angle, fascicles length and neural activation, thus inducing greater strength gains than concentric or isometric training programs. Eccentric exercise is commonly performed either against a constant external load (isotonic) or at constant velocity (isokinetic), inducing different mechanical constraints. These different mechanical constraints could induce structural and neural adaptive strategies specific to each type of exercise. The literature tends to show that isotonic mode leads to a greater strength gain than isokinetic mode. This observation could be explained by a greater neuromuscular activation after IT training. However, the specific muscle adaptations induced by each mode remain difficult to determine due to the lack of standardized, comparative studies. 2010 Elsevier Masson SAS. All rights reserved.

  18. Creatine supplementation does not decrease oxidative stress and inflammation in skeletal muscle after eccentric exercise.

    Science.gov (United States)

    Silva, Luciano A; Tromm, Camila B; Da Rosa, Guilherme; Bom, Karoliny; Luciano, Thais F; Tuon, Talita; De Souza, Cláudio T; Pinho, Ricardo A

    2013-01-01

    Thirty-six male rats were used; divided into 6 groups (n = 6): saline; creatine (Cr); eccentric exercise (EE) plus saline 24 h (saline + 24 h); eccentric exercise plus Cr 24 h (Cr + 24 h); eccentric exercise plus saline 48 h (saline + 48 h); and eccentric exercise plus Cr 48 h (Cr + 48 h). Cr supplementation was administered as a solution of 300 mg · kg body weight(-1) · day(-1) in 1 mL water, for two weeks, before the eccentric exercise. The animals were submitted to one downhill run session at 1.0 km · h(-1) until exhaustion. Twenty-four and forty-eight hours after the exercise, the animals were killed, and the quadriceps were removed. Creatine kinase levels, superoxide production, thiobarbituric acid reactive substances (TBARS) level, carbonyl content, total thiol content, superoxide dismutase, catalase, glutathione peroxidase, interleukin-1b (IL-1β), nuclear factor kappa B (NF-kb), and tumour necrosis factor (TNF) were analysed. Cr supplementation neither decreases Cr kinase, superoxide production, lipoperoxidation, carbonylation, total thiol, IL-1β, NF-kb, or TNF nor alters the enzyme activity of superoxide dismutase, catalase, and glutathione peroxides in relation to the saline group, respectively (P eccentric exercise. The present study suggests that Cr supplementation does not decrease oxidative stress and inflammation after eccentric contraction.

  19. Skeletal Muscle Remodeling in Response to Eccentric vs. Concentric Loading: Morphological, Molecular, and Metabolic Adaptations

    Science.gov (United States)

    Franchi, Martino V.; Reeves, Neil D.; Narici, Marco V.

    2017-01-01

    Skeletal muscle contracts either by shortening or lengthening (concentrically or eccentrically, respectively); however, the two contractions substantially differ from one another in terms of mechanisms of force generation, maximum force production and energy cost. It is generally known that eccentric actions generate greater force than isometric and concentric contractions and at a lower metabolic cost. Hence, by virtue of the greater mechanical loading involved in active lengthening, eccentric resistance training (ECC RT) is assumed to produce greater hypertrophy than concentric resistance training (CON RT). Nonetheless, prevalence of either ECC RT or CON RT in inducing gains in muscle mass is still an open issue, with some studies reporting greater hypertrophy with eccentric, some with concentric and some with similar hypertrophy within both training modes. Recent observations suggest that such hypertrophic responses to lengthening vs. shortening contractions are achieved by different adaptations in muscle architecture. Whilst the changes in muscle protein synthesis in response to acute and chronic concentric and eccentric exercise bouts seem very similar, the molecular mechanisms regulating the myogenic adaptations to the two distinct loading stimuli are still incompletely understood. Thus, the present review aims to, (a) critically discuss the literature on the contribution of eccentric vs. concentric loading to muscular hypertrophy and structural remodeling, and, (b) clarify the molecular mechanisms that may regulate such adaptations. We conclude that, when matched for either maximum load or work, similar increase in muscle size is found between ECC and CON RT. However, such hypertrophic changes appear to be achieved through distinct structural adaptations, which may be regulated by different myogenic and molecular responses observed between lengthening and shortening contractions. PMID:28725197

  20. Skeletal Muscle Remodeling in Response to Eccentric vs. Concentric Loading: Morphological, Molecular, and Metabolic Adaptations

    Directory of Open Access Journals (Sweden)

    Martino V. Franchi

    2017-07-01

    Full Text Available Skeletal muscle contracts either by shortening or lengthening (concentrically or eccentrically, respectively; however, the two contractions substantially differ from one another in terms of mechanisms of force generation, maximum force production and energy cost. It is generally known that eccentric actions generate greater force than isometric and concentric contractions and at a lower metabolic cost. Hence, by virtue of the greater mechanical loading involved in active lengthening, eccentric resistance training (ECC RT is assumed to produce greater hypertrophy than concentric resistance training (CON RT. Nonetheless, prevalence of either ECC RT or CON RT in inducing gains in muscle mass is still an open issue, with some studies reporting greater hypertrophy with eccentric, some with concentric and some with similar hypertrophy within both training modes. Recent observations suggest that such hypertrophic responses to lengthening vs. shortening contractions are achieved by different adaptations in muscle architecture. Whilst the changes in muscle protein synthesis in response to acute and chronic concentric and eccentric exercise bouts seem very similar, the molecular mechanisms regulating the myogenic adaptations to the two distinct loading stimuli are still incompletely understood.Thus, the present review aims to, (a critically discuss the literature on the contribution of eccentric vs. concentric loading to muscular hypertrophy and structural remodeling, and, (b clarify the molecular mechanisms that may regulate such adaptations.We conclude that, when matched for either maximum load or work, similar increase in muscle size is found between ECC and CON RT. However, such hypertrophic changes appear to be achieved through distinct structural adaptations, which may be regulated by different myogenic and molecular responses observed between lengthening and shortening contractions.

  1. Comparison in eccentric exercise-induced muscle damage among four limb muscles.

    Science.gov (United States)

    Chen, Trevor C; Lin, Kun-Yi; Chen, Hsin-Lian; Lin, Ming-Ju; Nosaka, Kazunori

    2011-02-01

    This study tested the hypothesis that changes in indirect markers of muscle damage following maximal eccentric exercise would be smaller for the knee extensors (KE) and flexors (KF) compared with the elbow flexors (EF) and extensors (EE). A total of 17 sedentary men performed five sets of six maximal isokinetic (90° s(-1)) eccentric contractions of EF (range of motion, ROM: 90°-0°, 0 = full extension), EE (55°-145°), KF (90°-0°), and KE (30°-120°) using a different limb with a 4-5-week interval in a counterbalanced order. Changes in maximal isometric and concentric isokinetic strength, optimum angle, limb circumference, ROM, plasma creatine kinase activity and myoglobin concentration, muscle soreness, and echo-intensity of B-mode ultrasound images before and for 5 days following exercise were compared amongst the four exercises using two-way repeated-measures ANOVA. All variables changed significantly following EF, EE, and KF exercises, but KE exercise did not change the optimum angle, limb circumference, and echo-intensity. Compared with KF and KE, EF and EE showed significantly greater changes in all variables, without significant differences between EF and EE. Changes in all variables were significantly greater for KF than KE. For the same subjects, the magnitude of change in the dependent variables following exercise varied among the exercises. These results suggest that the two arm muscles are equally more susceptible to muscle damage than leg muscles, but KF is more susceptible to muscle damage than KE. The difference in the susceptibility to muscle damage seems to be associated with the use of muscles in daily activities.

  2. The Eccentric Behavior of Nearly Frozen Orbits

    Science.gov (United States)

    Sweetser, Theodore H.; Vincent, Mark A.

    2013-01-01

    Frozen orbits are orbits which have only short-period changes in their mean eccentricity and argument of periapse, so that they basically keep a fixed orientation within their plane of motion. Nearly frozen orbits are those whose eccentricity and argument of periapse have values close to those of a frozen orbit. We call them "nearly" frozen because their eccentricity vector (a vector whose polar coordinates are eccentricity and argument of periapse) will stay within a bounded distance from the frozen orbit eccentricity vector, circulating around it over time. For highly inclined orbits around the Earth, this distance is effectively constant over time. Furthermore, frozen orbit eccentricity values are low enough that these orbits are essentially eccentric (i.e., off center) circles, so that nearly frozen orbits around Earth are bounded above and below by frozen orbits.

  3. Associated decrements in rate of force development and neural drive after maximal eccentric exercise.

    Science.gov (United States)

    Farup, J; Rahbek, S K; Bjerre, J; de Paoli, F; Vissing, K

    2016-05-01

    The present study investigated the changes in contractile rate of force development (RFD) and the neural drive following a single bout of eccentric exercise. Twenty-four subjects performed 15 × 10 maximal isokinetic eccentric knee extensor contractions. Prior to and at 24, 48, 72, 96, and 168 h during post-exercise recovery, isometric RFD (30, 50 100, and 200 ms), normalized RFD [1/6,1/2, and 2/3 of maximal voluntary contraction (MVC)] and rate of electromyography rise (RER; 30, 50, and 75 ms) were measured. RFD decreased by 28-42% peaking at 48 h (P eccentric exercise. This association suggests that exercise-induced decrements in RFD can, in part, be explained decrements in neural drive. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  4. Introducing the Moon's Orbital Eccentricity

    Science.gov (United States)

    Oostra, Benjamin

    2014-11-01

    I present a novel way to introduce the lunar orbital eccentricity in introductory astronomy courses. The Moon is perhaps the clearest illustration of the general orbital elements such as inclination, ascending node, eccentricity, perigee, and so on. Furthermore, I like the students to discover astronomical phenomena for themselves, by means of a guided exercise, rather than just telling them the facts.1 The inclination and nodes may be found by direct observation, monitoring carefully the position of the Moon among the stars. Even the regression of the nodes may be discovered in this way2 To find the eccentricity from students' observations is also possible,3 but that requires considerable time and effort. if a whole class should discover it in a short time, here is a method more suitable for a one-day class or home assignment. The level I aim at is, more or less, advanced high school or first-year college students. I assume them to be acquainted with celestial coordinates and the lunar phases, and to be able to use algebra and trigonometry.

  5. Changes in Achilles tendon mechanical properties following eccentric heel drop exercise are specific to the free tendon.

    Science.gov (United States)

    Obst, S J; Newsham-West, R; Barrett, R S

    2016-04-01

    Mechanical loading of the Achilles tendon during isolated eccentric contractions could induce immediate and region-dependent changes in mechanical properties. Three-dimensional ultrasound was used to examine the immediate effect of isolated eccentric exercise on the mechanical properties of the distal (free tendon) and proximal (gastrocnemii) regions of the Achilles tendon. Participants (n = 14) underwent two testing sessions in which tendon measurements were made at rest and during a 30% and 70% isometric plantar flexion contractions immediately before and after either: (a) 3 × 15 eccentric heel drops or (b) 10-min rest. There was a significant time-by-session interaction for free tendon length and strain for all loading conditions (P eccentric exercise (P exercise compared with the gastrocnemii aponeurosis or tendon. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  6. Effect of sport massage on pressure pain threshold and tolerance in athletes under eccentric exercise

    Directory of Open Access Journals (Sweden)

    Abdullah Selim KAPLAN

    2014-08-01

    Full Text Available Extensive line of evidence suggest that pain threshold and tolerance alters following exercise, although the mechanisms have not been elucidated yet. In this st udy, we investigated the role of sport massage on pressure pain threshold and tolerance in athletes under eccentric exercise. Ten male athletes aged 23 ± 1 years with 9.67 ± 3.04 years of athletic training were recruited for this study . Following baseline measurements of pressure pain threshold and tolerance from m. biceps brachii and m. triceps brachii muscle and myofascial regions of the dominant upper extremity by using a digital algometer, subjects were underwent an acute bout of eccentric exercise. Par ticipants were completed 4 sets of eccentric exercise each comprising 20 repetitions of lifting 80% of their 1 RM by using a dumbbell. Pressure pain threshold and tolerance tests were repeated 10, 20 and 30 minutes, and 24 and 48 hours following exercise. One week after eccentric exercise, sport massage protocol for 10 minutes was manually administered to the dominant arm immediately after exercise, and all measurements were repeated at the same timeline as eccentric exercise. Results are presented as mean + standart deviation. Data of the same timeline were analyzed by using t test. A level of p<0.05 was accepted statistical significant. Eccentric exercise resulted to increase the pain tolerance from muscle and myofascia regions of m. biceps and triceps br achii, and sport massage was found to decrease the pain tolerance at 10 minutes from muscle regions of m. biceps and triceps brachii, 10, 20 and 30 minutes from myofascial region of biceps brachii, and 20 minutes, 24 and 48 hours from myofascial region of m. triceps brachii following acute bout of eccentric exercise in athletes. We concluded that sport massage reduces the hypoalgesic response during acute and delayed period of recovery after eccentric exercise.

  7. Concentric and eccentric time-under-tension during strengthening exercises: Validity and reliability of stretch-sensor recordings from an elastic exercise-band

    DEFF Research Database (Denmark)

    Rathleff, Michael Skovdal; Thorborg, Kristian; Bandholm, Thomas Quaade

    2013-01-01

    Total, single repetition and contraction-phase specific (concentric and eccentric) time-under-tension (TUT) are important exercise-descriptors, as they are linked to the physiological and clinical response in exercise and rehabilitation.......Total, single repetition and contraction-phase specific (concentric and eccentric) time-under-tension (TUT) are important exercise-descriptors, as they are linked to the physiological and clinical response in exercise and rehabilitation....

  8. Effect of a non-steroidal, anti-inflammatory drug (Indocin) on selected parameters of muscular function following concentric and eccentric work

    OpenAIRE

    Vejarano, Maria Eugenia

    1985-01-01

    Evidence from various studies indicates that eccentric contractions produce more post-exercise changes in muscular function than do concentric contractions. Delayed muscular soreness, the pain and tenderness present 1 or 2 days after exercise, is negatively correlated with muscular performance and occurs particularly after eccentric work. The action of an analgesic, anti-inflammatory drug (Indocin) on muscular soreness indicates it may be effective in accelerating recover...

  9. Effect of transcutaneous electromyostimulation on pressure pain threshold and tolerance in athletes under eccentric exercise

    Directory of Open Access Journals (Sweden)

    Selman Burak UĞURLU

    2014-08-01

    Full Text Available Exercise - induced hypoalgesia typically reported during and / or follow ing exercise. In this study, we investigated the role of transcutaneous electromyostimulation (EMS on pressure pain threshold and tolerance in athletes under eccentric exercise. Eleven male athletes aged 23,125 ± 0,99 years with 10,25 ± 2,66 years of athl etic training were recruited for this study . Following baseline measurements of pressure pain threshold and tolerance from m. biceps brachii and m. triceps brachii muscle and myofascial regions of the dominant upper extremity by using a digital algometer, subjects were underwent an acute bout of eccentric exercise. Participants were completed 4 sets of eccentric exercise each comprising 20 repetitions of lifting 80% of their 1 RM by using a dumbbell. Pressure pain threshold and tolerance tests were repeated 10, 20 and 30 minutes, and 24 and 48 hours following exercise. One week after acute exercise protocol, EMS protocol was applied to the participants immediately following eccentric exercise, and all measurements were repeated at the same timeline as eccent ric exercise. Standard EMS protocol at active recovery mode for 10 minutes was applied to the m. biceps brachii muscle by using surface electrodes. Results are presented as mean + standarts deviation. Data of the same timeline were analyzed by using repeat ed measures of ANOVA followed by Tukey’s post hoc test . A level of p<0.05 was accepted statistical significant. Eccentric exercise resulted to increase the pain tolerence in athletes, and EMS was found to decrease the pain tolerence 10 and 20 minutes at th e muscle region, and 10 and 30 minutes, and 24 hours at the myofascial region of m. biceps brachii, 10 min and 24 hr from muscle region, 10 and 30 min and 24 hr from myofascial region of M. triceps brachii following acute bout of eccentric exercise. We con cluded that EMS at active recovery phase mitigates the the hypoalgesic response following single bout of

  10. Decline eccentric squats increases patellar tendon loading compared to standard eccentric squats

    DEFF Research Database (Denmark)

    Kongsgaard, M; Aagaard, P; Roikjaer, S

    2006-01-01

    Recent studies have shown excellent clinical results using eccentric squat training on a 25 degrees decline board to treat patellar tendinopathy. It remains unknown why therapeutic management of patellar tendinopathy using decline eccentric squats offer superior clinical efficacy compared...

  11. Muscle fatigue experienced during maximal eccentric exercise is predictive of the plasma creatine kinase (CK) response.

    Science.gov (United States)

    Hody, S; Rogister, B; Leprince, P; Wang, F; Croisier, J-L

    2013-08-01

    Unaccustomed eccentric exercise may cause skeletal muscle damage with an increase in plasma creatine kinase (CK) activity. Although the wide variability among individuals in CK response to standardized lengthening contractions has been well described, the reasons underlying this phenomenon have not yet been understood. Therefore, this study investigated a possible correlation of the changes in muscle damage indirect markers after an eccentric exercise with the decline in muscle performance during the exercise. Twenty-seven healthy untrained male subjects performed three sets of 30 maximal isokinetic eccentric contractions of the knee extensors. The muscular work was recorded using an isokinetic dynamometer to assess muscle fatigue by means of various fatigue indices. Plasma CK activity, muscle soreness, and stiffness were measured before (pre) and one day after (post) exercise. The eccentric exercise bout induced significant changes of the three muscle damage indirect markers. Large inter-subject variability was observed for all criteria measured. More interestingly, the log (CK(post) /CK(pre)) and muscle stiffness appeared to be closely correlated with the relative work decrease (r = 0.84, r(2)  = 0.70 and r = 0.75, r(2)  = 0.56, respectively). This is the first study to propose that the muscle fatigue profile during maximal eccentric protocol could predict the magnitude of the symptoms associated with muscle damage in humans.

  12. Relationships between muscle power output using the stretch-shortening cycle and eccentric maximum strength.

    Science.gov (United States)

    Miyaguchi, Kazuyoshi; Demura, Shinichi

    2008-11-01

    This study aimed to examine the relationships between muscle power output using the stretch-shortening cycle (SSC) and eccentric maximum strength under elbow flexion. Eighteen young adult males pulled up a constant light load (2 kg) by ballistic elbow flexion under the following two preliminary conditions: 1) the static relaxed muscle state (SR condition), and 2) using the SSC with countermovement (SSC condition).Muscle power was determined from the product of the pulling velocity and the load mass by a power measurement instrument that adopted the weight-loading method. We assumed the pulling velocity to be the subject's muscle power parameters as a matter of convenience, because we used a constant load. The following two parameters were selected in reference to a previous study: 1) peak velocity (m x s(-1)) (peak power) and 2) 0.1-second velocity during concentric contraction (m x s(-1)) (initial power). Eccentric maximum strength by elbow flexion was measured by a handheld dynamometer.Initial power produced in the SSC condition was significantly larger than that in the SR condition. Eccentric maximum strength showed a significant and high correlation (r = 0.70) with peak power in the SSC condition but not in the SR condition. Eccentric maximum strength showed insignificant correlations with initial power in both conditions. In conclusion, it was suggested that eccentric maximum strength is associated with peak power in the SSC condition, but the contribution of the eccentric maximum strength to the SSC potentiation (initial power) may be low.

  13. Functional changes of human quadriceps muscle injured by eccentric exercise

    Directory of Open Access Journals (Sweden)

    F.V. Serrão

    2003-06-01

    Full Text Available The present study evaluated functional changes of quadriceps muscle after injury induced by eccentric exercise. Maximal isometric torque of quadriceps and the surface electromyography (root mean square, RMS, and median frequency, MDF of the vastus medialis oblique (VMO and vastus lateralis (VL muscles were examined before, immediately after and during the first 7 days after injury. Serum creatine kinase (CK levels and magnetic resonance imaging (MRI were used to identify muscle injury. The subject was used as her own control and percent refers to pre-injury data. Experiments were carried out with a sedentary 23-year-old female. Injury was induced by 4 bouts of 15 maximal isokinetic eccentric contractions (angular velocity of 5º/s; range of motion from 40º to 110º of knee flexion. The isometric torque of the quadriceps (knee at 90º flexion decreased 52% immediately after eccentric exercise and recovered on the 5th day. The highest reduction of RMS occurred on the 2nd day after injury in both VL (63% and VMO (66% and only VL recovered to the pre-injury level on the 7th day. Immediately after injury, the MDF decreased by 5 and 3% (VMO and VL, respectively and recovered one day later. Serum CK levels increased by 109% on the 2nd day and were still increased by 32% on the 7th day. MRI showed large areas of injury especially in the deep region of quadriceps. In conclusion, eccentric exercise decreased the isometric torque and electromyographic signals of quadriceps muscle, which were recovered in one week, despite the muscle regeneration signals.

  14. Dissociated time course recovery between rate of force development and peak torque after eccentric exercise.

    Science.gov (United States)

    Molina, Renato; Denadai, Benedito S

    2012-05-01

    This study investigated the association between isokinetic peak torque (PT) of quadriceps and the corresponding peak rate of force development (peak RFD) during the recovery of eccentric exercise. Twelve untrained men (aged 21·7 ± 2·3 year) performed 100 maximal eccentric contractions for knee extensors (10 sets of 10 repetitions with a 2-min rest between each set) on isokinetic dynamometer. PT and peak RFD accessed by maximal isokinetic knee concentric contractions at 60° s(-1) were obtained before (baseline) and at 24 and 48 h after eccentric exercise. Indirect markers of muscle damage included delayed onset of muscle soreness (DOMS) and plasma creatine kinase (CK) activity. The eccentric exercise resulted in elevated DOMS and CK compared with baseline values. At 24 h, PT (-15·3%, P = 0·002) and peak RFD (-13·1%, P = 0·03) decreased significantly. At 48 h, PT (-7·9%, P = 0·002) was still decreased but peak RFD have returned to baseline values. Positive correlation was found between PT and peak RFD at baseline (r = 0·62, P = 0·02), 24 h (r = 0·99, P = 0·0001) and 48 h (r = 0·68, P = 0·01) after eccentric exercise. The magnitude of changes (%) in PT and peak RFD from baseline to 24 h (r = 0·68, P = 0·01) and from 24 to 48 h (r = 0·68, P = 0·01) were significantly correlated. It can be concluded that the muscle damage induced by the eccentric exercise affects differently the time course of PT and peak RFD recovery during isokinetic concentric contraction at 60° s(-1). During the recovery from exercise-induced muscle damage, PT and peak RFD are determined but not fully defined by shared putative physiological mechanisms. © 2011 The Authors. Clinical Physiology and Functional Imaging © 2011 Scandinavian Society of Clinical Physiology and Nuclear Medicine.

  15. Arterial stiffness results from eccentrically biased downhill running exercise.

    Science.gov (United States)

    Burr, J F; Boulter, M; Beck, K

    2015-03-01

    There is increasing evidence that select forms of exercise are associated with vascular changes that are in opposition to the well-accepted beneficial effects of moderate intensity aerobic exercise. To determine if alterations in arterial stiffness occur following eccentrically accentuated aerobic exercise, and if changes are associated with measures of muscle soreness. Repeated measures experimental cohort. Twelve (m=8/f=4) moderately trained (VO₂max=52.2 ± 7.4 ml kg(-1)min(-1)) participants performed a downhill run at -12° grade using a speed that elicited 60% VO₂max for 40 min. Cardiovascular and muscle soreness measures were collected at baseline and up to 72 h post-running. Muscle soreness peaked at 48 h (p=<0.001). Arterial stiffness similarly peaked at 48 h (p=0.04) and remained significantly elevated above baseline through 72 h. Eccentrically accentuated downhill running is associated with arterial stiffening in the absence of an extremely prolonged duration or fast pace. The timing of alterations coincides with the well-documented inflammatory response that occurs from the muscular insult of downhill running, but whether the observed changes are a result of either systemic or local inflammation is yet unclear. These findings may help to explain evidence of arterial stiffening in long-term runners and following prolonged duration races wherein cumulative eccentric loading is high. Copyright © 2014 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

  16. The influence of cyclic concentric and eccentric submaximal muscle loading on cell viability in the rabbit knee joint.

    Science.gov (United States)

    Horisberger, Monika; Fortuna, Rafael; Leonard, Timothy R; Valderrabano, Victor; Herzog, Walter

    2012-03-01

    Cartilage loading is associated with the onset and progression of osteoarthritis and cell death may play an important role in these processes. Although much is known about cell death in joint impact loading, there is no information on joints loaded by muscular contractions. The aim of this study was to evaluate the influence of muscle generated eccentric and concentric submaximal joint loading on chondrocyte viability. We hypothesised that eccentric muscle activation leads to increased cell death rates compared to concentric loading and to controls. 16 rabbits received either 50 min of uni-lateral, cyclic eccentric (n=8) or concentric (n=8) knee loading. Muscle activation for these dynamic conditions was equivalent to an activation level that produced 20% of maximum isometric force. Contralateral joints served as unloaded controls. Cell viability was assessed using confocal microscopy. Eccentric contractions produced greater knee loading than concentric contractions. Sub-maximal contractions caused a significant increase in cell death in the loaded knees compared to the unloaded controls, and eccentric loading caused significantly more cell death than concentric loading. Cyclic sub-maximal muscle loading of the knee caused increased chondrocyte death in rabbits. These findings suggest that low levels of joint loading for prolonged periods, as occurs in endurance exercise or physical labour, may cause chondrocyte death, thereby predisposing joints to degeneration. Copyright © 2011 Elsevier Ltd. All rights reserved.

  17. Myocellular enzyme leakage, polymorphonuclear neutrophil activation and delayed onset muscle soreness induced by isokinetic eccentric exercise.

    Science.gov (United States)

    Croisier, J L; Camus, G; Deby-Dupont, G; Bertrand, F; Lhermerout, C; Crielaard, J M; Juchmès-Ferir, A; Deby, C; Albert, A; Lamy, M

    1996-01-01

    To address the question of whether delayed onset muscular soreness (DOMS) following intense eccentric muscle contraction could be due to increased production of the arachidonic acid derived product prostaglandin E2 (PGE2). 10 healthy male subjects were submitted to eccentric and concentric isokinetic exercises on a Kin Trex device at 60 degrees/s angular velocity. Exercise consisted of 8 stages of 5 maximal contractions of the knee extensor and flexor muscle groups of both legs separated by 1 min rest phases. There was an interval of at least 30 days between eccentric and concentric testing, and the order of the two exercise sessions was randomly assigned. The subjective presence and intensity of DOMS was evaluated using a visual analogue scale, immediately, following 24 h and 48 h after each test. Five blood samples were drawn from an antecubital vein: at rest before exercise, immediately after, after 30 min recovery, 24 h and 48 h after the tests. The magnitude of the acute inflammatory response to exercise was assessed by measuring plasma levels of polymorphonuclear elastase ([EL]), myeloperoxidase ([MPO]) and PGE2 ([PGE2]). Using two way analysis of variance, it appeared that only eccentric exercise significantly increased [EL] and DOMS, especially of the hamstring muscles. Furthermore, a significant decrease in eccentric peak torque of this muscle group only was observed on day 2 after eccentric work (- 21%; P < 0.002). Serum activity of creatine kinase and serum concentration of myoglobin increased significantly 24 and 48 h after both exercise tests. However, these variables reached significantly higher values following eccentric contractions 48 h after exercise. Mean [PGE2] in the two exercise modes remained unchanged over time and were practically equal at each time point. On the basis of these findings, we conclude that the magnitude of polymorphonuclear (PMN) activation, muscle damage, and DOMS are greater after eccentric than after concentric muscle

  18. Effects of eccentric exercise on trapezius electromyography during computer work with active and passive pauses

    DEFF Research Database (Denmark)

    Samani, Afshin; Holtermann, Andreas; Søgaard, Karen

    2009-01-01

    BACKGROUND: The aim of this laboratory study was to investigate the effects of eccentric exercises on the trapezius muscle spatial electromyographic (EMG) activity during computer work with active and passive pauses. METHODS: Twelve healthy male subjects performed computer work with passive (relax......) and active (30% maximum voluntary contraction of shoulder elevation) pauses given every 40s over 2 days, before, immediately and 24h after eccentric exercise. Surface EMG signals were recorded from four parts of the trapezius during computer work. FINDINGS: EMG amplitude during computer work decreased...... immediately after exercise (Pactive pauses compared with passive ones (P

  19. Behavior of fascicles and the myotendinous junction of human medial gastrocnemius following eccentric strength training.

    Science.gov (United States)

    Duclay, Julien; Martin, Alain; Duclay, Alice; Cometti, Gilles; Pousson, Michel

    2009-06-01

    This study is the first in which measurements of thickness, fascicle angle and length, and tendon elongation were combined to examine the impact of eccentric strength training on both muscle architecture and tendinous structures. Eighteen healthy male subjects were divided into an eccentric strength training group (n = 10) and a control group (n = 8). The training program consisted of 18 sessions of eccentric exercises over a 7-week period. All subjects were tested at baseline and after the last training session. Using ultrasound imaging, the fascicle angle and length and thickness of the medial gastrocnemius (MG) were analyzed at rest (i.e., theta(p), Fl(p), and t(p), respectively), at 50% of maximal voluntary contraction (MVC) (i.e., theta(50), Fl(50), and t(50), respectively), and during MVC (i.e., theta(100), Fl(100), and t(100), respectively). Tendon elongation (TE) was measured by tracking the proximal displacement of the myotendinous junction of the MG during ramp isometric contraction. During ramp isometric contraction, the slope of the load-deformation relationship of the gastrocnemius tendon above 50% MVC was defined as an index of stiffness. After training, muscle thickness and fascicle angle increased significantly at rest and during contraction, whereas fascicle length increased at rest and did not change during contraction. Furthermore, the stiffness of the gastrocnemius tendon increased significantly. The results suggest that the behavior of muscle architecture and tendon mechanical properties are affected differently by strength training.

  20. Neuromuscular Changes and Damage after Isoload versus Isokinetic Eccentric Exercise.

    Science.gov (United States)

    Doguet, Valentin; Nosaka, Kazunori; Plautard, Mathieu; Gross, Raphaël; Guilhem, GaËL; Guével, Arnaud; Jubeau, Marc

    2016-12-01

    This study compared the effects of isoload (IL) and isokinetic (IK) knee extensor eccentric exercises on changes in muscle damage and neuromuscular parameters to test the hypothesis that the changes would be different after IL and IK exercises. Twenty-two young men were paired based on their strength and placed in the IL (N = 11) or the IK (N = 11) group. The IL group performed 15 sets of 10 eccentric contractions with a 150% of predetermined one-repetition maximum load. The IK group performed 15 sets of several maximal eccentric contractions matched set by set for the total amount of work and mean angular velocity with the IL group. Muscle damage markers (voluntary isometric peak torque, muscle soreness, and creatine kinase activity) and neuromuscular variables (e.g., voluntary activation, H-reflex, M-wave, and evoked torque) were measured before, immediately after, and 24, 48, 72, and 96 h postexercise. Voluntary isometric peak torque decreased to the same extent (P = 0.94) in both groups immediately after (IL = -40.6% ± 13.8% vs IK = -42.4% ± 10.2%) to 96 h after the exercise (IL = -21.8% ± 28.5% vs IK = -26.7% ± 23.5%). Neither peak muscle soreness (IL = 48.1 ± 28.2 mm vs IK = 54.7 ± 28.9 mm, P = 0.57) nor creatine kinase activity (IL = 12,811 ± 22,654 U·L vs IK = 15,304 ± 24,739 U·L, P = 0.59) significantly differed between groups. H-reflex (IL = -23% vs IK = -35%) and M-wave (IL = -10% vs IK = -17%) significantly decreased immediately postexercise similarly between groups. The changes in muscle damage and neuromuscular function after the exercise are similar between IL and IK, suggesting that resistance modality has little effects on acute muscle responses.

  1. Effects of eccentric exercise on toll-like receptor 4 signaling pathway in peripheral blood mononuclear cells.

    Science.gov (United States)

    Fernandez-Gonzalo, Rodrigo; De Paz, José A; Rodriguez-Miguelez, Paula; Cuevas, María J; González-Gallego, Javier

    2012-06-01

    This study aimed to investigate the response of the toll-like receptor 4 (TLR4) signaling pathway to an acute bout of eccentric exercise, and to assess whether eccentric training attenuated the effects induced by acute eccentric exercise. Twenty men (22.4 ± 0.5 yr) were divided into a control group (CG, n = 8) and a training group (TG, n = 12). Both groups performed two acute eccentric bouts on a squat machine in a 9-wk interval. During this time, TG followed a 6-wk eccentric training program (3 session/wk; 3-5 sets of 10 repetitions with loads ranging between the 40 and 50% of maximal isometric voluntary contraction). CD14, TLR4, and TNF-α mRNA levels, and CD14, TLR4, myeloid differentiation factor 88, tumor necrosis factor receptor-associated factor 6, TIR-domain-containing adapter-inducing interferon-β, phospho-IκB kinases, phospho-IκB, phospho-ERK-1/2, and TNF-α protein concentration were measured in peripheral blood mononuclear cells, before, immediately, and 2 h after each eccentric bout. The first acute eccentric bout triggered a proinflammatory response mediated by an upregulation of all of the factors measured within the TLR4 signaling pathway. Following the training period and after the second acute bout, CG showed a similar proinflammatory response than that seen after the first bout. However, the eccentric training intervention decreased significantly the protein concentration of all factors analyzed in TG compared with results obtained after the first bout. These results suggest that the TLR4-signaling pathway plays a critical role in the proinflammatory response seen after acute eccentric exercise. This response was attenuated after an eccentric training program through myeloid differentiation factor 88-dependent and -independent pathways.

  2. Eccentricity distribution in the main asteroid belt

    Science.gov (United States)

    Malhotra, Renu; Wang, Xianyu

    2017-03-01

    The observationally complete sample of the main belt asteroids now spans more than two orders of magnitude in size and numbers more than 64 000 (excluding collisional family members). We undertook an analysis of asteroids' eccentricities and their interpretation with simple physical models. We find that a century old conclusion that the asteroids' eccentricities follow a Rayleigh distribution holds for the osculating eccentricities of large asteroids, but the proper eccentricities deviate from a Rayleigh distribution; there is a deficit of eccentricities smaller than ∼0.1 and an excess of larger eccentricities. We further find that the proper eccentricities do not depend significantly on asteroid size but have strong dependence on heliocentric distance; the outer asteroid belt follows a Rayleigh distribution, but the inner belt is strikingly different. Eccentricities in the inner belt can be modelled as a vector sum of a primordial eccentricity vector of random orientation and magnitude drawn from a Rayleigh distribution of parameter ∼0.06, and an excitation of random phase and magnitude ∼0.13. These results imply that when a late dynamical excitation of the asteroids occurred, it was independent of asteroid size and was stronger in the inner belt than in the outer belt. We discuss implications for the primordial asteroid belt and suggest that the observationally complete sample size of main belt asteroids is large enough that more sophisticated model-fitting of the eccentricities is warranted and could serve to test alternative theoretical models of the dynamical excitation history of asteroids and its links to the migration history of the giant planets.

  3. Superior Effects of Eccentric to Concentric Knee Extensor Resistance Training on Physical Fitness, Insulin Sensitivity and Lipid Profiles of Elderly Men

    Science.gov (United States)

    Chen, Trevor Chung-Ching; Tseng, Wei-Chin; Huang, Guan-Ling; Chen, Hsin-Lian; Tseng, Kuo-Wei; Nosaka, Kazunori

    2017-01-01

    It has been reported that eccentric training of knee extensors is effective for improving blood insulin sensitivity and lipid profiles to a greater extent than concentric training in young women. However, it is not known whether this is also the case for elderly individuals. Thus, the present study tested the hypothesis that eccentric training of the knee extensors would improve physical function and health parameters (e.g., blood lipid profiles) of older adults better than concentric training. Healthy elderly men (60–76 years) were assigned to either eccentric training or concentric training group (n = 13/group), and performed 30–60 eccentric or concentric contractions of knee extensors once a week. The intensity was progressively increased over 12 weeks from 10 to 100% of maximal concentric strength for eccentric training and from 50 to 100% for concentric training. Outcome measures were taken before and 4 days after the training period. The results showed that no sings of muscle damage were observed after any sessions. Functional physical fitness (e.g., 30-s chair stand) and maximal concentric contraction strength of the knee extensors increased greater (P ≤ 0.05) after eccentric training than concentric training. Homeostasis model assessment, oral glucose tolerance test and whole blood glycosylated hemoglobin showed improvement of insulin sensitivity only after eccentric training (P ≤ 0.05). Greater (P ≤ 0.05) decreases in fasting triacylglycerols, total, and low-density lipoprotein cholesterols were evident after eccentric training than concentric training, and high-density lipoprotein cholesterols increased only after eccentric training. These results support the hypothesis and suggest that it is better to focus on eccentric contractions in exercise medicine. PMID:28443029

  4. Superior Effects of Eccentric to Concentric Knee Extensor Resistance Training on Physical Fitness, Insulin Sensitivity and Lipid Profiles of Elderly Men.

    Science.gov (United States)

    Chen, Trevor Chung-Ching; Tseng, Wei-Chin; Huang, Guan-Ling; Chen, Hsin-Lian; Tseng, Kuo-Wei; Nosaka, Kazunori

    2017-01-01

    It has been reported that eccentric training of knee extensors is effective for improving blood insulin sensitivity and lipid profiles to a greater extent than concentric training in young women. However, it is not known whether this is also the case for elderly individuals. Thus, the present study tested the hypothesis that eccentric training of the knee extensors would improve physical function and health parameters (e.g., blood lipid profiles) of older adults better than concentric training. Healthy elderly men (60-76 years) were assigned to either eccentric training or concentric training group (n = 13/group), and performed 30-60 eccentric or concentric contractions of knee extensors once a week. The intensity was progressively increased over 12 weeks from 10 to 100% of maximal concentric strength for eccentric training and from 50 to 100% for concentric training. Outcome measures were taken before and 4 days after the training period. The results showed that no sings of muscle damage were observed after any sessions. Functional physical fitness (e.g., 30-s chair stand) and maximal concentric contraction strength of the knee extensors increased greater (P ≤ 0.05) after eccentric training than concentric training. Homeostasis model assessment, oral glucose tolerance test and whole blood glycosylated hemoglobin showed improvement of insulin sensitivity only after eccentric training (P ≤ 0.05). Greater (P ≤ 0.05) decreases in fasting triacylglycerols, total, and low-density lipoprotein cholesterols were evident after eccentric training than concentric training, and high-density lipoprotein cholesterols increased only after eccentric training. These results support the hypothesis and suggest that it is better to focus on eccentric contractions in exercise medicine.

  5. A randomized controlled trial of eccentric vs. concentric graded exercise in chronic tennis elbow (lateral elbow tendinopathy).

    Science.gov (United States)

    Peterson, Magnus; Butler, Stephen; Eriksson, Margaretha; Svärdsudd, Kurt

    2014-09-01

    To analyse treatment effects of eccentric vs. concentric graded exercise in chronic tennis elbow. Randomized controlled trial. Primary care in Uppsala County, Sweden. A total of 120 subjects with tennis elbow lasting more than three months were recruited from primary care and by advertisement. Eccentric (n = 60) or concentric exercise (n = 60), by lowering or lifting a weight, at home daily, for three months with gradually increasing load. Pain during muscle contraction and muscle elongation, as well as strength, was assessed at baseline and after one, two, three, six, and 12 months. Function and quality of life was assessed at baseline and after three, six and 12 months. The eccentric exercise group had faster regression of pain, with an average of 10% higher responder rate at all levels of pain reduction, both during muscle contraction and elongation, (p eccentric vs. the concentric group and a number-needed-to-treat of 10. The eccentric group also had a greater increase of muscle strength than the concentric (p Eccentric graded exercise reduced pain and increased muscle strength in chronic tennis elbow more effectively than concentric graded exercise. © The Author(s) 2014.

  6. Local NSAID infusion inhibits satellite cell proliferation in human skeletal muscle after eccentric exercise

    DEFF Research Database (Denmark)

    Mikkelsen, U R; Langberg, H; Helmark, I C

    2009-01-01

    exercise in vivo in human skeletal muscle. Eight young healthy males performed 200 maximal eccentric contractions with each leg. An NSAID was infused via a microdialysis catheter into the vastus lateralis muscle of one leg (NSAID leg) before, during, and for 4.5 h after exercise, with the other leg working...... of satellite cells 8 days after exercise. These results suggest that NSAIDs negatively affect satellite cell activity after unaccustomed eccentric exercise.......Despite the widespread consumption of nonsteroidal anti-inflammatory drugs (NSAIDs), the influence of these drugs on muscle satellite cells is not fully understood. The aim of the present study was to investigate the effect of a local NSAID infusion on satellite cells after unaccustomed eccentric...

  7. Acute alcohol consumption aggravates the decline in muscle performance following strenuous eccentric exercise.

    Science.gov (United States)

    Barnes, Matthew J; Mündel, Toby; Stannard, Stephen R

    2010-01-01

    This study investigated the effects of acute moderate alcohol intake on muscular performance during recovery from eccentric exercise-induced muscle damage. Eleven healthy males performed 300 maximal eccentric contractions of the quadriceps muscles of one leg on an isokinetic dynamometer. They then consumed a beverage containing 1g/kg bodyweight ethanol (as vodka and orange juice) (ALC). On another occasion they performed an equivalent bout of eccentric exercise on the contralateral leg after which they consumed an isocaloric quantity of orange juice (OJ). Measurement of maximal isokinetic (concentric and eccentric) and isometric torque produced across the knee, plasma creatine kinase (CK) concentrations and muscle soreness were made before and at 36 and 60h following each exercise bout. All measures of muscle performance were significantly reduced at 36 and 60h post-exercise compared to pre-exercise measures (all peccentric contractions, respectively. However, peak strength loss was significantly greater in ALC with the same performance measures decreasing by 34%, 40% and 34%, respectively. Post-exercise plasma creatine kinase activity and ratings of muscle soreness were not different between conditions (both p>0.05). These results indicate that consumption of even moderate amounts of alcohol following eccentric-based exercise magnifies the normally observed losses in dynamic and static strength. Therefore, to minimise exercise related losses in muscle function and expedite recovery, participants in sports involving eccentric muscle work should avoid alcohol-containing beverages in the post-event period. Copyright (c) 2009 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

  8. Eccentric Torque-Producing Capacity is Influenced by Muscle Length in Older Healthy Adults.

    Science.gov (United States)

    Melo, Ruth C; Takahashi, Anielle C M; Quitério, Robison J; Salvini, Tânia F; Catai, Aparecida M

    2016-01-01

    Considering the importance of muscle strength to functional capacity in the elderly, the study investigated the effects of age on isokinetic performance and torque production as a function of muscle length. Eleven younger (24.2 ± 2.9 years) and 16 older men (62.7 ± 2.5 years) were subjected to concentric and eccentric isokinetic knee extension/flexion at 60 and 120° · s(-1) through a functional range of motion. The older group presented lower peak torque (in newton-meters) than the young group for both isokinetic contraction types (age effect, p torque deficits in the older group were near 30 and 29% for concentric and eccentric contraction, respectively. Concentric peak torque was lower at 120° · s(-1) than at 60° · s(-1) for both groups (angular velocity effect, p knee extension torque was the only exercise tested that showed an interaction effect between age and muscle length (p torque responses to the muscle length between groups. Compared with the young group, the eccentric knee extension torque was 22-56% lower in the older group, with the deficits being lower in the shortened muscle length (22-27%) and higher (33-56%) in the stretched muscle length. In older men, the production of eccentric knee strength seems to be dependent on the muscle length. At more stretched positions, older subjects lose the capacity to generate eccentric knee extension torque. More studies are needed to assess the mechanisms involved in eccentric strength preservation with aging and its relationship with muscle length.

  9. Delayed recovery of velocity-dependent power loss following eccentric actions of the ankle dorsiflexors

    Science.gov (United States)

    Power, Geoffrey A.; Dalton, Brian H.; Rice, Charles L.

    2010-01-01

    Unaccustomed eccentric exercise has been shown to impair muscle function, although little is known regarding this impairment on muscle power. The purpose of this study was to investigate changes in neuromuscular properties of the ankle dorsiflexors during and after an eccentric contraction task and throughout recovery in 21 (10 men, 11 women) recreationally active young adults (25.8 ± 2.3 yr). All subjects performed 5 sets of 30 eccentric contractions at 80% of maximum isometric voluntary contraction (MVC) torque. Data were recorded at baseline, during the fatigue task, and for 30 min of recovery. There were no significant sex differences for all fatigue measures; thus data were pooled. After the fatigue task, MVC torque declined by 28% (P 99%) during and after the fatigue task (P > 0.05). Peak twitch torque was reduced by 21% at 2 min of recovery and progressively decreased to 35% by 30 min (P concentric power was reduced by 8% immediately after task termination and did not recover fully within 30 min (P contraction coupling and cross-bridge kinetics and reduced the number of functional sarcomeres in series, ultimately leading to velocity-dependent power loss. PMID:20576845

  10. Premature Contractions

    Science.gov (United States)

    ... Peripheral Artery Disease Venous Thromboembolism Aortic Aneurysm More Premature Contractions - PACs and PVCs Updated:Dec 15,2016 ... You felt this more-forceful beat. Types of premature contractions Premature atrial contractions (PACs) start in the ...

  11. Reduced short-interval intracortical inhibition after eccentric muscle damage in human elbow flexor muscles.

    Science.gov (United States)

    Pitman, Bradley M; Semmler, John G

    2012-09-01

    The purpose of this study was to use paired-pulse transcranial magnetic stimulation (TMS) to examine the effect of eccentric exercise on short-interval intracortical inhibition (SICI) after damage to elbow flexor muscles. Nine young (22.5 ± 0.6 yr; mean ± SD) male subjects performed maximal eccentric exercise of the elbow flexor muscles until maximal voluntary contraction (MVC) force was reduced by ∼40%. TMS was performed before, 2 h after, and 2 days after exercise under Rest and Active (5% MVC) conditions with motor-evoked potentials (MEPs) recorded from the biceps brachii (BB) muscle. Peripheral electrical stimulation of the brachial plexus was used to assess maximal M-waves, and paired-pulse TMS with a 3-ms interstimulus interval was used to assess changes in SICI at each time point. The eccentric exercise resulted in a 34% decline in strength (P muscle strength (27%, P muscle soreness (P muscle damage. When the test MEP amplitudes were matched between sessions, we found that SICI was reduced by 27% in resting and 23% in active BB muscle 2 h after exercise. SICI recovered 2 days after exercise when muscle pain and soreness were present, suggesting that delayed onset muscle soreness from eccentric exercise does not influence SICI. The change in SICI observed 2 h after exercise suggests that eccentric muscle damage has widespread effects throughout the motor system that likely includes changes in motor cortex.

  12. Neural control of lengthening contractions.

    Science.gov (United States)

    Duchateau, Jacques; Enoka, Roger M

    2016-01-01

    A number of studies over the last few decades have established that the control strategy employed by the nervous system during lengthening (eccentric) differs from those used during shortening (concentric) and isometric contractions. The purpose of this review is to summarize current knowledge on the neural control of lengthening contractions. After a brief discussion of methodological issues that can confound the comparison between lengthening and shortening actions, the review provides evidence that untrained individuals are usually unable to fully activate their muscles during a maximal lengthening contraction and that motor unit activity during submaximal lengthening actions differs from that during shortening actions. Contrary to common knowledge, however, more recent studies have found that the recruitment order of motor units is similar during submaximal shortening and lengthening contractions, but that discharge rate is systematically lower during lengthening actions. Subsequently, the review examines the mechanisms responsible for the specific control of maximal and submaximal lengthening contractions as reported by recent studies on the modulation of cortical and spinal excitability. As similar modulation has been observed regardless of contraction intensity, it appears that spinal and corticospinal excitability are reduced during lengthening compared with shortening and isometric contractions. Nonetheless, the modulation observed during lengthening contractions is mainly attributable to inhibition at the spinal level.

  13. Effects of fast-velocity eccentric resistance training on early and late rate of force development.

    Science.gov (United States)

    Oliveira, Anderson Souza; Corvino, Rogério Bulhões; Caputo, Fabrizio; Aagaard, Per; Denadai, Benedito Sérgio

    2016-01-01

    This study examined whether short-term maximal resistance training employing fast-velocity eccentric knee extensor actions would induce improvements in maximal isometric torque and rate of force development (RFD) at early (100 ms) of rising torque. Twenty healthy men were assigned to two experimental groups: eccentric resistance training (TG) or control (CG). Participants on the TG trained three days a week for a total of eight weeks. Training consisted of maximal unilateral eccentric knee extensors actions performed at 180 °s-1. Maximal isometric knee extensor torque (MVC) and incremental RFD in successive 50 ms time-windows from the onset contraction were analysed in absolute terms (RFDINC) or when normalised relative to MVC (RFDREL). After eight weeks, TG demonstrated increases in MVC (28%), RFDINC (0-50 ms: 30%; 50-100 ms: 31%) and RFDREL (0-50 ms: 29%; 50-100 ms: 32%). Moreover, no changes in the late phase of incremental RFD were observed in TG. No changes were found in the CG. In summary, we have demonstrated, in active individuals, that a short period of resistance training performed with eccentric fast-velocity isokinetic muscle contractions is able to enhance RFDINC and RFDREL obtained at the early phase of rising joint torque.

  14. Eccentric exercise in treatment of Achilles tendinopathy

    DEFF Research Database (Denmark)

    Nørregaard, J; Larsen, C C; Bieler, T

    2007-01-01

    Prognosis and treatment of Achilles tendon pain (achillodynia) has been insufficiently studied. The purpose of the present study was to examine the long-term effect of eccentric exercises compared with stretching exercises on patients with achillodynia.......Prognosis and treatment of Achilles tendon pain (achillodynia) has been insufficiently studied. The purpose of the present study was to examine the long-term effect of eccentric exercises compared with stretching exercises on patients with achillodynia....

  15. Mechanical, hormonal, and hypertrophic adaptations to 10 weeks of eccentric and stretch-shortening cycle exercise training in old males

    NARCIS (Netherlands)

    Vaczi, Mark; Nagy, Szilvia A.; Koszegi, Tamas; Ambrus, Mira; Bogner, Peter; Perlaki, Gabor; Orsi, Gergely; Toth, Katalin; Hortobagyi, Tibor

    2014-01-01

    The growth promoting effects of eccentric (ECC) contractions are well documented but it is unknown if the rate of stretch per se plays a role in such muscular responses in healthy aging human skeletal muscle. We tested the hypothesis that exercise training of the quadriceps muscle with low rate ECC

  16. Mechanical, hormonal, and hypertrophic adaptations to 10 weeks of eccentric and stretch-shortening cycle exercise training in old males

    NARCIS (Netherlands)

    Vaczi, Mark; Nagy, Szilvia A.; Koszegi, Tamas; Ambrus, Mira; Bogner, Peter; Perlaki, Gabor; Orsi, Gergely; Toth, Katalin; Hortobagyi, Tibor

    2014-01-01

    The growth promoting effects of eccentric (ECC) contractions are well documented but it is unknown if the rate of stretch per se plays a role in such muscular responses in healthy aging human skeletal muscle. We tested the hypothesis that exercise training of the quadriceps muscle with low rate ECC

  17. Changes in H reflex and neuromechanical properties of the trapezius muscle after 5 weeks of eccentric training: a randomized controlled trial.

    Science.gov (United States)

    Vangsgaard, Steffen; Taylor, Janet L; Hansen, Ernst A; Madeleine, Pascal

    2014-06-15

    Trapezius muscle Hoffman (H) reflexes were obtained to investigate the neural adaptations induced by a 5-wk strength training regimen, based solely on eccentric contractions of the shoulder muscles. Twenty-nine healthy subjects were randomized into an eccentric training group (n = 15) and a reference group (n = 14). The eccentric training program consisted of nine training sessions of eccentric exercise performed over a 5-wk period. H-reflex recruitment curves, the maximal M wave (Mmax), maximal voluntary contraction (MVC) force, rate of force development (RFD), and electromyographic (EMG) voluntary activity were recorded before and after training. H reflexes were recorded from the middle part of the trapezius muscle by electrical stimulation of the C3/4 cervical nerves; Mmax was measured by electrical stimulation of the accessory nerve. Eccentric strength training resulted in significant increases in the maximal trapezius muscle H reflex (Hmax) (21.4% [5.5-37.3]; P = 0.01), MVC force (26.4% [15.0-37.7]; P training group (r = 0.57; P = 0.03). These results indicate that the net excitability of the trapezius muscle H-reflex pathway increased after 5 wk of eccentric training. This is the first study to investigate and document changes in the trapezius muscle H reflex following eccentric strength training.

  18. Effects of flexibility training on eccentric exercise-induced muscle damage.

    Science.gov (United States)

    Chen, Che-Hsiu; Nosaka, Kazunori; Chen, Hsin-Lian; Lin, Ming-Ju; Tseng, Kuo-Wei; Chen, Trevor C

    2011-03-01

    This study investigated whether flexibility training would attenuate muscle damage induced by maximal eccentric exercise. Thirty untrained young men were allocated to static stretching (SS), proprioceptive neuromuscular facilitation (PNF), or control group (n = 10 per group). The SS consisted of 30 sets of a 30-s standard SS with a 30-s rest between sets, and the PNF included 5 sets of the 30-s standard SS followed by 3 sets of three "contract-relax-agonist-contract" procedures. These were performed three times a week for 8 wk, and all subjects performed six sets of 10 maximal isokinetic (30°·s) lengthening contractions of the knee flexors after the 8-wk training or 8 wk after the baseline measures (control). Changes in indirect markers of muscle damage before and for 5 d after the eccentric exercise were compared among the groups. The range of motion (ROM) of the hip joint increased by 25°, and the optimum angle of the knee flexors shifted (P knee flexor muscle strength and smaller changes in optimum angle, ROM, muscle soreness, and plasma creatine kinase activity and myoglobin concentration without significant differences between the groups. The preeccentric exercise ROM or optimum angle was significantly (P eccentric exercise-induced muscle damage and that flexible muscles are less susceptible to the damage.

  19. Assessment of Muscle Pain Induced by Elbow-Flexor Eccentric Exercise.

    Science.gov (United States)

    Lau, Wing Yin; Blazevich, Anthony J; Newton, Michael J; Wu, Sam Shi Xuan; Nosaka, Kazunori

    2015-11-01

    Delayed-onset muscle soreness (DOMS) is a common muscle pain that many people experience and is often used as a model of acute muscle pain. Researchers have reported the effects of various interventions on DOMS, but different DOMS assessment protocols used in these studies make it difficult to compare the effects. To investigate DOMS characteristics after elbow-flexor eccentric exercise to establish a standardized DOMS assessment protocol. Descriptive laboratory study. Research laboratory. Ten healthy, untrained men (21-39 years). Participants performed 10 sets of 6 maximal isokinetic eccentric contractions of the elbow flexors. Indirect muscle-damage markers were maximal voluntary isometric contraction torque, range of motion, and serum creatine kinase activity. Muscle pain was assessed before exercise, immediately postexercise, and 1 to 5 days postexercise using (1) a visual analog scale (VAS), (2) a category ratio-10 scale (CR-10) when applying static pressure and palpation at different sites (3, 9, and 15 cm above the elbow crease), and (3) pressure-pain thresholds (PPTs) at 50 sites (pain mapping). Maximal voluntary isometric contraction and range of motion decreased and creatine kinase activity increased postexercise, indicating muscle damage. Palpation induced greater pain than static pressure, and longitudinal and transverse palpations induced greater pain than circular palpation (P exercise, but the pain-sensitive regions shifted to the central and distal regions of the biceps brachii at 1 to 3 days postexercise (P eccentric exercise.

  20. Detecting gravitational waves from highly eccentric compact binaries

    CERN Document Server

    Tai, Kai Sheng; Pretorius, Frans

    2014-01-01

    In dense stellar regions, highly eccentric binaries of black holes and neutron stars can form through various n-body interactions. Such a binary could emit a significant fraction of its binding energy in a sequence of largely isolated gravitational wave bursts prior to merger. Given expected black hole and neutron star masses, many such systems will emit these repeated bursts at frequencies within the sensitive band of contemporary ground-based gravitational wave detectors. Unfortunately, existing gravitational wave searches are ill-suited to detect these signals. In this work, we adapt a "power stacking" method to the detection of gravitational wave signals from highly eccentric binaries. We implement this method as an extension of the Q-transform, a projection onto a multiresolution basis of windowed complex exponentials that has previously been used to analyze data from the network of LIGO/Virgo detectors. Our method searches for excess power over an ensemble of time-frequency tiles. We characterize the pe...

  1. Combination of eccentric exercise and neuromuscular electrical stimulation to improve quadriceps function post-ACL reconstruction.

    Science.gov (United States)

    Lepley, Lindsey K; Wojtys, Edward M; Palmieri-Smith, Riann M

    2015-06-01

    Neuromuscular electrical stimulation (NMES) has been shown to reduce quadriceps activation failure (QAF), and eccentric exercise has been shown to lessen muscle atrophy post-ACL reconstruction. Given that these are two critical components of quadriceps strength, intervention combining these therapies may be effective at reinstituting quadriceps function post-reconstruction. Thus, the aim of this study was to evaluate the effectiveness of a combined NMES and eccentric exercise intervention to improve the recovery of quadriceps activation and strength post-reconstruction. Thirty-six individuals post-injury were placed into four treatment groups (N&E, NMES and eccentrics; E-only, eccentrics only; N-only, NMES-only; and STND, standard of care) and ten healthy controls participated. N&E and N-only received the NMES protocol 2× per week for the first 6 weeks post-reconstruction. N&E and E-only received the eccentric exercise protocol 2× per week beginning 6 weeks post-reconstruction. Quadriceps activation was assessed via the superimposed burst technique and quantified via the central activation ratio. Quadriceps strength was assessed via maximal voluntary isomeric contractions (Nm/kg). Data was gathered on three occasions: pre-operative, 12-weeks-post-surgery and at return-to-play. No differences in pre-operative measures existed (P>0.05). E-only recovered quadriceps activation better than N-only or STND (P0.05). Eccentric exercise was capable of restoring levels of quadriceps activation and strength that were similar to those of healthy adults and better than NMES alone. Level 3, Parallel longitudinal study. Copyright © 2014 Elsevier B.V. All rights reserved.

  2. Orbital eccentricities in primordial black hole binaries

    Science.gov (United States)

    Cholis, Ilias; Kovetz, Ely D.; Ali-Haïmoud, Yacine; Bird, Simeon; Kamionkowski, Marc; Muñoz, Julian B.; Raccanelli, Alvise

    2016-10-01

    It was recently suggested that the merger of ˜30 M⊙ primordial black holes (PBHs) may provide a significant number of events in gravitational-wave observatories over the next decade, if they make up an appreciable fraction of the dark matter. Here we show that measurement of the eccentricities of the inspiralling binary black holes can be used to distinguish these binaries from those produced by more traditional astrophysical mechanisms. These PBH binaries are formed on highly eccentric orbits and can then merge on time scales that in some cases are years or less, retaining some eccentricity in the last seconds before the merger. This is to be contrasted with massive-stellar-binary, globular-cluster, or other astrophysical origins for binary black holes (BBHs) in which the orbits have very effectively circularized by the time the BBH enters the observable LIGO window. Here we discuss the features of the gravitational-wave signals that indicate this eccentricity and forecast the sensitivity of LIGO and the Einstein Telescope to such effects. We show that if PBHs make up the dark matter, then roughly one event should have a detectable eccentricity given LIGO's expected sensitivity and observing time of six years. The Einstein Telescope should see O (10 ) such events after ten years.

  3. Eccentric Exercise to Enhance Neuromuscular Control.

    Science.gov (United States)

    Lepley, Lindsey K; Lepley, Adam S; Onate, James A; Grooms, Dustin R

    Neuromuscular alterations are a major causal factor of primary and secondary injuries. Though injury prevention programs have experienced some success, rates of injuries have not declined, and after injury, individuals often return to activity with functionality below clinical recommendations. Considering alternative therapies to the conventional concentric exercise approach, such as one that can target neuromuscular injury risk and postinjury alterations, may provide for more effective injury prevention and rehabilitation protocols. Peer-reviewed sources available on the Web of Science and MEDLINE databases from 2000 through 2016 were gathered using searches associated with the keywords eccentric exercise, injury prevention, and neuromuscular control. Eccentric exercise will reduce injury risk by targeting specific neural and morphologic alterations that precipitate neuromuscular dysfunction. Clinical review. Level 4. Neuromuscular control is influenced by alterations in muscle morphology and neural activity. Eccentric exercise beneficially modifies several underlying factors of muscle morphology (fiber typing, cross-sectional area, working range, and pennation angle), and emerging evidence indicates that eccentric exercise is also beneficial to peripheral and central neural activity (alpha motorneuron recruitment/firing, sarcolemma activity, corticospinal excitability, and brain activation). There is mounting evidence that eccentric exercise is not only a therapeutic intervention influencing muscle morphology but also targets unique alterations in neuromuscular control, influencing injury risk.

  4. Collisional evolution of eccentric planetesimal swarms

    CERN Document Server

    Wyatt, M C; Payne, M J; Churcher, L J

    2009-01-01

    Models for the steady state collisional evolution of low eccentricity planetesimal belts identify debris disks with hot dust at 1AU, like eta Corvi and HD69830, as anomalous since collisional processing should have removed most of the planetesimal mass over their >1 Gyr lifetimes. This paper looks at the effect of large planetesimal eccentricities (e>>0.3) on their collisional lifetime and the amount of mass that can remain at late times M_{late}. For an axisymmetric planetesimal disk with common pericentres and eccentricities e, we find that M_{late} \\propto e^{-5/3}(1+e)^{4/3}(1-e)^{-3}. For a scattered disk-like population (i.e., common pericentres), in the absence of dynamical evolution, the mass evolution at late times would be as if only planetesimals with the largest eccentricity were present. Despite the increased remaining mass, higher eccentricities do not increase the hot emission from the collisional cascade until e>0.99, partly because most collisions occur near pericentre thus increasing the dus...

  5. Low-Frequency Fatigue Assessed as Double to Single Twitch Ratio after Two Bouts of Eccentric Exercise of the Elbow Flexors.

    Science.gov (United States)

    Janecki, Damian; Jaskólska, Anna; Marusiak, Jarosław; Jaskólski, Artur

    2016-12-01

    The aim of this study was to assess low-frequency fatigue as a double to single twitch ratio after repeated eccentric exercise of the elbow flexors. Maximal isometric torque, single and double twitch responses and low-frequency fatigue were assessed on the elbow flexors in 16 untrained male volunteers before, immediately after, 24 and 48 hours following two bouts of eccentric exercise consisted of 30 repetitions of lowering a dumbbell adjusted to ~75% of each individual's maximal isometric torque. Maximal isometric torque and electrically evoked responses decreased significantly in all measurements after the first bout of eccentric exercise (p single twitch ratio could be used as a sensitive tool in the evaluation of muscle recovery and adaptation to repeated eccentric exercise.

  6. Effect of creatine supplementation on muscle damage and repair following eccentrically-induced damage to the elbow flexor muscles.

    Science.gov (United States)

    McKinnon, Neal B; Graham, Mitchell T; Tiidus, Peter M

    2012-01-01

    We investigated effects of creatine (Cr) supplementation (CrS) on exercise-induced muscle damage. Untrained males and females (N = 27) ages 18-25, with no CrS history in the past 4 months, were randomly assigned to CrS (creatine and carbohydrate) (n = 9), placebo (P) (carbohydrate only) (n = 9), or control (C) (no supplements) groups (n = 9). Participants followed a 5-day Cr loading protocol of 40 g·day(-1), divided for 5 days prior to exercise, reduced to 10 g g·day(-1) for 5 days following exercise. Testing consisted of 5 maximal isometric contractions at 90 arm flexion with the preferred arm on a CYBEX NORM dynamometer, assessed prior to, immediately following, and 24, 48, 72, and 96 hours post muscle-damaging procedures. Damage was induced to the elbow flexor muscles using 6 sets of 10 eccentric contractions at 75 °/sec, 90 °/sec and 120 °/sec. Participants were asked to rate their muscle soreness on a scale of 1-10. Data was analyzed using repeated-measures ANOVA, with an alpha of 0.05. No significant differences were found between muscle force loss and rate of recovery or muscle soreness between groups over the 96 hr recovery period (p > 0.05). Across all 3 experimental groups an initial decrease in force was observed, followed by a gradual recovery. Significant differences were found between baseline and all others times (p = 0.031,0 .022, 0.012, 0.001 respectively), and between the 48 hour and 96 hour time periods (p = 0.034). A weak negative correlation between subjectively rated muscle soreness and mean peak isometric force loss (R(2) = 0.0374 at 96 hours), suggested that muscle soreness and muscle force loss may not be directly related. In conclusion, 5 days of Cr loading, followed by a Cr maintenance protocol did not reduce indices of muscle damage or speed recovery of upper body muscles following eccentrically induced muscle damage.

  7. EFFECT OF CREATINE SUPPLEMENTATION ON MUSCLE DAMAGE AND REPAIR FOLLOWING ECCENTRICALLY-INDUCED DAMAGE TO THE ELBOW FLEXOR MUSCLES

    Directory of Open Access Journals (Sweden)

    Neal B. McKinnon

    2012-12-01

    Full Text Available We investigated effects of creatine (Cr supplementation (CrS on exercise-induced muscle damage. Untrained males and females (N = 27 ages 18-25, with no CrS history in the past 4 months, were randomly assigned to CrS (creatine and carbohydrate (n = 9, placebo (P (carbohydrate only (n = 9, or control (C (no supplements groups (n = 9. Participants followed a 5-day Cr loading protocol of 40 g·day-1, divided for 5 days prior to exercise, reduced to 10 g g·day-1 for 5 days following exercise. Testing consisted of 5 maximal isometric contractions at 90 arm flexion with the preferred arm on a CYBEX NORM dynamometer, assessed prior to, immediately following, and 24, 48, 72, and 96 hours post muscle-damaging procedures. Damage was induced to the elbow flexor muscles using 6 sets of 10 eccentric contractions at 75 °/sec, 90 °/sec and 120 °/sec. Participants were asked to rate their muscle soreness on a scale of 1-10. Data was analyzed using repeated-measures ANOVA, with an alpha of 0.05. No significant differences were found between muscle force loss and rate of recovery or muscle soreness between groups over the 96 hr recovery period (p > 0.05. Across all 3 experimental groups an initial decrease in force was observed, followed by a gradual recovery. Significant differences were found between baseline and all others times (p = 0.031,0 .022, 0.012, 0.001 respectively, and between the 48 hour and 96 hour time periods (p = 0.034. A weak negative correlation between subjectively rated muscle soreness and mean peak isometric force loss (R2 = 0.0374 at 96 hours, suggested that muscle soreness and muscle force loss may not be directly related. In conclusion, 5 days of Cr loading, followed by a Cr maintenance protocol did not reduce indices of muscle damage or speed recovery of upper body muscles following eccentrically induced muscle damage

  8. Gravitational waves from spinning eccentric binaries

    CERN Document Server

    Csizmadia, Péter; Rácz, István; Vasúth, Mátyás

    2012-01-01

    This paper is to introduce a new software called CBwaves which provides a fast and accurate computational tool to determine the gravitational waveforms yielded by generic spinning binaries of neutron stars and/or black holes on eccentric orbits. This is done within the post-Newtonian (PN) framework by integrating the equations of motion and the spin precession equations while the radiation field is determined by a simultaneous evaluation of the analytic waveforms. In applying CBwaves various physically interesting scenarios have been investigated. In particular, we have studied the appropriateness of the adiabatic approximation, and justified that the energy balance relation is indeed insensitive to the specific form of the applied radiation reaction term. By studying eccentric binary systems it is demonstrated that circular template banks are very ineffective in identifying binaries even if they possess tiny residual orbital eccentricity. In addition, by investigating the validity of the energy balance relat...

  9. Muscle damage of resistance-trained men after two bouts of eccentric bench press exercise.

    Science.gov (United States)

    Meneghel, Adilson J; Verlengia, Rozangela; Crisp, Alex H; Aoki, Marcelo S; Nosaka, Kazunori; da Mota, Gustavo R; Lopes, Charles R

    2014-10-01

    The present study tested the hypothesis that resistance-trained individuals would also show less muscle damage in the second than in the first eccentric exercise bout (i.e., repeated bout effect) as shown in untrained individuals. This study investigated changes in indirect markers of muscle damage after 2 bouts of free weight eccentric exercise performed by 8 resistance-trained men. The participants (24.4 ± 1.2 years) performed 4 sets of 8 eccentric actions (3 seconds for each repetition) at 70% of eccentric 1 repetition maximum (1RM) load in a bench press exercise with 2 minutes of rest between sets, and repeated the same exercise 2 weeks later. Bench press 1RM, delayed onset muscle soreness (DOMS) assessed by a 6-point Likert scale, serum creatine kinase (CK) activity, and plasma prostaglandin E2 concentration (PGE2) were measured before and 24, 48, 72, and 96 hours after the exercise, and the changes were compared between bouts. The changes in the variables were smaller (p ≤ 0.05) after the second than the first bout indicated by a smaller decline in 1RM strength (first bout: -10.2 ± 1.0% vs. second bout: -5.7 ± 1.5%), peak DOMS (3.8 ± 0.4 vs. 1.7 ± 0.5), peak CK (637.3 ± 133.3 vs. 305.4 ± 63.6 IU·L), and peak PGE2 (761.2 ± 171.0 vs. 307.2 ± 48.3 pg·mL). These results show a typical repeated bout effect. Thus, it is concluded that the repeated bout effect occurs in resistance-trained individuals.

  10. Unstable force analysis for induction motor eccentricity

    Science.gov (United States)

    Han, Xu; Palazzolo, Alan

    2016-05-01

    The increasing popularity of motors in machinery trains has led to an intensified interest in the forces they produce that may influence machinery vibration. Motor design typically assumes a uniform air gap, however in practice all motors operate with the rotor slightly displaced from the motor centerline in what is referred to as an eccentric position. Rotor center eccentricity can cause a radially unbalanced magnetic field when the motor is operating. This will results in both a radial force pulling the motor further away from the center, and a tangential force which can induce a vibration stability problem. In this paper, a magnetic equivalent circuit MEC modeling method is proposed to calculate both the radial and tangential motor eccentric force. The treatment of tangential force determination is rarely addressed, but it is very important for rotordynamic vibration stability evaluation. The proposed model is also coupled with the motor electric circuit model to provide capability for transient vibration simulations. FEM is used to verify the MEC model. A parametric study is performed on the motor radial and tangential eccentric forces. Also a Jeffcott rotor model is used to study the influence of the motor eccentric force on mechanical vibration stability and nonlinear behavior. Furthermore, a stability criteria for the bearing damping is provided. The motor radial and tangential eccentric forces are both curved fitted to include their nonlinearity in time domain transient simulation for both a Jeffcott rotor model and a geared machinery train with coupled torsional-lateral motion. Nonlinear motions are observed, including limit cycles and bifurcation induced vibration amplitude jumps.

  11. Testing eccentricity pumping mechanisms to model eccentric long period sdB binaries with MESA

    CERN Document Server

    Vos, Joris; Marchant, Pablo; Van Winckel, Hans

    2015-01-01

    Hot subdwarf-B stars in long-period binaries are found to be on eccentric orbits, even though current binary-evolution theory predicts those objects to be circularised before the onset of Roche-lobe overflow (RLOF). We aim to find binary-evolution mechanisms that can explain these eccentric long-period orbits, and reproduce the currently observed period-eccentricity diagram. Three different processes are considered; tidally-enhanced wind mass-loss, phase-dependent RLOF on eccentric orbits and the interaction between a circumbinary disk and the binary. The binary module of the stellar-evolution code MESA (Modules for Experiments in Stellar Astrophysics) is extended to include the eccentricity-pumping processes. The effects of different input parameters on the final period and eccentricity of a binary-evolution model are tested with MESA. The end products of models with only tidally-enhanced wind mass-loss can indeed be eccentric, but these models need to lose too much mass, and invariably end up with a helium ...

  12. Eccentric connectivity index and eccentric distance sum of some graph operations

    Directory of Open Access Journals (Sweden)

    Buzohragul Eskender

    2013-03-01

    Full Text Available Let $G=(V,E$ be a connected graph. The eccentric connectivity index of $G$, $xi^{c}(G$, is defined as $xi^{c}(G=sum_{vin V(G}deg(vec(v$, where $deg(v$ is the degree of a vertex $v$ and $ec(v$ is its eccentricity. The eccentric distance sum of $G$ is defined as $xi^{d}(G=sum_{vin V(G}ec(vD(v$, where $D(v=sum_{uin V(G}d_{G}(u,v$ and $d_{G}(u,v$ is the distance between $u$ and $v$ in $G$. In this paper, we calculate the eccentric connectivity index and eccentric distance sum of generalized hierarchical product of graphs. Moreover, we present explicit formulae for the eccentric connectivity index of $F$-sum graphs in terms of some invariants of the factors. As applications, we present exact formulae for the values of the eccentric connectivity index of some graphs of chemical interest such as $C_{4}$ nanotubes, $C_{4}$ nanotoris and hexagonal chains.

  13. Muscle fascicle behavior during eccentric cycling and its relation to muscle soreness.

    Science.gov (United States)

    Peñailillo, Luis; Blazevich, Anthony J; Nosaka, Kazunori

    2015-04-01

    A single bout of eccentric exercise confers a protective effect against muscle damage and soreness in subsequent eccentric exercise bouts, but the mechanisms underpinning this effect are unclear. This study compared vastus lateralis (VL) muscle-tendon behavior between two eccentric cycling bouts to test the hypothesis that muscle-tendon behavior would be different between bouts and would be associated with the protective effect. Eleven untrained men (27.1 ± 7.0 yr) performed two bouts of eccentric cycling (ECC1 and ECC2) separated by 2 wk for 10 min at 65% of maximal concentric workload (191.9 ± 44.2 W) each. Muscle soreness (by visual analog scale) and maximal voluntary isometric contraction (MVC) torque of the knee extensors were assessed before and 1-2 d after exercise. Using ultrasonography, VL fascicle length and angle changes during cycling were assessed, and tendinous tissue (TT) length changes were estimated. VL EMG amplitude, crank torque, and knee joint angles were measured during cycling. Soreness was greater (P knee angles were evident between bouts. However, fascicle elongation was 16% less during ECC2 than ECC1 (P knee joint angle during ECC2 than ECC1 (P = 0.055). These results suggest that a lesser fascicle elongation and earlier TT elongation were associated with reduced muscle soreness after ECC2 than ECC1; thus, changes in muscle-tendon behavior may be an important mechanism underpinning the protective effect.

  14. Flywheel resistance training calls for greater eccentric muscle activation than weight training.

    Science.gov (United States)

    Norrbrand, Lena; Pozzo, Marco; Tesch, Per A

    2010-11-01

    Changes in muscle activation and performance were studied in healthy men in response to 5 weeks of resistance training with or without "eccentric overload". Subjects, assigned to either weight stack (grp WS; n = 8) or iso-inertial "eccentric overload" flywheel (grp FW; n = 9) knee extensor resistance training, completed 12 sessions of four sets of seven concentric-eccentric actions. Pre- and post-measurements comprised maximal voluntary contraction (MVC), rate of force development (RFD) and training mode-specific force. Root mean square electromyographic (EMG(RMS)) activity of mm. vastus lateralis and medialis was assessed during MVC and used to normalize EMG(RMS) for training mode-specific concentric (EMG(CON)) and eccentric (EMG(ECC)) actions at 90°, 120° and 150° knee joint angles. Grp FW showed greater (p  0.05), MVC and training-specific strength increased (p exercise compared to standard weight lifting could be attributed to its unique iso-inertial loading features. Hence, the resulting greater mechanical stress may explain the robust muscle hypertrophy reported earlier in response to flywheel resistance training.

  15. Chronic Eccentric Exercise and Antioxidant Supplementation: Effects on Lipid Profile and Insulin Sensitivity.

    Science.gov (United States)

    Yfanti, Christina; Tsiokanos, Athanasios; Fatouros, Ioannis G; Theodorou, Anastasios A; Deli, Chariklia K; Koutedakis, Yiannis; Jamurtas, Athanasios Z

    2017-09-01

    Eccentric exercise has been shown to exert beneficial effects in both lipid profile and insulin sensitivity. Antioxidant supplementation during chronic exercise is controversial as it may prevent the physiological training-induced adaptations. The aim of this study was to investigate: 1) the minimum duration of the eccentric exercise training required before changes on metabolic parameters are observed and 2) whether antioxidant supplementation during training would interfere with these adaptations. Sixteen young healthy men were randomized into the Vit group (1 g of vitamin C and 400 IU vitamin E daily) and the placebo (PL) group. Subjects received the supplementation for 9 weeks. During weeks 5-9 all participants went through an eccentric exercise training protocol consisting of two exercise sessions (5 sets of 15 eccentric maximal voluntary contractions) per week. Plasma triglycerides (TG), total cholesterol (TC), high density lipoprotein (HDL), low density lipoprotein (LDL), apolipoproteins (Apo A1, Apo B and Lpa) and insulin sensitivity (HOMA) were assessed before the supplementation (week 0), at weeks 5, 6, 7, 8 and 9. TG, TC and LDL were significantly lower compared to pre supplementation at both weeks 8 and 9 (Peccentric exercise training is required before beneficial effects in lipid profile can be observed in healthy young men. Concomitant antioxidant supplementation does not interfere with the training-induced adaptations.

  16. Metabolic demand and muscle damage induced by eccentric cycling of knee extensor and flexor muscles.

    Science.gov (United States)

    Peñailillo, Luis; Guzmán, Nicolás; Cangas, José; Reyes, Alvaro; Zbinden-Foncea, Hermann

    2017-03-01

    The aim of this study was to examine the metabolic demand and extent of muscle damage of eccentric cycling targeting knee flexor (FLEX) and knee extensor (EXT) muscles. Eight sedentary men (23.3 ± 0.7 y) underwent two eccentric cycling sessions (EXT and FLEX) of 30 min each, at 60% of the maximum power output. Oxygen consumption (VO2), heart rate (HR) and rated perceived exertion (RPE) were measured during cycling. Countermovement and squat jumps (CMJ and SJ), muscle flexibility, muscle soreness and pain pressure threshold (PPT) of knee extensor and flexor muscles were measured before, immediately after and 1-4 days after cycling. FLEX showed greater VO2 (+23%), HR (+14%) and RPE (+18%) than EXT. CMJ and SJ performance decreased similarly after cycling. Muscle soreness increased more after EXT than FLEX and PPT decreased in knee extensor muscles after EXT and decreased in knee flexor muscles after FLEX. Greater loss of muscle flexibility in knee flexor muscles after FLEX was observed. Eccentric cycling of knee flexor muscles is metabolically more demanding than that of knee extensors, however muscle damage induced is similar. Knee flexors experienced greater loss of muscle flexibility possibly due to increased muscle stiffness following eccentric contractions.

  17. Reduced firing rates of high threshold motor units in response to eccentric overload.

    Science.gov (United States)

    Balshaw, Tom G; Pahar, Madhu; Chesham, Ross; Macgregor, Lewis J; Hunter, Angus M

    2017-01-01

    Acute responses of motor units were investigated during submaximal voluntary isometric tasks following eccentric overload (EO) and constant load (CL) knee extension resistance exercise. Ten healthy resistance-trained participants performed four experimental test sessions separated by 5 days over a 20 day period. Two sessions involved constant load and the other two used eccentric overload. EO and CL used both sessions for different target knee eccentric extension phases; one at 2 sec and the other at 4 sec. Maximal voluntary contractions (MVC) and isometric trapezoid efforts for 10 sec at 70% MVC were completed before and after each intervention and decomposed electromyography was used to measure motor unit firing rate. The firing rate of later recruited, high-threshold motor units declined following the 2-sec EO but was maintained following 2sec CL (P units were maintained for both loading types following 4-sec extension phases. MVC and rate of force development where maintained following both EO and CL and 2 and 4 sec phases. This study demonstrates a slower firing rate of high-threshold motor units following fast eccentric overload while MVC was maintained. This suggests that there was a neuromuscular stimulus without cost to the force-generating capacity of the knee extensors. © 2017 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society.

  18. Cardiovascular Response and Serum Interleukin-6 Level in Concentric Vs. Eccentric Exercise.

    Science.gov (United States)

    Agarwal, Mayank; Singh, Shraddha; Narayan, Jagdish; Pandey, Shivani; Tiwari, Sunita; Sharma, Priyanka

    2017-04-01

    Cardiovascular Disease (CVD) is a leading cause of morbidity and mortality in India. Resistance exercise is strongly recommended for implementation in CVD prevention programs. Dynamic resistance exercise comprises of concentric (muscle shortening) and eccentric (muscle lengthening) phase. The contraction of skeletal muscle promotes the synthesis and secretion of cytokines and peptides from myocytes, known as 'myokines'. Interleukin-6 (IL-6) is the first myokine to be released in the blood in response to exercise. To compare the cardiovascular response and serum IL-6 level in concentric and eccentric exercise done at same absolute workload. In this non-randomised crossover study 24, apparently healthy and young male adults performed an acute bout of concentric and eccentric exercise. Systolic Blood Pressure (SBP), Diastolic Blood Pressure (DBP), Heart Rate (HR), Mean Arterial Pressure (MAP), Pulse Pressure (PP) and serum IL-6 were measured just before and immediately after exercise. Paired t-test or Wilcoxon signed-rank test were applied to compare the data within-group and in-between group. SBP, HR, MAP, PP, DBP and IL-6 level increased significantly after both, concentric and eccentric exercise. The mean change in SBP, HR, MAP, PP, and IL-6 after concentric exercise (18.54±3.06, 57.21±10.73, 8.35±1.40, 15.25±5.29, 5.40±3.13 respectively) was significantly higher than after eccentric exercise (13.38±1.72, 43.25±8.34, 6.50±1.0, 10.21±3.16, 4.36±2.54 respectively). A non-significant rise in DBP was obtained after concentric exercise (3.25±2.79) as compared to eccentric exercise (3.08±1.89). Eccentric exercise not only caused a lesser cardiovascular demand as compared to concentric exercise but also a significant increment in IL-6 level. Exercise-induced IL-6 may prevent the initiation and development of CVD. Hence, eccentric exercise training might be recommended for reducing morbidity and mortality in individuals with- or at a risk of developing CVD.

  19. Whey protein supplementation accelerates satellite cell proliferation during recovery from eccentric exercise.

    Science.gov (United States)

    Farup, Jean; Rahbek, Stine Klejs; Knudsen, Inge Skovgaard; de Paoli, Frank; Mackey, Abigail L; Vissing, Kristian

    2014-11-01

    Human skeletal muscle satellite cells (SCs) are essential for muscle regeneration and remodeling processes in healthy and clinical conditions involving muscle breakdown. However, the potential influence of protein supplementation on post-exercise SC regulation in human skeletal muscle has not been well investigated. In a comparative human study, we investigated the effect of hydrolyzed whey protein supplementation following eccentric exercise on fiber type-specific SC accumulation. Twenty-four young healthy subjects received either hydrolyzed whey protein + carbohydrate (whey, n = 12) or iso-caloric carbohydrate (placebo, n = 12) during post-exercise recovery from 150 maximal unilateral eccentric contractions. Prior to and 24, 48 and 168 h post-exercise, muscle biopsies were obtained from the exercise leg and analyzed for fiber type-specific SC content. Maximal voluntary contraction (MVC) and serum creatine kinase (CK) were evaluated as indices of recovery from muscle damage. In type II fiber-associated SCs, the whey group increased SCs/fiber from 0.05 [0.02; 0.07] to 0.09 [0.06; 0.12] (p eccentric exercise.

  20. Muscle soreness, swelling, stiffness and strength loss after intense eccentric exercise.

    Science.gov (United States)

    Cleak, M J; Eston, R G

    1992-01-01

    High-intensity eccentric contractions induce performance decrements and delayed onset muscle soreness. The purpose of this investigation was to study the magnitude and time course of such decrements and their interrelationships in 26 young women of mean(s.d.) age 21.4(3.3) years. Subjects performed 70 maximal eccentric contractions of the elbow flexors on a pulley system, specially designed for the study. The non-exercised arm acted as the control. Measures of soreness, tenderness, swelling (SW), relaxed elbow joint angle (RANG) and isometric strength (STR) were taken before exercise, immediately after exercise (AE), analysis of variance and at 24-h intervals for 11 days. There were significant (P < 0.01, analysis of variance) changes in all factors. Peak effects were observed between 24 and 96 h AE. With the exception of STR, which remained lower (P < 0.01), all variables returned to baseline levels by day 11. A non-significant correlation between pain and STR indicated that pain was not a major factor in strength loss. Also, although no pain was evident, RANG was decreased immediately AE. There was no relationship between SW, RANG and pain. The prolonged nature of these symptoms indicates that repair to damaged soft tissue is a slow process. Strength loss is considered particularly important as it continues when protective pain and tenderness have disappeared. This has implications for the therapeutic management of patients with myopathologies and those receiving eccentric exercise for rehabilitation. PMID:1490222

  1. Orbital eccentricities in primordial black holes binaries

    CERN Document Server

    Cholis, Ilias; Ali-Haïmoud, Yacine; Bird, Simeon; Kamionkowski, Marc; Muñoz, Julian B; Raccanelli, Alvise

    2016-01-01

    It was recently suggested that the merger of $\\sim30\\,M_\\odot$ primordial black holes (PBHs) may provide a significant number of events in gravitational-wave observatories over the next decade, if they make up an appreciable fraction of the dark matter. Here we show that measurement of the eccentricities of the inspiralling binary black holes can be used to distinguish these binaries from those produced by more traditional astrophysical mechanisms. These PBH binaries are formed on highly eccentric orbits and can then merge on timescales that in some cases are years or less, retaining some eccentricity in the last seconds before the merger. This is to be contrasted with massive-stellar-binary, globular-cluster, or other astrophysical origins for binary black holes (BBHs) in which the orbits have very effectively circularized by the time the BBH enters the observable LIGO window. Here we discuss the features of the gravitational-wave signals that indicate this eccentricity and forecast the sensitivity of LIGO a...

  2. Density and Eccentricity of Kepler Planets

    CERN Document Server

    Wu, Yanqin

    2012-01-01

    We analyze the transit timing variations obtained by the Kepler mission for 22 sub-jovian planet pairs (17 published, 5 new) that lie close to mean motion resonances. We find that the TTV phases for most of these pairs lie close to zero, consistent with an eccentricity distribution that has a very low RMS value of e ~ 0.01; but about a quarter of the pairs possess much higher eccentricities, up to 0.1 - 0.4. For the low-eccentricity pairs, we are able to statistically remove the effect of eccentricity to obtain planet masses from TTV data. These masses, together with those measured by radial velocity, yield a best fit mass-radius relation M~3 M_E (R/R_E). This corresponds to a constant surface escape velocity of 20km/s. We separate the planets into two distinct groups, "mid-sized" (those greater than 3 R_E), and "compact" (those smaller). All mid-sized planets are found to be less dense than water and therefore contain extensive H/He envelopes, likely comparable in mass to that of their cores. We argue that t...

  3. Chain hexagonal cacti with the extremal eccentric distance sum.

    Science.gov (United States)

    Qu, Hui; Yu, Guihai

    2014-01-01

    Eccentric distance sum (EDS), which can predict biological and physical properties, is a topological index based on the eccentricity of a graph. In this paper we characterize the chain hexagonal cactus with the minimal and the maximal eccentric distance sum among all chain hexagonal cacti of length n, respectively. Moreover, we present exact formulas for EDS of two types of hexagonal cacti.

  4. Muscular hypertrophy and changes in cytokine production after eccentric training in the rat skeletal muscle.

    Science.gov (United States)

    Ochi, Eisuke; Nakazato, Koichi; Ishii, Naokata

    2011-08-01

    We investigated the time course effects of eccentric training on muscular size, strength, and growth factor/cytokine production by using an isokinetic-exercise system for rats. Male Wistar rats (n = 34) were randomly assigned into 4 groups: 5 session eccentric-training group (ECC5S, n = 10); 5 session sham-operated group (CON5S, n = 10); 10 session eccentric-training group (ECC10S, n = 7); 10 session sham-operated group (CON10S, n = 7). In each group, a session of either training or sham operation was performed every 2 days. The training consisted of 4 sets of forced dorsiflexion (5 repetitions) combined with electric stimulation of plantar flexors. The wet weight of medial gastrocnemius muscle did not increase significantly after 5 sessions of training, whereas that after 10 sessions of training significantly increased with a concomitant increase in the cross-sectional area (CSA) of muscle fibers (weight, p eccentric training for 20 days cause increases in muscular size and strength associated with increases in IL-6, follistatin, phospho-stat-3, and a decrease in myostatin. The delayed responses of IL-6, myostatin, phospho-stat-3, and follistatin would be due to the chronic effects of repeated training and possibly important for muscular hypertrophy.

  5. Protein hydrolysates and recovery of muscle damage following eccentric exercise

    Directory of Open Access Journals (Sweden)

    Dale M.J.

    2015-01-01

    Full Text Available Background: A whey protein hydrolysate (NatraBoost XR; WPHNB has been shown to speed repair muscle damage. We sought to determine whether this benefit is specific to this hydrolysate to evaluate a marker for quality control. Methods: Three hydrolysates of the same whey protein isolate (WPI were prepared (WPHNB, WPH1 and WPH2. Isometric knee extensor strength was measured in 39 sedentary male participants before and after 100 maximal eccentric contractions of the knee extensors to induce muscle damage. Participants were then randomised to consume 250 ml of flavoured water (FW, n=9, or 250 ml of FW containing 25 g of either NatraBoost XR (n=3, WPH1 (n=9, WPH2 (n=9 or WPI (n=9. Strength was reassessed over the next seven days while the supplements were consumed daily. Fibroblasts were cultured for 48 hr in the presence of the different hydrolysates, WPI, saline or fetal bovine serum to ascertain effects on cell proliferation. Results: Strength was reduced in all treatment groups after eccentric exercise (P<0.001. Strength recovered steadily over 7 days in the FW, WPI, WPH1 and WPH2 treatment groups (P<0.001, with no difference between treatments (P=0.87. WPHNB promoted faster strength recovery compared with the other treatments (P<0.001. Fibroblast proliferation was greater with WPHNB compared with saline, WPI or the other hydrolysates (P<0.001. Conclusions: Promoting recovery from muscle damage seems unique to WPHNB. In vitro fibroblast proliferation may be a useful marker for quality control. It is not clear whether effects on fibroblast proliferation contribute to the in vivo effect of WPHNB on muscle damage.

  6. Protein hydrolysates and recovery of muscle damage following eccentric exercise

    Directory of Open Access Journals (Sweden)

    Dale M.J.

    2015-01-01

    Full Text Available Background: A whey protein hydrolysate (NatraBoost XR; WPHNB has been shown to speed repair muscle damage. We sought to determine whether this benefit is specific to this hydrolysate to evaluate a marker for quality control. Methods: Three hydrolysates of the same whey protein isolate (WPI were prepared (WPHNB, WPH1 and WPH2. Isometric knee extensor strength was measured in 39 sedentary male participants before and after 100 maximal eccentric contractions of the knee extensors to induce muscle damage. Participants were then randomised to consume 250 ml of flavoured water (FW, n=9, or 250 ml of FW containing 25 g of either NatraBoost XR (n=3, WPH1 (n=9, WPH2 (n=9 or WPI (n=9. Strength was reassessed over the next seven days while the supplements were consumed daily. Fibroblasts were cultured for 48 hr in the presence of the different hydrolysates, WPI, saline or fetal bovine serum to ascertain effects on cell proliferation. Results: Strength was reduced in all treatment groups after eccentric exercise (P<0.001. Strength recovered steadily over 7 days in the FW, WPI, WPH1 and WPH2 treatment groups (P<0.001, with no difference between treatments (P=0.87. WPHNB promoted faster strength recovery compared with the other treatments (P<0.001. Fibroblast proliferation was greater with WPHNB compared with saline, WPI or the other hydrolysates (P<0.001. Conclusions: Promoting recovery from muscle damage seems unique to WPHNB. In vitro fibroblast proliferation may be a useful marker for quality control. It is not clear whether effects on fibroblast proliferation contribute to the in vivo effect of WPHNB on muscle damage.

  7. Post-exercise muscle soreness after eccentric exercise: psychophysical effects and implications on mean arterial pressure.

    Science.gov (United States)

    Bajaj, P; Graven-Nielsen, T; Arendt-Nielsen, L

    2001-10-01

    The aim of the study was to examine the time course of changes in pressure pain threshold (PPT), visual analogue scale (VAS) pain and tenderness scores, McGill Pain Questionnaire (MPQ) descriptors, pain areas, skin temperature and mean arterial pressure (MAP) following intensive eccentric exercise. In 11 healthy male subjects, eccentric exercise of the first dorsal interosseous muscle (FDI) of the right hand with 114% maximum voluntary contraction weight (MVC) was used to induce post-exercise muscle soreness (PEMS) in the right hand, while the left hand served as a control. At 24 h to 48 h all the pain profiles indicated the presence of PEMS in the right hand when compared to before exercise (Prole of central mechanisms in the PEMS, thereby giving further insight into clinical aspects of muscle pain.

  8. Administrative contracts

    Directory of Open Access Journals (Sweden)

    Vukićević-Petković Milica

    2015-01-01

    Full Text Available Administrative contracts are a special type of contract where usually one of the contracting parties is a public law body and which is concluded for the performance of public service and the realization of a public interest. They go a long way since its inception to its eventual final acceptance of all the legal systems. One of the enduring characteristics of this type of contract is their disquised or unnoticed existence. This is why only monitoring their development may lead to a complete understanding of the importance and essence of this institution as well as the need for its complete legal regulation.

  9. Electrical contracting

    CERN Document Server

    Neidle, Michael

    2013-01-01

    Electrical Contracting, Second Edition is a nine-chapter text guide for the greater efficiency in planning and completing installations for the design, installation and control of electrical contracts. This book starts with a general overview of the efficient cabling and techniques that must be employed for safe wiring design, as well as the cost estimation of the complete electrical contract. The subsequent chapters are devoted to other electrical contracting requirements, including electronic motor control, lighting, and electricity tariffs. A chapter focuses on the IEE Wiring Regulations an

  10. Effect of New Zealand blueberry consumption on recovery from eccentric exercise-induced muscle damage

    Directory of Open Access Journals (Sweden)

    McLeay Yanita

    2012-07-01

    Full Text Available Abstract Background Exercise-induced muscle damage (EIMD is accompanied by localized oxidative stress / inflammation which, in the short-term at least, is associated with impaired muscular performance. Dietary antioxidants have been shown to reduce excessive oxidative stress; however, their effectiveness in facilitating recovery following EIMD is not clear. Blueberries demonstrate antioxidant and anti-inflammatory properties. In this study we examine the effect of New Zealand blueberries on EIMD after strenuous eccentric exercise. Methods In a randomized cross-over design, 10 females consumed a blueberry smoothie or placebo of a similar antioxidant capacity 5 and 10 hours prior to and then immediately, 12 and 36 hours after EIMD induced by 300 strenuous eccentric contractions of the quadriceps. Absolute peak and average peak torque across the knee, during concentric, isometric, and eccentric actions were measured. Blood biomarkers of oxidative stress, antioxidant capacity, and inflammation were assessed at 12, 36 and 60 hours post exercise. Data were analyzed using a two-way ANOVA. Results A significant (p p = 0.047 interaction effect was seen for peak isometric tension suggesting a faster rate of recovery in the blueberry intervention group. A similar trend was observed for concentric and eccentric strength. An increase in oxidative stress and inflammatory biomarkers was also observed in both treatment groups following EIMD. Although a faster rate of decrease in oxidative stress was observed in the blueberry group, it was not significant (p  Conclusions This study demonstrates that the ingestion of a blueberry smoothie prior to and after EIMD accelerates recovery of muscle peak isometric strength. This effect, although independent of the beverage’s inherent antioxidant capacity, appears to involve an up-regulation of adaptive processes, i.e. endogenous antioxidant processes, activated by the combined actions of the eccentric exercise

  11. Maximal force, voluntary activation and muscle soreness after eccentric damage to human elbow flexor muscles

    Science.gov (United States)

    Prasartwuth, O; Taylor, JL; Gandevia, SC

    2005-01-01

    Muscle damage reduces voluntary force after eccentric exercise but impaired neural drive to the muscle may also contribute. To determine whether the delayed-onset muscle soreness, which develops ∼1 day after exercise, reduces voluntary activation and to identify the possible site for any reduction, voluntary activation of elbow flexor muscles was examined with both motor cortex and motor nerve stimulation. We measured maximal voluntary isometric torque (MVC), twitch torque, muscle soreness and voluntary activation in eight subjects before, immediately after, 2 h after, 1, 2, 4 and 8 days after eccentric exercise. Motor nerve stimulation and motor cortex stimulation were used to derive twitch torques and measures of voluntary activation. Eccentric exercise immediately reduced the MVC by 38 ± 3% (mean ±s.d., n = 8). The resting twitch produced by motor nerve stimulation fell by 82 ± 6%, and the estimated resting twitch by cortical stimulation fell by 47 ± 15%. While voluntary torque recovered after 8 days, both measures of the resting twitch remained depressed. Muscle tenderness occurred 1–2 days after exercise, and pain during contractions on days 1–4, but changes in voluntary activation did not follow this time course. Voluntary activation assessed with nerve stimulation fell 19 ± 6% immediately after exercise but was not different from control values after 2 days. Voluntary activation assessed by motor cortex stimulation was unchanged by eccentric exercise. During MVCs, absolute increments in torque evoked by nerve and cortical stimulation behaved differently. Those to cortical stimulation decreased whereas those to nerve stimulation tended to increase. These findings suggest that reduced voluntary activation contributes to the early force loss after eccentric exercise, but that it is not due to muscle soreness. The impairment of voluntary activation to nerve stimulation but not motor cortical stimulation suggests that the activation deficit lies in the

  12. Does intermittent pneumatic leg compression enhance muscle recovery after strenuous eccentric exercise?

    Science.gov (United States)

    Cochrane, D J; Booker, H R; Mundel, T; Barnes, M J

    2013-11-01

    Intermittent pneumatic compression (IPC) has gained rapid popularity as a post-exercise recovery modality. Despite its widespread use and anecdotal claims for enhancing muscle recovery there is no scientific evidence to support its use. 10 healthy, active males performed a strenuous bout of eccentric exercise (3 sets of 100 repetitions) followed by IPC treatment or control performed immediately after exercise and at 24 and 48 h post-exercise. Muscular performance measurements were taken prior to exercise and 24, 48 and 72 h post-exercise and included single-leg vertical jump (VJ) and peak and average isometric [knee angle 75º] (ISO), concentric (CON) and eccentric (ECC) contractions performed at slow (30° · s⁻¹) and fast (180° · s⁻¹) velocities. Plasma creatine kinase (CK) samples were taken at pre- and post-exercise 24, 48 and 72 h. Strenuous eccentric exercise resulted in a significant decrease in peak ISO, peak and average CON (30° · s⁻¹) at 24 h compared to pre-exercise for both IPC and control, however VJ performance remained unchanged. There were no significant differences between conditions (IPC and control) or condition-time interactions for any of the contraction types (ISO, CON, ECC) or velocities (CON, ECC 30° · s⁻¹ and 180° · s⁻¹). However, CK was significantly elevated at 24 h compared to pre-exercise in both conditions (IPC and control). IPC did not attenuate muscle force loss following a bout of strenuous eccentric exercise in comparison to a control. While IPC has been used in the clinical setting to treat pathologic conditions, the parameters used to treat muscle damage following strenuous exercise in healthy participants are likely to be very different than those used to treat pathologic conditions.

  13. The effect of gender on force, muscle activity, and frontal plane knee alignment during maximum eccentric leg-press exercise.

    Science.gov (United States)

    Liebensteiner, Michael C; Platzer, Hans-Peter; Burtscher, Martin; Hanser, Friedrich; Raschner, Christian

    2012-03-01

    To investigate for gender differences during eccentric leg-press exercise. Tears of the anterior cruciate ligament (ACL) are considered to be related to eccentric tasks, altered neuromuscular control (e.g., reduced co-contraction of hamstrings), and increased knee abduction (valgus alignment). Based on these observations and the fact that ACL tears are more common in women, it was hypothesized that men and women differ significantly with regard to key parameters of force, knee stabilization, and muscle activity when exposed to maximum eccentric leg extension. Thirteen women and thirteen men were matched for age and physical activity. They performed maximum isokinetic eccentric leg-pressing against footplates of varied stability. The latter was done because earlier studies had shown that perturbational test conditions might be relevant in respect of ACL injuries. Key parameters of force, frontal plane knee stabilization, and muscle recruitment of significant muscles crossing the knee were recorded. The 'force stabilization deficit' (difference between maximum forces under normal and perturbed leg-pressing) did not differ significantly between genders. Likewise, parameters of muscle activity and frontal plane leg stabilization revealed no significant differences between men and women. This study is novel, in that gender differences in parameters of force, muscle activity, and leg kinematic were investigated during functional conditions of eccentric leg-pressing. No gender differences were observed in the measured parameters. However, the conclusion should be viewed with caution because the findings concurred with, but also contrasted, previous research in this field. Diagnostic study, Level III.

  14. Eccentricity Pumping Through Circumbinary Disks in Hot Subdwarf Binaries

    Science.gov (United States)

    Vos, J.

    2015-12-01

    Hot subdwarf-B stars in long-period binaries are found to be on eccentric orbits, even though current binary-evolution theory predicts these objects to be circularized before the onset of Roche-lobe overflow (RLOF). We have tested three different eccentricity pumping processes on their viability to reproduce the observed wide sdB population; tidally-enhanced wind mass-loss, phase-dependent RLOF on eccentric orbits and the interaction between a circumbinary (CB) disk and the binary. The binary module of the stellar-evolution code Modules for Experiments in Stellar Astrophysics (MESA) is extended to include the eccentricity-pumping processes, and a parameter study is carried out. We find that models including phase-dependent RLOF or a CB disk can reach the observed periods and eccentricities. However, the models cannot explain the observed correlation between period and eccentricity. Nor can circular short period systems be formed when eccentricity pumping mechanisms are active.

  15. Effects of Retinal Eccentricity on Human Manual Control

    Science.gov (United States)

    Popovici, Alexandru; Zaal, Peter M. T.

    2017-01-01

    This study investigated the effects of viewing a primary flight display at different retinal eccentricities on human manual control behavior and performance. Ten participants performed a pitch tracking task while looking at a simplified primary flight display at different horizontal and vertical retinal eccentricities, and with two different controlled dynamics. Tracking performance declined at higher eccentricity angles and participants behaved more nonlinearly. The visual error rate gain increased with eccentricity for single-integrator-like controlled dynamics, but decreased for double-integrator-like dynamics. Participants' visual time delay was up to 100 ms higher at the highest horizontal eccentricity compared to foveal viewing. Overall, vertical eccentricity had a larger impact than horizontal eccentricity on most of the human manual control parameters and performance. Results might be useful in the design of displays and procedures for critical flight conditions such as in an aerodynamic stall.

  16. Fuzzy contractibility

    OpenAIRE

    GÜNER, Erdal

    2007-01-01

    Abstract. In this paper, .rstly some fundamental concepts are included re- lating to fuzzy topological spaces. Secondly, the fuzzy connected set is intro- duced. Finally, de.ning fuzzy contractible space, it is shown that X is a fuzzy contractible space if and only if X is fuzzy homotopic equivalent with a fuzzy single-point space.

  17. A COX-2 inhibitor reduces muscle soreness, but does not influence recovery and adaptation after eccentric exercise

    DEFF Research Database (Denmark)

    Paulsen, G; Egner, I M; Drange, M

    2010-01-01

    The aim of this study was to investigate the effect of a cyclooxygenase (COX)-2 inhibitor on the recovery of muscle function, inflammation, regeneration after, and adaptation to, unaccustomed eccentric exercise. Thirty-three young males and females participated in a double-blind, placebo...... by celecoxib. In summary, celecoxib, a COX-2 inhibitor, did not detectably affect recovery of muscle function or markers of inflammation and regeneration after unaccustomed eccentric exercise, nor did the drug influence the repeated-bout effect. However, it alleviated muscle soreness.......-controlled experiment. Seventy unilateral, voluntary, maximal eccentric actions with the elbow flexors were performed twice (bouts 1 and 2) with the same arm, separated by 3 weeks. The test group participants were administered 400 mg/day of celecoxib for 9 days after bout 1. After both bouts 1 and 2, concentric...

  18. Isokinetic eccentric exercise as a model to induce and reproduce pathophysiological alterations related to delayed onset muscle soreness

    DEFF Research Database (Denmark)

    Lund, Henrik; Vestergaard-Poulsen, P; Kanstrup, I.L.

    1998-01-01

    Physiological alterations following unaccustomed eccentric exercise in an isokinetic dynamometer of the right m. quadriceps until exhaustion were studied, in order to create a model in which the physiological responses to physiotherapy could be measured. In experiment I (exp. I), seven selected...... parameters were measured bilaterally in 7 healthy subjects at day 0 as a control value. Then after a standardized bout of eccentric exercise the same parameters were measured daily for the following 7 d (test values). The measured parameters were: the ratio of phosphocreatine to inorganic phosphate (PCr...... (133Xenon washout technique). This was repeated in experiment II (exp. II) 6-12 months later in order to study reproducibility. In experiment III (exp. III), the normal fluctuations over 8 d of the seven parameters were measured, without intervention with eccentric exercise in 6 other subjects. All...

  19. Effects of eccentric exercise on systemic concentrations of pro- and anti-inflammatory cytokines and prostaglandin (E2): comparison between young and postmenopausal women.

    Science.gov (United States)

    Conceição, Miguel Soares; Libardi, Cleiton Augusto; Nogueira, Felipe Romano Damas; Bonganha, Valéria; Gáspari, Arthur Fernandes; Chacon-Mikahil, Mara Patrícia Traina; Cavaglieri, Cláudia Regina; Madruga, Vera Aparecida

    2012-09-01

    The present study aimed to analyze the magnitude of muscle damage and inflammatory responses induced by eccentric exercise in young (YW) and postmenopausal women (PMW). Seventeen healthy women (nine YW, 23.89 ± 2.03 years; and eight PMW, 51.13 ± 5.08 years) performed five sets of six maximal eccentric actions of the elbow flexors. Changes in isometric strength, range of motion, muscle soreness, and upper-arm circumference were evaluated pre, post, 24, 48, and 72 h following eccentric exercise. Changes in creatine kinase activity, interleukin 6 (IL-6), interleukin 10 (IL-10), tumor necrosis factor-α (TNF-α), and prostaglandin E(2) (PGE(2)) were measured pre, 24, 48, and 72 h following eccentric exercise. For intra and inter-group analysis, a two-way repeated measures ANOVA was applied followed by a Tukey's post hoc test. Pearson's correlation was used to analyze the correlations between variables. It was observed no differences between groups for the markers of muscle damage, although significant modifications (p eccentric exercise compared to pre. Further, IL-10 was higher for YW than PMW 72 h post-eccentric exercise. Significant correlations (p eccentric exercise compared to PMW.

  20. Deployment Repeatability

    Science.gov (United States)

    2016-04-01

    controlled to great precision, but in a Cubesat , there may be no attitude determination at all. Such a Cubesat might treat sun angle and tumbling rates as...could be sensitive to small differences in motor controller timing. In these cases, the analyst might choose to model the entire deployment path, with...knowledge of the material damage model or motor controller timing precision. On the other hand, if many repeated and environmentally representative

  1. Eccentric Connectivity Index of Chemical Trees

    CERN Document Server

    c, Aleksandar Ili\\'

    2011-01-01

    The eccentric connectivity index $\\xi^c$ is a distance--based molecular structure descriptor that was recently used for mathematical modeling of biological activities of diverse nature. We prove that the broom has maximum $\\xi^c$ among trees with a fixed maximum vertex degree, and characterize such trees with minimum $\\xi^c$\\,. In addition, we propose a simple linear algorithm for calculating $\\xi^c$ of trees.

  2. Eccentric exercise and delayed onset muscle soreness of the quadriceps induce adjustments in agonist-antagonist activity, which are dependent on the motor task.

    Science.gov (United States)

    Vila-Chã, C; Hassanlouei, H; Farina, D; Falla, D

    2012-02-01

    This study investigates the effects of eccentric exercise and delayed onset muscle soreness (DOMS) of the quadriceps on agonist-antagonist activity during a range of motor tasks. Ten healthy volunteers (age, mean ± SD, 24.9 ± 3.2 years) performed maximum voluntary contractions (MVC) and explosive isometric contractions of the knee extensors followed by isometric contractions at 2.5, 5, 10, 15, 20, and 30% MVC at baseline, immediately after and 24 h after eccentric exercise of the quadriceps. During each task, force of the knee extensors and surface EMG of the vasti and hamstrings muscles were recorded concurrently. Rate of force development (RFD) was computed from the explosive isometric contraction, and the coefficient of variation of the force (CoV) signal was estimated from the submaximal contractions. Twenty-four hours after exercise, the subjects rated their perceived pain intensity as 4.1 ± 1.2 (score out of 10). The maximum RFD and MVC of the knee extensors was reduced immediately post- and 24 h after eccentric exercise compared to baseline (average across both time points: 19.1 ± 17.1% and 11.9 ± 9.8% lower, respectively, P eccentric exercise (up to 66% higher than baseline, P exercise during the presence of DOMS (P exercise and was accompanied by increased antagonist EMG for the explosive contraction only. On the contrary, reduced force steadiness was accompanied by a general increase in EMG amplitude of the vasti muscles and was accompanied by increased antagonist activity, but only at higher force levels (>15% MVC). This study shows that eccentric exercise and subsequent DOMS of the quadriceps reduce the maximal force, rate of force development and force steadiness of the knee extensors, and is accompanied by different adjustments of agonist and antagonist muscle activities.

  3. Isokinetic eccentric resistance training prevents loss in mechanical muscle function after running

    DEFF Research Database (Denmark)

    Oliveira, Anderson S. C.; Caputo, Fabrizio; Aagaard, Per

    2013-01-01

    The aim of the study was to verify whether 8 weeks of resistance training employing maximal isokinetic eccentric (IERT) knee extensor actions would reduce the acute force loss observed after high-intensity treadmill running exercise. It was hypothesized that specific IERT would induce protective...... effects against muscle fatigue and ultrastructural damages, preventing or reducing the loss in mechanical muscle function after running. Subjects were tested before and after IERT protocol for maximal isometric, concentric and eccentric isokinetic knee extensor strength (60° and 180° s(-1)). In a second...... session, subjects performed treadmill running (~35 min) and the previously mentioned measurements were repeated immediately after running. Subsequently, subjects were randomized to training (n = 12) consisting of 24 sessions of maximal IERT knee extensors actions at 180° s(-1), or served as controls (n...

  4. Habitable Climates: The Influence of Eccentricity

    CERN Document Server

    Dressing, Courtney D; Scharf, Caleb A; Raymond, Sean N

    2010-01-01

    Radiative equilibrium studies that place Earth-like exoplanets on different circular orbits from the parent star do not fully sample the range of plausible habitability conditions in planetary systems. In the outer regions of the habitable zone, the risk of transitioning into a globally frozen "snowball" state poses a threat to the habitability. Here, we use a one-dimensional energy balance climate model (EBM) to examine how obliquity, spin rate, orbital eccentricity, and the fraction of the surface covered by ocean might influence the onset of such a snowball state. Since, for constant semimajor axis, the annual mean stellar irradiation scales with (1-e^2)^(-1/2), one might expect the greatest habitable semimajor axis to scale as (1-e^2)^(-1/4). We find that this standard simple ansatz provides a reasonable lower bound on the outer boundary of the habitable zone, but the influence of both obliquity and ocean fraction can be profound in the context of planets on eccentric orbits. For planets with eccentricity...

  5. Roll Eccentricity Control Using Identified Eccentricity of Top/Bottom Rolls by Roll Force

    Science.gov (United States)

    Imanari, Hiroyuki; Koshinuma, Kazuyoshi

    Roll eccentricity is a periodic disturbance caused by a structure of back up rolls in rolling mills, and it affects product thickness accuracy. It cannot be measured directly by sensors, so it should be identified by measured thickness or measured roll force. When there is a large difference of diameters between top and bottom back up roll, the performance of roll eccentricity control using feedback signals of roll force or thickness has not been so good. Also it has been difficult for the control to be applied from the most head end because it is necessary to identify the roll eccentricity during rolling. A new roll eccentricity control has been developed to improve these disadvantages and to get better performance. The method identifies top and bottom roll eccentricity respectively from one signal of roll force and it can start the control from head end. In this paper the new control method is introduced and actual application results to a hot strip mill are shown.

  6. Orbital evolution of eccentric planets in radiative discs

    Science.gov (United States)

    Bitsch, B.; Kley, W.

    2010-11-01

    Context. With an average eccentricity of about 0.29, the eccentricity distribution of extrasolar planets is markedly different from the solar system. Among other scenarios considered, it has been proposed that eccentricity may grow through planet-disc interaction. Recently, it has been noticed that the thermodynamical state of the disc can significantly influence the migration properties of growing protoplanets. However, the evolution of planetary eccentricity in radiative discs has not been considered yet. Aims: In this paper we study the evolution of planets on eccentric orbits that are embedded in a three-dimensional viscous disc and analyse the disc's effect on the orbital evolution of the planet. Methods: We use the three-dimensional hydrodynamical code NIRVANA that includes full tensor viscosity and implicit radiation transport in the flux-limited diffusion approximation. The code uses the FARGO-algorithm to speed up the simulations. First we measure the torque and power exerted on the planet by the disc for fixed orbits, and then we let the planet start with initial eccentricity and evolve it in the disc. Results: For locally isothermal discs we confirm previous results and find eccentricity damping and inward migration for planetary cores. For low eccentricity (e ⪉ 2 H/r) the damping is exponential, while for higher e it follows dot{e} ∝ e-2. In the case of radiative discs, the planets experience an inward migration as long as its eccentricity lies above a certain threshold. After the damping of eccentricity cores with masses below 33 MEarth begin to migrate outward in radiative discs, while higher mass cores always migrate inward. For all planetary masses studied (up to 200 MEarth) we find eccentricity damping. Conclusions: In viscous discs the orbital eccentricity of embedded planets is damped during the evolution independent of the mass. Hence, planet-disc interaction does not seem to be a viable mechanism to explain the observed high eccentricity of

  7. Changes in passive tension after stretch of unexercised and eccentrically exercised human plantarflexor muscles.

    Science.gov (United States)

    Reisman, Simone; Allen, Trevor J; Proske, Uwe

    2009-03-01

    The study measured the effect of stretch on passive mechanical properties in unexercised and eccentrically exercised plantarflexor muscles, to obtain insight into how stretch might serve athletes as a warm-up strategy. Passive torque, voluntary contraction strength and muscle soreness were measured before and after a large amplitude stretch given before and after a period of eccentric exercise and at 0, 1, 2 and 24 h later. Stretch of the unexercised muscle led to a 20% fall in passive torque which recovered within an hour. About 40% of the fall could be recovered immediately with a voluntary contraction. After eccentric exercise there was a rise in passive torque by 20% at 2 h post-exercise. This rise was postulated to result from an injury contracture in muscle fibres damaged by the exercise. It was accompanied by a fall in maximum voluntary torque and the development of muscle soreness at 24 h. Stretch of the exercised muscle led to a fall in passive torque and rise in pain threshold. It is proposed that in response to a stretch there is a fall in passive tension in the muscle due to stable cross-bridges in sarcomeres which could be recovered with a voluntary contraction and an additional component attributable to the elastic filament, titin. The size of the fall was not significantly different between exercised and unexercised muscle. These observations provide a physiological basis for the effects of passive stretches on skeletal muscle and help to explain why they are used as a popular warm-up strategy.

  8. Relevance of ellipse eccentricity for camera calibration

    Science.gov (United States)

    Mordwinzew, W.; Tietz, B.; Boochs, F.; Paulus, D.

    2015-05-01

    Plane circular targets are widely used within calibrations of optical sensors through photogrammetric set-ups. Due to this popularity, their advantages and disadvantages are also well studied in the scientific community. One main disadvantage occurs when the projected target is not parallel to the image plane. In this geometric constellation, the target has an elliptic geometry with an offset between its geometric and its projected center. This difference is referred to as ellipse eccentricity and is a systematic error which, if not treated accordingly, has a negative impact on the overall achievable accuracy. The magnitude and direction of eccentricity errors are dependent on various factors. The most important one is the target size. The bigger an ellipse in the image is, the bigger the error will be. Although correction models dealing with eccentricity have been available for decades, it is mostly seen as a planning task in which the aim is to choose the target size small enough so that the resulting eccentricity error remains negligible. Besides the fact that advanced mathematical models are available and that the influence of this error on camera calibration results is still not completely investigated, there are various additional reasons why bigger targets can or should not be avoided. One of them is the growing image resolution as a by-product from advancements in the sensor development. Here, smaller pixels have a lower S/N ratio, necessitating more pixels to assure geometric quality. Another scenario might need bigger targets due to larger scale differences whereas distant targets should still contain enough information in the image. In general, bigger ellipses contain more contour pixels and therefore more information. This supports the target-detection algorithms to perform better even at non-optimal conditions such as data from sensors with a high noise level. In contrast to rather simple measuring situations in a stereo or multi-image mode, the impact

  9. Normative values of eccentric hip abduction strength in novice runners

    DEFF Research Database (Denmark)

    Ramskov, D; Pedersen, M B; Kastrup, K

    2014-01-01

    .354) Nm/kg. CONCLUSION: Normative values for maximal eccentric hip abduction strength in novice runners can be calculated by taking into account the differences in strength across genders and the decline in strength that occurs with increasing age. Age and gender were associated with maximal eccentric hip......PURPOSE: Low eccentric strength of the hip abductors, might increase the risk of patellofemoral pain syndrome and iliotibial band syndrome in runners. No normative values for maximal eccentric hip abduction strength have been established. Therefore the purpose of this study was to establish...... normative values of maximal eccentric hip abduction strength in novice runners. METHODS: Novice healthy runners (n = 831) were recruited through advertisements at a hospital and a university. Maximal eccentric hip abduction strength was measured with a hand-held dynamometer. The demographic variables...

  10. Eccentric resistance training intensity may affect the severity of exercise induced muscle damage.

    Science.gov (United States)

    Hasenoehrl, Timothy; Wessner, Barbara; Tschan, Harald; Vidotto, Claudia; Crevenna, Richard; Csapo, Robert

    2017-09-01

    The aim of the present study was to assess the role of eccentric exercise intensity in the development of and recovery from delayed onset muscle soreness (DOMS). Using a cross-over study design, 15 healthy, male college students were tested on two occasions. The training stimulus consisted of an exhaustive series of eccentric muscle contractions of the elbow flexors at either 100% (high intensity) or 50% (low intensity) of the individual concentric one-repetition maximum. Blood samples were taken at baseline as well as 24, 48, 72 and 96 hours postexercise, and analyzed for creatine kinase, myoglobin, interleukin-6 and prostaglandin-2. Additionally, upper arm circumference (CIRC) and DOMS-related sensation of pain (PAIN) were measured. Following high intensity training, CIRC was significantly greater (P=0.007). Further, creatine kinase, myoglobin and interleukin-6 tended to be higher, although the main effect of the factor "intensity" just failed to reach significance (creatine kinase: P=0.056, myoglobin: P=0.064, interleukin-6: P=0.091). No differences were found for prostaglandin-2 (P=0.783) and PAIN (P=0.147). When performed at greater intensity, fatiguing eccentric resistance exercise of the elbow flexors leads to greater muscle swelling and, potentially, increases in serum markers reflecting lesions in the muscle's cellular membrane.

  11. Contract Renewal Information - all Contracts

    Data.gov (United States)

    Department of Housing and Urban Development — Multifamily Portfolio datasets (section 8 contracts) - The information has been compiled from multiple data sources within FHA or its contractors. HUD oversees more...

  12. Contract theory and EU Contract Law

    OpenAIRE

    2016-01-01

    This paper explores the relationship between contract theory and European contract law. In particular, it confronts the leading contract law theories with the main characteristics of EU contract law. The conclusion is that the two do not match well. In particular, monist normative contract theories are largely irreconcilable with the contract law of the EU. The paper further addresses the main implications of this mismatch, both for contract theory and for EU contract law. It suggests that in...

  13. Flow Mode Magnetorheological Dampers with an Eccentric Gap

    OpenAIRE

    Choi, Young-Tai; Norman M. Wereley

    2014-01-01

    This paper analyzes flow mode magnetorheological (MR) dampers with an eccentric annular gap (i.e., a nonuniform annular gap). To this end, an MR damper analysis for an eccentric annular gap is constructed based on approximating the eccentric annular gap using a rectangular duct with a variable gap, as well as a Bingham-plastic constitutive model of the MR fluid. Performance of flow mode MR dampers with an eccentric gap was assessed analytically using both field-dependent damping force and dam...

  14. Estimating Neural Control from Concentric vs. Eccentric Surface Electromyographic Representations during Fatiguing, Cyclic Submaximal Back Extension Exercises

    Science.gov (United States)

    Ebenbichler, Gerold R.; Unterlerchner, Lena; Habenicht, Richard; Bonato, Paolo; Kollmitzer, Josef; Mair, Patrick; Riegler, Sara; Kienbacher, Thomas

    2017-01-01

    Purpose: To investigate the differences in neural control of back muscles activated during the eccentric vs. the concentric portions of a cyclic, submaximal, fatiguing trunk extension exercise via the analysis of amplitude and time-frequency parameters derived from surface electromyographic (SEMG) data. Methods: Using back dynamometers, 87 healthy volunteers performed three maximum voluntary isometric trunk extensions (MVC's), an isometric trunk extension at 80% MVC, and 25 cyclic, dynamic trunk extensions at 50% MVC. Dynamic testing was performed with the trunk angular displacement ranging from 0° to 40° and the trunk angular velocity set at 20°/s. SEMG data was recorded bilaterally from the iliocostalis lumborum at L1, the longissimus dorsi at L2, and the multifidus muscles at L5. The initial value and slope of the root mean square (RMS-SEMG) and the instantaneous median frequency (IMDF-SEMG) estimates derived from the SEMG recorded during each exercise cycle were used to investigate the differences in MU control marking the eccentric vs. the concentric portions of the exercise. Results: During the concentric portions of the exercise, the initial RMS-SEMG values were almost twice those observed during the eccentric portions of the exercise. The RMS-SEMG values generally increased during the concentric portions of the exercise while they mostly remained unchanged during the eccentric portions of the exercise with significant differences between contraction types. Neither the initial IMDF-SEMG values nor the time-course of the IMDF-SEMG values significantly differed between the eccentric and the concentric portions of the exercise. Conclusions: The comparison of the investigated SEMG parameters revealed distinct neural control strategies during the eccentric vs. the concentric portions of the cyclic exercise. We explain these differences by relying upon the principles of orderly recruitment and common drive governing motor unit behavior. PMID:28559851

  15. Estimating Neural Control from Concentric vs. Eccentric Surface Electromyographic Representations during Fatiguing, Cyclic Submaximal Back Extension Exercises

    Directory of Open Access Journals (Sweden)

    Gerold R. Ebenbichler

    2017-05-01

    Full Text Available Purpose: To investigate the differences in neural control of back muscles activated during the eccentric vs. the concentric portions of a cyclic, submaximal, fatiguing trunk extension exercise via the analysis of amplitude and time-frequency parameters derived from surface electromyographic (SEMG data.Methods: Using back dynamometers, 87 healthy volunteers performed three maximum voluntary isometric trunk extensions (MVC's, an isometric trunk extension at 80% MVC, and 25 cyclic, dynamic trunk extensions at 50% MVC. Dynamic testing was performed with the trunk angular displacement ranging from 0° to 40° and the trunk angular velocity set at 20°/s. SEMG data was recorded bilaterally from the iliocostalis lumborum at L1, the longissimus dorsi at L2, and the multifidus muscles at L5. The initial value and slope of the root mean square (RMS-SEMG and the instantaneous median frequency (IMDF-SEMG estimates derived from the SEMG recorded during each exercise cycle were used to investigate the differences in MU control marking the eccentric vs. the concentric portions of the exercise.Results: During the concentric portions of the exercise, the initial RMS-SEMG values were almost twice those observed during the eccentric portions of the exercise. The RMS-SEMG values generally increased during the concentric portions of the exercise while they mostly remained unchanged during the eccentric portions of the exercise with significant differences between contraction types. Neither the initial IMDF-SEMG values nor the time-course of the IMDF-SEMG values significantly differed between the eccentric and the concentric portions of the exercise.Conclusions: The comparison of the investigated SEMG parameters revealed distinct neural control strategies during the eccentric vs. the concentric portions of the cyclic exercise. We explain these differences by relying upon the principles of orderly recruitment and common drive governing motor unit behavior.

  16. Effect of New Zealand blueberry consumption on recovery from eccentric exercise-induced muscle damage

    Science.gov (United States)

    2012-01-01

    Background Exercise-induced muscle damage (EIMD) is accompanied by localized oxidative stress / inflammation which, in the short-term at least, is associated with impaired muscular performance. Dietary antioxidants have been shown to reduce excessive oxidative stress; however, their effectiveness in facilitating recovery following EIMD is not clear. Blueberries demonstrate antioxidant and anti-inflammatory properties. In this study we examine the effect of New Zealand blueberries on EIMD after strenuous eccentric exercise. Methods In a randomized cross-over design, 10 females consumed a blueberry smoothie or placebo of a similar antioxidant capacity 5 and 10 hours prior to and then immediately, 12 and 36 hours after EIMD induced by 300 strenuous eccentric contractions of the quadriceps. Absolute peak and average peak torque across the knee, during concentric, isometric, and eccentric actions were measured. Blood biomarkers of oxidative stress, antioxidant capacity, and inflammation were assessed at 12, 36 and 60 hours post exercise. Data were analyzed using a two-way ANOVA. Results A significant (p eccentric torque was observed 12 hours following exercise in both treatment groups. During the 60 hour recovery period, a significant (p = 0.047) interaction effect was seen for peak isometric tension suggesting a faster rate of recovery in the blueberry intervention group. A similar trend was observed for concentric and eccentric strength. An increase in oxidative stress and inflammatory biomarkers was also observed in both treatment groups following EIMD. Although a faster rate of decrease in oxidative stress was observed in the blueberry group, it was not significant (p exercise and interestingly coincided with a gradual increase in plasma antioxidant capacity, whereas biomarkers for inflammation were still elevated after 60 hours recovery. Conclusions This study demonstrates that the ingestion of a blueberry smoothie prior to and after EIMD accelerates

  17. Muscular force production during non-isometric contractions: Towards numerical muscle modeling

    OpenAIRE

    Kosterina, Natalia

    2009-01-01

    The main objective of the study was to investigate skeletal muscle force production during isometric contractions, active muscle stretches and shortenings. The motivation behind this work is to improve the dominant model of muscle contraction force generation based on the theories of Hill. The effect of force modification was observed after concentric and eccentric contractions and also stretch-shortening cycles. It has been shown that this force modification is not related to lengthening/sho...

  18. Increased residual force enhancement in older adults is associated with a maintenance of eccentric strength.

    Directory of Open Access Journals (Sweden)

    Geoffrey A Power

    Full Text Available Despite an age-related loss of voluntary isometric and concentric strength, muscle strength is well maintained during lengthening muscle actions (i.e., eccentric strength in old age. Additionally, in younger adults during lengthening of an activated skeletal muscle, the force level observed following the stretch is greater than the isometric force at the same muscle length. This feature is termed residual force enhancement (RFE and is believed to be a combination of active and passive components of the contractile apparatus. The purpose of this study was to provide an initial assessment of RFE in older adults and utilize aging as a muscle model to explore RFE in a system in which isometric force production is compromised, but structural mechanisms of eccentric strength are well-maintained. Therefore, we hypothesised that older adults will experience greater RFE compared with young adults. Following a reference maximal voluntary isometric contraction (MVC of the dorsiflexors in 10 young (26.1 ± 2.7 y and 10 old (76.0 ± 6.5 y men, an active stretch was performed at 15°/s over a 30° ankle joint excursion ending at the same muscle length as the reference MVCs (40° of plantar flexion. Any additional torque compared with the reference MVC therefore represented RFE. In older men RFE was ~2.5 times greater compared to young. The passive component of force enhancement contributed ~37% and ~20% to total force enhancement, in old and young respectively. The positive association (R(2 = 0.57 between maintained eccentric strength in old age and RFE indicates age-related mechanisms responsible for the maintenance of eccentric strength likely contributed to the observed elevated RFE. Additionally, as indicated by the greater passive force enhancement, these mechanisms may be related to increased muscle series elastic stiffness in old age.

  19. Multiarticular isokinetic high-load eccentric training induces large increases in eccentric and concentric strength and jumping performance.

    Science.gov (United States)

    Papadopoulos, Christos; Theodosiou, Konstantinos; Bogdanis, Gregory C; Gkantiraga, Evangelia; Gissis, Ioannis; Sambanis, Michalis; Souglis, Athanasios; Sotiropoulos, Aristomenis

    2014-09-01

    This study investigated the effects of short-term eccentric exercise training using a custom-made isokinetic leg press device, on concentric and eccentric strength and explosiveness as well as jumping performance. Nineteen healthy males were divided into an eccentric (ECC, n = 10) and a control group (CG, n = 9). The ECC group trained twice per week for 8 weeks using an isokinetic hydraulic leg press machine against progressively increasing resistance ranging from 70 to 90% of maximal eccentric force. Jumping performance and maximal force generating capacity were measured before and after eccentric training. In the ECC group, drop jump (DJ) height and maximal power were increased by 13.6 ± 3.2% (p knee, and hip joint angles were also reduced by 33.9 ± 1.1%, 31.1 ± 1.0%, and 32.4 ± 1.6% (all p eccentric and concentric leg press force was increased by 64.9 ± 5.5% (p eccentric force, explosiveness, and DJ performance were markedly increased after only 16 training sessions, possibly because of the high eccentric load attained during the bilateral eccentric leg press exercise performed on this custom-made device.

  20. Eccentric exercise facilitates mesenchymal stem cell appearance in skeletal muscle.

    Directory of Open Access Journals (Sweden)

    M Carmen Valero

    Full Text Available Eccentric, or lengthening, contractions result in injury and subsequently stimulate the activation and proliferation of satellite stem cells which are important for skeletal muscle regeneration. The discovery of alternative myogenic progenitors in skeletal muscle raises the question as to whether stem cells other than satellite cells accumulate in muscle in response to exercise and contribute to post-exercise repair and/or growth. In this study, stem cell antigen-1 (Sca-1 positive, non-hematopoetic (CD45⁻ cells were evaluated in wild type (WT and α7 integrin transgenic (α7Tg mouse muscle, which is resistant to injury yet liable to strain, 24 hr following a single bout of eccentric exercise. Sca-1⁺CD45⁻ stem cells were increased 2-fold in WT muscle post-exercise. The α7 integrin regulated the presence of Sca-1⁺ cells, with expansion occurring in α7Tg muscle and minimal cells present in muscle lacking the α7 integrin. Sca-1⁺CD45⁻ cells isolated from α7Tg muscle following exercise were characterized as mesenchymal-like stem cells (mMSCs, predominantly pericytes. In vitro multiaxial strain upregulated mMSC stem cells markers in the presence of laminin, but not gelatin, identifying a potential mechanistic basis for the accumulation of these cells in muscle following exercise. Transplantation of DiI-labeled mMSCs into WT muscle increased Pax7⁺ cells and facilitated formation of eMHC⁺DiI⁻ fibers. This study provides the first demonstration that mMSCs rapidly appear in skeletal muscle in an α7 integrin dependent manner post-exercise, revealing an early event that may be necessary for effective repair and/or growth following exercise. The results from this study also support a role for the α7 integrin and/or mMSCs in molecular- and cellular-based therapeutic strategies that can effectively combat disuse muscle atrophy.

  1. Moderate Load Eccentric Exercise; A Distinct Novel Training Modality.

    Science.gov (United States)

    Hoppeler, Hans

    2016-01-01

    Over the last 20 years a number of studies have been published using progressive eccentric exercise protocols on motorized ergometers or similar devices that allow for controlled application of eccentric loads. Exercise protocols ramp eccentric loads over an initial 3 weeks period in order to prevent muscle damage and delayed onset muscle soreness. Final training loads reach 400-500 W in rehabilitative settings and over 1200 W in elite athletes. Training is typically carried out three times per week for durations of 20-30 min. This type of training has been characterizes as moderate load eccentric exercise. It has also been denoted RENEW (Resistance Exercise via Negative Eccentric Work by LaStayo et al., 2014). It is distinct from plyometric exercises (i.e., drop jumps) that impose muscle loads of several thousand Watts on muscles and tendons. It is also distinct from eccentric overload training whereby loads in a conventional strength training setting are increased in the eccentric phase of the movement to match concentric loads. Moderate load eccentric exercise (or RENEW) has been shown to be similarly effective as conventional strength training in increasing muscle strength and muscle volume. However, as carried out at higher angular velocities of joint movement, it reduces joint loads. A hallmark of moderate load eccentric exercise is the fact that the energy requirements are typically 4-fold smaller than in concentric exercise of the same load. This makes moderate load eccentric exercise training the tool of choice in medical conditions with limitations in muscle energy supply. The use and effectiveness of moderate load eccentric exercise has been demonstrated mostly in small scale studies for cardiorespiratory conditions, sarcopenia of old age, cancer, diabetes type 2, and neurological conditions. It has also been used effectively in the prevention and rehabilitation of injuries of the locomotor system in particular the rehabilitation after anterior cruciate

  2. Asymmetric transition disks: Vorticity or eccentricity?

    CERN Document Server

    Zsom, A; Ghanbari, J

    2013-01-01

    Context. Transition disks typically appear in resolved millimeter observations as giant dust rings surrounding their young host stars. More accurate observations with ALMA have shown several of these rings to be in fact asymmetric: they have lopsided shapes. It has been speculated that these rings act as dust traps, which would make them important laboratories for studying planet formation. It has been shown that an elongated giant vortex produced in a disk with a strong viscosity jump strikingly resembles the observed asymmetric rings. Aims. We aim to study a similar behavior for a disk in which a giant planet is embedded. However, a giant planet can induce two kinds of asymmetries: (1) a giant vortex, and (2) an eccentric disk. We studied under which conditions each of these can appear, and how one can observationally distinguish between them. This is important because only a vortex can trap particles both radially and azimuthally, while the eccentric ring can only trap particles in radial direction. Method...

  3. Eccentric muscle damage has variable effects on motor unit recruitment thresholds and discharge patterns in elbow flexor muscles.

    Science.gov (United States)

    Dartnall, Tamara J; Rogasch, Nigel C; Nordstrom, Michael A; Semmler, John G

    2009-07-01

    The purpose of this study was to determine the effect of eccentric muscle damage on recruitment threshold force and repetitive discharge properties of low-threshold motor units. Ten subjects performed four tasks involving isometric contraction of elbow flexors while electromyographic (EMG) data were recorded from human biceps brachii and brachialis muscles. Tasks were 1) maximum voluntary contraction (MVC); 2) constant-force contraction at various submaximal targets; 3) motor unit recruitment threshold task; and 4) minimum motor unit discharge rate task. These tasks were performed on three separate days before, immediately after, and 24 h after eccentric exercise of elbow flexor muscles. MVC force declined (42%) immediately after exercise and remained depressed (29%) 24 h later, indicative of muscle damage. Mean motor unit recruitment threshold for biceps brachii was 8.4+/-4.2% MVC, (n=34) before eccentric exercise, and was reduced by 41% (5.0+/-3.0% MVC, n=34) immediately after and by 39% (5.2+/-2.5% MVC, n=34) 24 h after exercise. No significant changes in motor unit recruitment threshold were observed in the brachialis muscle. However, for the minimum tonic discharge rate task, motor units in both muscles discharged 11% faster (10.8+/-2.0 vs. 9.7+/-1.7 Hz) immediately after (n=29) exercise compared with that before (n=32). The minimum discharge rate variability was greater in brachialis muscle immediately after exercise (13.8+/-3.1%) compared with that before (11.9+/-3.1%) and 24 h after exercise (11.7+/-2.4%). No significant changes in minimum discharge rate variability were observed in the biceps brachii motor units after exercise. These results indicate that muscle damage from eccentric exercise alters motor unit recruitment thresholds for >or=24 h, but the effect is not the same in the different elbow flexor muscles.

  4. Contracts and Contracting: A Primer.

    Science.gov (United States)

    Terra, Sandra M; Zimmerling, John

    2016-01-01

    The underlying guiding principles of case management services and practices of the Case Management Body of Knowledge include the following: "Case managers must possess the education, skills, knowledge, competencies, and experiences needed to effectively render appropriate, safe, and quality services to clients/support systems" and "Case management services are offered according to the clients' benefits as stipulated in their health insurance plans (http://www.cmbodyofknowledge.com/content/case-management-knowledge-2). Fulfilling these principles requires that the case manager engage in negotiating and contract execution.This article explores the concepts of negotiation and some of the many ways case managers contribute to the contracting process. Acute care hospitals, individual practice, managed care. Case managers can provide valuable information during the contracting process, in many settings. In the managed care arena, case management can help identify the types of services needed by the population the organization serves. The same understanding of data can assist during the payer contracting process in the acute care setting and ensure that the hospital is fairly reimbursed by third party payers. The independent practitioners will, undoubtedly, face the need to negotiate for themselves as well as their clients. The case manager, regardless of the setting, benefits from an understanding of the principles and processes associated with negotiation and contracting.

  5. Effects of Eccentric Strength Training on Different Maximal Strength and Speed-Strength Parameters of the Lower Extremity.

    Science.gov (United States)

    Wirth, Klaus; Keiner, Michael; Szilvas, Elena; Hartmann, Hagen; Sander, Andre

    2015-07-01

    The aim of this investigation was to analyze the effects of an eccentric strength training protocol using supramaximal loads (>1 repetition maximum [1RM]) on different maximal and explosive strength parameters of the lower extremity. The eccentric maximal strength (EX max), maximal isometric strength ("maximal voluntary contraction" [MVC]), 1RM, explosive strength ("rate of force development" [RFD]), countermovement jump, and squat jump height were tested before and after a training period of 6 weeks. The training group was composed of 15 individuals with low-weight training experience and a control group of 13 subjects, also with a low-weight training experience. The lower extremities were trained 3 days per week using a 45° leg press. Each training session comprised 5 sets of 3 repetitions with a 6-minute rest between each set. The training weights were adjusted continuously during each training session and between training sessions. In each case, a load was chosen that could be lowered unilaterally in a controlled manner by the subjects. For the concentric part of the exercise, 2 investigators lifted the weight to the starting position. After 6 weeks, strength training with supramaximal loads showed a significant increase in EX max (28.2%, p strength training in the leg press generates equal and significant improvements in unilateral eccentric and bilateral eccentric-concentric maximal strength, with a nonsignificant transfer to vertical jump performances and unilateral isometric force production.

  6. Effect of eccentric exercise with reduced muscle glycogen on plasma interleukin-6 and neuromuscular responses of musculus quadriceps femoris.

    Science.gov (United States)

    Gavin, James P; Myers, Stephen D; Willems, Mark E T

    2016-07-01

    Eccentric exercise can result in muscle damage and interleukin-6 (IL-6) secretion. Glycogen availability is a potent stimulator of IL-6 secretion. We examined effects of eccentric exercise in a low-glycogen state on neuromuscular function and plasma IL-6 secretion. Twelve active men (23 ± 4 yr, 179 ± 5 cm, 77 ± 10 kg, means ± SD) completed two downhill treadmill runs (gradient, -12%, 5 × 8 min; speed, 12.1 ± 1.1 km/h) with normal (NG) and reduced muscle glycogen (RG) in randomized order and at least 6 wk apart. Muscle glycogen was reduced using an established cycling protocol until exhaustion and dietary manipulation the evening before the morning run. Physiological responses were measured up to 48 h after the downhill runs. During recovery, force deficits of musculus quadriceps femoris by maximal isometric contractions were similar. Changes in low-frequency fatigue were larger with RG. Voluntary activation and plasma IL-6 levels were similar in recovery between conditions. It is concluded that unaccustomed, damaging eccentric exercise with low muscle glycogen of the m. quadriceps femoris 1) exacerbated low-frequency fatigue but 2) had no additional effect on IL-6 secretion. Neuromuscular impairment after eccentric exercise with low muscle glycogen appears to have a greater peripheral component in early recovery.

  7. Agile Contracts

    DEFF Research Database (Denmark)

    Pries-Heje, Jan; Pries-Heje, Lene

    2014-01-01

    with “endless” re-negotiation of the requirements; you need a more flexible way to develop IS. A new way of coping with many changes is to use an agile development approach and a fixed budget and resources contract. This paper presents an example case. We analyse the case and design a guideline for how...

  8. Fish oil supplementation reduces markers of oxidative stress but not muscle soreness after eccentric exercise.

    Science.gov (United States)

    Gray, Patrick; Chappell, Andrew; Jenkinson, Alison McE; Thies, Frank; Gray, Stuart R

    2014-04-01

    Due to the potential anti-inflammatory properties of fish-derived long chain n-3 fatty acids, it has been suggested that athletes should regularly consume fish oils-although evidence in support of this recommendation is not clear. While fish oils can positively modulate immune function, it remains possible that, due to their high number of double bonds, there may be concurrent increases in lipid peroxidation. The current study aims to investigate the effect of fish oil supplementation on exercise-induced markers of oxidative stress and muscle damage. Twenty males underwent a 6-week double-blind randomized placebo-controlled supplementation trial involving two groups (fish oil or placebo). After supplementation, participants undertook 200 repetitions of eccentric knee contractions. Blood samples were taken presupplementation, postsupplementation, immediately, 24, 48, and 72 hr postexercise and muscle soreness/maximal voluntary contraction (MVC) assessed. There were no differences in creatine kinase, protein carbonyls, endogenous DNA damage, muscle soreness or MVC between groups. Plasma thiobarbituric acid reactive substances (TBARS) were lower (p < .05) at 48 and 72 hr post exercise and H2O2 stimulated DNA damage was lower (p < .05) immediately postexercise in the fish oil, compared with the control group. The current study demonstrates that fish oil supplementation reduces selected markers of oxidative stress after a single bout of eccentric exercise.

  9. Isometric and eccentric force generation assessment of skeletal muscles isolated from murine models of muscular dystrophies.

    Science.gov (United States)

    Moorwood, Catherine; Liu, Min; Tian, Zuozhen; Barton, Elisabeth R

    2013-01-31

    Critical to the evaluation of potential therapeutics for muscular disease are sensitive and reproducible physiological assessments of muscle function. Because many pre-clinical trials rely on mouse models for these diseases, isolated muscle function has become one of the standards for Go/NoGo decisions in moving drug candidates forward into patients. We will demonstrate the preparation of the extensor digitorum longus (EDL) and diaphragm muscles for functional testing, which are the predominant muscles utilized for these studies. The EDL muscle geometry is ideal for isolated muscle preparations, with two easily accessible tendons, and a small size that can be supported by superfusion in a bath. The diaphragm exhibits profound progressive pathology in dystrophic animals, and can serve as a platform for evaluating many potential therapies countering fibrosis, and promoting myofiber stability. Protocols for routine testing, including isometric and eccentric contractions, will be shown. Isometric force provides assessment of strength, and eccentric contractions help to evaluate sarcolemma stability, which is disrupted in many types of muscular dystrophies. Comparisons of the expected results between muscles from wildtype and dystrophic muscles will also be provided. These measures can complement morphological and biochemical measurements of tissue homeostasis, as well as whole animal assessments of muscle function.

  10. The Retrogressive movement of eccentric vortex in the Column Vessel

    OpenAIRE

    赤澤, 孝; Akazawa, Takashi

    2012-01-01

    Our experiment found that the center of an eccentric vortex retrogrades and move nutationally when modeled using an eccentric vortex of water in the column vessel. This paper reports that this retrogressive movement is established and caused by the propagation of only one wave. This result is in line with the findings of previous experiments.

  11. Response of electrostatic probes to eccentric charge distributions

    DEFF Research Database (Denmark)

    Johansson, Torben; McAllister, Iain Wilson

    2001-01-01

    The response of an electrostatic probe mounted in an electrode is examined with reference to eccentric charge distributions. The study involves using the probe λ function to derive a characteristic parameter. This parameter enables the response of the probe to different degrees of eccentricity...

  12. Introducing the Moon's Orbital Eccentricity

    Science.gov (United States)

    Oostra, Benjamin

    2014-01-01

    I present a novel way to introduce the lunar orbital eccentricity in introductory astronomy courses. The Moon is perhaps the clearest illustration of the general orbital elements such as inclination, ascending node, eccentricity, perigee, and so on. Furthermore, I like the students to discover astronomical phenomena for themselves, by means of a…

  13. Accurate and efficient waveforms for compact binaries on eccentric orbits

    CERN Document Server

    Huerta, E A; McWilliams, Sean T; O'Shaughnessy, Richard; Yunes, Nicolas

    2014-01-01

    Compact binaries that emit gravitational waves in the sensitivity band of ground-based detectors can have non-negligible eccentricities just prior to merger, depending on the formation scenario. We develop a purely analytic, frequency-domain model for gravitational waves emitted by compact binaries on orbits with small eccentricity, which reduces to the quasi-circular post-Newtonian approximant TaylorF2 at zero eccentricity and to the post-circular approximation of Yunes et al. (2009) at small eccentricity. Our model uses a spectral approximation to the (post-Newtonian) Kepler problem to model the orbital phase as a function of frequency, accounting for eccentricity effects up to ${\\cal{O}}(e^8)$ at each post-Newtonian order. Our approach accurately reproduces an alternative time-domain eccentric waveform model for eccentricities $e\\in [0, 0.4]$ and binaries with total mass less than 12 solar masses. As an application, we evaluate the signal amplitude that eccentric binaries produce in different networks of e...

  14. Eccentric exercise decreases maximal insulin action in humans

    DEFF Research Database (Denmark)

    Asp, Svend; Daugaard, J R; Kristiansen, S

    1996-01-01

    1. Unaccustomed eccentric exercise decreases whole-body insulin action in humans. To study the effects of one-legged eccentric exercise on insulin action in muscle and systemically, the euglycaemic clamp technique combined with arterial and bilateral femoral venous catheterization was used. Seven...... subjects participated in two euglycaemic clamps, performed in random order. One clamp was preceded 2 days earlier by one-legged eccentric exercise (post-eccentric exercise clamp (PEC)) and one was without the prior exercise (control clamp (CC)). 2. During PEC the maximal insulin-stimulated glucose uptake......) necessary to maintain euglycaemia during maximal insulin stimulation was lower during PEC compared with CC (15.7%, 81.3 +/- 3.2 vs. 96.4 +/- 8.8 mumol kg-1 min-1, P eccentric exercise, muscle and whole-body insulin action is impaired at maximal...

  15. Normative values of eccentric hip abduction strength in novice runners

    DEFF Research Database (Denmark)

    Jørgensen, Daniel Ramskov; Pedersen, Mette Broen; Kastrup, Kristrian

    2014-01-01

    normative values of maximal eccentric hip abduction strength in novice runners. METHODS: Novice healthy runners (n = 831) were recruited through advertisements at a hospital and a university. Maximal eccentric hip abduction strength was measured with a hand-held dynamometer. The demographic variables......PURPOSE: Low eccentric strength of the hip abductors, might increase the risk of patellofemoral pain syndrome and iliotibial band syndrome in runners. No normative values for maximal eccentric hip abduction strength have been established. Therefore the purpose of this study was to establish...... associated with maximal eccentric hip abduction strength from a univariate analysis were included in a multivariate linear regression model. Based on the results from the regression model, a regression equation for normative hip abduction strength is presented. RESULTS: A SIGNIFICANT DIFFERENCE IN MAXIMAL...

  16. Local and global dynamics of eccentric astrophysical discs

    CERN Document Server

    Ogilvie, Gordon I

    2014-01-01

    We formulate a local dynamical model of an eccentric disc in which the dominant motion consists of elliptical Keplerian orbits. The model is a generalization of the well known shearing sheet, and is suitable for both analytical and computational studies of the local dynamics of eccentric discs. It is spatially homogeneous in the horizontal dimensions but has a time-dependent geometry that oscillates at the orbital frequency. We show how certain averages of the stress tensor in the local model determine the large-scale evolution of the shape and mass distribution of the disc. The simplest solutions of the local model are laminar flows consisting of a (generally nonlinear) vertical oscillation of the disc. Eccentric discs lack vertical hydrostatic equilibrium because of the variation of the vertical gravitational acceleration around the eccentric orbit, and in some cases because of the divergence of the orbital velocity field associated with an eccentricity gradient. We discuss the properties of the laminar sol...

  17. Eccentric double white dwarfs as LISA sources in globular clusters

    CERN Document Server

    Willems, B; Vecchio, A; Ivanova, N; Rasio, F A; Fregeau, J M; Belczynski, K

    2007-01-01

    We consider the formation of double white dwarfs (DWDs) through dynamical interactions in globular clusters. Such interactions can readily give rise to eccentric DWDs, in contrast to the exclusively circular population that is expected to form in the Galactic disk. We show that for a 5-year Laser Interferometer Space Antenna (LISA) mission and distances as far as the Large Magellanic Cloud, multiple harmonics from eccentric DWDs can be detected at a signal-to-noise ratio higher than 8 for at least a handful of eccentric DWDs, given their formation rate and typical merger lifetimes estimated from current cluster simulations. Consequently the association of eccentricity with stellar-mass LISA sources does not uniquely involve neutron stars, as is usually assumed. Due to the difficulty of detecting these systems with present and planned electromagnetic observatories, LISA could provide unique dynamical identifications of eccentric DWDs in globular clusters.

  18. Crowding by a repeating pattern.

    Science.gov (United States)

    Rosen, Sarah; Pelli, Denis G

    2015-01-01

    Theinability to recognize a peripheral target among flankers is called crowding. For a foveal target, crowding can be distinguished from overlap masking by its sparing of detection, linear scaling with eccentricity, and invariance with target size.Crowding depends on the proximity and similarity of the flankers to the target. Flankers that are far from or dissimilar to the target do not crowd it. On a gray page, text whose neighboring letters have different colors, alternately black and white, has enough dissimilarity that it might escape crowding. Since reading speed is normally limited by crowding, escape from crowding should allow faster reading. Yet reading speed is unchanged (Chung & Mansfield, 2009). Why? A recent vernier study found that using alternating-color flankers produces strong crowding (Manassi, Sayim, & Herzog, 2012). Might that effect occur with letters and reading? Critical spacing is the minimum center-to-center target-flanker spacing needed to correctly identify the target. We measure it for a target letter surrounded by several equidistant flanker letters of the same polarity, opposite polarity, or mixed polarity: alternately white and black. We find strong crowding in the alternating condition, even though each flanker letter is beyond its own critical spacing (as measured in a separate condition). Thus a periodic repeating pattern can produce crowding even when the individual elements do not. Further, in all conditions we find that, once a periodic pattern repeats (two cycles), further repetition does not affect critical spacing of the innermost flanker.

  19. Adaptation to Damaging Dance and Repeated-Sprint Activity in Women.

    Science.gov (United States)

    Brown, Meghan A; Howatson, Glyn; Keane, Karen M; Stevenson, Emma J

    2016-09-01

    Brown, MA, Howatson, G, Keane, KM, and Stevenson, EJ. Adaptation to damaging dance and repeated-sprint activity in women. J Strength Cond Res 30(9): 2574-2581, 2016-The repeated bout effect (RBE) refers to the prophylactic effect from damaging exercise after a single previous bout of exercise. There is a paucity of data examining the RBE in women, and investigations using exercise paradigms beyond isolated eccentric contractions are scarce. In light of the limited literature, this investigation aimed to determine whether 2 different sport-specific exercise bouts would elicit a RBE in women. Twenty-one female dancers (19 ± 1 years) completed either a dance-specific protocol (n = 10) or sport-specific repeated-sprint protocol (n = 11). Delayed-onset muscle soreness (DOMS), limb girths, creatine kinase (CK), countermovement jump height, reactive strength index, maximal voluntary contraction, and 30-meter sprint time were recorded before and 0, 24, 48, and 72 hours after exercise. An identical exercise bout was conducted approximately 4 weeks after the initial bout, during which time the subjects maintained habitual training and dietary behaviors. DOMS and 30-meter sprint time decreased after a second bout of both activities (p = 0.003; (Equation is included in full-text article.)= 0.38 and p = 0.008; and (Equation is included in full-text article.)= 0.31, respectively). Circulating CK was also lower at 24, 48, and 72 hours after the second bout, independent of group (p = 0.010 and (Equation is included in full-text article.)= 0.23). Compared with the repeated-sprint protocol, the magnitude of change in DOMS was greater after a subsequent bout of the dance protocol (p = 0.010 and (Equation is included in full-text article.)= 0.19). These data are the first to demonstrate that dance and repeated-sprint activity resulting in muscle damage in women confers a protective effect against muscle damage after a subsequent bout.

  20. Contract theory and EU Contract Law

    NARCIS (Netherlands)

    Hesselink, M.W.; Twigg-Flesner, C.

    2016-01-01

    This paper explores the relationship between contract theory and European contract law. In particular, it confronts the leading contract law theories with the main characteristics of EU contract law. The conclusion is that the two do not match well. In particular, monist normative contract theories

  1. Contract theory and EU Contract Law

    NARCIS (Netherlands)

    Hesselink, M.W.; Twigg-Flesner, C.

    2016-01-01

    This paper explores the relationship between contract theory and European contract law. In particular, it confronts the leading contract law theories with the main characteristics of EU contract law. The conclusion is that the two do not match well. In particular, monist normative contract theories

  2. Red-giant stars in eccentric binaries

    Directory of Open Access Journals (Sweden)

    Beck P. G.

    2015-01-01

    Full Text Available The unparalleled photometric data obtained by NASA’s Kepler Space Telescope has led to improved understanding of red-giant stars and binary stars. We discuss the characterization of known eccentric system, containing a solar-like oscillating red-giant primary component. We also report several new binary systems that are candidates for hosting an oscillating companion. A powerful approach to study binary stars is to combine asteroseimic techniques with light curve fitting. Seismology allows us to deduce the properties of red giants. In addition, by modeling the ellipsoidal modulations we can constrain the parameters of the binary system. An valuable independent source are ground-bases, high-resolution spectrographs.

  3. FUZZY ECCENTRICITY AND GROSS ERROR IDENTIFICATION

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The dominant and recessive effect made by exceptional interferer is analyzed in measurement system based on responsive character, and the gross error model of fuzzy clustering based on fuzzy relation and fuzzy equipollence relation is built. The concept and calculate formula of fuzzy eccentricity are defined to deduce the evaluation rule and function of gross error, on the base of them, a fuzzy clustering method of separating and discriminating the gross error is found. Utilized in the dynamic circular division measurement system, the method can identify and eliminate gross error in measured data, and reduce measured data dispersity. Experimental results indicate that the use of the method and model enables repetitive precision of the system to improve 80% higher than the foregoing system, to reach 3.5 s, and angle measurement error is less than 7 s.

  4. Highly eccentric inspirals into a black hole

    Science.gov (United States)

    Osburn, Thomas; Warburton, Niels; Evans, Charles R.

    2016-03-01

    We model the inspiral of a compact stellar-mass object into a massive nonrotating black hole including all dissipative and conservative first-order-in-the-mass-ratio effects on the orbital motion. The techniques we develop allow inspirals with initial eccentricities as high as e ˜0.8 and initial separations as large as p ˜50 to be evolved through many thousands of orbits up to the onset of the plunge into the black hole. The inspiral is computed using an osculating elements scheme driven by a hybridized self-force model, which combines Lorenz-gauge self-force results with highly accurate flux data from a Regge-Wheeler-Zerilli code. The high accuracy of our hybrid self-force model allows the orbital phase of the inspirals to be tracked to within ˜0.1 radians or better. The difference between self-force models and inspirals computed in the radiative approximation is quantified.

  5. Eccentric Exercise Versus Eccentric Exercise and Soft Tissue Treatment (Astym) in the Management of Insertional Achilles Tendinopathy.

    Science.gov (United States)

    McCormack, Joshua R; Underwood, Frank B; Slaven, Emily J; Cappaert, Thomas A

    Eccentric exercise is commonly used in the management of Achilles tendinopathy (AT) but its effectiveness for insertional AT has been questioned. Soft tissue treatment (Astym) combined with eccentric exercise could result in better outcomes than eccentric exercise alone. Soft tissue treatment (Astym) plus eccentric exercise will be more effective than eccentric exercise alone for subjects with insertional AT. Prospective randomized controlled trial. Level 2. Sixteen subjects were randomly assigned to either a soft tissue treatment (Astym) and eccentric exercise group or an eccentric exercise-only group. Intervention was completed over a 12-week period, with outcomes assessed at baseline, 4, 8, 12, 26, and 52 weeks. Outcomes included the Victorian Institute of Sport Assessment Achilles-Specific Questionnaire (VISA-A), the numeric pain rating scale (NPRS), and the global rating of change (GROC). Significantly greater improvements on the VISA-A were noted in the soft tissue treatment (Astym) group over the 12-week intervention period, and these differences were maintained at the 26- and 52-week follow-ups. Both groups experienced a similar statistically significant improvement in pain over the short and long term. A significantly greater number of subjects in the soft tissue treatment (Astym) group achieved a successful outcome at 12 weeks. Soft tissue treatment (Astym) plus eccentric exercise was more effective than eccentric exercise only at improving function during both short- and long-term follow-up periods. Soft tissue treatment (Astym) plus eccentric exercise appears to be a beneficial treatment program that clinicians should consider incorporating into the management of their patients with insertional AT.

  6. Nonlinear hydrodynamical evolution of eccentric Keplerian discs in two dimensions: validation of secular theory

    CERN Document Server

    Barker, Adrian J

    2016-01-01

    We perform global two-dimensional hydrodynamical simulations of Keplerian discs with free eccentricity over thousands of orbital periods. Our aim is to determine the validity of secular theory in describing the evolution of eccentric discs, and to explore their nonlinear evolution for moderate eccentricities. Linear secular theory is found to correctly predict the structure and precession rates of discs with small eccentricities. However, discs with larger eccentricities (and eccentricity gradients) are observed to precess faster (retrograde relative to the orbital motion), at a rate that depends on their eccentricities (and eccentricity gradients). We derive analytically a nonlinear secular theory for eccentric gas discs, which explains this result as a modification of the pressure forces whenever eccentric orbits in a disc nearly intersect. This effect could be particularly important for highly eccentric discs produced in tidal disruption events, or for narrow gaseous rings; it might also play a role in cau...

  7. The Impact of Adding an Eccentric-Exercise Component to the Rehabilitation Program of Patients With Shoulder Impingement: A Critically Appraised Topic.

    Science.gov (United States)

    Valier, Alison R; Averett, Ryan S; Anderson, Barton E; Welch Bacon, Cailee E

    2016-05-01

    Shoulder pain is a common musculoskeletal complaint and is often associated with shoulder impingement. The annual incidence of shoulder pain is estimated to be 7% of all injuries, and is the third-most-common type of musculoskeletal pain. Initial treatment of shoulder impingement follows a conservative plan and emphasizes rehabilitation programs as opposed to surgical interventions. Shoulder rehabilitation programs commonly focus on strengthening the muscles of the shoulder complex and, more specifically, the rotator cuff. The rotator cuff is a primary dynamic stabilizer of the glenohumeral joint, using both eccentric and concentric contractions. The posterior rotator cuff, including teres minor and infraspinatus, works eccentrically to decelerate the arm during overhead throwing. Exercises to strengthen the rotator cuff and the surrounding dynamic stabilizers of the shoulder girdle vary and include activities such as internal and external rotation, full-can lifts, and rhythmic stabilizations. Traditionally, shoulder rehabilitation programs have focused on isotonic concentric contractions. Common strengthening exercises typically involve movements that result in shortening the muscle length while simultaneously loading the muscles. However, recent attention has been given to eccentric exercises, which involve lengthening of the muscle during loading, for the treatment of a variety of different tendinopathies including those of the Achilles and patellar tendons. The eccentric, or lengthening, motion is thought to be beneficial for people who are involved in activities that place eccentric stress on their shoulder, such as overhead throwers. Based on studies related to the Achilles tendon, eccentric exercise may positively influence the tendon structure by increasing collagen production and decreasing neovascularization. The changes that occur as a result of eccentric exercises may improve function, strength, and performance and decrease pain more than concentric

  8. A 2 week routine stretching programme did not prevent contraction-induced injury in mouse muscle.

    Science.gov (United States)

    Black, Jonathon D J; Freeman, Marcus; Stevens, E Don

    2002-10-01

    Most athletes stretch as part of their training regimen and it is commonly believed that this practice prevents muscle injury. We tested this belief using an animal model, in situ mouse extensor digitorum longus (EDL) muscle. One lower hindlimb was slowly stretched for 1 min on alternate days for 12 days; the other leg served as a control. The mouse was lightly anaesthetized during the stretching protocol (isofluorane). Both legs were tested in situ by measuring maximum isometric force and maximum work before and after an eccentric contraction that was designed to cause a contraction-induced injury. The difference between a contraction before and after (i.e. the deficit) was used as a measure of damage caused by the eccentric contraction. There was a threshold for force deficit at a peak to peak eccentric excursion amplitude of 19.5 % (i.e. L(o) +/- 9.75 %, where L(o) is muscle length at peak isometric force). There was a significant increase in force deficit, work deficit, and curve shift with an increase in eccentric excursion amplitude above the threshold. There was no statistical difference in the force deficit, work deficit, or curve shift between the stretched leg and the control leg (P > 0.05). A routine stretching programme, at least at the intensities employed in this experiment, did not prevent contraction-induced injury in the in situ mouse EDL muscle.

  9. Neuromuscular adaptations to isoload versus isokinetic eccentric resistance training.

    Science.gov (United States)

    Guilhem, Gaël; Cornu, Christophe; Maffiuletti, Nicola A; Guével, Arnaud

    2013-02-01

    The purpose of this study was to compare neuromuscular adaptations induced by work-matched isoload (IL) versus isokinetic (IK) eccentric resistance training. A total of 31 healthy subjects completed a 9-wk IL (n = 11) or IK (n = 10) training program for the knee extensors or did not train (control group; n = 10). The IL and IK programs consisted of 20 training sessions, which entailed three to five sets of eight repetitions in the respective modalities. The amount of work and the mean angular velocity were strictly matched between IL and IK conditions. Neuromuscular tests were performed before and after training and consisted of the assessment of quadriceps muscle strength, muscle architecture (vastus lateralis), EMG activity, and antagonist coactivation. IL, but not IK, eccentric resistance training enhanced eccentric strength at short muscle length (+20%), high-velocity eccentric strength (+15%), muscle thickness (+10%), and fascicle angle measured at rest (+11%; P eccentric movements (i.e., at short muscle lengths), which results in greater torque and angular velocities compared with IK actions, is the main determinant of strength and neuromuscular adaptations to eccentric training. These findings have important consequences for the optimization of IL and IK eccentric exercise for resistance training and rehabilitation purposes.

  10. Thermal hydraulics of rod bundles: The effect of eccentricity

    Energy Technology Data Exchange (ETDEWEB)

    Chauhan, Amit K., E-mail: amit_fmlab@yahoo.co.in [Fluid Mechanics Laboratory, Department of Applied Mechanics, Indian Institute of Technology Madras, Chennai 600036 (India); Prasad, B.V.S.S.S., E-mail: prasad@iitm.ac.in [Thermal Turbomachines Laboratory, Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai 600036 (India); Patnaik, B.S.V., E-mail: bsvp@iitm.ac.in [Fluid Mechanics Laboratory, Department of Applied Mechanics, Indian Institute of Technology Madras, Chennai 600036 (India)

    2013-10-15

    Highlights: • Present CFD investigation explores, whole bundle eccentricity for the first time. • Fluid flow and thermal characteristics in various subchannels are analyzed. • Mass flux distribution is particularly analyzed to study eccentricity effect. • Higher eccentricity resulted in a shoot up in rod surface temperature distribution. • Both tangential and radial flow in rod bundles has resulted due to eccentricity. -- Abstract: The effect of eccentricity on the fluid flow and heat transfer through a 19-rod bundle is numerically carried out. When the whole bundle shifts downwards with respect to the outer (pressure) tube, flow redistribution happens. This in turn is responsible for changes in mass flux, pressure and differential flow development in various subchannels. The heat flux imposed on the surface of the fuel rods and the mass flux through the subchannels determines the coolant outlet temperatures. The simulations are performed for a coolant flow Reynolds number of 4 × 10{sup 5}. For an eccentricity value of 0.7, the mass flux in the bottom most subchannel (l) was found to decrease by 10%, while the surface temperature of the fuel rod in the vicinity of this subchannel increased by 250% at the outlet section. Parameters of engineering interest including skin friction coefficient, Nusselt number, etc., have been systematically explored to study the effect of eccentricity on the rod bundle.

  11. Eccentricity effect of micropatterned surface on contact angle.

    Science.gov (United States)

    Kashaninejad, Navid; Chan, Weng Kong; Nguyen, Nam-Trung

    2012-03-13

    This article experimentally shows that the wetting property of a micropatterned surface is a function of the center-to-center offset distance between successive pillars in a column, referred to here as eccentricity. Studies were conducted on square micropatterns which were fabricated on a silicon wafer with pillar eccentricity ranging from 0 to 6 μm for two different pillar diameters and spacing. Measurement results of the static as well as the dynamic contact angles on these surfaces revealed that the contact angle decreases with increasing eccentricity and increasing relative spacing between the pillars. Furthermore, quantification of the contact angle hysteresis (CAH) shows that, for the case of lower pillar spacing, CAH could increase up to 41%, whereas for the case of higher pillar spacing, this increment was up to 35%, both corresponding to the maximum eccentricity of 6 μm. In general, the maximum obtainable hydrophobicity corresponds to micropillars with zero eccentricity. As the pillar relative spacing decreases, the effect of eccentricity on hydrophobicity becomes more pronounced. The dependence of the wettability conditions of the micropatterned surface on the pillar eccentricity is attributed to the contact line deformation resulting from the changed orientation of the pillars. This finding provides additional insights in design and fabrication of efficient micropatterned surfaces with controlled wetting properties.

  12. Low level laser therapy before eccentric exercise reduces muscle damage markers in humans.

    Science.gov (United States)

    Baroni, Bruno Manfredini; Leal Junior, Ernesto Cesar Pinto; De Marchi, Thiago; Lopes, André Luiz; Salvador, Mirian; Vaz, Marco Aurélio

    2010-11-01

    The purpose of the present study was to determine the effect of low level laser therapy (LLLT) treatment before knee extensor eccentric exercise on indirect markers of muscle damage. Thirty-six healthy men were randomized in LLLT group (n = 18) and placebo group (n = 18). After LLLT or placebo treatment, subjects performed 75 maximal knee extensors eccentric contractions (five sets of 15 repetitions; velocity = 60° seg(-1); range of motion = 60°). Muscle soreness (visual analogue scale--VAS), lactate dehydrogenase (LDH) and creatine kinase (CK) levels were measured prior to exercise, and 24 and 48 h after exercise. Muscle function (maximal voluntary contraction--MVC) was measured before exercise, immediately after, and 24 and 48 h post-exercise. Groups had no difference on kineanthropometric characteristics and on eccentric exercise performance. They also presented similar baseline values of VAS (0.00 mm for LLLT and placebo groups), LDH (LLLT = 186 IU/l; placebo = 183 IU/l), CK (LLLT = 145 IU/l; placebo = 155 IU/l) and MVC (LLLT = 293 Nm; placebo = 284 Nm). VAS data did not show group by time interaction (P = 0.066). In the other outcomes, LLLT group presented (1) smaller increase on LDH values 48 h post-exercise (LLLT = 366 IU/l; placebo = 484 IU/l; P = 0.017); (2) smaller increase on CK values 24 h (LLLT = 272 IU/l; placebo = 498 IU/l; P = 0.020) and 48 h (LLLT = 436 IU/l; placebo = 1328 IU/l; P exercise; (3) smaller decrease on MVC immediately after exercise (LLLT = 189 Nm; placebo = 154 Nm; P = 0.011), and 24 h (LLLT = 249 Nm; placebo = 205 Nm; P = 0.004) and 48 h (LLLT = 267 Nm; placebo = 216 Nm; P = 0.001) post-exercise compared with the placebo group. In conclusion, LLLT treatment before eccentric exercise was effective in terms of attenuating the increase of muscle proteins in the blood serum and the decrease in muscle force.

  13. Comparison of acute responses to isotonic or isokinetic eccentric muscle action: differential outcomes in skeletal muscle damage and implications for rehabilitation.

    Science.gov (United States)

    Alemany, J A; Delgado-Díaz, D C; Mathews, H; Davis, J M; Kostek, M C

    2014-01-01

    Both isotonic and isokinetic eccentric muscle contractions are commonly used in muscle research laboratories to induce muscle damage, yet, the muscle damage outcomes between these 2 modes of eccentric contraction have not been compared. The purpose of this study was to compare modes of contraction for differences in muscle damage. 16 men were placed in the isotonic (IT: 110% of maximal isometric torque) or the isokinetic (IK: 120°/s) group, with each group performing 200 eccentric muscle actions of the knee extensors. Isometric peak torque, perceived soreness and CK activity were measured immediately pre and post exercise, and 48-h post exercise. Mean total work (~1700 J) and peak torque per set (~265 Nm) decreased over the 200 repetitions (ptorque (-13%), creatine kinase activity (+200%) and self-perceived muscular soreness (+4 unit change). Significant group×time interactions (ptorque was 22% lower, and creatine kinase and self-perceived muscular soreness were 330% and 3 unit difference higher in the IT as compared to the IK groups, 48-h post exercise. When equating for total work, skeletal muscle damage markers are higher during IT vs. IK modes. This reflects differences inherent in contraction type and suggests that this should be taken into account during physical rehabilitation.

  14. Intramuscular and surface EMG power spectrum from dynamic and static contractions.

    Science.gov (United States)

    Christensen, H; Søgaard, K; Jensen, B R; Finsen, L; Sjøgaard, G

    1995-03-01

    During sustained static contractions an increase in the root mean square (rms) amplitude and a decrease in mean power frequency (MPF), or median power frequency (MF) of the electromyographic (EMG) signal are indicators for the development of muscle fatigue. However, when studying dynamic contractions the interpretation of these variables has been questioned. Therefore, the purpose was to compare the EMG variables recorded from a non-fatigued muscle during a slow low level dynamic contraction to those during a static contraction of similar force level. Surface and intramuscular EMG registrations were obtained from the brachial biceps muscle during: (a) a static isotonic contraction, (b) a dynamic contraction and (c) a static anisotonic contraction. During contractions (a) and (b) the recruitment pattern was analysed using the precision decomposition method. No differences in rms, MPF or MF between the dynamic and static contractions or between the concentric and eccentric phase of the dynamic contraction were found. Furthermore 60% of the identified motor units were active both in the concentric and the eccentric phase. This indicates that motor control during a slow dynamic contraction at low force level does not influence the power spectrum. We suggest that in occupational studies a possible muscle fatigue development with time can be estimated using EMG recordings from the work tasks.

  15. Eccentric Exercise Program Design: A Periodization Model for Rehabilitation Applications.

    Science.gov (United States)

    Harris-Love, Michael O; Seamon, Bryant A; Gonzales, Tomas I; Hernandez, Haniel J; Pennington, Donte; Hoover, Brian M

    2017-01-01

    The applied use of eccentric muscle actions for physical rehabilitation may utilize the framework of periodization. This approach may facilitate the safe introduction of eccentric exercise and appropriate management of the workload progression. The purpose of this data-driven Hypothesis and Theory paper is to present a periodization model for isokinetic eccentric strengthening of older adults in an outpatient rehabilitation setting. Exemplar and group data are used to describe the initial eccentric exercise prescription, structured familiarization procedures, workload progression algorithm, and feasibility of the exercise regimen. Twenty-four men (61.8 ± 6.3 years of age) completed a 12-week isokinetic eccentric strengthening regimen involving the knee extensors. Feasibility and safety of the regimen was evaluated using serial visual analog scale (VAS, 0-10) values for self-reported pain, and examining changes in the magnitude of mean eccentric power as a function of movement velocity. Motor learning associated with the familiarization sessions was characterized through torque-time curve analysis. Total work was analyzed to identify relative training plateaus or diminished exercise capacity during the progressive phase of the macrocycle. Variability in the mean repetition interval decreased from 68 to 12% during the familiarization phase of the macrocycle. The mean VAS values were 2.9 ± 2.7 at the start of the regimen and 2.6 ± 2.9 following 12 weeks of eccentric strength training. During the progressive phase of the macrocycle, exercise workload increased from 70% of the estimated eccentric peak torque to 141% and total work increased by 185% during this training phase. The slope of the total work performed across the progressive phase of the macrocycle ranged from -5.5 to 29.6, with the lowest slope values occurring during microcycles 8 and 11. Also, mean power generation increased by 25% when eccentric isokinetic velocity increased from 60 to 90° s(-1) while

  16. Eccentric Exercise Program Design: A Periodization Model for Rehabilitation Applications

    Science.gov (United States)

    Harris-Love, Michael O.; Seamon, Bryant A.; Gonzales, Tomas I.; Hernandez, Haniel J.; Pennington, Donte; Hoover, Brian M.

    2017-01-01

    The applied use of eccentric muscle actions for physical rehabilitation may utilize the framework of periodization. This approach may facilitate the safe introduction of eccentric exercise and appropriate management of the workload progression. The purpose of this data-driven Hypothesis and Theory paper is to present a periodization model for isokinetic eccentric strengthening of older adults in an outpatient rehabilitation setting. Exemplar and group data are used to describe the initial eccentric exercise prescription, structured familiarization procedures, workload progression algorithm, and feasibility of the exercise regimen. Twenty-four men (61.8 ± 6.3 years of age) completed a 12-week isokinetic eccentric strengthening regimen involving the knee extensors. Feasibility and safety of the regimen was evaluated using serial visual analog scale (VAS, 0–10) values for self-reported pain, and examining changes in the magnitude of mean eccentric power as a function of movement velocity. Motor learning associated with the familiarization sessions was characterized through torque-time curve analysis. Total work was analyzed to identify relative training plateaus or diminished exercise capacity during the progressive phase of the macrocycle. Variability in the mean repetition interval decreased from 68 to 12% during the familiarization phase of the macrocycle. The mean VAS values were 2.9 ± 2.7 at the start of the regimen and 2.6 ± 2.9 following 12 weeks of eccentric strength training. During the progressive phase of the macrocycle, exercise workload increased from 70% of the estimated eccentric peak torque to 141% and total work increased by 185% during this training phase. The slope of the total work performed across the progressive phase of the macrocycle ranged from −5.5 to 29.6, with the lowest slope values occurring during microcycles 8 and 11. Also, mean power generation increased by 25% when eccentric isokinetic velocity increased from 60 to 90° s−1

  17. Lengthening-contractions in isolated myocardium impact force development and worsen cardiac contractile function in the mdx mouse model of muscular dystrophy

    OpenAIRE

    Xu, Ying; Delfín, Dawn A.; Rafael-Fortney, Jill A; Janssen, Paul M.L.

    2010-01-01

    Lengthening-contractions exert eccentric stress on myofibers in normal myocardium. In congestive heart failure caused by a variety of diseases, the impact of lengthening-contractions of myocardium likely becomes more prevalent and severe. The present study introduces a method to investigate the role of stretching imposed by repetitive lengthening-contractions in myocardium under near-physiological conditions. By exerting various stretch-release ramps while the muscle is contracting, consecuti...

  18. Effect of Eccentricity and Radius Ratio on Fluid Flow and Heat Transfer Inside and Eccentric Semicircular Enclosure

    Institute of Scientific and Technical Information of China (English)

    ProdipKumarDas; ShohelMahmud

    2000-01-01

    The problem of laminar natural convective heat transfer inside an eccentric semicircular enclosure of different radius ratio and eccentricity is investigated numerically,At the same time,combined effect of the radius ratio and eccentricity on fluid flow is also observed with isothermal upper and lower surface.Here laminar,steady nuatural convection heat transfer are predicted for radius ratio R*=1.75,2.0,2.25,2.5.Simulation was carried out for a range of eccentricity,ε=0.0 to 0.6.Governing equations are solved using finite volume method with a body fitted grid with collocated variable arrangement for a range of Grashof numer 101-107 based on R0.Results are presented in the form of constant stream function,isothermal lines,local Nusselt number and average Nusselt number at different angular position.Eccentricity has little dominance on heat transfer rate.But significant effect of eccentricity is observed on flow field.Radius ratio has significant effect on natural convection heat transfer as well as on flow field.At higher eccentricity,bi-cellular flow is observed with one crescent-shape vortex at narrower coross section.This crescent shaped vortex is broken down into two cells with the increase of radius ratio that means transition Grashof number for bi-cellular flow to tri-cellular flow is decreased with the increase of radius ratio.Eccentricity also has the same effect of flow field.Eccentricity has little effect on heat transfer but with the increase of radius ratio.average heat trasfer rate increases.

  19. On Some Bounds and Exact Formulae for Connective Eccentric Indices of Graphs under Some Graph Operations

    Directory of Open Access Journals (Sweden)

    Nilanjan De

    2014-01-01

    Full Text Available The connective eccentric index of a graph is a topological index involving degrees and eccentricities of vertices of the graph. In this paper, we have studied the connective eccentric index for double graph and double cover. Also we give the connective eccentric index for some graph operations such as joins, symmetric difference, disjunction, and splice of graphs.

  20. Characterizing Spinning Black Hole Binaries in Eccentric Orbits with LISA

    CERN Document Server

    Key, Joey Shapiro

    2010-01-01

    The Laser Interferometer Space Antenna (LISA) is designed to detect gravitational wave signals from astrophysical sources, including those from coalescing binary systems of compact objects such as black holes. Colliding galaxies have central black holes that sink to the center of the merged galaxy and begin to orbit one another and emit gravitational waves. Some galaxy evolution models predict that the binary black hole system will enter the LISA band with significant orbital eccentricity, while other models suggest that the orbits will already have circularized. Using a full seventeen parameter waveform model that includes the effects of orbital eccentricity, spin precession and higher harmonics, we investigate how well the source parameters can be inferred from simulated LISA data. Defining the reference eccentricity as the value one year before merger, we find that for typical LISA sources, it will be possible to measure the eccentricity to an accuracy of parts in a thousand. The accuracy with which the ec...

  1. FOREVER ALONE? TESTING SINGLE ECCENTRIC PLANETARY SYSTEMS FOR MULTIPLE COMPANIONS

    Energy Technology Data Exchange (ETDEWEB)

    Wittenmyer, Robert A.; Horner, Jonathan; Tinney, C. G.; Bailey, J.; Salter, G. S.; Wright, D. [Department of Astrophysics, School of Physics, Faculty of Science, The University of New South Wales, Sydney, NSW 2052 (Australia); Wang Songhu; Zhou Jilin [Department of Astronomy and Key Laboratory of Modern Astronomy and Astrophysics in Ministry of Education, Nanjing University, Nanjing 210093 (China); Butler, R. P. [Department of Terrestrial Magnetism, Carnegie Institution of Washington, 5241 Broad Branch Road, NW, Washington, DC 20015-1305 (United States); Jones, H. R. A. [University of Hertfordshire, Centre for Astrophysics Research, Science and Technology Research Institute, College Lane, AL10 9AB Hatfield (United Kingdom); O' Toole, S. J. [Australian Astronomical Observatory, P.O. Box 915, North Ryde, NSW 1670 (Australia); Carter, B. D., E-mail: rob@phys.unsw.edu.au [Faculty of Sciences, University of Southern Queensland, Toowoomba, Queensland 4350 (Australia)

    2013-09-15

    Determining the orbital eccentricity of an extrasolar planet is critically important for understanding the system's dynamical environment and history. However, eccentricity is often poorly determined or entirely mischaracterized due to poor observational sampling, low signal-to-noise, and/or degeneracies with other planetary signals. Some systems previously thought to contain a single, moderate-eccentricity planet have been shown, after further monitoring, to host two planets on nearly circular orbits. We investigate published apparent single-planet systems to see if the available data can be better fit by two lower-eccentricity planets. We identify nine promising candidate systems and perform detailed dynamical tests to confirm the stability of the potential new multiple-planet systems. Finally, we compare the expected orbits of the single- and double-planet scenarios to better inform future observations of these interesting systems.

  2. Forever alone? Testing single eccentric planetary systems for multiple companions

    CERN Document Server

    Wittenmyer, Robert A; Horner, Jonathan; Tinney, C G; Butler, R P; Jones, H R A; O'Toole, S J; Bailey, J; Carter, B D; Salter, G S; Wright, D

    2013-01-01

    Determining the orbital eccentricity of an extrasolar planet is critically important for understanding the system's dynamical environment and history. However, eccentricity is often poorly determined or entirely mischaracterized due to poor observational sampling, low signal-to-noise, and/or degeneracies with other planetary signals. Some systems previously thought to contain a single, moderate-eccentricity planet have been shown, after further monitoring, to host two planets on nearly-circular orbits. We investigate published apparent single-planet systems to see if the available data can be better fit by two lower-eccentricity planets. We identify nine promising candidate systems and perform detailed dynamical tests to confirm the stability of the potential new multiple-planet systems. Finally, we compare the expected orbits of the single- and double-planet scenarios to better inform future observations of these interesting systems.

  3. Exoplanet Orbital Eccentricities Derived From LAMOST-Kepler Analysis

    CERN Document Server

    Xie, Ji-Wei; Zhu, Zhaohuan; Huber, Daniel; Zheng, Zheng; De Cat, P; Fu, J N; Liu, Hui-Gen; Luo, Ali; Wu, Yue; Zhang, Haotong; Zhang, Hui; Zhou, Ji-Lin; Cao, Zihuang; Hou, Yonghui; Wang, Yuefei; Zhang, Yong

    2016-01-01

    The nearly circular (mean eccentricity ~0.06) and coplanar (mean mutual inclination ~3 deg) orbits of the Solar System planets motivated Kant and Laplace to put forth the hypothesis that planets are formed in disks, which has developed into the widely accepted theory of planet formation. Surprisingly, the first several hundred extrasolar planets (mostly Jovian) discovered using the Radial Velocity (RV) technique are commonly on eccentric orbits ( ~ 0.3). This raises a fundamental question: Are the Solar System and its formation special? The Kepler mission has found thousands of transiting planets dominated by sub-Neptunes, but most of their orbital eccentricities remain unknown. By using the precise spectroscopic host star parameters from the LAMOST observations, we measure the eccentricity distributions for a large (698) and homogeneous Kepler planet sample with transit duration statistics. Nearly half of the planets are in systems with single transiting planets (singles), while the other half are multiple-t...

  4. Near- and Far-Field Optical Response of Eccentric Nanoshells.

    Science.gov (United States)

    Peña-Rodríguez, Ovidio; Díaz-Núñez, Pablo; Rodríguez-Iglesias, Vladimir; Montaño-Priede, Luis; Rivera, Antonio; Pal, Umapada

    2017-12-01

    We study the optical response of eccentric nanoshells (i.e., spherical nanoparticles with an eccentric spherical inclusion) in the near and the far field through finite-difference time-domain simulations. Plasmon hybridization theory is used to explain the obtained results. The eccentricity generates a far-field optical spectrum with various plasmon peaks. The number, position, and width of the peaks depend on the core offset. Near-field enhancements in the surroundings of these structures are significantly larger than those obtained for equivalent concentric nanoshells and, more importantly, they are almost independent of the illumination conditions. This opens up the door for using eccentric nanoshells in applications requiring intense near-field enhancements.

  5. Kepler Planet Masses and Eccentricities from TTV Analysis

    CERN Document Server

    Hadden, Sam

    2016-01-01

    We conduct a uniform analysis of the transit timing variations (TTVs) of 145 planets from 55 Kepler multiplanet systems to infer planet masses and eccentricities. Eighty of these planets do not have previously reported mass and eccentricity measurements. We employ two complementary methods to fit TTVs: Markov chain Monte Carlo simulations based on N-body integration and an analytic fitting approach. Mass measurements of 49 planets, including 12 without previously reported masses, meet our criterion for classification as robust. Using mass and radius measurements, we infer the masses of planets' gaseous envelopes for both our TTV sample as well as transiting planets with radial velocity observations. Insight from analytic TTV formulae allows us to partially circumvent degeneracies inherent to inferring eccentricities from TTV observations. We find that planet eccentricities are generally small, typically a few percent, but in many instances are non-zero.

  6. Growth of eccentric modes in disc-planet interactions

    CERN Document Server

    Teyssandier, Jean

    2016-01-01

    We formulate a set of linear equations that describe the behaviour of small eccentricities in a protoplanetary system consisting of a gaseous disc and a planet. Eccentricity propagates through the disc by means of pressure and self-gravity, and is exchanged with the planet via secular interactions. Excitation and damping of eccentricity can occur through Lindblad and corotation resonances, as well as viscosity. We compute normal modes of the coupled disc-planet system in the case of short-period giant planets orbiting inside an inner cavity, possibly carved by the stellar magnetosphere. Three-dimensional effects allow for a mode to be trapped in the inner parts of the disc. This mode can easily grow within the disc's lifetime. An eccentric mode dominated by the planet can also grow, although less rapidly. We compute the structure and growth rates of these modes and their dependence on the assumed properties of the disc.

  7. Comparison of oxygen consumption in rats during uphill (concentric) and downhill (eccentric) treadmill exercise tests.

    Science.gov (United States)

    Chavanelle, Vivien; Sirvent, Pascal; Ennequin, Gaël; Caillaud, Kévin; Montaurier, Christophe; Morio, Béatrice; Boisseau, Nathalie; Richard, Ruddy

    2014-09-01

    The study of the physiological adaptations of skeletal muscle in response to eccentric (ECC) contraction is based on protocols in which exercise intensities are determined relative to the concentric (CON) reference exercise (as percentage of the CON maximal oxygen consumption, or VO2max). In order to use similar exercise protocols in rats, we compared the VO2 values during uphill (CON) and downhill (ECC) running tests. VO2 was measured in 15 Wistar rats during incremental treadmill running exercises with different slopes: level (0%), positive (+15% incline: CON+15%) and negative (i15% incline: ECC-15%; and 130% incline: ECC-30%). Similar VO2 values were obtained in the ECC-30% and CON+15% running conditions at the three target speeds (15, 25 and 35 cm/sec). Conversely, VO2 values were lower (p < 0.05) in the ECC-15% than in the CON+15% condition (CON+15% VO2/ECC-15% VO2 ratios ranging from 1.86 to 2.05 at the three target speeds). Thus, doubling the downhill slope gradient in ECC condition leads to an oxygen consumption level that is not significantly different as in CON condition. These findings can be useful for designing animal research protocols to study the effects of ECC and CON exercise in ageing population or subjects suffering from cardiovascular diseases. Key PointsVO2 in rats during treadmill race in eccentric and concentric conditions were measured.A novel breath-by-breath device allowing direct access to the animal was used.THREE DIFFERENT SLOPES: +15%, -15% and -30% were used.VO2 values obtained in the -30% eccentric and the +15% concentric conditions were not significantly different.

  8. Influence of vibration on delayed onset of muscle soreness following eccentric exercise

    Science.gov (United States)

    Bakhtiary, Amir H; Safavi‐Farokhi, Ziaeddin; Aminian‐Far, Atefeh

    2007-01-01

    Delayed onset muscle soreness (DOMS), which may occur after eccentric exercise, may cause some reduction in ability in sport activities. For this reason, several studies have been designed on preventing and controlling DOMS. As vibration training (VT) may improve muscle performance, we designed this study to investigate the effect of VT on controlling and preventing DOMS after eccentric exercise. Methods Fifty healthy non‐athletic volunteers were assigned randomly into two experimental, VT (n = 25) and non‐VT (n = 25) groups. A vibrator was used to apply 50 Hz vibration on the left and right quadriceps, hamstring and calf muscles for 1 min in the VT group, while no vibration was applied in the non‐VT group. Then, both groups walked downhill on a 10° declined treadmill at a speed of 4 km/hour. The measurements included the isometric maximum voluntary contraction force (IMVC) of left and right quadriceps muscles, pressure pain threshold (PPT) 5, 10 and 15 cm above the patella and mid‐line of the calf muscles of both lower limbs before and the day after treadmill walking. After 24 hours, the serum levels of creatine‐kinase (CK), and DOMS level by visual analogue scale were measured. Results The results showed decreased IMVC force (P = 0.006), reduced PPT (P = 0.0001) and significantly increased mean of DOMS and CK levels in the non‐VT group, compared to the VT group (P = 0.001). Conclusion A comparison by experimental groups indicates that VT before eccentric exercise may prevent and control DOMS. Further studies should be undertaken to ascertain the stability and effectiveness of VT in athletics. PMID:17138635

  9. Comparison of Oxygen Consumption in Rats During Uphill (Concentric) and Downhill (Eccentric) Treadmill Exercise Tests

    Science.gov (United States)

    Chavanelle, Vivien; Sirvent, Pascal; Ennequin, Gaël; Caillaud, Kévin; Montaurier, Christophe; Morio, Béatrice; Boisseau, Nathalie; Richard, Ruddy

    2014-01-01

    The study of the physiological adaptations of skeletal muscle in response to eccentric (ECC) contraction is based on protocols in which exercise intensities are determined relative to the concentric (CON) reference exercise (as percentage of the CON maximal oxygen consumption, or VO2max). In order to use similar exercise protocols in rats, we compared the VO2 values during uphill (CON) and downhill (ECC) running tests. VO2 was measured in 15 Wistar rats during incremental treadmill running exercises with different slopes: level (0%), positive (+15% incline: CON+15%) and negative (i15% incline: ECC-15%; and 130% incline: ECC-30%). Similar VO2 values were obtained in the ECC-30% and CON+15% running conditions at the three target speeds (15, 25 and 35 cm/sec). Conversely, VO2 values were lower (p VO2/ECC-15% VO2 ratios ranging from 1.86 to 2.05 at the three target speeds). Thus, doubling the downhill slope gradient in ECC condition leads to an oxygen consumption level that is not significantly different as in CON condition. These findings can be useful for designing animal research protocols to study the effects of ECC and CON exercise in ageing population or subjects suffering from cardiovascular diseases. Key Points VO2 in rats during treadmill race in eccentric and concentric conditions were measured. A novel breath-by-breath device allowing direct access to the animal was used. Three different slopes: +15%, -15% and -30% were used. VO2 values obtained in the -30% eccentric and the +15% concentric conditions were not significantly different. PMID:25177200

  10. Anterior cruciate ligament injury after more than 20 years. II. Concentric and eccentric knee muscle strength.

    Science.gov (United States)

    Tengman, E; Brax Olofsson, L; Stensdotter, A K; Nilsson, K G; Häger, C K

    2014-12-01

    The long-term consequences on knee muscle strength some decades after rupture of the anterior cruciate ligament (ACL) are not established. The aims of our study were to examine peak torque more than 20 years after ACL injury and to compare their knee muscle strength to that of healthy controls. We tested 70 individuals with unilateral ACL injury 23 ± 2 years after injury, whereof 33 (21 men) were treated with physiotherapy in combination with ACL reconstruction (ACLR ) and 37 (23 men) with physiotherapy alone (ACLPT ). These were compared with 33 age- and gender-matched controls (21 men). A Kin-Com(®) dynamometer (90°/s) was used to measure peak torque in knee flexion and extension in both concentric and eccentric contractions. Knee extension peak torque, concentric and eccentric, was ∼10% lower for the injured leg compared with the non-injured leg for both ACLR (P < 0.001; P < 0.001) and ACLPT (P = 0.007; P = 0.002). The ACLPT group also showed reduced eccentric knee flexion torque of the injured leg (P = 0.008). The strength of the non-injured leg in both ACL groups was equal to that of controls. No difference was seen for those with no-or-low degree of knee osteoarthritis compared to those with moderate-to-high degree of osteoarthritis. ACL injury may lead to a persistent reduction of peak torque in the injured leg, which needs to be considered across the lifespan.

  11. Achilles tendinopathy modulates force frequency characteristics of eccentric exercise.

    Science.gov (United States)

    Grigg, Nicole L; Wearing, Scott C; O'Toole, John M; Smeathers, James E

    2013-03-01

    Previous research has demonstrated that ground reaction force (GRF) recorded during eccentric ankle exercise is characterized by greater power in the 8- to 12-Hz bandwidth when compared with that recorded during concentric ankle exercise. Subsequently, it was suggested that vibrations in this bandwidth may underpin the beneficial effect of eccentric loading in tendon repair. However, this observation has been made only in individuals without Achilles tendinopathy. This research compared the force frequency characteristics of eccentric and concentric exercises in individuals with and without Achilles tendinopathy. Eleven male adults with unilateral midportion Achilles tendinopathy and nine control male adults without tendinopathy participated in the research. Kinematics and GRF were recorded while the participants performed a common eccentric rehabilitation exercise protocol and a concentric equivalent. Ankle joint kinematics and the frequency power spectrum of the resultant GRF were calculated. Eccentric exercise was characterized by a significantly greater proportion of spectral power between 4.5 and 11.5 Hz when compared with concentric exercise. There were no significant differences between limbs in the force frequency characteristics of concentric exercise. Eccentric exercise, in contrast, was defined by a shift in the power spectrum of the symptomatic limb, resulting in a second spectral peak at 9 Hz, rather than 10 Hz in the control limb. Compared with healthy tendon, Achilles tendinopathy was characterized by lower frequency vibrations during eccentric rehabilitation exercises. This finding may be associated with changes in neuromuscular activation and tendon stiffness that have been shown to occur with tendinopathy and provides a possible rationale for the previous observation of a different biochemical response to eccentric exercise in healthy and injured Achilles tendons.

  12. TTVFaster: First order eccentricity transit timing variations (TTVs)

    Science.gov (United States)

    Agol, Eric; Deck, Katherine

    2016-04-01

    TTVFaster implements analytic formulae for transit time variations (TTVs) that are accurate to first order in the planet-star mass ratios and in the orbital eccentricities; the implementations are available in several languages, including IDL, Julia, Python and C. These formulae compare well with more computationally expensive N-body integrations in the low-eccentricity, low mass-ratio regime when applied to simulated and to actual multi-transiting Kepler planet systems.

  13. Eccentric hamstring strength and hamstring injury risk in Australian footballers.

    Science.gov (United States)

    Opar, David A; Williams, Morgan D; Timmins, Ryan G; Hickey, Jack; Duhig, Steven J; Shield, Anthony J

    2015-04-01

    Are eccentric hamstring strength and between-limb imbalance in eccentric strength, measured during the Nordic hamstring exercise, risk factors for hamstring strain injury (HSI)? Elite Australian footballers (n = 210) from five different teams participated. Eccentric hamstring strength during the Nordic exercise was obtained at the commencement and conclusion of preseason training and at the midpoint of the season. Injury history and demographic data were also collected. Reports on prospectively occurring HSI were completed by the team medical staff. Relative risk (RR) was determined for univariate data, and logistic regression was employed for multivariate data. Twenty-eight new HSI were recorded. Eccentric hamstring strength below 256 N at the start of the preseason and 279 N at the end of the preseason increased the risk of future HSI 2.7-fold (RR, 2.7; 95% confidence interval, 1.3 to 5.5; P = 0.006) and 4.3-fold (RR, 4.3; 95% confidence interval, 1.7 to 11.0; P = 0.002), respectively. Between-limb imbalance in strength of greater than 10% did not increase the risk of future HSI. Univariate analysis did not reveal a significantly greater RR for future HSI in athletes who had sustained a lower limb injury of any kind within the last 12 months. Logistic regression revealed interactions between both athlete age and history of HSI with eccentric hamstring strength, whereby the likelihood of future HSI in older athletes or athletes with a history of HSI was reduced if an athlete had high levels of eccentric strength. Low levels of eccentric hamstring strength increased the risk of future HSI. Interaction effects suggest that the additional risk of future HSI associated with advancing age or previous injury was mitigated by higher levels of eccentric hamstring strength.

  14. Flow of viscoplastic fluids in eccentric annular geometries

    DEFF Research Database (Denmark)

    Szabo, Peter; Hassager, Ole

    1992-01-01

    A classification of flowfields for the flow of a Bingham fluid in general eccentric annular geometries is presented. Simple arguments show that a singularity can exist in the stress gradient on boundaries between zones with yielded and un-yielded fluid respectively. A Finite Element code is used...... to verify this property of the Bingham fluid. An analytical solution for the flowfield in case of small eccentricities is derived....

  15. Chronic Adaptations to Eccentric Training: A Systematic Review.

    Science.gov (United States)

    Douglas, Jamie; Pearson, Simon; Ross, Angus; McGuigan, Mike

    2017-05-01

    Resistance training is an integral component of physical preparation for athletes. A growing body of evidence indicates that eccentric strength training methods induce novel stimuli for neuromuscular adaptations. The purpose of this systematic review was to determine the effects of eccentric training in comparison to concentric-only or traditional (i.e. constrained by concentric strength) resistance training. Searches were performed using the electronic databases MEDLINE via EBSCO, PubMed and SPORTDiscus via EBSCO. Full journal articles investigating the long-term (≥4 weeks) effects of eccentric training in healthy (absence of injury or illness during the 4 weeks preceding the training intervention), adult (17-35 years), human participants were selected for the systematic review. A total of 40 studies conformed to these criteria. Eccentric training elicits greater improvements in muscle strength, although in a largely mode-specific manner. Superior enhancements in power and stretch-shortening cycle (SSC) function have also been reported. Eccentric training is at least as effective as other modalities in increasing muscle cross-sectional area (CSA), while the pattern of hypertrophy appears nuanced and increased CSA may occur longitudinally within muscle (i.e. the addition of sarcomeres in series). There appears to be a preferential increase in the size of type II muscle fibres and the potential to exert a unique effect upon fibre type transitions. Qualitative and quantitative changes in tendon tissue that may be related to the magnitude of strain imposed have also been reported with eccentric training. Eccentric training is a potent stimulus for enhancements in muscle mechanical function, and muscle-tendon unit (MTU) morphological and architectural adaptations. The inclusion of eccentric loads not constrained by concentric strength appears to be superior to traditional resistance training in improving variables associated with strength, power and speed

  16. Exoplanet orbital eccentricity: multiplicity relation and the Solar System.

    Science.gov (United States)

    Limbach, Mary Anne; Turner, Edwin L

    2015-01-06

    The known population of exoplanets exhibits a much wider range of orbital eccentricities than Solar System planets and has a much higher average eccentricity. These facts have been widely interpreted to indicate that the Solar System is an atypical member of the overall population of planetary systems. We report here on a strong anticorrelation of orbital eccentricity with multiplicity (number of planets in the system) among cataloged radial velocity (RV) systems. The mean, median, and rough distribution of eccentricities of Solar System planets fits an extrapolation of this anticorrelation to the eight-planet case rather precisely despite the fact that no more than two Solar System planets would be detectable with RV data comparable to that in the exoplanet sample. Moreover, even if regarded as a single or double planetary system, the Solar System lies in a reasonably heavily populated region of eccentricity-multiplicity space. Thus, the Solar System is not anomalous among known exoplanetary systems with respect to eccentricities when its multiplicity is taken into account. Specifically, as the multiplicity of a system increases, the eccentricity decreases roughly as a power law of index -1.20. A simple and plausible but ad hoc and model-dependent interpretation of this relationship implies that ∼ 80% of the one-planet and 25% of the two-planet systems in our sample have additional, as yet undiscovered, members but that systems of higher observed multiplicity are largely complete (i.e., relatively rarely contain additional undiscovered planets). If low eccentricities indeed favor high multiplicities, habitability may be more common in systems with a larger number of planets.

  17. Eccentricity in Zone Routing Protocol for MANET

    Directory of Open Access Journals (Sweden)

    Mrs Komal Nair

    2012-06-01

    Full Text Available A Mobile Ad-Hoc Network (MANET is a decentralized network of autonomous mobile nodes, able to communicate with each other over wireless links. Due to the mobility of the nodes, the topology ofthe network changes spontaneously, therefore use of conventional routing tables maintained at fixed points (routers is not suggested. Such a network may operate in a standalone fashion. There are variousrouting protocols available for MANETs. The most popular ones are DSR, DSDV and ZRP .The zone routing protocol (ZRP is a hybrid routing protocol that proactively maintains routes within a localregion of the network. ZRP can be configured for a particular network through adjustment of a single parameter, the routing zone radius. In this paper, we address the issue of configuring the ZRP to providethe best performance for a particular network at any time with the concept of eccentricity. The results illustrate the important characteristics of different protocols based on their performance and thus suggest some improvements in the respective protocol. The tools used for the simulation are NS2 which is the main simulator, NAM (Network Animator and Tracegraph which is used for preparing the graphs from the trace files.

  18. Highly eccentric inspirals into a black hole

    CERN Document Server

    Osburn, Thomas; Evans, Charles R

    2015-01-01

    We model the inspiral of a compact stellar-mass object into a massive non-rotating black hole including all dissipative and conservative first-order-in-the-mass-ratio effects on the orbital motion. The techniques we develop allow inspirals with initial eccentricities as high as $e\\sim0.8$ and initial separations as large as $\\sim 100M$ to be evolved through many thousands of orbits up to the onset of the plunge into the black hole. The inspiral is computed using an osculating elements scheme driven by a hybridized self-force model, which combines Lorenz-gauge self-force results with highly accurate flux data from a Regge-Wheeler-Zerilli code. The high accuracy of our hybrid self-force model allows the orbital phase of the inspirals to be tracked to within $\\sim0.1$ radians or better. The difference between self-force models and inspirals computed in the radiative approximation is quantified.

  19. The Solar System and the Exoplanet Orbital Eccentricity - Multiplicity Relation

    CERN Document Server

    Limbach, Mary Anne

    2014-01-01

    The known population of exoplanets exhibits a much wider range of orbital eccentricities than Solar System planets and has a much higher average eccentricity. These facts have been widely interpreted to indicate that the Solar System is an atypical member of the overall population of planetary systems. We report here on a strong anti-correlation of orbital eccentricity with multiplicity (number of planets in the system) among catalogued RV systems. The mean, median and rough distribution of eccentricities of Solar System planets fits an extrapolation of this anti-correlation to the eight planet case rather precisely. Thus, the Solar System is not anomalous among known exoplanetary systems with respect to eccentricities when its multiplicity is taken into account. Specifically, as the multiplicity of a system increases the eccentricity decreases roughly as a power law of index -1.20. A simple and plausible but ad hoc model of this relationship implies that approximately 80% of the one planet and 25% of the two...

  20. Exoplanet orbital eccentricities derived from LAMOST-Kepler analysis.

    Science.gov (United States)

    Xie, Ji-Wei; Dong, Subo; Zhu, Zhaohuan; Huber, Daniel; Zheng, Zheng; De Cat, Peter; Fu, Jianning; Liu, Hui-Gen; Luo, Ali; Wu, Yue; Zhang, Haotong; Zhang, Hui; Zhou, Ji-Lin; Cao, Zihuang; Hou, Yonghui; Wang, Yuefei; Zhang, Yong

    2016-10-11

    The nearly circular (mean eccentricity [Formula: see text]) and coplanar (mean mutual inclination [Formula: see text]) orbits of the solar system planets motivated Kant and Laplace to hypothesize that planets are formed in disks, which has developed into the widely accepted theory of planet formation. The first several hundred extrasolar planets (mostly Jovian) discovered using the radial velocity (RV) technique are commonly on eccentric orbits ([Formula: see text]). This raises a fundamental question: Are the solar system and its formation special? The Kepler mission has found thousands of transiting planets dominated by sub-Neptunes, but most of their orbital eccentricities remain unknown. By using the precise spectroscopic host star parameters from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) observations, we measure the eccentricity distributions for a large (698) and homogeneous Kepler planet sample with transit duration statistics. Nearly half of the planets are in systems with single transiting planets (singles), whereas the other half are multiple transiting planets (multiples). We find an eccentricity dichotomy: on average, Kepler singles are on eccentric orbits with [Formula: see text] 0.3, whereas the multiples are on nearly circular [Formula: see text] and coplanar [Formula: see text] degree) orbits similar to those of the solar system planets. Our results are consistent with previous studies of smaller samples and individual systems. We also show that Kepler multiples and solar system objects follow a common relation [[Formula: see text](1-2)[Formula: see text

  1. Initial partonic eccentricity fluctuations in a multiphase transport model

    Science.gov (United States)

    Ma, L.; Ma, G. L.; Ma, Y. G.

    2016-10-01

    Initial partonic eccentricities in Au+Au collisions at center-of-mass energy √{sN N}=200 GeV are investigated by using a multiphase transport model with a string-melting scenario. The initial eccentricities in different order of harmonics are studied by using participant and cumulant definitions. Eccentricity in terms of second-, fourth- and sixth-order cumulants as a function of number of participant nucleons are compared systematically with the traditional participant definition. The ratio of the cumulant eccentricities ɛ {4 }/ɛ {2 } and ɛ {6 }/ɛ {4 } are studied in comparison with the ratio of the corresponding flow harmonics. The conversion coefficients (vn/ɛn ) are explored up to fourth-order harmonics based on the cumulant method. Furthermore, studies on transverse momentum (pT) and pseudorapidity (η ) dependencies of eccentricities and their fluctuations are presented. As in ideal hydrodynamics, initial eccentricities are expected to be closely related to the final flow harmonics in relativistic heavy-ion collisions, studies of the fluctuating initial condition in the AMPT model will shed light on the tomography properties of the initial source geometry.

  2. Different Levels of Eccentric Resistance during Eight Weeks of Training Affect Muscle Strength and Lean Tissue Mass

    Science.gov (United States)

    English, K. L.; Loehr, J. A.; Lee, S. M. C.; Laughlin, M. S.; Hagan, R. D.

    2008-01-01

    Coupling concentric and eccentric muscle contractions appears to be important in the development of muscle strength and hypertrophy. The interim Resistive Exercise Device (iRED) currently used aboard the International Space Station does not seem to be as effective as free weight training in ambulatory subjects and has not completely protected against muscular deconditioning due to space flight. The lack of protection during space flight could be caused by iRED's proportionally lower eccentric resistance (60-70%) compared to concentric resistance. PURPOSE: To determine the effects of 8 wks of lower body resistive exercise training using five levels of eccentric resistance on muscle strength and lean tissue mass. METHODS: Forty untrained males (34.9 +/- 7 yrs, 80.9 +/- 9.8 kg, 178.2 +/- 7.1 cm; mean +/- SD) completed three 1-repetition maximum (1-RM) strength tests for both the supine leg press (LP) and supine heel raise (HR) prior to training; subjects were matched for LP strength and randomly assigned to one of five training groups. Concentric load (% 1-RM) was constant across groups during training, but each group trained with different levels of eccentric load (0%, 33%, 66%, 100%, or 138% of concentric). Subjects trained 3 d / wk for 8 wks using a periodized program for LP and HR based on percentages of the highest pre-training 1-RM. LP and HR 1-RM and leg lean mass (LLM; assessed by DEXA) were measured pre- and post-training. A two-way ANOVA was used to analyze all dependent measures. Tukey's post hoc tests were used to test significant main effects. Within group pre- to post-training changes were compared using paired t-tests with a Bonferroni adjustment. Statistical significance was set a priori at p 0.05. All data are expressed as mean +/- SE. RESULTS: LP 1-RM strength increased significantly in all groups pre- to post-training. The 138% group increase (20.1 +/- 3.7%) was significantly greater than the 0% (7.9 +/- 2.8%), 33% (7.7 +/- 4.6%), and 66% (7.5 +/- 4

  3. Different Levels of Eccentric Resistance during Eight Weeks of Training Affect Muscle Strength and Lean Tissue Mass

    Science.gov (United States)

    English, K. L.; Loehr, J. A.; Lee, S. M. C.; Laughlin, M. S.; Hagan, R. D.

    2008-01-01

    Coupling concentric and eccentric muscle contractions appears to be important in the development of muscle strength and hypertrophy. The interim Resistive Exercise Device (iRED) currently used aboard the International Space Station does not seem to be as effective as free weight training in ambulatory subjects and has not completely protected against muscular deconditioning due to space flight. The lack of protection during space flight could be caused by iRED's proportionally lower eccentric resistance (60-70%) compared to concentric resistance. PURPOSE: To determine the effects of 8 wks of lower body resistive exercise training using five levels of eccentric resistance on muscle strength and lean tissue mass. METHODS: Forty untrained males (34.9 +/- 7 yrs, 80.9 +/- 9.8 kg, 178.2 +/- 7.1 cm; mean +/- SD) completed three 1-repetition maximum (1-RM) strength tests for both the supine leg press (LP) and supine heel raise (HR) prior to training; subjects were matched for LP strength and randomly assigned to one of five training groups. Concentric load (% 1-RM) was constant across groups during training, but each group trained with different levels of eccentric load (0%, 33%, 66%, 100%, or 138% of concentric). Subjects trained 3 d / wk for 8 wks using a periodized program for LP and HR based on percentages of the highest pre-training 1-RM. LP and HR 1-RM and leg lean mass (LLM; assessed by DEXA) were measured pre- and post-training. A two-way ANOVA was used to analyze all dependent measures. Tukey's post hoc tests were used to test significant main effects. Within group pre- to post-training changes were compared using paired t-tests with a Bonferroni adjustment. Statistical significance was set a priori at p 0.05. All data are expressed as mean +/- SE. RESULTS: LP 1-RM strength increased significantly in all groups pre- to post-training. The 138% group increase (20.1 +/- 3.7%) was significantly greater than the 0% (7.9 +/- 2.8%), 33% (7.7 +/- 4.6%), and 66% (7.5 +/- 4

  4. Whey protein hydrolysate augments tendon and muscle hypertrophy independent of resistance exercise contraction mode

    DEFF Research Database (Denmark)

    Farup, Jean; Rahbek, S K; Vendelbo, M H

    2014-01-01

    In a comparative study, we investigated the effects of maximal eccentric or concentric resistance training combined with whey protein or placebo on muscle and tendon hypertrophy. 22 subjects were allocated into either a high-leucine whey protein hydrolysate + carbohydrate group (WHD...... or contraction mode effects. In conclusion, high-leucine whey protein hydrolysate augments muscle and tendon hypertrophy following 12 weeks of resistance training – irrespective of contraction mode....

  5. Isokinetic eccentric resistance training prevents loss in mechanical muscle function after running.

    Science.gov (United States)

    Oliveira, Anderson Souza; Caputo, Fabrizio; Aagaard, Per; Corvino, Rogério Bulhões; Gonçalves, Mauro; Denadai, Benedito Sergio

    2013-09-01

    The aim of the study was to verify whether 8 weeks of resistance training employing maximal isokinetic eccentric (IERT) knee extensor actions would reduce the acute force loss observed after high-intensity treadmill running exercise. It was hypothesized that specific IERT would induce protective effects against muscle fatigue and ultrastructural damages, preventing or reducing the loss in mechanical muscle function after running. Subjects were tested before and after IERT protocol for maximal isometric, concentric and eccentric isokinetic knee extensor strength (60° and 180° s(-1)). In a second session, subjects performed treadmill running (~35 min) and the previously mentioned measurements were repeated immediately after running. Subsequently, subjects were randomized to training (n = 12) consisting of 24 sessions of maximal IERT knee extensors actions at 180° s(-1), or served as controls (n = 8). The effects of acute running-induced fatigue and training on isokinetic and isometric peak torque, and rate of force development (RFD) were investigated. Before IERT, running-induced eccentric torque loss at 180° s(-1) was -8 %, and RFD loss was -11 %. Longitudinal IERT led to reduced or absent acute running-induced losses in maximal IERT torque at 180° s(-1) (+2 %), being significantly reduced compared to before IERT (p 0.05). In conclusion, IERT yields a reduced strength loss after high-intensity running workouts, which may suggest a protective effect against fatigue and/or morphological damages. However, IERT may not avoid reductions in explosive muscle actions. In turn, this may allow more intense training sessions to be performed, facilitating the adaptive response to running training.

  6. Creatine supplementation enhances muscle force recovery after eccentrically-induced muscle damage in healthy individuals

    Directory of Open Access Journals (Sweden)

    Cribb Paul J

    2009-06-01

    Full Text Available Abstract Background Eccentric exercise-induced damage leads to reductions in muscle force, increased soreness, and impaired muscle function. Creatine monohydrate's (Cr ergogenic potential is well established; however few studies have directly examined the effects of Cr supplementation on recovery after damage. We examined the effects of Cr supplementation on muscle proteins and force recovery after eccentrically-induced muscle damage in healthy individuals. Methods Fourteen untrained male participants (22.1 ± 2.3 yrs, 173 ± 7.7 cm, 76.2 ± 9.3 kg were randomly separated into 2 supplement groups: i Cr and carbohydrate (Cr-CHO; n = 7; or ii carbohydrate (CHO; n = 7. Participants consumed their supplement for a period of 5 days prior to, and 14 days following a resistance exercise session. Participants performed 4 sets of 10 eccentric-only repetitions at 120% of their maximum concentric 1-RM on the leg press, leg extension and leg flexion exercise machine. Plasma creatine kinase (CK and lactate dehydrogenase (LDH activity were assessed as relevant blood markers of muscle damage. Muscle strength was examined by voluntary isokinetic knee extension using a Cybex dynamometer. Data were analyzed using repeated measures ANOVA with an alpha of 0.05. Results The Cr-supplemented group had significantly greater isokinetic (10% higher and isometric (21% higher knee extension strength during recovery from exercise-induced muscle damage. Furthermore, plasma CK activity was significantly lower (by an average of 84% after 48 hrs (P Conclusion The major finding of this investigation was a significant improvement in the rate of recovery of knee extensor muscle function after Cr supplementation following injury.

  7. Dichoptic suppression of mfVEP amplitude: effect of retinal eccentricity and simulated unilateral visual impairment.

    Science.gov (United States)

    Leaney, John; Klistorner, Alexander; Arvind, Hemamalini; Graham, Stuart L

    2010-12-01

    To investigate the effect of retinal eccentricity on the phenomenon of dichoptic suppression of the mfVEP amplitude and to examine the relationship between the degree of simulated unilateral visual impairment and the possible release of dichoptic suppression in the contralateral eye. Eight subjects with corrected visual acuity (VAc) >6/6 and stereoacuity >60 sec arc underwent monocular and dichoptic pattern-pulse mfVEP. Dichoptic stimulation was repeated with refractively induced blur of one eye with +4-D and +6-D lenses above distance correction. Dichoptic recording resulted in significant reduction of averaged mfVEP amplitude (19.8% ± 4.9%, paired t-test, P = 0.00003). The magnitude of suppression, while statistically significant at all eccentricities, was significantly larger in the central part of the visual field and diminished toward the periphery. Refractive blur, used to simulate visual impairment produced variable degrees of amplitude reduction in the blurred eye and resulted in amplitude increases in the contralateral eye. There was a highly significant correlation between the magnitude of amplitude reduction in the blurred eye and increase in amplitude (i.e., release of dichoptic suppression) in the contralateral eye (r = 0.91, P < 0.0001). The study demonstrated that dichoptic stimulation results in eccentricity-dependent suppression of mfVEP amplitude. Factors affecting visual performance of one eye (monocular blur) promote the release of dichoptic suppression in the fellow (unaffected) eye. This phenomenon leads to an increase in intereye asymmetry and therefore may improve early detection of ocular diseases, especially monocular pathologic processes.

  8. Crowding and eccentricity determine reading rate.

    Science.gov (United States)

    Pelli, Denis G; Tillman, Katharine A; Freeman, Jeremy; Su, Michael; Berger, Tracey D; Majaj, Najib J

    2007-10-26

    Bouma's law of crowding predicts an uncrowded central window through which we can read and a crowded periphery through which we cannot. The old discovery that readers make several fixations per second, rather than a continuous sweep across the text, suggests that reading is limited by the number of letters that can be acquired in one fixation, without moving one's eyes. That "visual span" has been measured in various ways, but remains unexplained. Here we show (1) that the visual span is simply the number of characters that are not crowded and (2) that, at each vertical eccentricity, reading rate is proportional to the uncrowded span. We measure rapid serial visual presentation (RSVP) reading rate for text, in both original and scrambled word order, as a function of size and spacing at central and peripheral locations. As text size increases, reading rate rises abruptly from zero to maximum rate. This classic reading rate curve consists of a cliff and a plateau, characterized by two parameters, critical print size and maximum reading rate. Joining two ideas from the literature explains the whole curve. These ideas are Bouma's law of crowding and Legge's conjecture that reading rate is proportional to visual span. We show that Legge's visual span is the uncrowded span predicted by Bouma's law. This result joins Bouma and Legge to explain reading rate's dependence on letter size and spacing. Well-corrected fluent observers reading ordinary text with adequate light are limited by letter spacing (crowding), not size (acuity). More generally, it seems that this account holds true, independent of size, contrast, and luminance, provided only that text contrast is at least four times the threshold contrast for an isolated letter. For any given spacing, there is a central uncrowded span through which we read. This uncrowded span model explains the shape of the reading rate curve. We test the model in several ways. We use a "silent substitution" technique to measure the

  9. Repeat-until-success quantum repeaters

    Science.gov (United States)

    Bruschi, David Edward; Barlow, Thomas M.; Razavi, Mohsen; Beige, Almut

    2014-09-01

    We propose a repeat-until-success protocol to improve the performance of probabilistic quantum repeaters. Conventionally, these rely on passive static linear-optics elements and photodetectors to perform Bell-state measurements (BSMs) with a maximum success rate of 50%. This is a strong impediment for entanglement swapping between distant quantum memories. Every time a BSM fails, entanglement needs to be redistributed between the corresponding memories in the repeater link. The key ingredients of our scheme are repeatable BSMs. Under ideal conditions, these turn probabilistic quantum repeaters into deterministic ones. Under realistic conditions, our protocol too might fail. However, using additional threshold detectors now allows us to improve the entanglement generation rate by almost orders of magnitude, at a nominal distance of 1000 km, compared to schemes that rely on conventional BSMs. This improvement is sufficient to make the performance of our scheme comparable to the expected performance of some deterministic quantum repeaters.

  10. Cardiovascular and Muscular Consequences of Work-Matched Interval-Type of Concentric and Eccentric Pedaling Exercise on a Soft Robot

    Science.gov (United States)

    Flück, Martin; Bosshard, Rebekka; Lungarella, Max

    2017-01-01

    reduced after eccentric and concentric exercise. The results highlight that the deployed interval-type of eccentric leg exercise reduces metabolic strain of the cardiovasculature and muscle compared to concentric exercise, to recommended levels for cardio-rehabilitation (i.e., 50–70% of peak heart rate). Increases in blood glucose concentration indicate that resistance to contraction-induced glucose uptake after the deployed eccentric protocol is unrelated to muscle fatigue. PMID:28912726

  11. Cardiovascular and Muscular Consequences of Work-Matched Interval-Type of Concentric and Eccentric Pedaling Exercise on a Soft Robot.

    Science.gov (United States)

    Flück, Martin; Bosshard, Rebekka; Lungarella, Max

    2017-01-01

    after eccentric and concentric exercise. The results highlight that the deployed interval-type of eccentric leg exercise reduces metabolic strain of the cardiovasculature and muscle compared to concentric exercise, to recommended levels for cardio-rehabilitation (i.e., 50-70% of peak heart rate). Increases in blood glucose concentration indicate that resistance to contraction-induced glucose uptake after the deployed eccentric protocol is unrelated to muscle fatigue.

  12. Cardiovascular and Muscular Consequences of Work-Matched Interval-Type of Concentric and Eccentric Pedaling Exercise on a Soft Robot

    Directory of Open Access Journals (Sweden)

    Martin Flück

    2017-08-01

    similarly reduced after eccentric and concentric exercise. The results highlight that the deployed interval-type of eccentric leg exercise reduces metabolic strain of the cardiovasculature and muscle compared to concentric exercise, to recommended levels for cardio-rehabilitation (i.e., 50–70% of peak heart rate. Increases in blood glucose concentration indicate that resistance to contraction-induced glucose uptake after the deployed eccentric protocol is unrelated to muscle fatigue.

  13. Joint-specific power loss after eccentric exercise.

    Science.gov (United States)

    Elmer, Steven J; Martin, James C

    2010-09-01

    Previous investigators have reported changes in maximal power after eccentric exercise. The influence of eccentric joint-specific power absorption on subsequent concentric joint-specific power production during multijoint actions has not been reported. Our purposes were to determine the extent to which ankle, knee, and hip joint actions absorbed power during eccentric cycling (ECCcyc) and to evaluate changes in power produced by those joint actions during subsequent maximal concentric cycling (CONcyc). We hypothesized that joint actions that absorbed the most power during ECCcyc would exhibit the greatest reductions in power during subsequent maximal CONcyc. Nineteen cyclists performed baseline trials of maximal single-leg CONcyc immediately before and 24 h after acute single-leg ECCcyc (5 min, 40% maximum single-leg CONcyc power). Pedal forces and limb kinematics were determined with a force-sensing pedal and instrumented spatial linkage system, respectively. Joint-specific powers were calculated using inverse dynamics and averaged over complete crank revolutions and over extension and flexion phases. The largest power-absorbing actions during ECCcyc were eccentric knee extensor activity (-185 +/- 12 W) followed by eccentric hip extensor activity (-92 +/- 12 W). Power absorbed through ankle joint actions was small (-10 +/- 2 W). At 24 h, pedal power produced during maximal CONcyc was reduced by 11% +/- 3% relative to baseline. Compared with baseline, knee extension power was reduced by 19% +/- 0 7%, whereas hip extension power did not differ. Power absorbed through eccentric knee extension actions significantly reduced knee extension power produced during subsequent maximal CONcyc. Even with reduced knee extensor function, participants were able to deliver 89% of their baseline power to the environment. These results have implications for individuals who must continue to perform multijoint activities after eccentric exercise.

  14. Eccentric endurance exercise economically improves metabolic and inflammatory risk factors.

    Science.gov (United States)

    Zeppetzauer, Markus; Drexel, Heinz; Vonbank, Alexander; Rein, Philipp; Aczel, Stefan; Saely, Christoph H

    2013-08-01

    Exercise is a cornerstone of cardiovascular prevention. Because many individuals are not willing or not able to perform regular exercise, new methods of exercise (like eccentric exercise) are necessary. Eccentric endurance exercise is supposed to be less strenuous than concentric exercise but its effects on glucose and lipid metabolism in relation to energy expenditure are unclear. We randomly allocated 45 healthy sedentary individuals to one of two groups, each hiking upwards or downwards for 2 months, with a crossover for a further 2 months; for the opposite way, a cable car was used. The difference in altitude was 540 metres; the distance was covered between three and five times a week. Energy expenditure was assessed for each hiking period. Both eccentric and concentric endurance exercise improved glucose tolerance vs. baseline (by 4.1%, p = 0.136; 6.2%, p = 0.023, respectively). Of note, adjustment for energy expenditure per exercise unit (127 ± 22 kcal/unit with eccentric and 442 ± 78 kcal/unit with concentric exercise) revealed a significantly greater improvement of glucose tolerance per kilocalorie spent by eccentric than by concentric exercise (4-times more economical; 0.1123 mg h/dl/kcal vs. 0.0245 mg h/dl/kcal; p = 0.038). Also the decrease of low-density lipoprotein (LDL) cholesterol per kilocalorie spent was significantly stronger with eccentric exercise (0.0982 mg/dl/kcal vs. 0.0346 mg/dl/kcal, p = 0.014). Serum levels of C-reactive protein and creatine kinase activity were reduced in both groups. Eccentric endurance exercise economically improves glucose tolerance and LDL cholesterol. It therefore is a promising new exercise modality for individuals who are not able to participate in more strenuous exercise regimens.

  15. Exoplanet orbital eccentricity: Multiplicity relation and the Solar System

    Science.gov (United States)

    Limbach, Mary Anne; Turner, Edwin L.

    2015-01-01

    The known population of exoplanets exhibits a much wider range of orbital eccentricities than Solar System planets and has a much higher average eccentricity. These facts have been widely interpreted to indicate that the Solar System is an atypical member of the overall population of planetary systems. We report here on a strong anticorrelation of orbital eccentricity with multiplicity (number of planets in the system) among cataloged radial velocity (RV) systems. The mean, median, and rough distribution of eccentricities of Solar System planets fits an extrapolation of this anticorrelation to the eight-planet case rather precisely despite the fact that no more than two Solar System planets would be detectable with RV data comparable to that in the exoplanet sample. Moreover, even if regarded as a single or double planetary system, the Solar System lies in a reasonably heavily populated region of eccentricity−multiplicity space. Thus, the Solar System is not anomalous among known exoplanetary systems with respect to eccentricities when its multiplicity is taken into account. Specifically, as the multiplicity of a system increases, the eccentricity decreases roughly as a power law of index –1.20. A simple and plausible but ad hoc and model-dependent interpretation of this relationship implies that ∼80% of the one-planet and 25% of the two-planet systems in our sample have additional, as yet undiscovered, members but that systems of higher observed multiplicity are largely complete (i.e., relatively rarely contain additional undiscovered planets). If low eccentricities indeed favor high multiplicities, habitability may be more common in systems with a larger number of planets. PMID:25512527

  16. Exoplanet orbital eccentricities derived from LAMOST-Kepler analysis

    Science.gov (United States)

    Xie, Ji-Wei; Dong, Subo; Zhu, Zhaohuan; Huber, Daniel; Zheng, Zheng; De Cat, Peter; Fu, Jianning; Liu, Hui-Gen; Luo, Ali; Wu, Yue; Zhang, Haotong; Zhang, Hui; Zhou, Ji-Lin; Cao, Zihuang; Hou, Yonghui; Wang, Yuefei; Zhang, Yong

    2016-10-01

    The nearly circular (mean eccentricity e¯≈0.06) and coplanar (mean mutual inclination i¯≈3°) orbits of the solar system planets motivated Kant and Laplace to hypothesize that planets are formed in disks, which has developed into the widely accepted theory of planet formation. The first several hundred extrasolar planets (mostly Jovian) discovered using the radial velocity (RV) technique are commonly on eccentric orbits (e¯≈0.3). This raises a fundamental question: Are the solar system and its formation special? The Kepler mission has found thousands of transiting planets dominated by sub-Neptunes, but most of their orbital eccentricities remain unknown. By using the precise spectroscopic host star parameters from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) observations, we measure the eccentricity distributions for a large (698) and homogeneous Kepler planet sample with transit duration statistics. Nearly half of the planets are in systems with single transiting planets (singles), whereas the other half are multiple transiting planets (multiples). We find an eccentricity dichotomy: on average, Kepler singles are on eccentric orbits with e¯≈0.3, whereas the multiples are on nearly circular (e¯=0.04-0.04+0.03) and coplanar (i¯=1.4-1.1+0.8 degree) orbits similar to those of the solar system planets. Our results are consistent with previous studies of smaller samples and individual systems. We also show that Kepler multiples and solar system objects follow a common relation [×i¯] between mean eccentricities and mutual inclinations. The prevalence of circular orbits and the common relation may imply that the solar system is not so atypical in the galaxy after all.

  17. Human Skeletal Muscle Stem Cells in Adaptations to Exercise; Effects of Resistance Exercise Contraction Mode and Protein Supplementation

    DEFF Research Database (Denmark)

    Farup, Jean

    2014-01-01

    . In conclusion, protein supplementation may accelerate SC proliferation as part of regeneration or remodeling processes after maximal eccentric exercise. Paper II. Whey protein hydrolysate augments tendon and muscle hypertrophy independent of exercise contraction mode. The aim of paper II was to investigate...... the effect of contraction mode specific resistance training and protein supplementation on whole muscle and tendon hypertrophy. Quadriceps muscle and patellar tendon cross-sectional area (CSA) was quantified using magnetic resonance imaging pre and post 12 weeks of eccentric (Ecc) or concentric (Conc...... compared to Placebo. Exercise contraction mode did not influence muscle or tendon hypertrophy. In conclusion, hydrolysed whey protein may augment both muscle and tendon hypertrophy independently of exercise contraction mode during training. Paper III. Influence of exercise contraction mode and protein...

  18. Effects of eccentric exercise on optimum length of the knee flexors and extensors during the preseason in professional soccer players.

    Science.gov (United States)

    Brughelli, Matt; Mendiguchia, Jurdan; Nosaka, Ken; Idoate, Fernando; Arcos, Asier Los; Cronin, John

    2010-05-01

    To assess the effects of eccentric exercise on optimum lengths of the knee flexors and extensors during the preseason in professional soccer. Twenty-eight athletes from a professional Spanish soccer team (Division II) were randomly assigned to an eccentric exercise intervention group (EG) or a control group (CG). Over the four-week period two athletes from the control group suffered RF injuries and two athletes were contracted by other clubs. After these exclusions, both groups (EG, n=13; and CG, n=11) performed regular soccer training during the four-week preseason period. After the four weeks, the optimum lengths of the knee flexors were significantly (Pknee extensors were significantly increased only in the EG by 6.5 degrees . Peak torque levels and ratios of quadriceps to hamstring (Q/H ratios) were not significantly altered throughout the study for either group. Eccentric exercise can increase the optimum lengths of both the knee extensors and knee extensors flexors during the preseason in professional soccer.

  19. Changes in the number of circulating CD34+cells after eccentric exercise of the elbow flexors in relation to muscle damage

    Institute of Scientific and Technical Information of China (English)

    Ho Seong Lee; Makii Muthalib; Takayuki Akimoto; Kazunori Nosaka

    2015-01-01

    Background:It has been reported that strenuous exercise increases the number of bone marrow-derived progenitor cells such as CD34+cells in the blood, but no previous studies have investigated the changes in circulating CD34+cells following resistance exercise. This study tested the hypothesis that the number of CD34+cells in the blood would increase after eccentric exercise of the elbow flexors, but decrease in recovery, and the magnitude of the changes would be dependent on the magnitude of muscle damage. Methods:Nine men (28.0 ± 6.6 years) performed exercises consisting of 10 sets of six maximal voluntary eccentric contractions of the elbow flexors with their non-dominant arm. Six of them performed the same exercise with the same arm 4 weeks later. Changes in indirect markers of muscle damage were measured before, within 10 min after, and at 24, 48, 72, and 96 h after eccentric exercise. Differential leukocyte counts (total leukocytes, neutrophils, lymphocytes, monocytes) and CD34+cells in the blood were measured before, immediately after, and at 2, 24, 48, 72, and 96 h following the exercises. Results:After eccentric exercise, significant ( p<0.05) decreases in maximal voluntary isometric contraction torque and increases in delayed onset muscle soreness and plasma creatine kinase activity were observed. However, no significant changes in leukocytes and CD34+cells were evident. The changes in muscle damage markers were significantly ( p<0.05) smaller following the second exercise session as compared with the first exercise session, but the changes in leukocytes and CD34+cells were not significantly different between sessions. Conclusion:These results did not support the hypothesis, and showed that eccentric exercise-induced muscle damage to the elbow flexors did not influence the number of circulating CD34+cells.

  20. Effects of a shoulder injury prevention strength training program on eccentric external rotator muscle strength and glenohumeral joint imbalance in female overhead activity athletes.

    Science.gov (United States)

    Niederbracht, Yvonne; Shim, Andrew L; Sloniger, Mark A; Paternostro-Bayles, Madeline; Short, Thomas H

    2008-01-01

    Imbalance of the eccentrically-activated external rotator cuff muscles versus the concentrically-activated internal rotator cuff muscles is a primary risk factor for glenohumeral joint injuries in overhead activity athletes. Nonisokinetic dynamometer based strength training studies, however, have focused exclusively on resulting concentric instead of applicable eccentric strength gains of the external rotator cuff muscles. Furthermore, previous strength training studies did not result in a reduction in glenoumeral joint muscle imbalance, thereby suggesting that currently used shoulder strength training programs do not effectively reduce the risk of shoulder injury to the overhead activity athlete. Two collegiate women tennis teams, consisting of 12 women, participated in this study throughout their preseason training. One team (n = 6) participated in a 5-week, 4 times a week, external shoulder rotator muscle strength training program next to their preseason tennis training. The other team (n = 6) participated in a comparable preseason tennis training program, but did not conduct any upper body strength training. Effects of this strength training program were evaluated by comparing pre- and posttraining data of 5 maximal eccentric external immediately followed by concentric internal contractions on a Kin-Com isokinetic dynamometer (Chattecx Corp., Hixson, Tennessee). Overall, the shoulder strength training program significantly increased eccentric external total work without significant effects on concentric internal total work, concentric internal mean peak force, or eccentric external mean peak force. In conclusion, by increasing the eccentric external total exercise capacity without a subsequent increase in the concentric internal total exercise capacity, this strength training program potentially decreases shoulder rotator muscle imbalances and the risk for shoulder injuries to overhead activity athletes.

  1. Eccentric error and compensation in rotationally symmetric laser triangulation

    Institute of Scientific and Technical Information of China (English)

    Wang Lei; Gao Jun; Wang Xiaojia; Johannes Eckstein; Peter Ott

    2007-01-01

    Rotationally symmetric triangulation (RST) sensor has more flexibility and less uncertainty limits becauseof the abaxial rotationally symmetric optical system.But if the incident laser is eccentric,the symmetry of the imagewill descend,and it will result in the eccentric error especially when some part of the imaged ring is blocked.Themodel of rotationally symmetric triangulation that meets the Schimpflug condition is presented in this paper.The errorfrom eccentric incident 1aser is analysed.It iS pointed out that the eccentric error is composed of two parts.one is acosine in circumference and proportional to the eccentric departure factor,and the other is a much smaller quadricfactor of the departure.When the ring is complete,the first error factor is zero because it is integrated in whole ring,but if some part of the ring iS blocked,the first factor will be the main error.Simulation verifies the result of the a-nalysis.At last,a compensation method to the error when some part of the ring is lost is presented based on neuralnetwork.The results of experiment show that the compensation will make the absolute maximum error descend tohalf,and the standard deviation of error descends to 1/3.

  2. Temporary Capture of Asteroids by an Eccentric Planet

    Science.gov (United States)

    Higuchi, A.; Ida, S.

    2017-04-01

    We have investigated the probability of temporary capture of asteroids in eccentric orbits by a planet in a circular or eccentric orbit through analytical and numerical calculations. We found that, in the limit of the circular orbit, the capture probability is ∼0.1% of encounters to the planet’s Hill sphere, independent of planetary mass and semimajor axis. In general, temporary capture becomes more difficult as the planet’s eccentricity ({e}{{p}}) increases. We found that the capture probability is almost independent of {e}{{p}} until a critical value ({e}{{p}}{{c}}) that is given by ≃5 times the Hill radius scaled by the planet’s semimajor axis. For {e}{{p}}> {e}{{p}}{{c}}, the probability decreases approximately in proportion to {e}{{p}}-1. The current orbital eccentricity of Mars is several times larger than {e}{{p}}{{c}}. However, since the range of secular change in Martian eccentricity overlaps {e}{{p}}{{c}}, the capture of minor bodies by Mars in the past is not ruled out.

  3. Effects of age and eccentricity on visual target detection

    Directory of Open Access Journals (Sweden)

    Nicole eGruber

    2014-01-01

    Full Text Available The aim of this study was to examine the effects of aging and target eccentricity on a visual search task comprising 30 images of everyday life projected into a hemisphere, realizing a ± 90° visual field. The task performed binocularly allowed participants to freely move their eyes to scan images for an appearing target or distractor stimulus (presented at 10°; 30°, and 50° eccentricity. The distractor stimulus required no response, while the target stimulus required acknowledgment by pressing the response button. 117 healthy subjects (mean age=49.63 years, SD=17.40 years, age range 20-78 years were studied. The results show that target detection performance decreases with age as well as with increasing eccentricity, especially for older subjects. Reaction time also increases with age and eccentricity, but in contrast to target detection, there is no interaction between age and eccentricity. Eye movement analysis showed that younger subjects exhibited a passive search strategy while older subjects exhibited an active search strategy probably as a compensation for their reduced peripheral detection performance.

  4. Repeatability of peripheral aberrations in young emmetropes.

    Science.gov (United States)

    Baskaran, Karthikeyan; Theagarayan, Baskar; Carius, Staffan; Gustafsson, Jörgen

    2010-10-01

    The purpose of this study is to assess the intrasession repeatability of ocular aberration measurements in the peripheral visual field with a commercially available Shack-Hartmann aberrometer (complete ophthalmic analysis system-high definition-vision research). The higher-order off-axis aberrations data in young healthy emmetropic eyes are also reported. The aberrations of the right eye of 18 emmetropes were measured using an aberrometer with an open field of view that allows peripheral measurements. Five repeated measures of ocular aberrations were obtained and assessed in steps of 10° out to ±40° in the horizontal visual field (nasal + and temporal -) and -20° in the inferior visual field. The coefficient of repeatability, coefficient of variation, and the intraclass correlation coefficient were calculated as a measure of intrasession repeatability. In all eccentric angles, the repeatability of the third- and fourth-order aberrations was better than the fifth and sixth order aberrations. The coefficient of variation was coefficient was >0.90 for the third and fourth order but reduced gradually for higher orders. There was no statistical significant difference in variance of total higher-order root mean square between on- and off-axis measurements (p > 0.05). The aberration data in this group of young emmetropes showed that the horizontal coma (C(3)(1)) was most positive at 40° in the temporal field, decreasing linearly toward negative values with increasing off-axis angle into the nasal field, whereas all other higher-order aberrations showed little or no change. The complete ophthalmic analysis system-high definition-vision research provides fast, repeatable, and valid peripheral aberration measurements and can be used efficiently to measure off-axis aberrations in the peripheral visual field.

  5. Iterative Contracts as Proactive Law Instruments

    DEFF Research Database (Denmark)

    Henschel, René Franz

    2012-01-01

    and incremental software development. In contrast to traditional IT project methodologies, where the product development takes place in a sequential design process, the iterative process is characterized by the so_ ware being developed through a series of repeated cycles in smaller portions at a time....... This software development process has driven the need for a new contract design that supports the product life cycle better than the traditional contracts. As will be shown in the analysis, the iterative contracts represent important legal innovation and can be categorized as a proactive law instrument that has...

  6. Investigating Dynamics of Eccentricity in Turbomachines

    Science.gov (United States)

    Baun, Daniel

    2010-01-01

    A methodology (and hardware and software to implement the methodology) has been developed as a means of investigating coupling between certain rotordynamic and hydrodynamic phenomena in turbomachines. Originally, the methodology was intended for application in an investigation of coupled rotordynamic and hydrodynamic effects postulated to have caused high synchronous vibration in the space shuttle s high-pressure oxygen turbopump (HPOTP). The methodology can also be applied in investigating (for the purpose of developing means of suppressing) undesired hydrodynamic rotor/stator interactions in turbomachines in general. The methodology and the types of phenomena that can be investigated by use of the methodology are best summarized by citing the original application as an example. In that application, in consideration of the high synchronous vibration in the space-shuttle main engine (SSME) HPOTP, it was determined to be necessary to perform tests to investigate the influence of inducer eccentricity and/or synchronous whirl motion on inducer hydrodynamic forces under prescribed flow and cavitation conditions. It was believed that manufacturing tolerances of the turbopump resulted in some induced runout of the pump rotor. Such runout, if oriented with an inducer blade, would cause that blade to run with tip clearance smaller than the tip clearances of the other inducer blades. It was hypothesized that the resulting hydraulic asymmetry, coupled with alternating blade cavitation, could give rise to the observed high synchronous vibration. In tests performed to investigate this hypothesis, prescribed rotor whirl motions have been imposed on a 1/3-scale water-rig version of the SSME LPOTP inducer (which is also a 4-biased inducer having similar cavitation dynamics as the HPOTP) in a magnetic-bearing test facility. The particular magnetic-bearing test facility, through active vibration control, affords a capability to impose, on the rotor, whirl orbits having shapes and

  7. CONTRACT CONSTRUCTION ACTIVITY

    Directory of Open Access Journals (Sweden)

    ANTOANETA CLAUDIA BUTUZA

    2010-01-01

    Full Text Available This paper presents the main types of contractual arrangements used worldwide in construction: traditional contracts, cost reimbursable type contracts, management contracts and other contractual arrangements such as partnership, offering two-phase, contracts in series and turnkey contracts. Also, based on a comparison of the main types of contractual arrangements a number of recommendations are suggested for choosing the appropriate type of contract construction project to be realized.

  8. Connective tissue regeneration in skeletal muscle after eccentric contraction-induced injury

    DEFF Research Database (Denmark)

    Mackey, Abigail Louise; Kjaer, Michael

    2016-01-01

    the adaptation throughout this process of both the connective tissue structures surrounding the myofibres, and the fibroblasts, the cells responsible for synthesising this connective tissue. However, the few studies investigating muscle connective tissue remodelling demonstrate a strong response that appears...... when the muscle connective tissue responses are compared, although further work is required to confirm this. Pharmacological agents (growth hormone and angiotensin II type I receptor blockers) are considered in the context of accelerating the muscle connective tissue adaptation to loading. Cautioning...

  9. Premature Ventricular Contractions (PVCs)

    Science.gov (United States)

    Diseases and Conditions Premature ventricular contractions (PVCs) By Mayo Clinic Staff Premature ventricular contractions (PVCs) are extra, abnormal heartbeats that begin in one of your heart's two ...

  10. Xanthine oxidase in human skeletal muscle following eccentric exercise

    DEFF Research Database (Denmark)

    Hellsten, Ylva; Frandsen, Ulrik; Orthenblad, N.

    1997-01-01

    1. The present study tested the hypothesis that the level of xanthine oxidase is elevated in injured human skeletal muscle in association with inflammatory events. Seven male subjects performed five bouts of strenuous one-legged eccentric exercise. Muscle biopsies from both the exercised and the ......1. The present study tested the hypothesis that the level of xanthine oxidase is elevated in injured human skeletal muscle in association with inflammatory events. Seven male subjects performed five bouts of strenuous one-legged eccentric exercise. Muscle biopsies from both the exercised...... the increase in xanthine oxidase in the muscle there were no detectable changes in the levels of muscle malondialdehyde or in plasma antioxidant capacity up to 4 days post-exercise. 5. It is concluded that eccentric exercise leads to an increased level of xanthine oxidase in human muscle and that the increase...

  11. Hot Jupiters from Coplanar High-eccentricity Migration

    Science.gov (United States)

    Petrovich, Cristobal

    2015-05-01

    We study the possibility that hot Jupiters (HJs) are formed through the secular gravitational interactions between two planets in eccentric orbits with relatively low mutual inclinations (≲ 20{}^\\circ ) and friction due to tides raised on the planet by the host star. We term this migration mechanism Coplanar High-eccentricity Migration (CHEM) because, like disk migration, it allows for migration to occur on the same plane in which the planets formed. CHEM can operate from the following typical initial configurations: (i) the inner planet in a circular orbit and the outer planet with an eccentricity ≳ 0.67 for {{m}in}/{{m}out}{{({{a}in}/{{a}out})}1/2}≲ 0.3; (ii) two eccentric (≳ 0.5) orbits for {{m}in}/{{m}out}{{({{a}in}/{{a}out})}1/2}≲ 0.16. A population synthesis study of hierarchical systems of two giant planets using the observed eccentricity distribution of giant planets shows that CHEM produces HJs with low stellar obliquities (≲ 30{}^\\circ ), with a semi-major axis distribution that matches the observations, and at a rate that can account for their observed occurrence. A different mechanism is needed to create large obliquity HJs, either a different migration channel or a mechanism that tilts the star or the protoplanetary disk. CHEM predicts that HJs should have distant (a≳ 5 AU) and massive (most likely ˜1-3 times more massive than the HJ) companions with relatively low mutual inclinations (≲ 20{}^\\circ ) and moderately high eccentricities (e˜ 0.2-0.5).

  12. On the Eccentricity Excitation in Post-main-sequence Binaries

    Science.gov (United States)

    Rafikov, Roman R.

    2016-10-01

    Several classes of stellar binaries with post-main-sequence (post-MS) components—millisecond pulsars with the white dwarf companions (MSP+WD) and periods of {P}b∼ 30 days, binaries hosting post-asymptotic giant branch stars, or barium stars with {P}b ∼ several years—feature high eccentricities (up to 0.4) despite the expectation of their efficient tidal circularization during their post-MS evolution. It was suggested that the eccentricities of these binaries can be naturally excited by their tidal coupling to the circumbinary disk, formed by the material ejected from the binary. Here we critically reassess this idea using simple arguments rooted in the global angular momentum conservation of the disk+binary system. Compared to previous studies, we (1) fully account for the viscous spreading of the circumbinary disk, (2) consider the possibility of reaccretion from the disk onto the binary (in agreement with simulations and empirical evidence), and (3) allow for the reduced viscosity after the disk expands, cools, and forms dust. These ingredients conspire to significantly lower the efficiency of eccentricity excitation by the disk tides. We find that explaining eccentricities of the post-MS binaries is difficult and requires massive (≳ {10}-2 {M}ȯ ), long-lived (≳ {10}5 years) circumbinary disks that do not reaccrete. While disk tides may account for the eccentricities of the MSP+WD binaries, we show reaccretion to also be detrimental for these systems. Reduced efficiency of the disk-driven excitation motivates the study of alternative mechanisms for producing the peculiar eccentricities of the post-MS binaries.

  13. Effects from Periastron Advance of Eccentric Binary Stars

    Institute of Scientific and Technical Information of China (English)

    李瑾; 仲元红; 潘宇

    2012-01-01

    In this paper,we discuss the coefficients of Gravitational waveform due to eccentric binaries periastron advance with evolved eccentricity.For the basic harmonic modes(n ≤ 5),the frequency split and corresponding relative strengths in the spectrum are figured out.Taking the well known binary systems PSRB 1913+16 and PSRB 1534+12 as examples,we study the dominant harmonic and its frequency split caused by periastron advance in the spectra,and give an estimation of detectability for PSRB 1913+16 and PSRB 1534+12,which are the promising targets for space observatories of gravitational wave.

  14. Transmission line resonance technique for eccentric core optical fibers

    Science.gov (United States)

    Georgantzos, E.; Boucouvalas, A. C.

    2016-12-01

    In several cases optical fibers in telecommunications have cores of non circular geometry. Fibre optic deformations appear in optical fibres for many reasons. Optical fibre core ellipticity for example where the fibre optic core is not perfectly circular due to fibre optic manufacturing tolerances, is measured and often is a problem. Optical fibre core eccentricity, where the fibre core is not on the axis of the fibre, but it is offset by a small length. This is another issue and very important for ensuring performance low loss splices and connector losses. Both of ellipticity and eccentricity are specified in accordance to international standards for fibre optic manufacturing telecommunications grade fibres. The present paper studies ellipticity and core eccentricity specifically and presents a new method for analysing their effect. We present an extension of the transmission line technique as a means of studying such fibers and deriving necessary parameters. Conformal mapping on the other hand is a simple mathematical tool by which we can generate sets of orthogonal two-dimensional coordinate systems. Shortly a conformal map of Cartesian two-dimensional space is defined by any analytical function W(z) where z, w, are: z = x + jy, W = θ + j φ The function deriving by the conformal mapping transformation h(θ ,φ )=| ∂w/∂z | = 1/|∂z/∂w|, can be used in order to define ∇A → and ∇×A → where A → is the magnetic or electric field in the derived orthogonal coordinate system. Useful conformal maps for fiber optics applications should have the property that the equation θ(x, y) = constant, is forming closed curves in a Cartesian two-dimensional space (x,y). If θ(x, y) = constant represents a set of co-eccentric circles, we obtain the normal case of conventional fibers with circular cores. If θ(x, y) = constant represents a set of eclipses, we are have the formation of elliptic core optical fibers. If θ(x, y) = constant represents a set of

  15. A complete waveform model for compact binaries on eccentric orbits

    Science.gov (United States)

    Huerta, Eliu; Agarwal, Bhanu; George, Daniel; Kumar, Prayush

    2016-03-01

    The detection of compact binaries with significant eccentricity in the sensitivity band of gravitational wave detectors will provide critical insights on the dynamics and formation channels of these events. In order to search for these systems and place constraints on their rates, we present an inspiral-merger-ringdown time domain waveform model that describes the GW emission from compact binaries on orbits with low to moderate values of eccentricity. We use this model to explore the detectability of these events in the context of advanced LIGO.

  16. Adding Fish Oil to Whey Protein, Leucine and Carbohydrate Over a 6 Week Supplementation Period Attenuates Muscle Soreness Following Eccentric Exercise in Competitive Soccer Players.

    Science.gov (United States)

    Philpott, Jordan D; Donnelly, Chris; Walshe, Ian H; Dick, James; Galloway, Stuart D R; Tipton, Kevin D; Witard, Oliver C

    2017-09-05

    Soccer players often experience eccentric exercise-induced muscle damage given the physical demands of soccer match-play. Since long chain n-3 polyunsaturated fatty acids (n-3PUFA) enhance muscle sensitivity to protein supplementation, dietary supplementation with a combination of fish oil-derived n-3PUFA, protein and carbohydrate may promote exercise recovery. This study examined the influence of adding n-3PUFA to a whey protein, leucine and carbohydrate containing beverage over a 6 week supplementation period on physiological markers of recovery measured over 3 days following eccentric exercise. Competitive soccer players were assigned to one of three conditions (2 × 200mL): FO (n=10) contained n-3PUFA (1100mg DHA/EPA - approx. 550mg DHA, 550mg EPA), whey protein (15g), leucine (1.8g) and carbohydrate (20g); PRO (n=10) contained whey protein (15g), leucine (1.8g) and carbohydrate (20g) and CHO (n=10) contained carbohydrate (24g). Eccentric exercise consisted of unilateral knee extension/flexion contractions on both legs separately. Maximal force production was impaired by 22% during the 72 hour recovery period following eccentric exercise (peccentric exercise in competitive soccer players.

  17. Hypomethylation is restricted to the D4Z4 repeat array in phenotypic FSHD.

    NARCIS (Netherlands)

    Greef, J.C. de; Wohlgemuth, M.; Chan, O.A.; Hansson, K.B.; Smeets, D.F.C.M.; Frants, R.R.; Weemaes, C.M.R.; Padberg, G.W.A.M.; Maarel, S.M. van der

    2007-01-01

    BACKGROUND: Patients with facioscapulohumeral muscular dystrophy (FSHD) show a contraction of the D4Z4 repeat array in the subtelomere of chromosome 4q. This D4Z4 contraction is associated with significant allele-specific hypomethylation of the repeat. Hypomethylation of D4Z4 is also observed in pat

  18. Progressive Resistance Exercise with Eccentric Loading for the Management of Knee Osteoarthritis

    National Research Council Canada - National Science Library

    Hernandez, Haniel J; McIntosh, Valerie; Leland, Azadeh; Harris-Love, Michael O

    2015-01-01

    .... The use of an eccentric training paradigm may prove to be beneficial for older adults with knee OA since eccentric muscle actions are involved in the energy absorption at the knee joint during gait...

  19. THE ROLE AND IMPLEMENTATION OF ECCENTRIC TRAINING IN ATHLETIC REHABILITATION: TENDINOPATHY, HAMSTRING STRAINS, AND ACL RECONSTRUCTION

    Science.gov (United States)

    Reiman, Michael

    2011-01-01

    The benefits and proposed physiological mechanisms of eccentric exercise have previously been elucidated and eccentric exercise has been used for well over seventy years. Traditionally, eccentric exercise has been used as a regular component of strength training. However, in recent years, eccentric exercise has been used in rehabilitation to manage a host of conditions. Of note, there is evidence in the literature supporting eccentric exercise for the rehabilitation of tendinopathies, muscle strains, and in anterior cruciate ligament (ACL) rehabilitation. The purpose of this Clinical Commentary is to discuss the physiologic mechanism of eccentric exercise as well as to review the literature regarding the utilization of eccentric training during rehabilitation. A secondary purpose of this commentary is to provide the reader with a framework for the implementation of eccentric training during rehabilitation of tendinopathies, muscle strains, and after ACL reconstruction. PMID:21655455

  20. Faculty Growth Contracts.

    Science.gov (United States)

    Seldin, Peter

    Growth contracts, described as faculty plans for personal and professional growth proposed by each member of the faculty, are examined. The rationale for growth contracts is explained and a list of some institutions using growth contracts or variations of the concept is provided. Growth contract advantages, the role of the evaluation committee or…

  1. Contracts in distributed systems

    CERN Document Server

    Bartoletti, Massimo; Zunino, Roberto; 10.4204/EPTCS.59.11

    2011-01-01

    We present a parametric calculus for contract-based computing in distributed systems. By abstracting from the actual contract language, our calculus generalises both the contracts-as-processes and contracts-as-formulae paradigms. The calculus features primitives for advertising contracts, for reaching agreements, and for querying the fulfilment of contracts. Coordination among principals happens via multi-party sessions, which are created once agreements are reached. We present two instances of our calculus, by modelling contracts as (i) processes in a variant of CCS, and (ii) as formulae in a logic. With the help of a few examples, we discuss the primitives of our calculus, as well as some possible variants.

  2. Orbital Eccentricity and the Stability of Planets in the Alpha Centauri System

    Science.gov (United States)

    Lissauer, Jack

    2016-01-01

    Planets on initially circular orbits are typically more dynamically stable than planets initially having nonzero eccentricities. However, the presence of a major perturber that forces periodic oscillations of planetary eccentricity can alter this situation. We investigate the dependance of system lifetime on initial eccentricity for planets orbiting one star within the alpha Centauri system. Our results show that initial conditions chosen to minimize free eccentricity can substantially increase stability compared to planets on circular orbits.

  3. A PLL Synthesizer with Learning Repeatable Fluctuation of Input Signal

    Science.gov (United States)

    Ono, Hiroyuki

    This paper describes a high frequency PLL (Phase Locked Loop) synthesizer with a function of learning then eliminating repeatable fluctuation of timing intervals on series input pulses. Typical spindle encoder generates digital pulses according to the revolution speed. The intervals of each pulse have repeatable fluctuation every revolution by eccentricity or warpage of the encoder scale disk. This method provides a programmable counter for the loop counter of PLL circuit and an interval counter with memory in order to learn the repeatable fluctuation. After the learning process, the PLL generates very pure tone clock signal based on the real flutter components of the spindle revolution speed without influenced by encoder errors. This method has been applied to a hard disk test system in order to generate 3GHz read/write clock.

  4. Contraction stress test by intermittent nipple stimulation.

    Science.gov (United States)

    Huddleston, J F; Sutliff, G; Robinson, D

    1984-05-01

    Although the nonstress test has generally supplanted the contraction stress test as the primary test for assessment of fetal well-being, the contraction stress test continues to be useful. Objectionable factors of the contraction stress test have included the time required to complete the test and the frequent necessity for intravenous oxytocin. The authors developed a contraction stress test protocol using contractions produced by intermittent nipple stimulation and used the method for 345 tests on 193 high-risk pregnancies during a 15-month period. The women were instructed to stimulate one breast, through their clothes, for two minutes and then to rest for five minutes. This cycle was repeated as necessary, but was interrupted whenever contractions began. Using this protocol, the authors were successful in achieving an adequate contraction frequency with every attempt, and hyperstimulation was not more frequent than previously reported with the standard contraction stress test. The average time requirement was 45 minutes. No unexplained stillbirths occurred after a negative test.

  5. The effect of eccentricity and spatiotemporal energy on motion silencing.

    Science.gov (United States)

    Choi, Lark Kwon; Bovik, Alan C; Cormack, Lawrence K

    2016-01-01

    The now well-known motion-silencing illusion has shown that salient changes among a group of objects' luminances, colors, shapes, or sizes may appear to cease when objects move rapidly (Suchow & Alvarez, 2011). It has been proposed that silencing derives from dot spacing that causes crowding, coherent changes in object color or size, and flicker frequencies combined with dot spacing (Choi, Bovik, & Cormack, 2014; Peirce, 2013; Turi & Burr, 2013). Motion silencing is a peripheral effect that does not occur near the point of fixation. To better understand the effect of eccentricity on motion silencing, we measured the amount of motion silencing as a function of eccentricity in human observers using traditional psychophysics. Fifteen observers reported whether dots in any of four concentric rings changed in luminance over a series of rotational velocities. The results in the human experiments showed that the threshold velocity for motion silencing almost linearly decreases as a function of log eccentricity. Further, we modeled the response of a population of simulated V1 neurons to our stimuli. We found strong matches between the threshold velocities on motion silencing observed in the human experiment and those seen in the energy model of Adelson and Bergen (1985). We suggest the plausible explanation that as eccentricity increases, the combined motion-flicker signal falls outside the narrow spatiotemporal frequency response regions of the modeled receptive fields, thereby reducing flicker visibility.

  6. Eccentric or Concentric Exercises for the Treatment of Tendinopathies?

    DEFF Research Database (Denmark)

    Couppé, Christian; Svensson, René B; Silbernagel, Karin Grävare

    2015-01-01

    with respect to parameters like load magnitude, speed of movement, and recovery period between exercise sessions. Future studies should control for these loading parameters, evaluate various exercise dosages, and also think beyond isolated eccentric exercises to arrive at firm recommendations regarding...

  7. Gluon field fluctuations in nuclear collisions: Multiplicity and eccentricity distributions

    CERN Document Server

    Schenke, Björn; Venugopalan, Raju

    2013-01-01

    We discuss different sources of fluctuations in nuclear collisions and their realization in the IP-Glasma model. We present results for multiplicity distributions in p+p and p+A collisions and compare eccentricity distributions in A+A collisions to the flow harmonic distributions in 10 centrality classes measured by the ATLAS collaboration.

  8. Reliability of power output during eccentric sprint cycling.

    Science.gov (United States)

    Brughelli, Matt; Van Leemputte, Marc

    2013-01-01

    The purpose of this study was to determine the reliability of power outputs during maximal intensity eccentric cycling over short durations (i.e., eccentric sprint cycling) on a "motor-driven" isokinetic ergometer. Fourteen physically active male subjects performed isokinetic eccentric cycling sprints at 40, 60, 80, 100, and 120 revolutions per minute (rpm) on 4 separate occasions (T1-T4). Each sprint lasted for 6 seconds, and absolute measures of mean power (MP) and peak power (PP) per revolution were recorded. Significant increases in MP and PP were observed between T1 and subsequent trials, but no significant differences were identified between T2, T3, and T4. The coefficient of variation (CV) and intraclass correlation coefficient (ICC) were calculated to reflect within-subject and between-session reliability of MP and PP at each cadence. The CV improved to below 10% for cadences of 60, 80, 100, and 120 rpm between T3 and T4, and the majority of ICC values improved to above 0.90. The remaining ICC values remained in the moderate range between T3 and T4 (i.e., 0.82-0.89). Coefficient of variation and ICC values for the 40 rpm cadence remained at unacceptable levels throughout the 4 trials and thus should be avoided in future investigations. The results of this study indicate that reliable power outputs may be obtained after 2 familiarization sessions during eccentric sprint cycling at cadences ranging from 60 to 120 rpm.

  9. Systemic cytokine response to three bouts of eccentric exercise

    Directory of Open Access Journals (Sweden)

    Stephen M. Cornish

    2014-01-01

    Full Text Available This research examined the changes in inflammatory cytokines interleukin 6 (IL-6, IL-1β, IL-10, as well as muscle force, muscle soreness, thigh circumference, and range of motion in response to 3 bouts of eccentric knee extension. Ten males were recruited to participate. The participants performed eccentric exercise on 3 consecutive days on the knee extensors on the right leg separated by 24 h. Participants performed 6 sets of 10 repetitions of isokinetic eccentric knee extension at 120° per second. Blood was sampled before and after each exercise bout and 24 h after the final exercise bout. Muscle isometric force, delayed onset muscle soreness (DOMS, thigh circumference, and range of motion were evaluated before and after each exercise bout and 24 h after the final exercise bout. There were no statistically significant differences noted for the changes in isometric strength, thigh circumference, and range of motion, or IL-6 over the 4 days (all p > 0.05. On the second day and third day there was a significant increase noted in DOMS as compared with baseline (p < 0.05. These results suggest that 3 consecutive days of eccentric exercise results in DOMS but does not produce a sustained systemic inflammatory reaction or changes in muscle function.

  10. Systemic cytokine response to three bouts of eccentric exercise

    Science.gov (United States)

    Cornish, Stephen M.; Johnson, Steven T.

    2014-01-01

    This research examined the changes in inflammatory cytokines interleukin 6 (IL-6), IL-1ß, IL-10, as well as muscle force, muscle soreness, thigh circumference, and range of motion in response to 3 bouts of eccentric knee extension. Ten males were recruited to participate. The participants performed eccentric exercise on 3 consecutive days on the knee extensors on the right leg separated by 24??h. Participants performed 6 sets of 10 repetitions of isokinetic eccentric knee extension at 120° per second. Blood was sampled before and after each exercise bout and 24?h after the final exercise bout. Muscle isometric force, delayed onset muscle soreness (DOMS), thigh circumference, and range of motion were evaluated before and after each exercise bout and 24?h after the final exercise bout. There were no statistically significant differences noted for the changes in isometric strength, thigh circumference, and range of motion, or IL-6 over the 4 days (all p > 0.05). On the second day and third day there was a significant increase noted in DOMS as compared with baseline (p eccentric exercise results in DOMS but does not produce a sustained systemic inflammatory reaction or changes in muscle function. PMID:24809007

  11. A massive millisecond pulsar in an eccentric binary

    Science.gov (United States)

    Barr, E. D.; Freire, P. C. C.; Kramer, M.; Champion, D. J.; Berezina, M.; Bassa, C. G.; Lyne, A. G.; Stappers, B. W.

    2017-02-01

    The recent discovery of a population of eccentric (e ˜ 0.1) millisecond pulsar (MSP) binaries with low-mass white dwarf companions in the Galactic field represents a challenge to evolutionary models that explain MSP formation as recycling: All such models predict that the orbits become highly circularized during a long period of accretion. The members of this new population exhibit remarkably similar properties (orbital periods, eccentricities, companion masses, spin periods), and several models have been put forward that suggest a common formation channel. In this work, we present the results of an extensive timing campaign focusing on one member of this new population, PSR J1946+3417. Through the measurement of both the advance of periastron and the Shapiro delay for this system, we determine the mass of the pulsar, mass of the companion and the inclination of the orbit to be 1.828(22) M⊙, 0.2656(19) M⊙ and 76.4 ± 0.6 degrees, respectively, under the assumption that general relativity is the true description of gravity. Notably, this is the third highest mass measured for any pulsar. Using these masses and the astrometric properties of PSR J1946+3417, we examine three proposed formation channels for eccentric MSP binaries. While our results are consistent with circumbinary disc-driven eccentricity growth or neutron star to strange star phase transition, we rule out rotationally delayed accretion-induced collapse as the mechanism responsible for the configuration of the PSR J1946+3417 system.

  12. Effect of eccentric versus concentric exercise training on mitochondrial function.

    Science.gov (United States)

    Isner-Horobeti, Marie-Eve; Rasseneur, Laurence; Lonsdorfer-Wolf, Evelyne; Dufour, Stéphane Pascal; Doutreleau, Stéphane; Bouitbir, Jamal; Zoll, Joffrey; Kapchinsky, Sophia; Geny, Bernard; Daussin, Frédéric Nicolas; Burelle, Yan; Richard, Ruddy

    2014-11-01

    The effect of eccentric (ECC) versus concentric (CON) training on metabolic properties in skeletal muscle is understood poorly. We determined the responses in oxidative capacity and mitochondrial H2 O2 production after eccentric (ECC) versus concentric (CON) training performed at similar mechanical power. Forty-eight rats performed 5- or 20-day eccentric (ECC) or concentric (CON) training programs. Mitochondrial respiration, H2 O2 production, citrate synthase activity (CS), and skeletal muscle damage were assessed in gastrocnemius (GAS), soleus (SOL) and vastus intermedius (VI) muscles. Maximal mitochondrial respiration improved only after 20 days of concentric (CON) training in GAS and SOL. H2 O2 production increased specifically after 20 days of eccentric ECC training in VI. Skeletal muscle damage occurred transiently in VI after 5 days of ECC training. Twenty days of ECC versus CON training performed at similar mechanical power output do not increase skeletal muscle oxidative capacities, but it elevates mitochondrial H2 O2 production in VI, presumably linked to transient muscle damage. © 2014 Wiley Periodicals, Inc.

  13. Eccentric binaries of compact objects in strong-field gravity

    Energy Technology Data Exchange (ETDEWEB)

    Gold, Roman

    2011-09-27

    In this thesis we study the dynamics as well as the resulting gravitational radiation from eccentric binaries of compact objects in the non-linear regime of General Relativity. For this purpose we solve Einstein's field equation numerically in a 3+1 decomposition using the moving-puncture technique. We focus our study on very particular orbits, arising as a purely relativistic phenomenon of the two-body problem in General Relativity, which are associated with unstable circular orbits. They are governed by a fast, nearly circular revolution at a short distance followed by a slow, radial motion on a nearly elliptic trajectory. Due to the unique features of their orbital trajectories they are called zoom-whirl orbits. We analyze how the peculiar dynamics manifests itself in the emitted gravitational radiation and to which extent one can infer the orbital properties from observations of the gravitational waves. In the first part, we consider black hole binaries. We perform a comprehensive parameter study by varying the initial eccentricity, computing and characterizing the resulting gravitational waveforms. We address aspects, which can only be obtained from non-perturbative methods, and which are crucial to the astrophysical relevance of these orbits. In particular, our results imply a fairly low amount of fine-tuning necessary to spot zoom-whirl effects. We find whirl orbits for values of the eccentricities, which fall in disjunct intervals extending to rather low values. Furthermore, we show that whirl effects just before merger cause a signal with significant amplitude. In the second part, we investigate neutron star binaries on eccentric orbits in full General Relativity, which has not been studied so far. We explore their phenomenology and study the consequences for the matter after the neutron stars have merged. In these evolutions the merged neutron stars sooner or later collapse to form a black hole. During the collapse most of the matter is accreted on

  14. Common epigenetic changes of D4Z4 in contraction-dependent and contraction-independent FSHD.

    NARCIS (Netherlands)

    Greef, J.C. de; Lemmers, R.J.; Engelen, B.G.M. van; Sacconi, S.; Venance, S.L.; Frants, R.R.; Tawil, R.; Maarel, S.M. van der

    2009-01-01

    Facioscapulohumeral muscular dystrophy (FSHD), caused by partial deletion of the D4Z4 macrosatellite repeat on chromosome 4q, has a complex genetic and epigenetic etiology. To develop FSHD, D4Z4 contraction needs to occur on a specific genetic background. Only contractions associated with the 4qA161

  15. Effect of muscle contraction levels on the force-length relationship of the human Achilles tendon during lengthening of the triceps surae muscle-tendon unit.

    Science.gov (United States)

    Sugisaki, Norihide; Kawakami, Yasuo; Kanehisa, Hiroaki; Fukunaga, Tetsuo

    2011-07-28

    Findings from animal experiments are sometimes contradictory to the idea that the tendon structure is a simple elastic spring in series with muscle fibers, and suggest influence of muscle contraction on the tendon mechanical properties. The purpose of the present study was to investigate the influence of muscle contraction levels on the force-length relationship of the human Achilles tendon during lengthening of the triceps surae muscle-tendon unit. For seven subjects, ankle dorsiflexion was performed without (passive condition) and with contraction of plantar flexor muscles (eccentric conditions, at 3 contraction levels) on an isokinetic dynamometer. Deformation of the Achilles tendon during each trial was measured using ultrasonography. The Achilles tendon force corresponding to the tendon elongation of 10mm in the passive condition was significantly smaller than those in the eccentric conditions (p<0.05 or p<0.01). Within the eccentric conditions, the Achilles tendon force corresponding to the tendon elongation of 10mm was significantly greater in the maximal contraction level than those in submaximal eccentric conditions (p<0.05 or p<0.01). In addition, the tendon stiffness was greater in higher contraction levels (p<0.05 or p<0.01). Present results suggest that the human tendon structure is not a simple elastic spring in series with muscle fibers.

  16. Eccentric exercise in adults with cardiorespiratory disease: a systematic review.

    Science.gov (United States)

    Ellis, Rachel; Shields, Nora; Lim, Kwang; Dodd, Karen J

    2015-12-01

    To determine if eccentric exercise is effective, tolerable and safe for adults with chronic cardiorespiratory disease. We searched electronic databases from inception until January 2015 (Medline, CINAHL, Embase, SportDiscus, PEDro, Cochrane Central and AMED) supplemented by citation tracking and reference list scanning. Included articles had to report effects of eccentric exercise, alone or as a primary component of intervention, of any intensity and duration, on adults with chronic cardiorespiratory disease. Trials needed to be reported as full text in a peer-reviewed journal and include control data (randomised, quasi-randomised and single group cross-over design trials). Any outcomes or comparison interventions were accepted. Methodological rigor was assessed using the PEDro scale. Of 22 potentially relevant articles, 10 met inclusion criteria. They reported results from seven trials with a total of 112 participants across the diseases. PEDro scores were low (median 3). Eccentric exercise increased strength and mobility to comparable levels as concentric exercise, however, it did so with lower oxygen consumption (effect size as large as d = -3.07 (-4.12, -1.80)), and four-fold power output (effect size d = -3.60 (-5.03, -1.66)). There were no adverse events reported for eccentric exercise. Pain was avoided with familiarisation sessions and individual exercise prescription. Eccentric exercise is beneficial and at least comparable with traditional exercise in improving walking and strength for people with chronic cardiorespiratory disease. It was well tolerated and we identified no safety concerns for the use of this intervention for this population. © The Author(s) 2015.

  17. Acute hormonal responses following different velocities of eccentric exercise.

    Science.gov (United States)

    Libardi, Cleiton A; Nogueira, Felipe R D; Vechin, Felipe C; Conceição, Miguel S; Bonganha, Valéria; Chacon-Mikahil, Mara Patricia T

    2013-11-01

    The aim of this study was to compare the acute hormonal responses following two different eccentric exercise velocities. Seventeen healthy, untrained, young women were randomly placed into two groups to perform five sets of six maximal isokinetic eccentric actions at slow (30° s(-1) ) and fast (210° s(-1) ) velocities with 60-s rest between sets. Growth hormone, cortisol, free and total testosterone were assessed by blood samples collected at baseline, immediately postexercise, 5, 15 and 30 min following eccentric exercise. Changes in hormonal responses over time were compared between groups, using a mixed model followed by a Tukey's post hoc test. The main findings of the present study were that the slow group showed higher growth hormone values immediately (5·08 ± 2·85 ng ml(-1) , P = 0·011), 5 (5·54 ± 3·01 ng ml(-1) , P = 0·004) and 15 min (4·30 ± 2·87 ng ml(-1) , P = 0·021) posteccentric exercise compared with the fast group (1·39 ± 2·41 ng ml(-1) , 1·34 ± 1·97 ng ml(-1) and 1·24 ± 1·87 ng ml(-1) , respectively), and other hormonal responses were not different between groups (P>0·05). In conclusion, slow eccentric exercise velocity enhances more the growth hormone(GH) response than fast eccentric exercise velocity without cortisol and testosterone increases. © 2013 Scandinavian Society of Clinical Physiology and Nuclear Medicine. Published by John Wiley & Sons Ltd.

  18. Shedding Light on the Eccentricity Valley: Gap Heating and Eccentricity Excitation of Giant Planets in Protoplanetary Disks

    CERN Document Server

    Tsang, David; Cumming, Andrew

    2013-01-01

    We show that the first order (non co-orbital) corotation torques are significantly modified by entropy gradients in a non-barotropic protoplanetary disk. Such non-barotropic torques can dramatically alter the balance that, for barotropic cases, results in the net eccentricity damping for giant gap-clearing planets embedded in the disk. We demonstrate that stellar illumination can heat the gap enough for the planet's orbital eccentricity to instead be excited. We also discuss the "Eccentricity Valley" noted in the known exoplanet population, where low-metallicity stars have a deficit of eccentric planets between $\\sim 0.1$ and $\\sim 1$ AU compared to metal-rich systems (Dawson & Murray-Clay 2013). We show that this feature in the planet distribution may be due to the self-shadowing of the disk by a rim located at the dust sublimation radius $\\sim 0.1$ AU, which is known to exist for several T Tauri systems. In the shadowed region between $\\sim 0.1$ and $\\sim 1$ AU lack of gap insolation allows disk interac...

  19. Effect of an eccentrically biased hamstring strengthening home program on knee flexor strength and the length-tension relationship.

    Science.gov (United States)

    Orishimo, Karl F; McHugh, Malachy P

    2015-03-01

    The purposes of this study were to document relative activation intensities of the hamstrings and gluteus maximus during 4 eccentric hamstring strengthening exercises and to assess the effects of a short-term strengthening program comprised of these exercises on knee flexor strength and the length-tension relationship. Twelve healthy subjects participated in this study. Electromyographic (EMG) activities from the biceps femoris, semitendinosus, and gluteus maximus were recorded as subjects performed (a) standing hip extension with elastic resistance, (b) trunk flexion in single limb stance (diver), (c) standing split (glider), and (d) supine sliding bridge (slider). Baseline isometric knee flexor strength was measured at 90, 70, 50, and 30° of flexion at the knee with the subject seated and the hip flexed to 50° from horizontal. After completing the 4-week training program, strength tests were repeated. Repeated-measures analysis of variance were used to compare EMG activity between muscles and to assess angle-specific strength improvements. Hamstring activity exceeded gluteus maximus activity for resisted hip extension, glider, and slider exercises (p Knee flexor strength improved by 9.0% (p = 0.005) but was not angle specific (training by angle p = 0.874). The short-term home training program effectively targeted the hamstrings and resulted in strength gains that were similar at short and long muscle lengths. These data demonstrate that hamstring strength can be improved using eccentrically biased unilateral exercises without the use of weights or other equipments.

  20. Piroxicam fails to reduce myocellular enzyme leakage and delayed onset muscle soreness induced by isokinetic eccentric exercise

    Directory of Open Access Journals (Sweden)

    J-L. Croisier

    1996-01-01

    Full Text Available To test the hypothesis that delayed onset muscular soreness (DOMS following intense eccentric muscle contraction could be due to increased production of prostaglandin E2 (PGE2, ten healthy male subjects were studied. Using a double-blind randomized crossover design, each subject performed two isokinetic tests separated by a period of at least 6 weeks: once with placebo, and once with piroxicam (Feldene®. They were given one capsule containing either placebo or piroxicam (20 mg per day for 6 days with initial doses given starting 3 days prior to isokinetic testing. Exercise consisted of eight stages of five maximal contractions of the knee extensor and flexor muscle groups of both legs separated by 1 min rest phases, on a Kin Trex device at 60°/s angular velocity. The subjective presence and intensity of DOMS were evaluated using a visual analogue scale immediately after, and 24 and 48 h after each test. The mean plasma concentration of PGE2 measured at rest and after exercise was significantly lower in the group treated with piroxicam (p < 0.05. However, statistical analysis (two-way ANOVA test revealed that exercise did not cause any significant change of mean plasma PGE2 over time in either of the two groups. Eccentric work was followed by severe muscle pain in extensor and flexor muscle groups. Maximal soreness was noted 48 h postexercise. Serum creatine kinase activity and the serum concentration of myoglobin increased significantly, and reached peak values 48 h after exercise in both experimental conditions (p < 0.001. By paired t-test, it appeared that there were no significant differences in the serum levels of these two markers of muscle damage between the two groups at any time point. We conclude that: (1 oral administration of piroxicam fails to reduce muscle damage and DOMS caused by strenuous eccentric exercise; and (2 the hypothetical role of increased PGE2 production in eccentric exercise-induced muscle damage, DOMS, and reduced

  1. Piroxicam fails to reduce myocellular enzyme leakage and delayed onset muscle soreness induced by isokinetic eccentric exercise

    Science.gov (United States)

    Croisier, J-L.; Monfils, T.; Deby-Dupon, G.; Fafchamps, M.; Venneman, I.; Crielaard, J-M.; Juchmès-Ferir, A.; Lhermerout, C.; Lamy, M.; Deby, C.

    1996-01-01

    To test the hypothesis that delayed onset muscular soreness (DOMS) following intense eccentric muscle contraction could be due to increased production of prostaglandin E2 (PGE2), ten healthy male subjects were studied. Using a double-blind randomized crossover design, each subject performed two isokinetic tests separated by a period of at least 6 weeks: once with placebo, and once with piroxicam (Feldene®). They were given one capsule containing either placebo or piroxicam (20 mg) per day for 6 days with initial doses given starting 3 days prior to isokinetic testing. Exercise consisted of eight stages of five maximal contractions of the knee extensor and flexor muscle groups of both legs separated by 1 min rest phases, on a Kin Trex device at 60°/s angular velocity. The subjective presence and intensity of DOMS were evaluated using a visual analogue scale immediately after, and 24 and 48 h after each test. The mean plasma concentration of PGE2 measured at rest and after exercise was significantly lower in the group treated with piroxicam (p < 0.05). However, statistical analysis (two-way ANOVA test) revealed that exercise did not cause any significant change of mean plasma PGE2 over time in either of the two groups. Eccentric work was followed by severe muscle pain in extensor and flexor muscle groups. Maximal soreness was noted 48 h postexercise. Serum creatine kinase activity and the serum concentration of myoglobin increased significantly, and reached peak values 48 h after exercise in both experimental conditions (p < 0.001). By paired t-test, it appeared that there were no significant differences in the serum levels of these two markers of muscle damage between the two groups at any time point. We conclude that: (1) oral administration of piroxicam fails to reduce muscle damage and DOMS caused by strenuous eccentric exercise; and (2) the hypothetical role of increased PGE2 production in eccentric exercise-induced muscle damage, DOMS, and reduced isokinetic

  2. ADMINISTRATIVE CONTRACTS. DELIMITATIONS

    Directory of Open Access Journals (Sweden)

    Liana Teodora PASCARIU

    2016-12-01

    Full Text Available Article examines whether all contracts of public persons are administrative contracts; in other words, if the administration may conclude contracts that, according to their legal nature, are not administrative. If we start from the definition of administrative contracts as it appears in Law no. 554/2004, these include contracts by public authorities which concern the enhancement of public property execution of works of public interest, public services, public procurement and other administrative contracts provided by special laws and subject to the jurisdiction of the administrative courts.

  3. Towards a general method for estimating the unbalanced magnetic pull in mixed eccentricities motion including sufficiently large eccentricities in a hydropower generator and their validation against EM simulations

    Science.gov (United States)

    Calleecharan, Yogeshwarsing; Jauregui, Ricardo; Aidanpää, Jan-Olov

    2013-08-01

    Electromagnetic (EM) analysis of hydropower generators is common practice but rotor whirling is little studied. This paper suggests a novel semi-analytical method for estimating the steady state unbalanced magnetic pull (UMP) when the rotor centre is undergoing mixed eccentricities motion. The ability to estimate the UMP for mixed eccentricities motion in finite element method (FEM)-based modelling software packages is rare. The proposed methodology in its formulation takes advantage of the fact that a purely dynamic eccentricity motion including non-synchronous whirling and a purely static eccentricity motion can be more amenable to implement in existing FEM-based EM modelling software products for UMP estimation. After these initial separate UMP results are obtained, the proposed method can be applied for virtually any mixed eccentricities motion cases up to sufficiently large eccentricities for quick analysis instead of running the mixed eccentricities simulations directly in a FEM-based software package. Good agreement between the UMP from the actual EM mixed eccentricities motion simulations in a commercial FEM-based software package and the UMP estimations by the novel method is made for a wide range of eccentricities that may commonly occur in practice. A modified feature selective validation (FSV) method, the FSV-UPC, is applied to assess the similarities and the differences in the UMP computations.

  4. Impaired neuromuscular function during isometric, shortening, and lengthening contractions after exercise-induced damage to elbow flexor muscles.

    Science.gov (United States)

    Turner, Tanya S; Tucker, Kylie J; Rogasch, Nigel C; Semmler, John G

    2008-08-01

    The purpose of this study was to examine the effect of exercise-induced damage of the elbow flexor muscles on steady motor performance during isometric, shortening, and lengthening contractions. Ten healthy individuals (age 22+/-4 yr) performed four tasks with the elbow flexor muscles: a maximum voluntary contraction, a one repetition maximum (1 RM), an isometric task at three joint angles (short, intermediate, and long muscle lengths), and a constant-load task during slow (approximately 7 degrees/s) shortening and lengthening contractions. Task performance was quantified as the fluctuations in wrist acceleration (steadiness), and electromyography was obtained from the biceps and triceps brachii muscles at loads of 10, 20, and 40% of 1 RM. Tasks were performed before, immediately after, and 24 h after eccentric exercise that resulted in indicators of muscle damage. Maximum voluntary contraction force and 1-RM load declined by approximately 45% immediately after exercise and remained lower at 24 h ( approximately 30% decrease). Eccentric exercise resulted in reduced steadiness and increased biceps and triceps brachii electromyography for all tasks. For the isometric task, steadiness was impaired at the short compared with the long muscle length immediately after exercise (Pshortening compared with the lengthening contractions after exercise (P=0.01), and steadiness remained impaired for shortening contractions 24 h later (P=0.01). These findings suggest that there are profound effects for the performance of these types of fine motor tasks when recovering from a bout of eccentric exercise.

  5. Quantum repeated games revisited

    CERN Document Server

    Frackiewicz, Piotr

    2011-01-01

    We present a scheme for playing quantum repeated 2x2 games based on the Marinatto and Weber's approach to quantum games. As a potential application, we study twice repeated Prisoner's Dilemma game. We show that results not available in classical game can be obtained when the game is played in the quantum way. Before we present our idea, we comment on the previous scheme of playing quantum repeated games.

  6. Concentrically trained cyclists are not more susceptible to eccentric exercise-induced muscle damage than are stretch-shortening exercise-trained runners.

    Science.gov (United States)

    Snieckus, Audrius; Kamandulis, Sigitas; Venckūnas, Tomas; Brazaitis, Marius; Volungevičius, Gintautas; Skurvydas, Albertas

    2013-03-01

    Here, we test the hypothesis that continuous concentric exercise training renders skeletal muscles more susceptible to damage in response to eccentric exercise. Elite road cyclists (CYC; n = 10, training experience 8.1 ± 2.0 years, age 22.9 ± 3.7 years), long-distance runners (LDR; n = 10, 9.9 ± 2.3 years, 24.4 ± 2.5 years), and healthy untrained (UT) men (n = 10; 22.4 ± 1.7 years) performed 100 submaximal eccentric contractions at constant angular velocity of 60° s(-1). Concentric isokinetic peak torque, isometric maximal voluntary contraction (MVC), and electrically induced knee extension torque were measured at baseline and immediately and 48 h after an eccentric exercise bout. Muscle soreness was assessed and plasma creatine kinase (CK) activity was measured at baseline and 48 h after exercise. Voluntary and electrically stimulated knee extension torque reduction were significantly greater (p exercise, MVC decreased by 32 % and 20 % in UT, 20 % and 5 % in LDR, and 25 % and 6 % in CYC. Electrically induced 20 Hz torque decreased at the same times by 61 and 29 % in UT, 40 and 17 % in LDR, and 26 and 14 % in CYC. Muscle soreness and plasma CK activity 48 h after exercise did not differ significantly between athletes and UT subjects. In conclusion, even though elite endurance athletes are more resistant to eccentric exercise-induced muscle damage than are UT people, stretch-shortening exercise-trained LDR have no advantage over concentrically trained CYC.

  7. Origin and Implications of high eccentricities in massive black hole binaries at sub-pc scales

    CERN Document Server

    Roedig, Constanze

    2011-01-01

    We outline the eccentricity evolution of sub-parsec massive black hole binaries (MBHBs) forming in galaxy mergers. In both stellar and gaseous environments, MBHBs are expected to grow large orbital eccentricities before they enter the gravitational wave (GW) observational domain. We re--visit the predicted eccentricities detectable by space based laser interferometers (as the proposed ELISA/NGO) for both environments. Close to coalescence, many MBHBs will still maintain detectable eccentricities, spanning a broad range from <10^{-5} up to <~ 0.5. Stellar and gas driven dynamics lead to distinct distributions, with the latter favoring larger eccentricities. At larger binary separations, when emitted GWs will be observed by pulsar timing arrays (PTAs), the expected eccentricities are usually quite large, in the range 0.01-0.7, which poses an important issue for signal modelling and detection algorithms. In this window, large eccentricities also have implications on proposed electromagnetic counterparts to...

  8. ELECTROMAGNETIC VIBRATION DISTURBING FORCES AT THE ECCENTRICITY OF ROTOR OF TURBOGENERATOR

    Directory of Open Access Journals (Sweden)

    Yu.M. Vaskovskyi

    2016-09-01

    Full Text Available Electromagnetic vibration disturbing forces in different variants of the rotor displacement from an axis of the stator bore is carried out. Investigation for ТG type ТGV-200-2 by finite element method in COMSOL Multiphysics is carried out. The field mathematical model of static and dynamic eccentricity is described. The amplitude vibration disturbing forces are greatest, when a static eccentricity direction coincides with an axis of the stator winding phase is shown. The diagnostic features static and dynamic eccentricities are formulated. The most value of forces in the point with minimal air gap is shown. The diagnostic features static and dynamic eccentricities and the method of diagnostic eccentricity are formulated. Diagnostic feature of static eccentricity is to change the amplitude Maxwell stress tensor is established. The dynamic eccentricity diagnostic features are appearance in the spectrum of vibration disturbing forces rotating and multiple harmonics.

  9. Contractibility of curves

    Directory of Open Access Journals (Sweden)

    Janusz Charatonik

    1991-11-01

    Full Text Available Results concerning contractibility of curves (equivalently: of dendroids are collected and discussed in the paper. Interrelations tetween various conditions which are either sufficient or necessary for a curve to be contractible are studied.

  10. Fault in Contract Law

    National Research Council Canada - National Science Library

    Eric A. Posner

    2009-01-01

    A promisor is strictly liable for breaching a contract, according to the standard account However, a negligence-based system of contract law can be given an economic interpretation, and this Article...

  11. Repeatability of Ocular Measurements with a Dual-Scheimpflug Analyzer in Healthy Eyes

    Directory of Open Access Journals (Sweden)

    Carmen Lopez de la Fuente

    2014-01-01

    Full Text Available Purpose. To assess the repeatability of the Galilei dual Scheimpflug analyzer (GDSA in anterior segment examination. Methods. Fifty-two eyes from 52 healthy volunteers were prospectively and consecutively recruited. Anatomic, axial, refractive, and instantaneous parameters were measured with GDSA to provide a complete characterization of the anterior segment. Repeatability was assessed calculating intraclass correlation coefficient (ICC, and coefficient of variation (COV. Results. Correlation among repeated measurements showed almost perfect reliability (ICC > 0.81 for all parameters except thinnest central corneal thickness (CCT (0.78, corneal thickness average out (0.79, and posterior axial curvature average out (0.60. Repeatability was excellent (COV < 10% for all parameters except anterior chamber volume and, superior iridocorneal angle and eccentricities. In these last three parameters, repeatability limits were excessively high compared to the mean. Conclusions. GDSA in healthy young persons had an almost perfect correlation in measuring anatomic, axial, instantaneous, and refractive parameters with greater variability for peripheral terms. Repeatability of anatomical parameters like pachymetry, anterior chamber, or iridocorneal angle and eccentricity were limited. In healthy young persons, the other evaluated parameters had very good repeatability and their limits of agreement showed excellent clinical results for this device.

  12. Democratic contract law

    OpenAIRE

    Hesselink, M.W.

    2015-01-01

    This article discusses the normative relationship between contract law and democracy. In particular, it argues that in order to be legitimate contract law needs to have a democratic basis. Private law is not different in this respect from public law. Thus, the first claim made in this article will be that also for contract law a democratic basis is a necessary condition for legitimacy. A fully democratic basis may also be a sufficient condition for a legitimate and just contract law. However,...

  13. Teaching about Contracts.

    Science.gov (United States)

    Froman, Michael; Kosnoff, Kathy

    1978-01-01

    Presents teaching strategies for introducing high school students to contract law. Offers as a case study a contract agreement between pro football players and team owners. Stresses basic elements of contracts (offer, acceptance, consideration, and understanding the bargaining process). Journal available from the American Bar Association, 1155…

  14. Contract law as fairness

    NARCIS (Netherlands)

    J. Klijnsma

    2015-01-01

    This article examines the implications for contract law of Rawls' theory of justice as fairness. It argues that contract law as an institution is part of the basic structure of society and as such subject to the principles of justice. Discussing the basic structure in relation to contract law is par

  15. An Eccentric Binary Millisecond Pulsar in the Galactic Plane

    Science.gov (United States)

    Champion, David J.; Ransom, Scott M.; Lazarus, Patrick; Camilo, Fernando; Bassa, Cess; Kaspi, Victoria M.; Nice, David J.; Freire, Paulo C. C.; Stairs, Ingrid H.; vanLeeuwen, Joeri; Stappers, Ben W.; Cordes, James M.; Hessels, Jason W. T.; Lorimer, Duncan R.; Arzoumanian, Zaven; Backer, Don C.; Bhat, N. D. Ramesh; Chatterjee, Shami; Cognard, Ismael; Deneva, Julia S.; Faucher-Giguere, Claude-Andre; Gaensler, Bryan M.; Han, JinLin; Jenet, Fredrick A.; Kasian, Laura

    2008-01-01

    Binary pulsar systems are superb probes of stellar and binary evolution and the physics of extreme environments. In a survey with the Arecibo telescope, we have found PSR J1903+0327, a radio pulsar with a rotational period of 2.15 milliseconds in a highly eccentric (e = 0.44) 95-day orbit around a solar mass (M.) companion. Infrared observations identify a possible main-sequence companion star. Conventional binary stellar evolution models predict neither large orbital eccentricities nor main-sequence companions around millisecond pulsars. Alternative formation scenarios involve recycling a neutron star in a globular cluster, then ejecting it into the Galactic disk, or membership in a hierarchical triple system. A relativistic analysis of timing observations of the pulsar finds its mass to be 1.74 +/- 0.04 Solar Mass, an unusually high value.

  16. The Eccentric Binary Millisecond Pulsar in NGC 1851

    CERN Document Server

    Freire, Paulo C C; Gupta, Yashwant

    2007-01-01

    PSR J0514-4002A is a 5-ms pulsar is located in the globular cluster NGC 1851; it belongs to a highly eccentric (e = 0.888) binary system. It is one of the earliest known examples of a numerous and fast-growing class of eccentric binary MSPs recently discovered in globular clusters. Using the GBT, we have obtained a phase-coherent timing solution for the pulsar, which includes a measurement of the rate of advance of periastron: 0.01289(4) degrees per year, which if due completely to general relativity, implies a total system mass of 2.453(14) solar masses. We also derive m_p 0.96 solar masses. The companion is likely to be a massive white dwarf star.

  17. Tidal disruption flares from stars on eccentric orbits

    Directory of Open Access Journals (Sweden)

    Loeb A.

    2012-12-01

    Full Text Available We study tidal disruption and subsequent mass fallback for stars approaching supermassive black holes on bound orbits, by performing three dimensional Smoothed Particle Hydrodynamics simulations with a pseudo-Newtonian potential. We find that the mass fallback rate decays with the expected -5/3 power of time for parabolic orbits, albeit with a slight deviation due to the self-gravity of the stellar debris. For eccentric orbits, however, there is a critical value of the orbital eccentricity, significantly below which all of the stellar debris is bound to the supermassive black hole. All the mass therefore falls back to the supermassive black hole in a much shorter time than in the standard, parabolic case. The resultant mass fallback rate considerably exceeds the Eddington accretion rate and substantially differs from the -5/3 power of time.

  18. Chaos in the Test Particle Eccentric Kozai-Lidov Mechanism

    CERN Document Server

    Li, Gongjie; Holman, Matt; Loeb, Abraham

    2014-01-01

    The Kozai-Lidov mechanism can be applied to a vast variety of astrophysical systems involving hierarchical three-body systems. Here, we study the Kozai-Lidov mechanism systematically in the test particle limit at the octupole level of approximation. We investigate the chaotic and quasiperiodic orbital evolution by studying surfaces of section and the Lyapunov exponents. We find that the resonances introduced by the octupole level of approximation cause orbits to flip from prograde to retrograde and back as well as cause significant eccentricity excitation, and the chaotic behaviors occur when the mutual inclination between the inner and the outer binary is high. We characterize the parameter space that allows large amplitude oscillations in eccentricity and inclination.

  19. Chaos in the test particle eccentric Kozai-Lidov mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Li, Gongjie; Naoz, Smadar; Holman, Matt; Loeb, Abraham, E-mail: gli@cfa.harvard.edu [Harvard-Smithsonian Center for Astrophysics, The Institute for Theory and Computation, 60 Garden Street, Cambridge, MA 02138 (United States)

    2014-08-20

    The Kozai-Lidov mechanism can be applied to a vast variety of astrophysical systems involving hierarchical three-body systems. Here, we study the Kozai-Lidov mechanism systematically in the test particle limit at the octupole level of approximation. We investigate the chaotic and quasi-periodic orbital evolution by studying the surfaces of section and the Lyapunov exponents. We find that the resonances introduced by the octupole level of approximation cause orbits to flip from prograde to retrograde and back as well as cause significant eccentricity excitation, and chaotic behavior occurs when the mutual inclination between the inner and the outer binary is high. We characterize the parameter space that allows large amplitude oscillations in eccentricity and inclination.

  20. Biomechanical characteristics of the eccentric Achilles tendon exercise

    DEFF Research Database (Denmark)

    Henriksen, Marius; Aaboe, Jens; Bliddal, Henning

    2009-01-01

    muscles were recorded. Joint kinematics, GRF frequency contents, average EMG amplitudes, and Achilles tendon loads were calculated. FINDINGS: The eccentric movement phase was characterized by a higher GRF frequency content in the 8-12 Hz range, and reduced EMG activity in the lower leg muscles...... into the biomechanics of the exercise may improve our understanding. METHODS: Sixteen healthy subjects performed one-legged full weight bearing ankle plantar and dorsiflexion exercises during which three-dimensional ground reaction forces (GRF), ankle joint kinematics and surface electromyography (EMG) of the lower leg....... No differences in Achilles tendon loads were found. INTERPRETATION: This descriptive study demonstrates differences in the movement biomechanics between the eccentric and concentric phases of one-legged full weight bearing ankle dorsal and plantar flexion exercises. In particular, the findings imply...

  1. Effects of antioxidant therapy in women exposed to eccentric exercise.

    Science.gov (United States)

    Bloomer, Richard J; Goldfarb, Alan H; McKenzie, Michael J; You, Tonjian; Nguyen, Linh

    2004-08-01

    The purpose of this study was to determine the effects of antioxidant therapy on indirect markers of muscle damage following eccentric exercise (EE). Eighteen women were randomized to an antioxidant supplement or a placebo before a bout of EE. Plasma creatine kinase (CK) activity, muscle soreness (MS), maximal isometric force (MIF), and range of motion (ROM) were assessed before and through 14 d postexercise. Eccentric exercise resulted in an increase in CK activity and MS, and a drop in MIF and ROM during the days following EE, which returned to baseline values 14 d after EE in both groups. Antioxidants attenuated the CK activity and MS response to the EE, while little difference was noted between groups in MIF or ROM. These findings suggest that antioxidant supplementation was helpful in reducing the elevations in plasma CK activity and MS, with little impact on MIF and ROM loss.

  2. Spectrum of 100-kyr glacial cycle: orbital inclination, not eccentricity.

    Science.gov (United States)

    Muller, R A; MacDonald, G J

    1997-08-05

    Spectral analysis of climate data shows a strong narrow peak with period approximately 100 kyr, attributed by the Milankovitch theory to changes in the eccentricity of the earth's orbit. The narrowness of the peak does suggest an astronomical origin; however the shape of the peak is incompatible with both linear and nonlinear models that attribute the cycle to eccentricity or (equivalently) to the envelope of the precession. In contrast, the orbital inclination parameter gives a good match to both the spectrum and bispectrum of the climate data. Extraterrestrial accretion from meteoroids or interplanetary dust is proposed as a mechanism that could link inclination to climate, and experimental tests are described that could prove or disprove this hypothesis.

  3. An Eccentric Binary Millisecond Pulsar in the Galactic Plane

    CERN Document Server

    Champion, D J; Lazarus, P; Camilo, F; Bassa, C; Kaspi, V M; Nice, D J; Freire, P C C; Stairs, I H; Van Leeuwen, J; Stappers, B W; Cordes, J M; Hessels, J W T; Lorimer, D R; Arzoumanian, Z; Backer, D C; Bhat, N D R; Chatterjee, S; Cognard, I; Deneva, J S; Faucher-Giguere, C -A; Gaensler, B M; Han, J L; Jenet, F A; Kasian, L; Kondratiev, V I; Krämer, M; Lazio, J; McLaughlin, M A; Venkataraman, A; Vlemmings, W

    2008-01-01

    Binary pulsar systems are superb probes of stellar and binary evolution and the physics of extreme environments. In a survey with the Arecibo telescope, we have found PSR J1903+0327, a radio pulsar with a rotational period of 2.15 ms in a highly eccentric (e = 0.44) 95-day orbit around a solar mass companion. Infrared observations identify a possible main-sequence companion star. Conventional binary stellar evolution models predict neither large orbital eccentricities nor main-sequence companions around millisecond pulsars. Alternative formation scenarios involve recycling a neutron star in a globular cluster then ejecting it into the Galactic disk or membership in a hierarchical triple system. A relativistic analysis of timing observations of the pulsar finds its mass to be 1.74+/-0.04 Msun, an unusually high value.

  4. António Reis and Margarida Cordeiro, eccentric filmmakers

    Directory of Open Access Journals (Sweden)

    Lucas Tavares Neves

    2016-02-01

    Full Text Available The international symposium "António Reis and Margarida Cordeiro, eccentric filmmakers" took place in Paris between the 3rd and the 4th of June, 2015. Speakers exchanged on the political, social and poetical aspects of the duo's cinematography, as well as on the reverberations of titles such as Jaime (1974 and Trás-os-montes (1976 on the Portuguese filmic landscape of the decades that followed.

  5. Eccentric Pumping Unit: Cost-effective and Reliable

    Institute of Scientific and Technical Information of China (English)

    Zhang Shaobo; Gao Heping; Chen Yibao; Shi Linsong; Zhang Huiwen

    1996-01-01

    @@ The beam-type pumping unit is the most widely used ty pe of pumping unit because of its simple geometry and its reliability. However. when its stroke exceeds five meters, the structure of the unit becomes massive and its cost becomes quite high. In order to make full use of the advantages of the beam pumping unit and to enhance its stroke. a new type of pumping unit - the ECCENTRIC PUMPING UNIT - has been designed after two years of the research work.

  6. Gluon field fluctuations in nuclear collisions: Multiplicity and eccentricity distributions

    Energy Technology Data Exchange (ETDEWEB)

    Schenke, Björn [Physics Department, Brookhaven National Laboratory, Upton, NY 11973 (United States); Tribedy, Prithwish [Variable Energy Cyclotron Centre, 1/AF Bidhan Nagar, Kolkata 700064 (India); Venugopalan, Raju [Physics Department, Brookhaven National Laboratory, Upton, NY 11973 (United States)

    2014-06-15

    We discuss different sources of fluctuations in nuclear collisions and their realization in the IP-Glasma model. We present results for multiplicity distributions in p+p and p+A collisions and compare eccentricity (ε{sub 2}, ε{sub 3}, ε{sub 4}) distributions in A + A collisions to the v{sub n} distributions in 10 centrality classes measured by the ATLAS Collaboration.

  7. Revisiting the Force-Joint Angle Relationship After Eccentric Exercise.

    Science.gov (United States)

    Welsh, Molly C; Allen, David L; Batliner, Matthew E; Byrnes, William C

    2015-12-01

    The purpose of this study was to evaluate force-angle curve fitting techniques pre-eccentric exercise, quantify changes in curve characteristics postexercise, and examine the relationship between curve changes and markers of muscle damage. Fourteen males unaccustomed to eccentric exercise performed 60 eccentric muscle actions of the elbow flexors. Maximal voluntary isometric force was measured throughout a range of angles pre- (Pre1 and Pre2), immediately post (IP), and 1, 2, 4, and 7 days postexercise. Force-angle curves for each visit were constructed using second-order polynomials. Changes in curve characteristics (optimal angle, peak force, curve height), range of motion, soreness, and creatine kinase activity were quantified. Optimal joint angle and force at optimal angle were significantly correlated from Pre1 to Pre2 (ICC = 0.821 and 0.979, respectively). Optimal angle was significantly right shifted (p = 0.035) by 10.4 ± 12.9° from Pre2 to IP and was restored by 1 day post exercise. Interestingly, the r value for curve fit was significantly decreased (p exercise (r = 0.750). Curve height was significantly decreased (39%) IP and restored to pre-exercise height by 4 days postexercise. There was no correlation between optimal angle or curve height and other damage markers. In conclusion, force-angle relationships can be accurately described using second-order polynomials. After eccentric exercise, the force-angle curve is flattened and shifted (downward and rightward), but these changes are not correlated to other markers of muscle damage. Changes in the force-angle relationship are multifaceted, but determining the physiological significance of these changes requires further investigation.

  8. Ischemic Preconditioning Blunts Muscle Damage Responses Induced by Eccentric Exercise.

    Science.gov (United States)

    Franz, Alexander; Behringer, Michael; Harmsen, Jan-Frieder; Mayer, Constantin; Krauspe, Rüdiger; Zilkens, Christoph; Schumann, Moritz

    2017-08-22

    Ischemic preconditioning (IPC) is known to reduce muscle damage induced by ischemia and reperfusion-injury (I/R-Injury) during surgery. Due to similarities between the pathophysiological formation of I/R-injury and eccentric exercise-induced muscle damage (EIMD), as characterized by an intracellular accumulation of Ca, an increased production of reactive oxygen species and increased pro-inflammatory signaling, the purpose of the present study was to investigate whether IPC performed prior to eccentric exercise may also protect against EIMD. Nineteen healthy men were matched to an eccentric only (ECC) (n=9) or eccentric proceeded by IPC group (IPC+ECC) (n=10). The exercise protocol consisted of bilateral biceps curls (3x10 repetitions at 80% of the concentric 1RM). In IPC+ECC, IPC was applied bilaterally at the upper arms by a tourniquet (200 mmHg) immediately prior to the exercise (3x5 minutes of occlusion, separated by 5 minutes of reperfusion). Creatine Kinase (CK), arm circumference, subjective pain (VAS score) and radial displacement (Tensiomyography, Dm) were assessed before IPC, pre-exercise, post-exercise, 20 minutes-, 2 hours-, 24 hours-, 48 hours- and 72 hours post-exercise. CK differed from baseline only in ECC at 48h (pexercise. After 24h, 48h and 72h, CK was increased in ECC compared to IPC+ECC (between groups: 24h: p=0.004, 48h: pexercise, when compared to IPC+ECC (between groups: all pexercise days in ECC (all peccentric exercise of the elbow flexors blunts EIMD and exercise-induced pain, while maintaining the contractile properties of the muscle.

  9. Transition from inspiral to plunge for eccentric equatorial Kerr orbits

    CERN Document Server

    O'Shaughnessy, R

    2003-01-01

    Ori and Thorne have discussed the duration and observability (with LISA) of the transition from circular, equatorial inspiral to plunge for stellar-mass objects into supermassive ($10^{5}-10^{8}M_{\\odot}$) Kerr black holes. We extend their computation to eccentric Kerr equatorial orbits. Even with orbital parameters near-exactly determined, we find that there is no universal length for the transition; rather, the length of the transition depends sensitively -- essentially randomly -- on initial conditions. Still, Ori and Thorne's zero-eccentricity results are essentially an upper bound on the length of eccentric transitions involving similar bodies (e.g., $a$ fixed). Hence the implications for observations are no better: if the massive body is $M=10^{6}M_{\\odot}$, the captured body has mass $m$, and the process occurs at distance $d$ from LISA, then $S/N \\lesssim (m/10 M_{\\odot})(1\\text{Gpc}/d)\\times O(1)$, with the precise constant depending on the black hole spin. For low-mass bodies ($m \\lesssim 7 M_\\odot$...

  10. Evidence for Reflected Light from the Most Eccentric Exoplanet Known

    CERN Document Server

    Kane, Stephen R; Hinkel, Natalie R; Roy, Arpita; Mahadevan, Suvrath; Dragomir, Diana; Matthews, Jaymie M; Henry, Gregory W; Chakraborty, Abhijit; Boyajian, Tabetha S; Wright, Jason T; Ciardi, David R; Fischer, Debra A; Butler, R Paul; Tinney, C G; Carter, Brad D; Jones, Hugh R A; Bailey, Jeremy; O'Toole, Simon J

    2015-01-01

    Planets in highly eccentric orbits form a class of objects not seen within our Solar System. The most extreme case known amongst these objects is the planet orbiting HD 20782, with an orbital period of 597 days and an eccentricity of 0.96. Here we present new data and analysis for this system as part of the Transit Ephemeris Refinement and Monitoring Survey (TERMS). We obtained CHIRON spectra to perform an independent estimation of the fundamental stellar parameters. New radial velocities from AAT and PARAS observations during periastron passage greatly improve the our knowledge of the eccentric nature of the orbit. The combined analysis of our Keplerian orbital and Hipparcos astrometry show that the inclination of the planetary orbit is > 1.25 degrees, ruling out stellar masses for the companion. Our long-term robotic photometry show that the star is extremely stable over long timescales. Photometric monitoring of the star during predicted transit and periastron times using MOST rule out a transit of the pla...

  11. [The recovery of visual performance in strabismus with eccentric fixation].

    Science.gov (United States)

    Rusu, V

    1997-01-01

    The purpose of this work is to realise a general view about the diagnosis, therapeutic methods and the results obtained in eccentric fixation strabismus. We realised a six years retrospective study on 144 eccentric strabismus, watching dynamic the evolution by testing: the orthophoric status, visual acuity, binocular vision and the type of fixation. Medium follow un time was of 19.6 months. In the end of the treatment we notice: visual acuity between 0.1-0.5 in 14% cases; central fixation in 52 children (36%); first degree of binocular vision in 15 children (10.4%) and second degree in 5 cases (3.47%). This study showed that the early installation of eccentric fixation strabismus was in 53% cases before reaching one year old and in 90% before two years old. The functional results was negative influenced by the delay in presentation (42% come after 2 years) and the difficulties in family cooperation (46.5% were followed up lesenban 6 months).

  12. Muscle preservation in long duration space missions: The eccentric factor

    Science.gov (United States)

    Buchanan, Paul; Dudley, Gary A.; Tesch, Per A.; Hather, Bruce M.

    1990-01-01

    In our quest to understand, and eventually prevent, the loss of muscle strength and mass that occurs during prolonged periods in microgravity, we have organized our research approach by systems and useful terrestrial analogs. Our hypothesis was that: The eccentric movement, or lengthening component, of dynamic, resistive exercise, is required for the production of the greatest gains in strength and muscle hypertrophy in the most metabolically efficient, and time effective manner. The exercises selected were leg presses, leg (knee) extensions, and hamstring curls. In this 30 week study, 38 male subjects, between the ages of 25 and 50, were divided into four groups. One group performed 5 sets of 8-12 repetitions per set of conventional concentric/eccentric (CON/ECC) exercises. Another group performed only the concentric (CON) movement on the same schedule. The third group performed twice the number of sets in the concentric only mode (CON/CON), and the last group served as controls. We interpret these data as convincing evidence that the eccentric component of heavy resistance training is required along with the concentric for the most effective increase in strength and muscle fiber size in the least time. We also conclude that such heavy exercise of any such muscle group need not consume inordinately long periods of time, and is quite satisfactorily effective when performed on 72 hour centers.

  13. Orbital Eccentricity Distribution of Solar-Neighbour Halo Stars

    CERN Document Server

    Hattori, Kohei

    2011-01-01

    We present theoretical calculations for the differential distribution of stellar orbital eccentricity for a sample of solar-neighbour halo stars. Two types of static, spherical gravitational potentials are adopted to define the eccentricity e for given energy E and angular momentum L, such as an isochrone potential and a Navarro-Frenk-White potential that can serve as two extreme ends covering in-between any realistic potential of the Milky Way halo. The solar-neighbour eccentricity distribution \\Delta N(e) is then formulated, based on a static distribution function of the form f(E,L) in which the velocity anisotropy parameter \\beta monotonically increases in the radial direction away from the galaxy center, such that beta is below unity (near isotropic velocity dispersion) in the central region and asymptotically approaches \\sim 1 (radially anisotropic velocity dispersion) in the far distant region of the halo. We find that \\Delta N(e) sensitively depends upon the radial profile of \\beta, and this sensitivit...

  14. Nonlinear dynamics in eccentric Taylor-Couette-Poiseuille flow

    Science.gov (United States)

    Pier, Benoît; Caulfield, C. P.

    2015-11-01

    The flow in the gap between two parallel but eccentric cylinders and driven by an axial pressure gradient and inner cylinder rotation is characterized by two geometrical parameters (radius ratio and eccentricity) and two dynamic parameters (axial and azimuthal Reynolds numbers). Such a theoretical configuration is a model for the flow between drill string and wellbore in the hydrocarbon drilling industry. The linear convective and absolute instability properties have been systematically derived in a recent study [Leclercq, Pier & Scott, J. Fluid Mech. 2013 and 2014]. Here we address the nonlinear dynamics resulting after saturation of exponentially growing small-amplitude perturbations. By using direct numerical simulations, a range of finite-amplitude states are found and characterized: nonlinear traveling waves (an eccentric counterpart of Taylor vortices, associated with constant hydrodynamic loading on the inner cylinder), modulated nonlinear waves (with time-periodic torque and flow rate) and more irregular states. In the nonlinear regime, the hydrodynamic forces are found to depart significantly from those prevailing for the base flow, even in situations of weak linear instability.

  15. Heartbeat Stars: A Class Of Tidally Excited Eccentric Binaries

    Science.gov (United States)

    Barclay, Thomas; Thompson, S. E.; Mullally, F.; Everett, M.; Howell, S. B.; Still, M.; Christiansen, J. L.; Rowe, J.; Kurtz, D. W.; Hambleton, K.

    2012-01-01

    We have discovered a class of eccentric binary systems undergoing dynamic tidal distortions and tidally induced pulsations in the Kepler data. Each has a uniquely shaped light curve that is characterized by periodic brightening or variability at time scales of 4-20 days which is frequently accompanied by shorter period oscillations. We can explain the dominant features of the entire class with changing tidal forces that occur in close, eccentric binary systems. In this case the large variety of light curve shapes arises from viewing systems at different angles. A hypothesis that is confirmed with radial velocity measurements that show an eccentric orbit. Prior to the discovery of these 17 new systems, KOI-54 was the only system with direct detection of these dynamic tides and tidally induced oscillations. While significant work remains to include all the physics required to accurately model these systems and begin to understand how tidal effects influence the system, in this presentation we present preliminary fits to the light curves and describe the properties of this class of stars as a whole.

  16. A simple model of the chaotic eccentricity of Mercury

    CERN Document Server

    Boué, Gwenaël; Farago, François

    2012-01-01

    Mercury's eccentricity is chaotic and can increase so much that collisions with Venus or the Sun become possible (Laskar, 1989, 1990, 1994, 2008, Batygin & Laughlin, 2008, Laskar & Gastineau, 2009). This chaotic behavior results from an intricate network of secular resonances, but in this paper, we show that a simple integrable model with only one degree of freedom is actually able to reproduce the large variations in Mercury's eccentricity, with the correct amplitude and timescale. We show that this behavior occurs in the vicinity of the separatrices of the resonance g1-g5 between the precession frequencies of Mercury and Jupiter. However, the main contribution does not come from the direct interaction between these two planets. It is due to the excitation of Venus' orbit at Jupiter's precession frequency g5. We use a multipolar model that is not expanded with respect to Mercury's eccentricity, but because of the proximity of Mercury and Venus, the Hamiltonian is expanded up to order 20 and more in t...

  17. Exploring a Stream of Highly-Eccentric Binaries with Kepler

    CERN Document Server

    Dong, Subo; Socrates, Aristotle

    2012-01-01

    With 16-month Kepler data, 14 long-period (40 d - 265 d) eclipsing binaries on highly eccentric orbits (minimum e between 0.5 and 0.85) are recognized from their closely separated primary and secondary eclipses (\\Delta t_I,II = 3 d - 10 d). These systems confirm the existence of a previously hinted binary population situated near a constant angular momentum track at P(1-e^2)^(3/2) ~ 15 d, close to the tidal circularization period P_circ. They may be presently migrating due to tidal dissipation and form a steady-state stream (~1% of stars) feeding the close-binary population (few percent of stars). If so, future Kepler data releases will reveal a growing number (dozens) of systems at longer periods, following dN/dlgP \\propto P^(1/3) with increasing eccentricities reaching e -> 0.98 for P -> 1000d. Radial-velocity follow up of long-period eclipsing binaries with no secondary eclipses could offer a significantly larger sample. Orders of magnitude more (hundreds) may reveal their presence from periodic "eccentric...

  18. Evidence for Reflected Light from the Most Eccentric Exoplanet Known

    Science.gov (United States)

    Kane, Stephen R.; Wittenmyer, Robert A.; Hinkel, Natalie R.; Roy, Arpita; Mahadevan, Suvrath; Dragomir, Diana; Matthews, Jaymie M.; Henry, Gregory W.; Chakraborty, Abhijit; Boyajian, Tabetha S.; Wright, Jason T.; Ciardi, David R.; Fischer, Debra A.; Butler, R. Paul; Tinney, C. G.; Carter, Brad D.; Jones, Hugh R. A.; Bailey, Jeremy; O'Toole, Simon J.

    2016-04-01

    Planets in highly eccentric orbits form a class of objects not seen within our solar system. The most extreme case known among these objects is the planet orbiting HD 20782, with an orbital period of 597 days and an eccentricity of 0.96. Here we present new data and analysis for this system as part of the Transit Ephemeris Refinement and Monitoring Survey. We obtained CHIRON spectra to perform an independent estimation of the fundamental stellar parameters. New radial velocities from Anglo-Australian Telescope and PARAS observations during periastron passage greatly improve our knowledge of the eccentric nature of the orbit. The combined analysis of our Keplerian orbital and Hipparcos astrometry show that the inclination of the planetary orbit is \\gt 1\\_\\_AMP\\_\\_fdg;22, ruling out stellar masses for the companion. Our long-term robotic photometry show that the star is extremely stable over long timescales. Photometric monitoring of the star during predicted transit and periastron times using Microvariability and Oscillations of STars rule out a transit of the planet and reveal evidence of phase variations during periastron. These possible photometric phase variations may be caused by reflected light from the planet’s atmosphere and the dramatic change in star-planet separation surrounding the periastron passage.

  19. Pure eccentric exercise does not activate blood coagulation.

    Science.gov (United States)

    Hilberg, Thomas; Gläser, Doreen; Prasa, Dagmar; Stürzebecher, Jörg; Gabriel, Holger H W

    2005-08-01

    Eccentric exercise can cause skeletal muscle damage with ultrastructural disruption, inflammation and increased proteolytic enzyme activity. It may be possible that these changes are able to trigger blood coagulation in vivo. The aim of the study was to investigate changes in blood coagulation via the measurement of aPTT, the thrombin potential (total [TTP] and endogenous [ETP], both intrinsic [in] and extrinsic [ex]) and the thrombin generation (prothrombinfragment 1 + 2 [F1 + 2] and thrombin-antithrombin complex [TAT]) after pure eccentric exercise. Seventeen healthy non-smokers (28 +/- 6 years, VO2-peak 59 +/- 7 ml/min/kg) underwent pure eccentric down jumps (9 x 28 isolated down jumps in 90 min, drop from a height of 55 cm), a cycle exercise (90% of the individual anaerobic threshold for 60-90 min) and a control experiment on different days. Blood samples were drawn after a 30-min rest, immediately, and 2 h after exercise. After the cycle exercise, a clear shortening by 12% (Pcoagulation.

  20. Behavior of high strength concrete columns under eccentric loads

    Directory of Open Access Journals (Sweden)

    Hany A. Kottb

    2015-04-01

    Full Text Available In recent decades, high strength concrete (HSC has been widely accepted by designers and contractors to be used in concrete structures, especially in high compressive stress elements. The research aims to study the behavior of high strength concrete columns under eccentric compression using experimental and analytical programs. The research is divided into two main parts; the first part is an experimental investigation for ten square columns tested at the Cairo University Concrete Research Laboratory. The main studied parameters were eccentricity of the applied load, column slenderness ratio; and ratios of longitudinal and transverse reinforcement. The second part is analytical analysis using nonlinear finite element program ANSYS11 on nineteen columns (ten tested square columns and nine rectangular section columns to study the effect of the previous parameters on the column ultimate load, mid-height displacement, and column cracking patterns. The analyzed columns revealed a good agreement with the experimental results with an average difference of 16% and 17% for column ultimate load and mid-height displacement respectively. Results showed an excellent agreement for cracking patterns. Predictions of columns capacities using the interaction diagrams based on ACI 318-08 stress block parameters indicated a safe design procedure of HSC columns under eccentric compression, with ACI 318-08 being more conservative for moderate reinforced HSC columns.

  1. Dynamics of prolate spheroidal mass distributions with varying eccentricity

    CERN Document Server

    Rathulnath, R

    2013-01-01

    In this paper we calculate the potential for a prolate spheroidal distribution as in a dark matter halo with a radially varying eccentricity. This is obtained by summing up the shell-by-shell contributions of isodensity surfaces, which are taken to be concentric and with a common polar axis and with an axis ratio that varies with radius. Interestingly, the constancy of potential inside a shell is shown to be a good approximation even when the isodensity contours are dissimilar spheroids, as long as the radial variation in eccentricity is small as seen in realistic systems. We consider three cases where the isodensity contours are more prolate at large radii, or are less prolate, or have a constant eccentricity. Other relevant physical quantities like the rotation velocity, the net orbital and vertical frequency due to the halo and an exponential disc of finite thickness embedded in it are obtained. We apply this to the kinematical origin of Galactic warp, and show that a prolate shaped halo is not conducive t...

  2. Predictions for a planet just inside Fomalhaut's eccentric ring

    CERN Document Server

    Quillen, A C

    2006-01-01

    We propose that the eccentricity and sharpness of the edge of Fomalhaut's disk are due to a planet just interior to the ring edge. The collision timescale consistent with the disk opacity is long enough that spiral density waves cannot be driven near the planet. The ring edge is likely to be located at the boundary of a chaotic zone in the corotation region of the planet. We find that this zone can open a gap in a particle disk as long as the collision timescale exceeds the removal or ejection timescale in the zone. We use the slope measured from the ring edge surface brightness profile to place an upper limit on the planet mass. The removal timescale in the chaotic zone is used to estimate a lower limit on the planet mass. The ring edge has eccentricity caused by by secular perturbations from the planet. These arguments imply that the planet has a mass between that of Neptune and that of Saturn, a semi-major axis of approximately 119 AU and longitude of periastron and eccentricity, 0.1, the same as that of t...

  3. Dynamics of Neptune's Trojans: II. Eccentric orbits and observed ones

    CERN Document Server

    Zhou, Li-Yong; Sun, Yi-Sui

    2010-01-01

    In a previous paper, we have presented a global view of the stability of Neptune Trojan (NT hereafter) on inclined orbit. We discuss in this paper the dependence of stability of NT orbits on the eccentricity. High-resolution dynamical maps are constructed using the results of extensive numerical integrations of orbits initialized on the fine grids of initial semimajor axis (a0) versus eccentricity (e0). The extensions of regions of stable orbits on the (a0, e0) plane at different inclinations are shown. The maximum eccentricities of stable orbits in three most stable regions at low (0, 12deg.), medium (22,36deg.) and high (51, 59deg.) inclination, are found to be 0.10, 0.12 and 0.04, respectively. The fine structures in the dynamical maps are described. Via the frequency analysis method, the mechanisms that portray the dynamical maps are revealed. The secondary resonances, concerning the frequency of the librating resonant angle and the frequency of the quasi 2:1 mean motion resonance between Neptune and Uran...

  4. A Simple Family of Models for Eccentric Keplerian Fluid Disks

    CERN Document Server

    Statler, T S

    2001-01-01

    In order to be in a long-lived configuration, the density in a fluid disk should be constant along streamlines to prevent compressional (PdV) work from being done cyclically around every orbit. In a pure Kepler potential, flow along aligned, elliptical streamlines of constant eccentricity will satisfy this condition. For most density profiles, differential precession driven by the pressure gradient will destroy the alignment; however, in the razor-thin approximation there is a family of simple equilibria in which the precession frequency is the same at all radii. These disks may therefore be long-lived at significant eccentricities. The density can be made axisymmetric as r goes to 0, while maintaining the precession rate, by relaxing the requirement of constancy along streamlines in an arbitrarily small transition region near the center. In the limit of small eccentricity, the models can be seen as acoustically perturbed axisymmetric disks, and the precession rate is shown to agree with linear theory. The pe...

  5. Contract modularity in design by contract languages

    OpenAIRE

    Rebêlo, Henrique Emanuel Mostaert

    2014-01-01

    Design by Contract (DbC) is a popular technique for developing programs using behavioral specifications. In this context, researchers have found that the realization of DbC is crosscutting and fares better when modularized by Aspect-Oriented Programming. However, previous efforts aimed at supporting crosscutting contracts modularly actually compromised the main DbC principles. For example, in AspectJ-style, reasoning about the correctness of a method call may require a whole-pr...

  6. Whey protein hydrolysate augments tendon and muscle hypertrophy independent of resistance exercise contraction mode.

    Science.gov (United States)

    Farup, J; Rahbek, S K; Vendelbo, M H; Matzon, A; Hindhede, J; Bejder, A; Ringgard, S; Vissing, K

    2014-10-01

    In a comparative study, we investigated the effects of maximal eccentric or concentric resistance training combined with whey protein or placebo on muscle and tendon hypertrophy. 22 subjects were allocated into either a high-leucine whey protein hydrolysate + carbohydrate group (WHD) or a carbohydrate group (PLA). Subjects completed 12 weeks maximal knee extensor training with one leg using eccentric contractions and the other using concentric contractions. Before and after training cross-sectional area (CSA) of m. quadriceps and patellar tendon CSA was quantified with magnetic resonance imaging and a isometric strength test was used to assess maximal voluntary contraction (MVC) and rate of force development (RFD). Quadriceps CSA increased by 7.3 ± 1.0% (P contraction mode. MVC and RFD increased by 15.6 ± 3.5% (P contraction mode effects. In conclusion, high-leucine whey protein hydrolysate augments muscle and tendon hypertrophy following 12 weeks of resistance training - irrespective of contraction mode. © 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  7. Contracts in distributed systems

    Directory of Open Access Journals (Sweden)

    Massimo Bartoletti

    2011-07-01

    Full Text Available We present a parametric calculus for contract-based computing in distributed systems. By abstracting from the actual contract language, our calculus generalises both the contracts-as-processes and contracts-as-formulae paradigms. The calculus features primitives for advertising contracts, for reaching agreements, and for querying the fulfilment of contracts. Coordination among principals happens via multi-party sessions, which are created once agreements are reached. We present two instances of our calculus, by modelling contracts as (i processes in a variant of CCS, and (ii as formulae in a logic. With the help of a few examples, we discuss the primitives of our calculus, as well as some possible variants.

  8. Multi-Beam Interference Transmission Spectrum Observed from an Eccentric Core Single-Mode Fiber

    Institute of Scientific and Technical Information of China (English)

    FAN Un-Yong; JIANG Wei-Wei; ZHAO Rui-Feng; PEI Li; JIAN Shui-Sheng

    2011-01-01

    @@ An eccentric core single-mode fiber, whose core is away from the axis of the fiber, is fabricated by using the fiber preform goniometric-groove method and the stack-and-draw method.An eccentric core single-mode fiber without coating is spliced between two single-mode fibers.Fundamental mode and cladding modes are excited at one splicing point between the eccentric core single-mode fiber and the single-mode fiber, and propagate in the eccentric core single-mode fiber, then interfere with each other at the other splicing point.Multi-beam interference transmission spectrum is observed.An in-line fiber interferometric strain sensor based on the eccentric core single-mode fiber is realized.%An eccentric core single-mode fiber, whose core is away from the axis of the fiber, is fabricated by using the fiber preform goniometric-groove method and the stack-and-draw method. An eccentric core single-mode fiber without coating is spliced between two single-mode fibers. Fundamental mode and cladding modes are excited at one splicing point between the eccentric core single-mode fiber and the single-mode fiber, and propagate in the eccentric core single-mode fiber, then interfere with each other at the other splicing point. Multi-beam interference transmission spectrum is observed. An in-line fiber interferometric strain sensor based on the eccentric core single-mode fiber is realized.

  9. Reconfigurable multiport EPON repeater

    Science.gov (United States)

    Oishi, Masayuki; Inohara, Ryo; Agata, Akira; Horiuchi, Yukio

    2009-11-01

    An extended reach EPON repeater is one of the solutions to effectively expand FTTH service areas. In this paper, we propose a reconfigurable multi-port EPON repeater for effective accommodation of multiple ODNs with a single OLT line card. The proposed repeater, which has multi-ports in both OLT and ODN sides, consists of TRs, BTRs with the CDR function and a reconfigurable electrical matrix switch, can accommodate multiple ODNs to a single OLT line card by controlling the connection of the matrix switch. Although conventional EPON repeaters require full OLT line cards to accommodate subscribers from the initial installation stage, the proposed repeater can dramatically reduce the number of required line cards especially when the number of subscribers is less than a half of the maximum registerable users per OLT. Numerical calculation results show that the extended reach EPON system with the proposed EPON repeater can save 17.5% of the initial installation cost compared with a conventional repeater, and can be less expensive than conventional systems up to the maximum subscribers especially when the percentage of ODNs in lightly-populated areas is higher.

  10. Revisiting the TALE repeat.

    Science.gov (United States)

    Deng, Dong; Yan, Chuangye; Wu, Jianping; Pan, Xiaojing; Yan, Nieng

    2014-04-01

    Transcription activator-like (TAL) effectors specifically bind to double stranded (ds) DNA through a central domain of tandem repeats. Each TAL effector (TALE) repeat comprises 33-35 amino acids and recognizes one specific DNA base through a highly variable residue at a fixed position in the repeat. Structural studies have revealed the molecular basis of DNA recognition by TALE repeats. Examination of the overall structure reveals that the basic building block of TALE protein, namely a helical hairpin, is one-helix shifted from the previously defined TALE motif. Here we wish to suggest a structure-based re-demarcation of the TALE repeat which starts with the residues that bind to the DNA backbone phosphate and concludes with the base-recognition hyper-variable residue. This new numbering system is consistent with the α-solenoid superfamily to which TALE belongs, and reflects the structural integrity of TAL effectors. In addition, it confers integral number of TALE repeats that matches the number of bound DNA bases. We then present fifteen crystal structures of engineered dHax3 variants in complex with target DNA molecules, which elucidate the structural basis for the recognition of bases adenine (A) and guanine (G) by reported or uncharacterized TALE codes. Finally, we analyzed the sequence-structure correlation of the amino acid residues within a TALE repeat. The structural analyses reported here may advance the mechanistic understanding of TALE proteins and facilitate the design of TALEN with improved affinity and specificity.

  11. The heat shock protein response following eccentric exercise in human skeletal muscle is unaffected by local NSAID infusion

    DEFF Research Database (Denmark)

    Mikkelsen, U R; Paulsen, G; Schjerling, P

    2013-01-01

    in muscle subjected to stress, and in several cell types including cardiac myocytes prostaglandins are important in induction of the HSP response. This study aimed to determine the influence of NSAIDs on the HSP response to eccentric exercise in human skeletal muscle. Healthy males performed 200 maximal...... eccentric contractions with each leg with intramuscular infusion of the NSAID indomethacin or placebo. Biopsies were obtained from m. vastus lateralis before and after (5, 28 hrs and 8 days) the exercise bout from both legs (NSAID vs unblocked leg) and analysed for expression of the HSPs HSP70, HSP27 and a......B-crystallin (mRNA and protein). NSAID did not affect the mRNA expression of any of the HSPs. Compared to pre values, the mRNA expression of all HSPs was increased; aB-crystallin, 3.6- and 5.4-fold; HSP70, 26- and 3.4-fold; and HSP27: 4.8- and 6.5-fold at 5 and 28 hrs post-exercise, respectively (all p ...

  12. Climate of an Earth-Like World with Changing Eccentricity

    Science.gov (United States)

    Kohler, Susanna

    2017-02-01

    Having a giant planet like Jupiter next door can really wreak havoc on your orbit! A new study examines what such a bad neighbor might mean for the long-term climate of an Earth-like planet.Influence of a Bad NeighborThe presence of a Jupiter-like giant planet in a nearby orbit can significantly affect how terrestrial planets evolve dynamically, causing elements like the planets orbital eccentricities and axial tilts to change over time. Earth is saved this inconvenience Jupiter isnt close enough to significantly influence us, and our large moon stabilizes our orbit against Jupiters tugs.Top panels: Authors simulationoutcomes for Case1, in which the planets eccentricity varies from 0 to 0.283 over 6500 years. Bottom panels: Outcomes for Case 2, in which the planets eccentricity varies from 0 to 0.066 over 4500 years. The highereccentricities reached in Case 1 causes the climate parameters to vary more widely. Click for a better look! [Way Georgakarakos 2017]Mars, on the other hand, isnt as lucky: its possible that Jupiters gravitational pull causes Marss axial tilt, for instance, to evolve through a range as large as 0 to 60 degrees on timescales of millions of years! Marss orbital eccentricity is similarly thought to vary due to Jupiters influence, and both of these factors play a major role in determining Marss climate.As exoplanet missions discover more planets many of which are Earth-like we must carefully consider which among these are most likely to be capable of sustaining life. If having a nearby neighbor like a Jupiter can tug an Earth-like world into an orbit with varying eccentricity, how does this affect the planets climate? Will the planet remain temperate? Or will it develop a runaway heating or cooling effect as it orbits, rendering it uninhabitable?Oceans and OrbitsTo examine these questions, two scientists have built the first ever 3D global climate model simulations of an Earth-like world using a fully coupled ocean (necessary for understanding

  13. Recursive quantum repeater networks

    CERN Document Server

    Van Meter, Rodney; Horsman, Clare

    2011-01-01

    Internet-scale quantum repeater networks will be heterogeneous in physical technology, repeater functionality, and management. The classical control necessary to use the network will therefore face similar issues as Internet data transmission. Many scalability and management problems that arose during the development of the Internet might have been solved in a more uniform fashion, improving flexibility and reducing redundant engineering effort. Quantum repeater network development is currently at the stage where we risk similar duplication when separate systems are combined. We propose a unifying framework that can be used with all existing repeater designs. We introduce the notion of a Quantum Recursive Network Architecture, developed from the emerging classical concept of 'recursive networks', extending recursive mechanisms from a focus on data forwarding to a more general distributed computing request framework. Recursion abstracts independent transit networks as single relay nodes, unifies software layer...

  14. Studies of an expanded trinucleotide repeat in transgenic mice

    Energy Technology Data Exchange (ETDEWEB)

    Bingham, P.; Wang, S.; Merry, D. [Univ. of Pennsylvania, Philadelphia, PA (United States)

    1994-09-01

    Spinal and bulbar muscular atrophy (SBMA) is a progressive motor neuron disease caused by expansion of a trinucleotide repeat in the androgen receptor gene (AR{sup exp}). AR{sup exp} repeats expand further or contract in approximately 25% of transmissions. Analogous {open_quotes}dynamic mutations{close_quotes} have been reported in other expanded trinucleotide repeat disorders. We have been developing a mouse model of this disease using a transgenic approach. Expression of the SBMA AR was documented in transgenic mice with an inducible promoter. No phenotypic effects of transgene expression were observed. We have extended our previous results on stability of the expanded trinucleotide repeat in transgenic mice in two lines carrying AR{sup exp}. Tail DNA was amplified by PCR using primers spanning the repeat on 60 AR{sup exp} transgenic mice from four different transgenic lines. Migration of the PCR product through an acrylamide gel showed no change of the 45 CAG repeat length in any progeny. Similarly, PCR products from 23 normal repeat transgenics showed no change from the repeat length of the original construct. Unlike the disease allele in humans, the expanded repeat AR cDNA in transgenic mice showed no change in repeat length with transmission. The relative stability of CAG repeats seen in the transgenic mice may indicate either differences in the fidelity of replicative enzymes, or differences in error identification and repair between mice and humans. Integration site or structural properties of the transgene itself might also play a role.

  15. Local NSAID infusion does not affect protein synthesis and gene expression in human muscle after eccentric exercise

    DEFF Research Database (Denmark)

    Mikkelsen, U R; Schjerling, P.; Langberg, Henning

    2011-01-01

    models, and inhibit the exercise-induced satellite cell proliferation and protein synthesis in humans. However, the cellular mechanisms eliciting these responses remain unknown. Eight healthy male volunteers performed 200 maximal eccentric contractions with each leg. To block prostaglandin synthesis......Unaccustomed exercise leads to satellite cell proliferation and increased skeletal muscle protein turnover. Several growth factors and cytokines may be involved in the adaptive responses. Non-steroidal anti-inflammatory drugs (NSAIDs) negatively affect muscle regeneration and adaptation in animal...... locally in the skeletal muscle, indomethacin (NSAID) was infused for 7.5 h via microdialysis catheters into m. vastus lateralis of one leg. Protein synthesis was determined by the incorporation of 1,2-(13) C(2) leucine into muscle protein from 24 to 28 h post-exercise. Furthermore, mRNA expression...

  16. Impact of eccentricity build-up and graveyard disposal Strategies on MEO navigation constellations

    Science.gov (United States)

    Radtke, Jonas; Domínguez-González, Raúl; Flegel, Sven K.; Sánchez-Ortiz, Noelia; Merz, Klaus

    2015-12-01

    With currently two constellations being in or close to the build-up phase, in a few years the Medium Earth Orbit (MEO) region will be populated with four complete navigation systems in relatively close orbital altitudes: The American GPS, Russian GLONASS, European Galileo, and Chinese BeiDou. To guarantee an appropriate visibility of constellation satellites from Earth, these constellations rely on certain defined orbits. For this, both the repeat pattern, which is basically defined by the semimajor axis and inclination, as well as the orbital planes, which are defined by the right ascension of ascending node, are determining values. To avoid an overcrowding of the region of interest, the disposal of satellites after their end-of-life is recommended. However, for the MEO region, no internationally agreed mitigation guidelines exist. Because of their distances to Earth, ordinary disposal manoeuvres leading to a direct or delayed re-entry due to atmospheric drag are not feasible: The needed fuel masses for such manoeuvres are by far above the reasonable limits and available fuel budgets. Thus, additional approaches have to be applied. For this, in general two options exist: disposal to graveyard orbits or the disposal to eccentricity build-up orbits. In the study performed, the key criterion for the graveyard strategy is that the disposed spacecraft must keep a safe minimum distance to the altitude of the active constellation on a long-term time scale of up to 200 years. This constraint imposes stringent requirements on the stability of the graveyard orbit. Similar disposals are also performed for high LEO satellites and disposed GEO payloads. The eccentricity build-up strategy on the other hand uses resonant effects between the Earth's geopotential, the Sun and the Moon. Depending on the initial conditions, these can cause a large eccentricity build-up, which finally can lead to a re-entry of the satellite. In this paper, the effects of applying either the first or

  17. Lengthening our perspective: morphological, cellular, and molecular responses to eccentric exercise.

    Science.gov (United States)

    Hyldahl, Robert D; Hubal, Monica J

    2014-02-01

    The response of skeletal muscle to unaccustomed eccentric exercise has been studied widely, yet it is incompletely understood. This review is intended to provide an up-to-date overview of our understanding of how skeletal muscle responds to eccentric actions, with particular emphasis on the underlying molecular and cellular mechanisms of damage and recovery. This review begins by addressing the question of whether eccentric actions result in physical damage to muscle fibers and/or connective tissue. We next review the symptomatic manifestations of eccentric exercise (i.e., indirect damage markers, such as delayed onset muscle soreness), with emphasis on their relatively poorly understood molecular underpinnings. We then highlight factors that potentially modify the muscle damage response following eccentric exercise. Finally, we explore the utility of using eccentric training to improve muscle function in populations of healthy and aging individuals, as well as those living with neuromuscular disorders. Copyright © 2013 Wiley Periodicals, Inc.

  18. Effect of eccentricity on junction and junctionless based silicon nanowire and silicon nanotube FETs

    Science.gov (United States)

    Scarlet, S. Priscilla; Ambika, R.; Srinivasan, R.

    2017-07-01

    In this paper, the effect of eccentricity on Junction-based Silicon Nanowire FET, Junction-based Silicon Nanotube FET, Junctionless-based Silicon Nanowire FET, and Junctionless-based Silicon Nanotube FET is investigated. Three kinds of eccentric structures are considered here. The impact of eccentricity on effective gate oxide thickness thereby gate oxide capacitance, and effective channel width are studied using 3D numerical simulations. Average radius of an ellipse is used to generate a model which captures the impact of eccentricity on gate oxide capacitance, and verified using TCAD simulations in MOS nanowire structure. The impact of eccentricity on ON current (ION), OFF current (IOFF), ION/IOFF ratio, and Unity gain cutoff frequency are investigated. Eccentricity increases the effective gate oxide thickness, the effective channel width, ION, and IOFF but reduces ION/IOFF ratio.

  19. Measurement accuracy of articulated arm CMMs with circular grating eccentricity errors

    Science.gov (United States)

    Zheng, Dateng; Yin, Sanfeng; Luo, Zhiyang; Zhang, Jing; Zhou, Taiping

    2016-11-01

    The 6 circular grating eccentricity errors model attempts to improve the measurement accuracy of an articulated arm coordinate measuring machine (AACMM) without increasing the corresponding hardware cost. We analyzed the AACMM’s circular grating eccentricity and obtained the 6 joints’ circular grating eccentricity error model parameters by conducting circular grating eccentricity error experiments. We completed the calibration operations for the measurement models by using home-made standard bar components. Our results show that the measurement errors from the AACMM’s measurement model without and with circular grating eccentricity errors are 0.0834 mm and 0.0462 mm, respectively. Significantly, we determined that measurement accuracy increased by about 44.6% when the circular grating eccentricity errors were corrected. This study is significant because it promotes wider applications of AACMMs both in theory and in practice.

  20. Effects of Eccentricity on the Dynamic Behavior for Electromechanical Integrated Toroidal Drive

    Directory of Open Access Journals (Sweden)

    Lizhong Xu

    2013-01-01

    Full Text Available In electromechanical integrated toroidal drive, eccentric center errors occur which has important influences on the dynamic behavior of the drive system. Here, the dynamic equations of the drive system with eccentric center are presented. Changes of the natural frequencies and vibrating modes along with eccentric center distance are analyzed. The forced responses of the drive system to eccentric center excitation are investigated. Results show that the eccentric center causes some natural frequencies to increase, and the other natural frequencies to drop. It also causes some vibrations to become weak, and the other vibrations to become strong. The eccentric center has more obvious effects on the dynamic behavior of the planets. The results are useful in design and manufacture of the drive systems.

  1. Unilateral eccentric exercise of the knee flexors affects muscle activation during gait.

    Science.gov (United States)

    Dover, Geoffrey C; Legge, Laura; St-Onge, Nancy

    2012-05-01

    Uni-lateral muscle soreness is common yet the effects on gait or electromyographic (EMG) activity are unknown. The purpose of our study was to induce delayed onset muscle soreness (DOMS) in the knee flexor group and measure the resultant change in EMG activity and knee motion during gait. Nine healthy subjects participated in the study. Measures of function, evoked tenderness of the biceps femoris, as well as knee angle, and EMG activity during gait were assessed prior and 48 h after an eccentric exercise protocol. DOMS was induced unilaterally in the knee flexors using an isokinetic dynamometer and subjects exercised until they could not generate 50% of their maximal voluntary isometric contraction (MVIC). There was a significant decrease in biceps femoris activity after DOMS during the last phase of gait. Moreover, there was a day × phase interaction for gastrocnemius activity with the last two phases displaying an increase in activity. There was no significant change in knee angle during gait. The decrease in biceps femoris activity as well as the increase in gastrocnemius activity could be evidence of a protective mechanism designed to decrease activity of the sore muscle while increasing the activity of a synergistic muscle. Copyright © 2012 Elsevier B.V. All rights reserved.

  2. Effects of submaximal eccentric exercise on muscle activity at different elbow joint angles.

    Science.gov (United States)

    Kisiel-Sajewicz, Katarzyna; Jaskólska, Anna; Janecki, Damian; Andrzejewska, Renata; Marusiak, Jarosław; Jaskólski, Artur

    2014-01-01

    Our s