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Sample records for sustained isometric contractions

  1. Forearm muscle oxygenation during sustained isometric contractions in rock climbers

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    Jan Kodejška

    2016-02-01

    Full Text Available Background. Bouldering and lead climbing are divergent disciplines of the sport of rock climbing. Bouldering moves are short and powerful, whilst sport climbing is longer and require a greater degree of endurance. Aim. The aim of this study was to compare forearm muscle oxygenation during sustained isometric contraction between lead climbers (LC and boulderers (BO. Methods. Eight BO and twelve LC completed maximal finger flexor strength test and sustained contractions to exhaustion at 60% of maximum voluntary contraction (MVC. Differences between BO and LC in maximal strength, time to exhaustion, force time integral (FTI, and tissue oxygenation (SmO2 were assessed by t-test for independent samples. Results. LC showed significantly lower level of average tissue oxygenation (BO 38.9% SmO2, s = 7.4; LC 28.7% SmO2, s = 7.1 and maximal tissue deoxygenation (BO 25.6% SmO2, s = 8.2; LC 13.5% SmO2, s = 8.5. LC demonstrated significantly lower finger flexor strength (519 N, s = 72 than BO (621 N, s = 142. LC sustained a longer time of contraction (not significantly (BO 52.2 s, s = 11.5; LC 60.6 s, s = 13 and achieved a similar value of FTI (BO 17421 Ns, s = 4291; LO 17476 Ns, s = 5036 in the endurance test. Conclusions. The results showed lower deoxygenation during sustained contraction in BO than LC despite similar FTI, indicating different local metabolic pathways in both groups.

  2. Descending pain modulation and its interaction with peripheral sensitization following sustained isometric muscle contraction in fibromyalgia

    DEFF Research Database (Denmark)

    Ge, H-Y; Nie, Hongling; Graven-Nielsen, Thomas

    2012-01-01

    OBJECTIVE: Sustained isometric muscle contraction (fatiguing contraction) recruits segmental and/or extrasegmental descending inhibition in healthy subjects but not in fibromyalgia (FM). We hypothesized that fatiguing contraction may shift descending pain modulation from inhibition towards...

  3. Intensity-dependent EMG response for the biceps brachii during sustained maximal and submaximal isometric contractions.

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    Carr, Joshua C; Beck, Travis W; Ye, Xin; Wages, Nathan P

    2016-09-01

    There have been recent attempts to characterize the mechanisms associated with fatigue-induced task failure. We compared the time to failure and the corresponding changes in the surface electromyogram (EMG) during sustained maximal and submaximal isometric force tasks. EMG activity was measured from the biceps brachii of 18 male participants as they sustained either a maximal or submaximal (60 % MVC) isometric contraction of the dominant elbow flexors until force could not be maintained above 55 % MVC. Intensity-dependent patterns of change were observed for EMG amplitude and mean power frequency (MNF) between the two force tasks. Interestingly, the only significant predictor of failure time was the rate of change in EMG MNF during the submaximal task (r (2) = 0.304). In addition, EMG amplitude at submaximal failure was significantly lower (p EMG response emphasize the basis of neuromuscular fatigue and task dependency. Additionally, our data suggest that the EMG MNF should be used when monitoring the progression of local muscle fatigue.

  4. Type 2 diabetes mellitus patients manifest characteristic spatial EMG potential distribution pattern during sustained isometric contraction.

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    Watanabe, Kohei; Miyamoto, Toshiaki; Tanaka, Yoji; Fukuda, Kazuhito; Moritani, Toshio

    2012-09-01

    The purpose of the present study is to investigate spatial surface electromyography (SEMG) potential distribution pattern in type 2 diabetes mellitus (T2DM) patients. Nine T2DM patients and nine age-matched healthy men (CON) performed a sustained isometric knee extension at 10% of maximal voluntary contraction for 120s. Multi-channel SEMG was recorded from the vastus lateralis muscle by means of 64 electrodes. To characterize spatial SEMG potential distribution pattern, modified entropy and correlation coefficients between same electrode locations were calculated at 15, 60 and 120s for the root mean square values. At 60 and 120s, modified entropy in T2DM was significantly lower than those in CON (p<0.05). Correlation coefficients for T2DM were significantly higher than those for CON at 60 and 120s (p<0.05). From these results, we suggested that T2DM patients continue to recruit limited and same motor units during the sustained contraction at low force level. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

  5. Blackcurrant Alters Physiological Responses and Femoral Artery Diameter during Sustained Isometric Contraction

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    Matthew David Cook

    2017-05-01

    Full Text Available Blackcurrant is rich in anthocyanins that may affect exercise-induced physiological responses. We examined tissue oxygen saturation, muscle activity, cardiovascular responses and femoral artery diameter during a submaximal sustained isometric contraction. In a randomised, double-blind, crossover design, healthy men (n = 13, age: 25 ± 4 years, BMI: 25 ± 3 kg·m−2, mean ± SD ingested New Zealand blackcurrant (NZBC extract (600 mg∙day−1 CurraNZ™ or placebo (PL for 7-days separated by 14-days washout. Participants produced isometric maximal voluntary contractions (iMVC and a 120-s 30%iMVC of the quadriceps with electromyography (EMG, near-infrared spectroscopy, hemodynamic and ultrasound recordings. There was no effect of NZBC extract on iMVC (NZBC: 654 ± 73, PL: 650 ± 78 N. During the 30%iMVC with NZBC extract, total peripheral resistance, systolic, diastolic, and mean arterial pressure were lower with increased cardiac output and stroke volume. With NZBC extract, EMG root mean square of the vastus medialis and muscle oxygen saturation were lower with higher total haemoglobin. During the 30%iMVC, femoral artery diameter was increased with NZBC extract at 30 (6.9%, 60 (8.2%, 90 (7.7% and 120 s (6.0%. Intake of NZBC extract for 7-days altered cardiovascular responses, muscle oxygen saturation, muscle activity and femoral artery diameter during a 120-s 30%iMVC of the quadriceps. The present study provides insight into the potential mechanisms for enhanced exercise performance with intake of blackcurrant.

  6. Methods for measuring maximal isometric grip strength during short and sustained contractions, including intra-rater reliability.

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    Lagerström, C; Nordgren, B

    1996-01-01

    The purposes of this study were to develop methods for measuring maximal isometric grip strength during short and sustained contractions in a laboratory setting, and to evaluate the test-retest reliability of these methods in short- and long-term perspectives. Eleven healthy men and women were assessed on four occasions. Maximal voluntary isometric grip strength (MVC) was measured in standardized and optional positions, and sustained maximal isometric strength (SMVC) in the standardized position. The results indicated that three trials in a session might be insufficient to obtain a true measure of MVC. The within-session and test-retest reliability of the described multi-trial procedure was considered satisfactory. The mean score of the last three trials tended to show the highest short-term and long-term variability. There were no clear differences between scores obtained in standardized and optional positions. The standardized position seemed more consistently to yield higher test-retest reliability and lower variability over time. The described method for measuring SMVC, expressed as area and peak score, had high test-retest reliability and an acceptable degree of short-term and long-term variability. The time taken to reach the peak score was not a reliable measure.

  7. LONG-LASTING SUPERNORMAL CONDUCTION-VELOCITY AFTER SUSTAINED MAXIMAL ISOMETRIC CONTRACTION IN HUMAN MUSCLE

    NARCIS (Netherlands)

    VANDERHOEVEN, JH; VANWEERDEN, TW; ZWARTS, MJ

    Local muscle fatigue (1 min maximal voluntary contraction) and recovery were studied by means of surface and invasive EMG on elbow flexors to record the changes in muscle fiber conduction velocity (MFCV), median power frequency (MPF), integrated EMG (IEMG), and force. The main finding was a

  8. Neuromuscular fatigue following isometric contractions with similar torque time integral.

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    Rozand, V; Cattagni, T; Theurel, J; Martin, A; Lepers, R

    2015-01-01

    Torque time integral (TTI) is the combination of intensity and duration of a contraction. The aim of this study was to compare neuromuscular alterations following different isometric sub-maximal contractions of the knee extensor muscles but with similar TTI. Sixteen participants performed 3 sustained contractions at different intensities (25%, 50%, and 75% of Maximal Voluntary Contraction (MVC) torque) with different durations (68.5±33.4 s, 35.1±16.8 s and 24.8±12.9 s, respectively) but similar TTI value. MVC torque, maximal voluntary activation level (VAL), M-wave characteristics and potentiated doublet amplitude were assessed before and immediately after the sustained contractions. EMG activity of the vastus lateralis (VL) and -rectus femoris (RF) muscles was recorded during the sustained contractions. MVC torque reduction was similar in the 3 conditions after the exercise (-23.4±2.7%). VAL decreased significantly in a similar extent (-3.1±1.3%) after the 3 sustained contractions. Potentiated doublet amplitude was similarly reduced in the 3 conditions (-19.7±1.5%), but VL and RF M-wave amplitudes remained unchanged. EMG activity of VL and RF muscles increased in the same extent during the 3 contractions (VL: 54.5±40.4%; RF: 53.1±48.7%). These results suggest that central and peripheral alterations accounting for muscle fatigue are similar following isometric contractions with similar TTI. TTI should be considered in the exploration of muscle fatigue during sustained isometric contractions. © Georg Thieme Verlag KG Stuttgart · New York.

  9. Monitoring elbow isometric contraction by novel wearable fabric sensing device

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    Wang, Xi; Tao, Xiaoming; So, Raymond C. H.; Shu, Lin; Yang, Bao; Li, Ying

    2016-12-01

    Fabric-based wearable technology is highly desirable in sports, as it is light, flexible, soft, and comfortable with little interference to normal sport activities. It can provide accurate information on the in situ deformation of muscles in a continuous and wireless manner. During elbow flexion in isometric contraction, upper arm circumference increases with the contraction of elbow flexors, and it is possible to monitor the muscles’ contraction by limb circumferential strains. This paper presents a new wireless wearable anthropometric monitoring device made from fabric strain sensors for the human upper arm. The materials, structural design and calibration of the device are presented. Using an isokinetic testing system (Biodex3®) and the fabric monitoring device simultaneously, in situ measurements were carried out on elbow flexors in isometric contraction mode with ten subjects for a set of positions. Correlations between the measured values of limb circumferential strain and normalized torque were examined, and a linear relationship was found during isometric contraction. The average correlation coefficient between them is 0.938 ± 0.050. This wearable anthropometric device thus provides a useful index, the limb circumferential strain, for upper arm muscle contraction in isometric mode.

  10. Neural adaptations in isometric contractions with EMG and force biofeedback

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    Francisco Locks

    2015-03-01

    Full Text Available This study aimed to evaluate the quadriceps femoris neural adaptations during isometric contractions using force and electromyogram (EMG signals as visual biofeedback. Forty-two participants were randomly assigned to three groups: EMG group, tested with EMG biofeedback; Force group, tested with force biofeedback; and Control group, tested without biofeedback. Evaluations were performed pre (baseline and post-tests to determine the maximum force and EMG amplitude during maximal voluntary isometric contraction (MVIC. The tests consisted of series of MVICs in which the participants were encouraged to surpass the force or EMG thresholds determined at baseline. The vastus lateralis EMG amplitude and knee extensor force increased significantly in all groups when compared the baseline and post-test evaluations values (p < .05. EMG percentage gain was significantly different between Force and Control groups (p < .01, while force percentage gain was not different between groups. Force biofeedback was more effective in producing neural adaptations.

  11. Neural adaptations in isometric contractions with EMG and force biofeedback

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    Francisco Locks; Heleodório Honorato dos Santos; Luis Carlos Carvalho; Lígia Raquel Ortiz Gomes Stolt; José Jamacy de Almeida Ferreira

    2015-01-01

    This study aimed to evaluate the quadriceps femoris neural adaptations during isometric contractions using force and electromyogram (EMG) signals as visual biofeedback. Forty-two participants were randomly assigned to three groups: EMG group, tested with EMG biofeedback; Force group, tested with force biofeedback; and Control group, tested without biofeedback. Evaluations were performed pre (baseline) and post-tests to determine the maximum force and EMG amplitude during maximal voluntary iso...

  12. Effect of muscle mass and intensity of isometric contraction on heart rate.

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    Gálvez, J M; Alonso, J P; Sangrador, L A; Navarro, G

    2000-02-01

    The purpose of this study was to determine the effect of muscle mass and the level of force on the contraction-induced rise in heart rate. We conducted an experimental study in a sample of 28 healthy men between 20 and 30 yr of age (power: 95%, alpha: 5%). Smokers, obese subjects, and those who performed regular physical activity over a certain amount of energetic expenditure were excluded from the study. The participants exerted two types of isometric contractions: handgrip and turning a 40-cm-diameter wheel. Both were sustained to exhaustion at 20 and 50% of maximal force. Twenty-five subjects finished the experiment. Heart rate increased a mean of 15.1 beats/min [95% confidence interval (CI): 5.5-24.6] from 20 to 50% handgrip contractions, and 20.7 beats/min (95% CI: 11.9-29.5) from 20 to 50% wheel-turn contractions. Heart rate also increased a mean of 13.3 beats/min (95% CI: 10.4-16.1) from handgrip to wheel-turn contractions at 20% maximal force, and 18.9 beats/min (95% CI: 9. 8-28.0) from handgrip to wheel-turn contractions at 50% maximal force. We conclude that the magnitude of the heart rate increase during isometric exercise is related to the intensity of the contraction and the mass of the contracted muscle.

  13. Muscle vibration sustains motor unit firing rate during submaximal isometric fatigue in humans.

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    Griffin, L; Garland, S J; Ivanova, T; Gossen, E R

    2001-09-15

    1. In keeping with the 'muscular wisdom hypothesis', many studies have documented that the firing rate of the majority of motor units decreased during fatiguing isometric contractions. The present study investigated whether the application of periodic muscle vibration, which strongly activates muscle spindles, would alter the modulation of motor unit firing rate during submaximal fatiguing isometric contractions. 2. Thirty-three motor units from the lateral head of the triceps brachii muscle were recorded from 10 subjects during a sustained isometric 20 % maximal voluntary contraction (MVC) of the elbow extensors. Vibration was interposed on the contraction for 2 s every 10 s. Twenty-two motor units were recorded from the beginning of the fatigue task. The discharge rate of the majority of motor units remained constant (12/22) or increased (4/22) with fatigue. Six motor units demonstrated a reduction in discharge rate that later returned toward initial values; these motor units had higher initial discharge rates than the other 16 motor units. 3. In a second series of experiments, four subjects held a sustained isometric 20 % MVC for 2 min and then vibration was applied as above for the remainder of the contraction. In this case, motor units initially demonstrated a decrease in firing rate that increased after the vibration was applied. Thus muscle spindle disfacilitation of the motoneurone pool may be associated with the decline of motor unit discharge rate observed during the first 2 min of the contraction. 4. In a third set of experiments, seven subjects performed the main experiment on one occasion and repeated the fatigue task without vibration on a second occasion. Neither the endurance time of the fatiguing contraction nor the MVC torque following fatigue was affected by the application of vibration. This finding calls into question the applicability of the muscular wisdom hypothesis to submaximal contractions.

  14. Motor Unit Activity during Fatiguing Isometric Muscle Contraction in Hemispheric Stroke Survivors

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    Lara McManus

    2017-11-01

    Full Text Available Enhanced muscle weakness is commonly experienced following stroke and may be accompanied by increased susceptibility to fatigue. To examine the contributions of central and peripheral factors to isometric muscle fatigue in stroke survivors, this study investigates changes in motor unit (MU mean firing rate, and action potential duration during, and directly following, a sustained submaximal fatiguing contraction at 30% maximum voluntary contraction (MVC. A series of short contractions of the first dorsal interosseous muscle were performed pre- and post-fatigue at 20% MVC, and again following a 10-min recovery period, by 12 chronic stroke survivors. Individual MU firing times were extracted using surface EMG decomposition and used to obtain the spike-triggered average MU action potential waveforms. During the sustained fatiguing contraction, the mean rate of change in firing rate across all detected MUs was greater on the affected side (-0.02 ± 0.03 Hz/s than on the less-affected side (-0.004 ± 0.003 Hz/s, p = 0.045. The change in firing rate immediately post-fatigue was also greater on the affected side than less-affected side (-13.5 ± 20 and 0.1 ± 19%, p = 0.04. Mean MU firing rates increased following the recovery period on the less-affected side when compared to the affected side (19.3 ± 17 and 0.5 ± 20%, respectively, p = 0.03. MU action potential duration increased post-fatigue on both sides (10.3 ± 1.2 to 11.2 ± 1.3 ms on the affected side and 9.9 ± 1.7 to 11.2 ± 1.9 ms on the less-affected side, p = 0.001 and p = 0.02, respectively, and changes in action potential duration tended to be smaller in subjects with greater impairment (p = 0.04. This study presents evidence of both central and peripheral fatigue at the MU level during isometric fatiguing contraction for the first time in stroke survivors. Together, these preliminary observations indicate that the response to an isometric fatiguing contraction differs between the

  15. Sub-sarcolemmal swelling of sarcoplasmic reticulum after isometric contractions in rat semimembranosus lateralis muscle

    NARCIS (Netherlands)

    Willems, M.E.T.; Huijing, P.A.J.B.M.; Friden, J.

    1999-01-01

    The decline in isometric force, swelling of sarcoplasmic reticulum and loss of desmin was measured in semimembranosus lateralis muscle of male Wistar rats immediately after a short series of brief (500 ms) maximal isometric contractions. For the active muscle, the series ended below (protocol A) and

  16. Differences between measured and resultant joint moments during isometric contractions at the ankle joint.

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    Arampatzis, Adamantios; Morey-Klapsing, Gaspar; Karamanidis, Kiros; DeMonte, Gianpiero; Stafilidis, Savvas; Brüggemann, Gert-Peter

    2005-04-01

    The purpose of this study was to examine two hypotheses: (a) during voluntary and electrically induced isometric contractions the moments measured at the dynamometer are different from the resultant moments in the same plane around the ankle joint and (b) at a given resultant moment during electrically induced isometric contractions the ankle angle while loading is different from the ankle angle while unloading. Twenty-seven long distance runners participated in the study. All subjects performed isometric maximal voluntary contractions (MVC) and contractions induced by electrostimulation at four different ankle-knee angle combinations on a Biodex-dynamometer. The kinematics of the leg were recorded using the vicon 624 system with eight cameras operating at 120 Hz. The main findings were: (a) the resultant moment at the ankle joint and the moment measured by the Biodex-dynamometer during isometric contractions are different, (b) during a plantar flexion effort the ankle angle changes significantly, whereas the knee angle shows only small and in most cases not significant changes, and (c) at identical resultant ankle joint moments the ankle angles are different between the loading and the unloading phases. The observed differences may lead to erroneous conclusions concerning the following: (a) diagnostic of muscle architecture, (b) estimation of the moment-ankle angle relationship and (c) estimation of the strain and hysteresis of tendons and aponeuroses.

  17. Effects of Contract-Relax, Static Stretching, and Isometric Contractions on Muscle-Tendon Mechanics.

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    Kay, Anthony D; Husbands-Beasley, Jade; Blazevich, Anthony J

    2015-10-01

    Loading characteristics of stretching techniques likely influence the specific mechanisms responsible for acute increases in range of motion (ROM). Therefore, the effects of a version of contract-relax (CR) proprioceptive neuromuscular facilitation stretching, static stretching (SS), and maximal isometric contraction (Iso) interventions were studied in 17 healthy human volunteers. Passive ankle moment was recorded on an isokinetic dynamometer, with EMG recording from the triceps surae, simultaneous real-time motion analysis, and ultrasound-imaging-recorded gastrocnemius medialis muscle and Achilles tendon elongation. Subjects then performed each intervention randomly on separate days before reassessment. Significant increases in dorsiflexion ROM (2.5°-5.3°; P stretching (P stretching and Iso (17.7%-22.1%; P 0.05), whereas significant reductions in muscle stiffness occurred after CR stretching and SS (16.0%-20.5%; P 0.05). Increases in peak passive moment (stretch tolerance) occurred after Iso (6.8%; P stretching (10.6%; P = 0.08), and SS (5.2%; P = 0.08); no difference in changes between conditions was found (P > 0.05). Significant correlations (rs = 0.69-0.82; P stretching suggest a broader adaptive response that likely explains its superior efficacy in acutely increasing ROM. Although mechanical changes appear tissue-specific between interventions, similar increases in stretch tolerance after all interventions are strongly correlated with changes in ROM.

  18. Spectral properties of electromyographic and mechanomyographic signals during isometric ramp and step contractions in biceps brachii.

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    Qi, Liping; Wakeling, James M; Green, Adam; Lambrecht, Kirstin; Ferguson-Pell, Martin

    2011-02-01

    The purposes of this study were: (1) to apply wavelet and principal component analysis to quantify the spectral properties of the surface EMG and MMG signals from biceps brachii during isometric ramp and step muscle contractions when the motor units are recruited in an orderly manner, and (2) to compare the recruitment patterns of motor unit during isometric ramp and step muscle contractions. Twenty healthy participants (age = 34 ± 10.7 years) performed step and ramped isometric contractions. Surface EMG and MMG were recorded from biceps brachii. The EMGs and MMGs were decomposed into their intensities in time-frequency space using a wavelet technique. The EMG and MMG spectra were then compared using principal component analysis (PCA) and ANCOVA. Wavelet combined PCA offers a quantitative measure of the contribution of high and low frequency content within the EMG and MMG. The ANCOVA indicated that there was no significant difference in EMG total intensity, EMG(MPF), first and second principal component loading scores (PCI and PCII) between ramp and step contractions, whereas the MMG(MPF) and MMG PCI loading scores were significantly higher during ramp contractions than during step contractions. These findings suggested that EMG and MMG may offer complimentary information regarding the interactions between motor unit recruitment and firing rate that control muscle force production. In addition, our results support the hypothesis that different motor unit recruitment strategy was used by the muscle when contracting under different conditions. Copyright © 2010 Elsevier Ltd. All rights reserved.

  19. Effects of Isometric Hand-Grip Muscle Contraction on Young Adults' Free Recall and Recognition Memory

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    Tomporowski, Phillip D.; Albrecht, Chelesa; Pendleton, Daniel M.

    2017-01-01

    Purpose: The purpose of this study was to determine if physical arousal produced by isometric hand-dynamometer contraction performed during word-list learning affects young adults' free recall or recognition memory. Method: Twenty-four young adults (12 female; M[subscript age] = 22 years) were presented with 4 20-item word lists. Moderate arousal…

  20. Age and Sex Effects on the Active Stiffness of Vastus Intermedius under Isometric Contraction

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    Cong-Zhi Wang

    2017-01-01

    Full Text Available Previously, a novel technique was proposed to quantify the relationship between the muscle stiffness and its nonfatigue contraction intensity. The method extended the measured range of isometric contraction to 100% maximum voluntary contraction (MVC using an ultrasonic shear wave measurement setup. Yet, it has not been revealed how this relationship could be affected by factors like age or sex. To clarify these questions, vastus intermedius (VI stiffness of 40 healthy subjects was assessed under 11 step levels of isometric contraction. The subjects were divided into four groups: young males, young females, elderly males, and elderly females (n=10 for each. In a relaxed state, no significant difference was observed between the male and female subjects (p=0.156 nor between the young and elderly subjects (p=0.221. However, when performing isometric contraction, the VI stiffness of males was found to be significantly higher than that of females at the same level (p<0.001, and that of the young was higher than the elderly (p<0.001. Meanwhile, for two knee joint angles used, the stiffness measured at a 90° knee joint angle was always significantly larger than that measured at 60° (p<0.001. Recognizing the active muscle stiffness of VI contributes to body stability, and these results may provide insight into the age and sex bias in musculoskeletal studies, such as those on fall risks.

  1. Differences between measured and resultant joint moments during voluntary and artificially elicited isometric knee extension contractions.

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    Arampatzis, Adamantios; Karamanidis, Kiros; De Monte, Gianpiero; Stafilidis, Savvas; Morey-Klapsing, Gaspar; Brüggemann, Gert-Peter

    2004-03-01

    Examine two hypotheses: (a) during isometric knee extension contractions the moment measured at the dynamometer is different from the resultant moment in the same plane around the knee joint and (b) during isometric contractions, at the same given resultant moment the knee angle while loading is different from the knee angle while unloading. Comparative study in which the geometrical and the kinetic differences between joint and dynamometer were determined. It is usually assumed that the moment measured by the dynamometer is equivalent to the resultant joint moment. The non-rigidity of the dynamometer-leg system can influence the equivalence of these two moments. Twenty seven subjects performed isometric maximal knee extension contractions and contractions induced by electrostimulation on a dynamometer. The kinematics of the leg were recorded using 8 cameras (120 Hz). The resultant moment at the knee joint and the moment measured by the dynamometer are different. During a knee extension effort the knee angle changes significantly. At identical resultant knee joint moments the knee angles are different when comparing the loading and the unloading phases. The differences between the measured and the resultant joint moments might influence the estimation of parameters as: muscle forces, moment-angle relationship and strain and hysteresis of tendons and aponeuroses. Torque dynamometers have been often used to estimate muscle forces, to examine neuromuscular processes and to determine the mechanical properties of tendons and aponeuroses.

  2. Thigh and calf blood flows after isometric contraction in untrained and trained subjects.

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    Kitamura, K; Shimaoka, M; Matsui, H; Miyamura, M

    1983-01-01

    The present study was undertaken to examine whether or not there were any differences between untrained and trained subjects in the changes of blood flow in the ipsilateral and contralateral lower limbs after isometric exercise. Blood flow of the thigh and calf in both right and left legs were measured simultaneously before and after isometric contraction with mercury-in-silastic strain gauge venous occlusion plethysmography. In the present study, the main pattern of blood flow responses in the active and non-active limbs was strikingly similar in all subjects: a significant fall in blood flow immediately after isometric contraction at a force of about 50% of maximal muscle strength for 15 sec was observed in the non-active lower limbs. Peak blood flow of the exercised thigh in the trained group was significantly higher than that in the untrained ones. From these results, it was suggested that higher blood flow after isometric exercise in the trained subjects may be due to the improvement of degree of vasodilation in the lower limb as a result of physical training.

  3. Handgrip Maximal Voluntary Isometric Contraction Does Not Correlate with Thenar Motor Unit Number Estimation

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    Arun Aggarwal

    2012-01-01

    Full Text Available In slowly progressive conditions, such as motor neurone disease (MND, 50–80% of motor units may be lost before weakness becomes clinically apparent. Despite this, maximal voluntary isometric contraction (MVIC has been reported as a clinically useful, reliable, and reproducible measure for monitoring disease progression in MND. We performed a study on a group of asymptomatic subjects that showed a lack of correlation between isometric grip strength and thenar MUNE. Motor unit number estimation (MUNE estimates the number of functioning lower motor neurones innervating a muscle or a group of muscles. We used the statistical electrophysiological technique of MUNE to estimate the number of motor units in thenar group of muscles in 69 subjects: 19 asymptomatic Cu, Zn superoxide dismutase 1 (SOD 1 mutation carriers, 34 family controls, and 16 population controls. The Jamar hand dynamometer was used to measure isometric grip strength. This study suggests that MUNE is more sensitive for monitoring disease progression than maximal voluntary isometric contraction (MVIC, as MUNE correlates with the number of functional motor neurones. This supports the observation that patients with substantial chronic denervation can maintain normal muscle twitch tension until 50–80% of motor units are lost and weakness is detectable.

  4. Image Based Calculation of Perfusion and Oxyhemoglobin Saturation in Skeletal Muscle during Submaximal Isometric Contractions

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    Elder, Christopher P.; Cook, Ryan N.; Chance, Marti A.; Copenhaver, Elizabeth A.; Damon, Bruce M.

    2010-01-01

    The relative oxygen saturation of hemoglobin (%HbO2) and the rate of perfusion (θ̇) are important physiological quantities, particularly in organs such as skeletal muscle in which oxygen delivery and use are tightly coupled. The purpose of this study was to demonstrate the image-based calculation of %HbO2 and quantification of perfusion in skeletal muscle during isometric contractions. This was accomplished by establishing an empirical relationship between the rate of RF-reversible dephasing ...

  5. Image Based Calculation of Perfusion and Oxyhemoglobin Saturation in Skeletal Muscle during Submaximal Isometric Contractions

    Science.gov (United States)

    Elder, Christopher P.; Cook, Ryan N.; Chance, Marti A.; Copenhaver, Elizabeth A.; Damon, Bruce M.

    2015-01-01

    The relative oxygen saturation of hemoglobin (%HbO2) and the rate of perfusion (θ̇) are important physiological quantities, particularly in organs such as skeletal muscle in which oxygen delivery and use are tightly coupled. The purpose of this study was to demonstrate the image-based calculation of %HbO2 and quantification of perfusion in skeletal muscle during isometric contractions. This was accomplished by establishing an empirical relationship between the rate of RF-reversible dephasing (R2′) and near infrared spectroscopy (NIRS)-observed oxyhemoglobin saturation (%HbO2) under conditions of arterial occlusion and constant blood volume. A calibration curve was generated and used to calculate %HbO2 from R2′ changes measured during contraction. Twelve young healthy subjects underwent 300 seconds of arterial occlusion and performed isometric contractions of the dorsiflexors at 30% of maximal contraction for 120s. Muscle perfusion was quantified during contraction by arterial spin labeling and measures of muscle T1. Comparisons between the %HbO2 values predicted from R2′ and that measured by NIRS revealed no differences between methods (p = 0.760). Muscle perfusion reached a value of 34.7 mL 100g−1 min−1 during contraction. These measurements hold future promise in measuring muscle oxygen consumption in healthy and diseased skeletal muscle. PMID:20806379

  6. Image-based calculation of perfusion and oxyhemoglobin saturation in skeletal muscle during submaximal isometric contractions.

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    Elder, Christopher P; Cook, Ryan N; Chance, Marti A; Copenhaver, Elizabeth A; Damon, Bruce M

    2010-09-01

    The relative oxygen saturation of hemoglobin and the rate of perfusion are important physiological quantities, particularly in organs such as skeletal muscle, in which oxygen delivery and use are tightly coupled. The purpose of this study was to demonstrate the image-based calculation of the relative oxygen saturation of hemoglobin and quantification of perfusion in skeletal muscle during isometric contractions. This was accomplished by establishing an empirical relationship between the rate of radiofrequency-reversible dephasing and near-infrared spectroscopy-observed oxyhemoglobin saturation (relative oxygen saturation of hemoglobin) under conditions of arterial occlusion and constant blood volume. A calibration curve was generated and used to calculate the relative oxygen saturation of hemoglobin from radiofrequency-reversible dephasing changes measured during contraction. Twelve young healthy subjects underwent 300 s of arterial occlusion and performed isometric contractions of the dorsiflexors at 30% of maximal contraction for 120 s. Muscle perfusion was quantified during contraction by arterial spin labeling and measures of muscle T(1). Comparisons between the relative oxygen saturation of hemoglobin values predicted from radiofrequency-reversible dephasing and that measured by near-infrared spectroscopy revealed no differences between methods (P = 0.760). Muscle perfusion reached a value of 34.7 mL 100 g(-1) min(-1) during contraction. These measurements hold future promise in measuring muscle oxygen consumption in healthy and diseased skeletal muscle. 2010 Wiley-Liss, Inc.

  7. A mathematical model of forces in the knee under isometric quadriceps contractions.

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    Huss, R A; Holstein, H; O'Connor, J J

    2000-02-01

    To predict the knee's response to isometric quadriceps contractions against a fixed tibial restraint.Design. Mathematical modelling of the human knee joint. Isometric quadriceps contraction is commonly used for leg muscle strengthening following ligament injury or reconstruction. It is desirable to know the ligament forces induced but direct measurement is difficult. The model, previously applied to the Lachmann or 'drawer' tests, combines an extensible fibre-array representation of the cruciate ligaments with a compressible 'thin-layer' representation of the cartilage. The model allows the knee configuration and force system to be calculated, given flexion angle, restraint position and loading. Inclusion of cartilage deformation increases relative tibio-femoral translation and decreases the ligament forces generated. For each restraint position, a range of flexion angles is found in which no ligament force is required, as opposed to a single flexion angle in the case of incompressible cartilage layers. Knee geometry and ligament elasticity are found to be the most important factors governing the joint's response to isometric quadriceps contractions, but cartilage deformation is found to be more important than in the Lachmann test. Estimation of knee ligament forces is important when devising exercise regimes following ligament injury or reconstruction. The finding of a 'neutral zone' of zero ligament force may have implications for rehabilitation of the ligament-injured knee.

  8. Dystonic neck muscles show a shift in relative autospectral power during isometric contractions.

    Science.gov (United States)

    De Bruijn, E; Nijmeijer, S W R; Forbes, P A; Koelman, J H T M; Van Der Helm, F C T; Tijssen, M A J; Happee, R

    2017-10-01

    To identify effects of a deviant motor drive in the autospectral power of dystonic muscles during voluntary contraction in cervical dystonia patients. Submaximal (20%) isometric head-neck tasks were performed with the head fixed, measuring surface EMG of the sternocleidomastoid, splenius capitis and semispinalis capitis in CD patients and controls. Autospectral power of muscle activity, and head forces was analyzed using cumulative distribution functions (CDF). A downward shift between the theta/low alpha-band (3-10Hz) and the high alpha/beta-band (10-30Hz) was detected using the CDF10, defined as the cumulative power from 3 to 10Hz relative to power from 3 to 30Hz. CDF10 was increased in dystonic muscles compared to controls and patient muscles unaffected by dystonia, due to a 3-10Hz power increase and a 10-30Hz decrease. CDF10 also increased in patient head forces. Submaximal isometric contractions with the head fixed provided a well-defined test condition minimizing effects of reflexive feedback and tremor. We associate shifts in autospectral power with prokinetic sensorimotor control. Analysis of autospectral power in isometric tasks with the head fixed is a promising approach in research and diagnostics of cervical dystonia. Copyright © 2017 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved.

  9. Discharge properties of motor units during steady isometric contractions performed with the dorsiflexor muscles

    Science.gov (United States)

    Klass, Malgorzata; Duchateau, Jacques; Enoka, Roger M.

    2012-01-01

    The purpose of this study was to record the discharge characteristics of tibialis anterior motor units over a range of target forces and to import these data, along with previously reported observations, into a computational model to compare experimental and simulated measures of torque variability during isometric contractions with the dorsiflexor muscles. The discharge characteristics of 44 motor units were quantified during brief isometric contractions at torques that ranged from recruitment threshold to an average of 22 ± 14.4% maximal voluntary contraction (MVC) torque above recruitment threshold. The minimal [range: 5.8–19.8 pulses per second (pps)] and peak (range: 8.6–37.5 pps) discharge rates of motor units were positively related to the recruitment threshold torque (R2 ≥ 0.266; P torque (R2 = 0.443; P torque increased above recruitment threshold torque. The variability in the simulated torque did not differ from the experimental values once the recruitment range was set to ∼85% MVC torque, and the association between motor twitch contraction times and peak twitch torque was defined as a weak linear association (R2 = 0.096; P muscle depended more on the distributions of mechanical properties than discharge properties across the population of motor units in the tibialis anterior. PMID:22442023

  10. 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.

  11. MEG Insight into the Spectral Dynamics Underlying Steady Isometric Muscle Contraction

    Science.gov (United States)

    Piitulainen, Harri; Zhou, Guangyu

    2017-01-01

    To gain fundamental knowledge on how the brain controls motor actions, we studied in detail the interplay between MEG signals from the primary sensorimotor (SM1) cortex and the contraction force of 17 healthy adult humans (7 females, 10 males). SM1 activity was coherent at ∼20 Hz with surface electromyogram (as already extensively reported) but also with contraction force. In both cases, the effective coupling was dominant in the efferent direction. Across subjects, the level of ∼20 Hz coherence between cortex and periphery positively correlated with the “burstiness” of ∼20 Hz SM1 (Pearson r ≈ 0.65) and peripheral fluctuations (r ≈ 0.9). Thus, ∼20 Hz coherence between cortex and periphery is tightly linked to the presence of ∼20 Hz bursts in SM1 and peripheral activity. However, the very high correlation with peripheral fluctuations suggests that the periphery is the limiting factor. At frequencies signals and ∼20 Hz SM1 envelope were coherent with both force and its absolute change rate. The effective coupling dominated in the efferent direction between (1) force and the ∼20 Hz SM1 envelope and (2) the absolute change rate of the force and SM1 signals. Together, our data favor the view that ∼20 Hz coherence between cortex and periphery during isometric contraction builds on the presence of ∼20 Hz SM1 oscillations and needs not rely on feedback from the periphery. They also suggest that effective cortical proprioceptive processing operates at <3 Hz frequencies, even during steady isometric contractions. SIGNIFICANCE STATEMENT Accurate motor actions are made possible by continuous communication between the cortex and spinal motoneurons, but the neurophysiological basis of this communication is poorly understood. Using MEG recordings in humans maintaining steady isometric muscle contractions, we found evidence that the cortex sends population-level motor commands that tend to structure according to the ∼20 Hz sensorimotor rhythm, and that

  12. Suppression of Oxidative Stress by Resveratrol After Isometric Contractions in Gastrocnemius Muscles of Aged Mice

    Science.gov (United States)

    Ryan, Michael J.; Jackson, Janna R.; Hao, Yanlei; Williamson, Courtney L.; Dabkowski, Erinne R.; Hollander, John M.

    2010-01-01

    This study tested the hypothesis that resveratrol supplementation would lower oxidative stress in exercised muscles of aged mice. Young (3 months) and aged (27 months) C57BL/6 mice received a control or a 0.05% trans-resveratrol-supplemented diet for 10 days. After 7 days of dietary intervention, 20 maximal electrically evoked isometric contractions were obtained from the plantar flexors of one limb in anesthetized mice. Exercise was conducted for three consecutive days. Resveratrol supplementation blunted the exercise-induced increase in xanthine oxidase activity in muscles from young (25%) and aged (53%) mice. Resveratrol lowered H2O2 levels in control (13%) and exercised (38%) muscles from aged animals, reduced Nox4 protein in both control and exercised muscles of young (30%) and aged mice (40%), and increased the ratio of reduced glutathione to oxidized glutathione in exercised muscles from young (38%) and aged (135%) mice. Resveratrol prevented the increase in lipid oxidation, increased catalase activity, and increased MnSOD activity in exercised muscles from aged mice. These data show that dietary resveratrol suppresses muscle indicators of oxidative stress in response to isometric contractions in aged mice. PMID:20507922

  13. Smooth muscle modeling and experimental identification: application to bladder isometric contraction

    Science.gov (United States)

    Laforêt, Jérémy; Guiraud, David; Andreu, David; Taillades, Hubert; Azevedo Coste, Christine

    2011-06-01

    This paper presents an original smooth muscle model based on the Huxley microscopic approach. This model is the main part of a comprehensive lower urinary track model. The latter is used for simulation studies and is assessed through experiments on rabbits, for which a subset of parameters is estimated, using intravesical pressure measurements in isometric conditions. Bladder contraction is induced by electrical stimulation that determines the onset and thus synchronizes simulation and experimental data. Model sensitivity versus parameter accuracy is discussed and allows the definition of a subset of four parameters that must be accurately identified in order to obtain good fitting between experimental and acquired data. Preliminary experimental data are presented as well as model identification results. They show that the model is able to follow the pressure changes induced by an artificial stimulus in isometric contractions. Moreover, the model gives an insight into the internal changes in calcium concentration and the ratio of the different chemical species present in the muscle cells, in particular the bounded and unbounded actin and myosin and the normalized concentration of intracellular calcium.

  14. Structural changes in isometrically contracting insect flight muscle trapped following a mechanical perturbation.

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    Shenping Wu

    Full Text Available The application of rapidly applied length steps to actively contracting muscle is a classic method for synchronizing the response of myosin cross-bridges so that the average response of the ensemble can be measured. Alternatively, electron tomography (ET is a technique that can report the structure of the individual members of the ensemble. We probed the structure of active myosin motors (cross-bridges by applying 0.5% changes in length (either a stretch or a release within 2 ms to isometrically contracting insect flight muscle (IFM fibers followed after 5-6 ms by rapid freezing against a liquid helium cooled copper mirror. ET of freeze-substituted fibers, embedded and thin-sectioned, provides 3-D cross-bridge images, sorted by multivariate data analysis into ~40 classes, distinct in average structure, population size and lattice distribution. Individual actin subunits are resolved facilitating quasi-atomic modeling of each class average to determine its binding strength (weak or strong to actin. ~98% of strong-binding acto-myosin attachments present after a length perturbation are confined to "target zones" of only two actin subunits located exactly midway between successive troponin complexes along each long-pitch helical repeat of actin. Significant changes in the types, distribution and structure of actin-myosin attachments occurred in a manner consistent with the mechanical transients. Most dramatic is near disappearance, after either length perturbation, of a class of weak-binding cross-bridges, attached within the target zone, that are highly likely to be precursors of strong-binding cross-bridges. These weak-binding cross-bridges were originally observed in isometrically contracting IFM. Their disappearance following a quick stretch or release can be explained by a recent kinetic model for muscle contraction, as behaviour consistent with their identification as precursors of strong-binding cross-bridges. The results provide a detailed

  15. Theta power decreases in preparation for voluntary isometric contractions performed with maximal subjective effort.

    Science.gov (United States)

    Weiss, T; Sust, M; Beyer, L; Hansen, E; Rost, R; Schmalz, T

    1995-07-07

    In order to find EEG parameters that can be attributed to movements performed with maximal subjective effort, EEG recordings and force measurements were realized in connection with isometric contractions (IMC). IMC were performed with submaximal and maximal subjective effort. Mean spectral power density within the theta band was found as an indicator for maximal subjective effort. The theta power across the parieto-occipital area decreases from rest through movements performed with submaximal force to movements performed with maximal effort. It is argued that this theta decrease possibly reflects a down-regulation of the posterior attention system in order to minimize the influences of external stimuli during the preparation for voluntary IMC performed with maximal subjective effort.

  16. Electron tomography of cryofixed, isometrically contracting insect flight muscle reveals novel actin-myosin interactions.

    Directory of Open Access Journals (Sweden)

    Shenping Wu

    2010-09-01

    Full Text Available Isometric muscle contraction, where force is generated without muscle shortening, is a molecular traffic jam in which the number of actin-attached motors is maximized and all states of motor action are trapped with consequently high heterogeneity. This heterogeneity is a major limitation to deciphering myosin conformational changes in situ.We used multivariate data analysis to group repeat segments in electron tomograms of isometrically contracting insect flight muscle, mechanically monitored, rapidly frozen, freeze substituted, and thin sectioned. Improved resolution reveals the helical arrangement of F-actin subunits in the thin filament enabling an atomic model to be built into the thin filament density independent of the myosin. Actin-myosin attachments can now be assigned as weak or strong by their motor domain orientation relative to actin. Myosin attachments were quantified everywhere along the thin filament including troponin. Strong binding myosin attachments are found on only four F-actin subunits, the "target zone", situated exactly midway between successive troponin complexes. They show an axial lever arm range of 77°/12.9 nm. The lever arm azimuthal range of strong binding attachments has a highly skewed, 127° range compared with X-ray crystallographic structures. Two types of weak actin attachments are described. One type, found exclusively in the target zone, appears to represent pre-working-stroke intermediates. The other, which contacts tropomyosin rather than actin, is positioned M-ward of the target zone, i.e. the position toward which thin filaments slide during shortening.We present a model for the weak to strong transition in the myosin ATPase cycle that incorporates azimuthal movements of the motor domain on actin. Stress/strain in the S2 domain may explain azimuthal lever arm changes in the strong binding attachments. The results support previous conclusions that the weak attachments preceding force generation are very

  17. Electron Tomography of Cryofixed, Isometrically Contracting Insect Flight Muscle Reveals Novel Actin-Myosin Interactions

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Shenping; Liu, Jun; Reedy, Mary C.; Tregear, Richard T.; Winkler, Hanspeter; Franzini-Armstrong, Clara; Sasaki, Hiroyuki; Lucaveche, Carmen; Goldman, Yale E.; Reedy, Michael K.; Taylor, Kenneth A. (UPENN); (Duke); (MRCLMB); (FSU); (Jikei-Med)

    2010-10-22

    Isometric muscle contraction, where force is generated without muscle shortening, is a molecular traffic jam in which the number of actin-attached motors is maximized and all states of motor action are trapped with consequently high heterogeneity. This heterogeneity is a major limitation to deciphering myosin conformational changes in situ. We used multivariate data analysis to group repeat segments in electron tomograms of isometrically contracting insect flight muscle, mechanically monitored, rapidly frozen, freeze substituted, and thin sectioned. Improved resolution reveals the helical arrangement of F-actin subunits in the thin filament enabling an atomic model to be built into the thin filament density independent of the myosin. Actin-myosin attachments can now be assigned as weak or strong by their motor domain orientation relative to actin. Myosin attachments were quantified everywhere along the thin filament including troponin. Strong binding myosin attachments are found on only four F-actin subunits, the 'target zone', situated exactly midway between successive troponin complexes. They show an axial lever arm range of 77{sup o}/12.9 nm. The lever arm azimuthal range of strong binding attachments has a highly skewed, 127{sup o} range compared with X-ray crystallographic structures. Two types of weak actin attachments are described. One type, found exclusively in the target zone, appears to represent pre-working-stroke intermediates. The other, which contacts tropomyosin rather than actin, is positioned M-ward of the target zone, i.e. the position toward which thin filaments slide during shortening. We present a model for the weak to strong transition in the myosin ATPase cycle that incorporates azimuthal movements of the motor domain on actin. Stress/strain in the S2 domain may explain azimuthal lever arm changes in the strong binding attachments. The results support previous conclusions that the weak attachments preceding force generation are

  18. Predictability of maximum voluntary isometric knee extension force from submaximal contractions in older adults.

    Science.gov (United States)

    Stackhouse, Scott K; Stevens, Jennifer E; Johnson, Christopher D; Snyder-Mackler, Lynn; Binder-Macleod, Stuart A

    2003-01-01

    The purposes of this study were to develop and test a model describing the relationship between the central activation ratio (CAR; a measure of voluntary muscle activation) and percent maximum voluntary contraction (%MVC) force for old adults and to provide a method for more accurate determination of voluntary muscle activation failure. Twenty-one adults (ages 64-81) performed isometric testing of the quadriceps at 25%, 50%, 75%, and 100% MVC. During each contraction, a 100-HZ, 120-ms train of electrical pulses was delivered to the quadriceps muscle to quantify voluntary muscle activation. Similar to a young, healthy population (ages 20-35), a curvilinear relationship existed between the CAR and %MVC force for older adults. Predictions of subjects' MVCs using the linear model of CAR-%MVC force relationship generally demonstrated poor agreement with actual MVCs. Predictions of MVC from submaximal contractions (25%, 50%, and 75%) using a previously identified curvilinear young adult CAR-%MVC relationship were good [ICC (2,1): 0.81, 0.96, and 0.82, respectively]. Similar agreement was obtained from the curvilinear older adult CAR-%MVC relationship. These data suggest that the CAR-%MVC relationship is similar in young and older adult subjects and that curvilinear models of this relationship can predict MVC forces in older adults more accurately. Reexamination of the relationship between the CAR and %MVC force may allow a more accurate determination of how failure of voluntary muscle activation contributes to weakness in old adults.

  19. A Review of Classification Techniques of EMG Signals during Isotonic and Isometric Contractions

    Directory of Open Access Journals (Sweden)

    Nurhazimah Nazmi

    2016-08-01

    Full Text Available In recent years, there has been major interest in the exposure to physical therapy during rehabilitation. Several publications have demonstrated its usefulness in clinical/medical and human machine interface (HMI applications. An automated system will guide the user to perform the training during rehabilitation independently. Advances in engineering have extended electromyography (EMG beyond the traditional diagnostic applications to also include applications in diverse areas such as movement analysis. This paper gives an overview of the numerous methods available to recognize motion patterns of EMG signals for both isotonic and isometric contractions. Various signal analysis methods are compared by illustrating their applicability in real-time settings. This paper will be of interest to researchers who would like to select the most appropriate methodology in classifying motion patterns, especially during different types of contractions. For feature extraction, the probability density function (PDF of EMG signals will be the main interest of this study. Following that, a brief explanation of the different methods for pre-processing, feature extraction and classifying EMG signals will be compared in terms of their performance. The crux of this paper is to review the most recent developments and research studies related to the issues mentioned above.

  20. A Review of Classification Techniques of EMG Signals during Isotonic and Isometric Contractions

    Science.gov (United States)

    Nazmi, Nurhazimah; Abdul Rahman, Mohd Azizi; Yamamoto, Shin-Ichiroh; Ahmad, Siti Anom; Zamzuri, Hairi; Mazlan, Saiful Amri

    2016-01-01

    In recent years, there has been major interest in the exposure to physical therapy during rehabilitation. Several publications have demonstrated its usefulness in clinical/medical and human machine interface (HMI) applications. An automated system will guide the user to perform the training during rehabilitation independently. Advances in engineering have extended electromyography (EMG) beyond the traditional diagnostic applications to also include applications in diverse areas such as movement analysis. This paper gives an overview of the numerous methods available to recognize motion patterns of EMG signals for both isotonic and isometric contractions. Various signal analysis methods are compared by illustrating their applicability in real-time settings. This paper will be of interest to researchers who would like to select the most appropriate methodology in classifying motion patterns, especially during different types of contractions. For feature extraction, the probability density function (PDF) of EMG signals will be the main interest of this study. Following that, a brief explanation of the different methods for pre-processing, feature extraction and classifying EMG signals will be compared in terms of their performance. The crux of this paper is to review the most recent developments and research studies related to the issues mentioned above. PMID:27548165

  1. Test-retest reliability of muscle fiber conduction velocity and fractal dimension of surface EMG during isometric contractions.

    Science.gov (United States)

    Beretta-Piccoli, Matteo; D'Antona, Giuseppe; Zampella, Cristian; Barbero, Marco; Clijsen, Ron; Cescon, Corrado

    2017-04-01

    The aim of this study was to determine the test-retest reliability of muscle fiber conduction velocity (CV) and fractal dimension (FD) obtained from multichannel surface electromyographic (sEMG) recordings. Forty healthy recreationally active subjects (20 men and 20 women) performed two elbow flexions on two trials with a 1 week interval. The first was a 20% maximal voluntary contraction (MVC) of 120 s, and the second at 60% MVC held until exhaustion. sEMG signals were detected from the biceps brachii, using bi-dimensional arrays. Initial values and slope of CV and FD were used for the reliability analysis. The intraclass correlation coefficient (ICC) values for the isometric contraction at 20% MVC were (-0.09) and 0.67 for CV and FD respectively; whereas the ICC values at 60% MVC were 0.78 and 0.82 for CV and FD respectively. The Bland Altman plots for the two isometric contractions showed a mean difference close to zero, with no evident outliers between the repeated measurements: at 20% MVC 0.001 53 for FD and  -0.0277 for CV, and at 60% MVC 0.006 66 for FD and 0.009 07 for CV. Overall, our findings suggest that during isometric fatiguing contractions, CV and FD slopes are reliable variables, with potential application in clinical populations.

  2. A comparison of two gluteus maximus EMG maximum voluntary isometric contraction positions.

    Science.gov (United States)

    Contreras, Bret; Vigotsky, Andrew D; Schoenfeld, Brad J; Beardsley, Chris; Cronin, John

    2015-01-01

    Background. The purpose of this study was to compare the peak electromyography (EMG) of the most commonly-used position in the literature, the prone bent-leg (90°) hip extension against manual resistance applied to the distal thigh (PRONE), to a novel position, the standing glute squeeze (SQUEEZE). Methods. Surface EMG electrodes were placed on the upper and lower gluteus maximus of thirteen recreationally active females (age = 28.9 years; height = 164 cm; body mass = 58.2 kg), before three maximum voluntary isometric contraction (MVIC) trials for each position were obtained in a randomized, counterbalanced fashion. Results. No statistically significant (p < 0.05) differences were observed between PRONE (upper: 91.94%; lower: 94.52%) and SQUEEZE (upper: 92.04%; lower: 85.12%) for both the upper and lower gluteus maximus. Neither the PRONE nor SQUEEZE was more effective between all subjects. Conclusions. In agreement with other studies, no single testing position is ideal for every participant. Therefore, it is recommended that investigators employ multiple MVIC positions, when possible, to ensure accuracy. Future research should investigate a variety of gluteus maximus MVIC positions in heterogeneous samples.

  3. A comparison of two gluteus maximus EMG maximum voluntary isometric contraction positions

    Science.gov (United States)

    Contreras, Bret; Schoenfeld, Brad J.; Beardsley, Chris; Cronin, John

    2015-01-01

    Background. The purpose of this study was to compare the peak electromyography (EMG) of the most commonly-used position in the literature, the prone bent-leg (90°) hip extension against manual resistance applied to the distal thigh (PRONE), to a novel position, the standing glute squeeze (SQUEEZE). Methods. Surface EMG electrodes were placed on the upper and lower gluteus maximus of thirteen recreationally active females (age = 28.9 years; height = 164 cm; body mass = 58.2 kg), before three maximum voluntary isometric contraction (MVIC) trials for each position were obtained in a randomized, counterbalanced fashion. Results. No statistically significant (p < 0.05) differences were observed between PRONE (upper: 91.94%; lower: 94.52%) and SQUEEZE (upper: 92.04%; lower: 85.12%) for both the upper and lower gluteus maximus. Neither the PRONE nor SQUEEZE was more effective between all subjects. Conclusions. In agreement with other studies, no single testing position is ideal for every participant. Therefore, it is recommended that investigators employ multiple MVIC positions, when possible, to ensure accuracy. Future research should investigate a variety of gluteus maximus MVIC positions in heterogeneous samples. PMID:26417543

  4. A comparison of two gluteus maximus EMG maximum voluntary isometric contraction positions

    Directory of Open Access Journals (Sweden)

    Bret Contreras

    2015-09-01

    Full Text Available Background. The purpose of this study was to compare the peak electromyography (EMG of the most commonly-used position in the literature, the prone bent-leg (90° hip extension against manual resistance applied to the distal thigh (PRONE, to a novel position, the standing glute squeeze (SQUEEZE.Methods. Surface EMG electrodes were placed on the upper and lower gluteus maximus of thirteen recreationally active females (age = 28.9 years; height = 164 cm; body mass = 58.2 kg, before three maximum voluntary isometric contraction (MVIC trials for each position were obtained in a randomized, counterbalanced fashion.Results. No statistically significant (p < 0.05 differences were observed between PRONE (upper: 91.94%; lower: 94.52% and SQUEEZE (upper: 92.04%; lower: 85.12% for both the upper and lower gluteus maximus. Neither the PRONE nor SQUEEZE was more effective between all subjects.Conclusions. In agreement with other studies, no single testing position is ideal for every participant. Therefore, it is recommended that investigators employ multiple MVIC positions, when possible, to ensure accuracy. Future research should investigate a variety of gluteus maximus MVIC positions in heterogeneous samples.

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

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    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.

  6. Normalizing shoulder EMG: An optimal set of maximum isometric voluntary contraction tests considering reproducibility.

    Science.gov (United States)

    Schwartz, Cédric; Tubez, François; Wang, François-Charles; Croisier, Jean-Louis; Brüls, Olivier; Denoël, Vincent; Forthomme, Bénédicte

    2017-08-18

    Normalization of the electromyography (EMG) signal is often performed relatively to maximal voluntary activations (MVA) obtained during maximum isometric voluntary contraction (MVIC). The first aim was to provide an inter-session reproducible protocol to normalize the signal of eight shoulder muscles. The protocol should also lead to a level of activation >90% of MVA for >90% of the volunteers. The second aim was to evaluate the influence of the method used to extract the MVA from the EMG envelope on the normalized EMG signal. Thirteen volunteers performed 12 MVICs twice (one week interval). Several time constants (100ms to 2s) were compared when extracting the MVA from the EMG envelope. The EMG activity was also acquired during an arm elevation. Our results show that a combination of nine MVIC tests was required to meet our requirements including reproducibility. Both the number of MVIC tests and the size of the time constant influence the normalized EMG signal during the dynamic activity (variations up to 15%). A time constant of 1s was a good compromise to extract the MVA. These findings are valuable to improve the reproducibility of EMG signal normalization. Copyright © 2017 Elsevier Ltd. All rights reserved.

  7. Effect of visual feedback information on isometric contraction of forearm flexor muscles in men and women after ischemic stroke.

    Science.gov (United States)

    Darbutas, Tomas; Juodžbalienė, Vilma; Skurvydas, Albertas; Krutulytė, Gražina; Rimdeikienė, Inesa; Brazaitis, Marius

    2012-01-01

    The aim of this study was to determine the effect of visual feedback information (VFI) on the isometric contraction of the forearm flexor muscles in men and women after an ischemic stroke when doing a physical load at 20% of strength. The study included healthy subjects (n=20) and subjects after ischemic stroke (n=20). The study was conducted in Lithuanian Sports University. The measurements of maximum voluntary strength (MVS) and accurate isometric contraction were performed using an isokinetic dynamometer Biodex System Pro 3. The absolute errors of isometric contraction of the right arm muscles at 20% of MVS were similar in all the groups during the attempt with visual feedback information. The smallest absolute errors of the healthy subjects were 1.42±0.35 Nm when the task was performed with visual feedback and the greatest absolute errors were 4.69±0.95 Nm (P<0.01) while performing the task without visual feedback. Meanwhile, the smallest and greatest absolute errors of the subjects after ischemic stroke were 1.32±0.45 Nm and 5.05±0.63 Nm, respectively, while performing the task without visual feedback (P<0.01). Maximum voluntary strength was greater in all the groups of men. The absolute errors of isometric contractions of the right and left arm muscles tended to increase in both the men and the women when there was no visual feedback information. The women and the men after an ischemic stroke produced greater absolute errors when performing the task with the right and left arm without visual feedback information than the healthy subjects.

  8. Central activation, metabolites, and calcium handling during fatigue with repeated maximal isometric contractions in human muscle.

    Science.gov (United States)

    Cairns, Simeon P; Inman, Luke A G; MacManus, Caroline P; van de Port, Ingrid G L; Ruell, Patricia A; Thom, Jeanette M; Thompson, Martin W

    2017-08-01

    To determine the roles of calcium (Ca 2+ ) handling by sarcoplasmic reticulum (SR) and central activation impairment (i.e., central fatigue) during fatigue with repeated maximal voluntary isometric contractions (MVC) in human muscles. Contractile performance was assessed during 3 min of repeated MVCs (7-s contraction, 3-s rest, n = 17). In ten participants, in vitro SR Ca 2+ -handling, metabolites, and fibre-type composition were quantified in biopsy samples from quadriceps muscle, along with plasma venous [K + ]. In 11 participants, central fatigue was compared using tetanic stimulation superimposed on MVC in quadriceps and adductor pollicis muscles. The decline of peak MVC force with fatigue was similar for both muscles. Fatigue resistance correlated directly with % type I fibre area in quadriceps (r = 0.77, P = 0.009). The maximal rate of ryanodine-induced Ca 2+ -release and Ca 2+ -uptake fell by 31 ± 26 and 28 ± 13%, respectively. The tetanic force depression was correlated with the combined reduction of ATP and PCr, and increase of lactate (r = 0.77, P = 0.009). Plasma venous [K + ] increased from 4.0 ± 0.3 to 5.4 ± 0.8 mM over 1-3-min exercise. Central fatigue occurred during the early contractions in the quadriceps in 7 out of 17 participants (central activation ratio fell from 0.98 ± 0.05 to 0.86 ± 0.11 at 1 min), but dwindled at exercise cessation. Central fatigue was seldom apparent in adductor pollicis. Fatigue with repeated MVC in human limb muscles mainly involves peripheral aspects which include impaired SR Ca 2+ -handling and we speculate that anaerobic metabolite changes are involved. A faster early force loss in quadriceps muscle with some participants is attributed to central fatigue.

  9. Alterations in Neural Control of Constant Isometric Contraction with the Size of Error Feedback.

    Directory of Open Access Journals (Sweden)

    Ing-Shiou Hwang

    Full Text Available Discharge patterns from a population of motor units (MUs were estimated with multi-channel surface electromyogram and signal processing techniques to investigate parametric differences in low-frequency force fluctuations, MU discharges, and force-discharge relation during static force-tracking with varying sizes of execution error presented via visual feedback. Fourteen healthy adults produced isometric force at 10% of maximal voluntary contraction through index abduction under three visual conditions that scaled execution errors with different amplification factors. Error-augmentation feedback that used a high amplification factor (HAF to potentiate visualized error size resulted in higher sample entropy, mean frequency, ratio of high-frequency components, and spectral dispersion of force fluctuations than those of error-reducing feedback using a low amplification factor (LAF. In the HAF condition, MUs with relatively high recruitment thresholds in the dorsal interosseous muscle exhibited a larger coefficient of variation for inter-spike intervals and a greater spectral peak of the pooled MU coherence at 13-35 Hz than did those in the LAF condition. Manipulation of the size of error feedback altered the force-discharge relation, which was characterized with non-linear approaches such as mutual information and cross sample entropy. The association of force fluctuations and global discharge trace decreased with increasing error amplification factor. Our findings provide direct neurophysiological evidence that favors motor training using error-augmentation feedback. Amplification of the visualized error size of visual feedback could enrich force gradation strategies during static force-tracking, pertaining to selective increases in the discharge variability of higher-threshold MUs that receive greater common oscillatory inputs in the β-band.

  10. Alterations in Neural Control of Constant Isometric Contraction with the Size of Error Feedback.

    Science.gov (United States)

    Hwang, Ing-Shiou; Lin, Yen-Ting; Huang, Wei-Min; Yang, Zong-Ru; Hu, Chia-Ling; Chen, Yi-Ching

    2017-01-01

    Discharge patterns from a population of motor units (MUs) were estimated with multi-channel surface electromyogram and signal processing techniques to investigate parametric differences in low-frequency force fluctuations, MU discharges, and force-discharge relation during static force-tracking with varying sizes of execution error presented via visual feedback. Fourteen healthy adults produced isometric force at 10% of maximal voluntary contraction through index abduction under three visual conditions that scaled execution errors with different amplification factors. Error-augmentation feedback that used a high amplification factor (HAF) to potentiate visualized error size resulted in higher sample entropy, mean frequency, ratio of high-frequency components, and spectral dispersion of force fluctuations than those of error-reducing feedback using a low amplification factor (LAF). In the HAF condition, MUs with relatively high recruitment thresholds in the dorsal interosseous muscle exhibited a larger coefficient of variation for inter-spike intervals and a greater spectral peak of the pooled MU coherence at 13-35 Hz than did those in the LAF condition. Manipulation of the size of error feedback altered the force-discharge relation, which was characterized with non-linear approaches such as mutual information and cross sample entropy. The association of force fluctuations and global discharge trace decreased with increasing error amplification factor. Our findings provide direct neurophysiological evidence that favors motor training using error-augmentation feedback. Amplification of the visualized error size of visual feedback could enrich force gradation strategies during static force-tracking, pertaining to selective increases in the discharge variability of higher-threshold MUs that receive greater common oscillatory inputs in the β-band.

  11. Real-time muscle state estimation from EMG signals during isometric contractions using Kalman filters.

    Science.gov (United States)

    Menegaldo, Luciano L

    2017-12-01

    State-space control of myoelectric devices and real-time visualization of muscle forces in virtual rehabilitation require measuring or estimating muscle dynamic states: neuromuscular activation, tendon force and muscle length. This paper investigates whether regular (KF) and extended Kalman filters (eKF), derived directly from Hill-type muscle mechanics equations, can be used as real-time muscle state estimators for isometric contractions using raw electromyography signals (EMG) as the only available measurement. The estimators' amplitude error, computational cost, filtering lags and smoothness are compared with usual EMG-driven analysis, performed offline, by integrating the nonlinear Hill-type muscle model differential equations (offline simulations-OS). EMG activity of the three triceps surae components (soleus, gastrocnemius medialis and gastrocnemius lateralis), in three torque levels, was collected for ten subjects. The actualization interval (AI) between two updates of the KF and eKF was also varied. The results show that computational costs are significantly reduced (70x for KF and 17[Formula: see text] for eKF). The filtering lags presented sharp linear relationships with the AI (0-300 ms), depending on the state and activation level. Under maximum excitation, amplitude errors varied in the range 10-24% for activation, 5-8% for tendon force and 1.4-1.8% for muscle length, reducing linearly with the excitation level. Smoothness, measured by the ratio between the average standard variations of KF/eKF and OS estimations, was greatly reduced for activation but converged exponentially to 1 for the other states by increasing AI. Compared to regular KF, extended KF does not seem to improve estimation accuracy significantly. Depending on the particular application requirements, the most appropriate KF actualization interval can be selected.

  12. Changes in tetrodotoxin-resistant C-fibre activity during fatiguing isometric contractions in the rat.

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    Ivana Kalezic

    Full Text Available It is by now well established that tetrodotoxin-resistant (TTX-R afferent fibres from muscle in the rat exhibit a multisensitive profile, including nociception. TTX-R afferent fibres play an important role in motor control, via spinal and supraspinal loops, but their activation and function during muscle exercise and fatigue are still unknown. Therefore, the specific effect of isometric fatiguing muscle contraction on the responsiveness of TTX-R C-fibres has been investigated in this study. To quantify the TTX-R afferent input we recorded the cord dorsum potential (CDP, which is the result of the electrical fields set up within the spinal cord by the depolarisation of the interneurons located in the dorsal horn, activated by an incoming volley of TTX-R muscle afferents. The changes in TTX-R CDP size before, during and after fatiguing electrical stimulation of the gastrocnemius-soleus (GS muscle have been taken as a measure of TTX-R C-unit activation. At the end of the fatiguing protocol, following an exponential drop in force, TTX-R CDP area decreased in the majority of trials (9/14 to 0.75 ± 0.03% (mean ± SEM of the pre-fatigue value. Recovery to the control size of the TTX-R CDP was incomplete after 10 min. Furthermore, fatiguing trials could sensitise a fraction of the TTX-R C-fibres responding to muscle pinch. The results suggest a long-lasting activation of the TTX-R muscle afferents after fatiguing stimulation. The role of this behaviour in chronic muscle fatigue in connection with pain development is discussed. Accumulation of metabolites released into the interstitium during fatiguing stimulation might be one of the reasons underlying the C-fibres' long-lasting activation.

  13. Planckian Power Spectral Densities from Human Calves during Posture Maintenance and Controlled Isometric Contractions.

    Directory of Open Access Journals (Sweden)

    J E Lugo

    Full Text Available The relationship between muscle anatomy and physiology and its corresponding electromyography activity (EMGA is complex and not well understood. EMGA models may be broadly divided in stochastic and motor-unit-based models. For example, these models have successfully described many muscle physiological variables such as the value of the muscle fiber velocity and the linear relationship between median frequency and muscle fiber velocity. However they cannot explain the behavior of many of these variables with changes in intramuscular temperature, or muscle PH acidity, for instance. Here, we propose that the motor unit action potential can be treated as an electromagnetic resonant mode confined at thermal equilibrium inside the muscle. The motor units comprising the muscle form a system of standing waves or modes, where the energy of each mode is proportional to its frequency. Therefore, the power spectral density of the EMGA is well described and fit by Planck's law and from its distribution we developed theoretical relationships that explain the behavior of known physiological variables with changes in intramuscular temperature or muscle PH acidity, for instance.EMGA of the calf muscle was recorded during posture maintenance in seven participants and during controlled isometric contractions in two participants. The power spectral density of the EMGA was then fit with the Planckian distribution. Then, we inferred nine theoretical relationships from the distribution and compared the theoretically derived values with experimentally obtained values.The power spectral density of EMGA was fit by Planckian distributions and all the theoretical relationships were validated by experimental results.Only by considering the motor unit action potentials as electromagnetic resonant modes confined at thermal equilibrium inside the muscle suffices to predict known or new theoretical relationships for muscle physiological variables that other models have failed

  14. Isometric contractions reduce plantar flexor moment, Achilles tendon stiffness, and neuromuscular activity but remove the subsequent effects of stretch.

    Science.gov (United States)

    Kay, Anthony D; Blazevich, Anthony J

    2009-10-01

    The effects of isometric contractions and passive stretching on muscle-tendon mechanics and muscle activity were studied in 16 healthy human volunteers. First, peak concentric and passive ankle joint moment data were recorded on an isokinetic dynamometer with electromyographic monitoring of the triceps surae; real-time motion analysis of the lower leg and ultrasound imaging of the Achilles-medial gastrocnemius muscle-tendon junction were simultaneously conducted. Second, the subjects performed six 8-s maximal voluntary isometric contractions (MVICs) before repeating the passive and active trials. Although there was no decrease in isometric joint moment after MVICs, peak concentric moment was significantly reduced (11.5%, P static plantar flexor stretches before being retested 2 and 30 min after stretch. The stretch protocol caused no significant change in any measure. At 30 min after stretching, significant recovery in concentric moment and muscle activity was detected at dorsiflexed joint angles, while Achilles tendon stiffness and passive joint moment remained significantly reduced. These data show that the performance of MVICs interrupts the normal stretch-induced losses in active and passive plantar flexor joint moment and neuromuscular activity, largely because concentric strength and tendon properties were already affected. Importantly, the decrease in Achilles tendon stiffness remained 30 min later, which may be an important etiological factor for muscle-tendon strain injury risk.

  15. The effects of isometric contraction of shoulder muscles on cervical multifidus muscle dimensions in healthy office workers.

    Science.gov (United States)

    Rahnama, Leila; Rezasoltani, Asghar; Khalkhali Zavieh, Minoo; Noori Kochi, Farhang; Akbarzadeh Baghban, Alireza

    2014-07-01

    It is argued that cervical multifidus muscles (CMM) are responsible for providing neck stability. However, whether they are actually activated during the tasks performed by the upper extremities to the neck is still unknown. Therefore, the aim of this study was to examine the effects of isometric contraction of shoulder muscles on the dimensions of CMM. Twenty three healthy males voluntarily participated in this study. Ultrasonography imaging of CMM was conducted at rest and at 25%, 50%, 75%, and 100% of maximal voluntary contraction of shoulder muscles in 6 directions of shoulder movements. Anterior-posterior dimension (APD), lateral dimension (LD), shape ratio and multiplied linear dimension (MLD) of cervical multifidus were measured. The APD of CMM was increased while LD and shape ratio were decreased by shoulder muscles contraction (P < 0.01). Copyright © 2013 Elsevier Ltd. All rights reserved.

  16. Shear modulus estimation on vastus intermedius of elderly and young females over the entire range of isometric contraction.

    Directory of Open Access Journals (Sweden)

    Cong-Zhi Wang

    Full Text Available Elderly people often suffer from sarcopenia in their lower extremities, which gives rise to the increased susceptibility of fall. Comparing the mechanical properties of the knee extensor/flexors on elderly and young subjects is helpful in understanding the underlying mechanisms of the muscle aging process. However, although the stiffness of skeletal muscle has been proved to be positively correlated to its non-fatiguing contraction intensity by some existing methods, this conclusion has not been verified above 50% maximum voluntary contraction (MVC due to the limitation of their measurement range. In this study, a vibro-ultrasound system was set up to achieve a considerably larger measurement range on muscle stiffness estimation. Its feasibility was verified on self-made silicone phantoms by comparing with the mechanical indentation method. The system was then used to assess the stiffness of vastus intermedius (VI, one of the knee extensors, on 10 healthy elderly female subjects (56.7 ± 4.9 yr and 10 healthy young female subjects (27.6 ± 5.0 yr. The VI stiffness in its action direction was confirmed to be positively correlated to the % MVC level (R2 = 0.999 over the entire range of isometric contraction, i.e. from 0% MVC (relaxed state to 100% MVC. Furthermore, it was shown that there was no significant difference between the mean VI shear modulus of the elderly and young subjects in a relaxed state (p > 0.1. However, when performing step isometric contraction, the VI stiffness of young female subjects was found to be larger than that of elderly participants (p < 0.001, especially at the relatively higher contraction levels. The results expanded our knowledge on the mechanical property of the elderly's skeletal muscle and its relationship with intensity of active contraction. Furthermore, the vibro-ultrasound system has a potential to become a powerful tool for investigating the elderly's muscle diseases.

  17. Loss of knee extensor torque complexity during fatiguing isometric muscle contractions occurs exclusively above the critical torque.

    Science.gov (United States)

    Pethick, Jamie; Winter, Samantha L; Burnley, Mark

    2016-06-01

    The complexity of knee extensor torque time series decreases during fatiguing isometric muscle contractions. We hypothesized that because of peripheral fatigue, this loss of torque complexity would occur exclusively during contractions above the critical torque (CT). Nine healthy participants performed isometric knee extension exercise (6 s of contraction, 4 s of rest) on six occasions for 30 min or to task failure, whichever occurred sooner. Four trials were performed above CT (trials S1-S4, S1 being the lowest intensity), and two were performed below CT (at 50% and 90% of CT). Global, central, and peripheral fatigue were quantified using maximal voluntary contractions (MVCs) with femoral nerve stimulation. The complexity of torque output was determined using approximate entropy (ApEn) and the detrended fluctuation analysis-α scaling exponent (DFA-α). The MVC torque was reduced in trials below CT [by 19 ± 4% (means ± SE) in 90%CT], but complexity did not decrease [ApEn for 90%CT: from 0.82 ± 0.03 to 0.75 ± 0.06, 95% paired-samples confidence intervals (CIs), 95% CI = -0.23, 0.10; DFA-α from 1.36 ± 0.01 to 1.32 ± 0.03, 95% CI -0.12, 0.04]. Above CT, substantial reductions in MVC torque occurred (of 49 ± 8% in S1), and torque complexity was reduced (ApEn for S1: from 0.67 ± 0.06 to 0.14 ± 0.01, 95% CI = -0.72, -0.33; DFA-α from 1.38 ± 0.03 to 1.58 ± 0.01, 95% CI 0.12, 0.29). Thus, in these experiments, the fatigue-induced loss of torque complexity occurred exclusively during contractions performed above the CT. Copyright © 2016 the American Physiological Society.

  18. In-Vivo Measurement of Muscle Tension: Dynamic Properties of the MC Sensor during Isometric Muscle Contraction

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    Srđan Đorđević

    2014-09-01

    Full Text Available Skeletal muscle is the largest tissue structure in our body and plays an essential role for producing motion through integrated action with bones, tendons, ligaments and joints, for stabilizing body position, for generation of heat through cell respiration and for blood glucose disposal. A key function of skeletal muscle is force generation. Non-invasive and selective measurement of muscle contraction force in the field and in clinical settings has always been challenging. The aim of our work has been to develop a sensor that can overcome these difficulties and therefore enable measurement of muscle force during different contraction conditions. In this study, we tested the mechanical properties of a “Muscle Contraction” (MC sensor during isometric muscle contraction in different length/tension conditions. The MC sensor is attached so that it indents the skin overlying a muscle group and detects varying degrees of tension during muscular contraction. We compared MC sensor readings over the biceps brachii (BB muscle to dynamometric measurements of force of elbow flexion, together with recordings of surface EMG signal of BB during isometric contractions at 15° and 90° of elbow flexion. Statistical correlation between MC signal and force was very high at 15° (r = 0.976 and 90° (r = 0.966 across the complete time domain. Normalized SD or σN = σ/max(FMC was used as a measure of linearity of MC signal and elbow flexion force in dynamic conditions. The average was 8.24% for an elbow angle of 90° and 10.01% for an elbow of angle 15°, which indicates high linearity and good dynamic properties of MC sensor signal when compared to elbow flexion force. The next step of testing MC sensor potential will be to measure tension of muscle-tendon complex in conditions when length and tension change simultaneously during human motion.

  19. Muscle shear elastic modulus is linearly related to muscle torque over the entire range of isometric contraction intensity.

    Science.gov (United States)

    Ateş, Filiz; Hug, François; Bouillard, Killian; Jubeau, Marc; Frappart, Thomas; Couade, Mathieu; Bercoff, Jeremy; Nordez, Antoine

    2015-08-01

    Muscle shear elastic modulus is linearly related to muscle torque during low-level contractions (muscle force. However, it is not known if this relationship remains valid for higher intensities. The aim of this study was to determine: (i) the relationship between muscle shear elastic modulus and muscle torque over the entire range of isometric contraction and (ii) the influence of the size of the region of interest (ROI) used to average the shear modulus value. Ten healthy males performed two incremental isometric little finger abductions. The joint torque produced by Abductor Digiti Minimi was considered as an index of muscle torque and elastic modulus. A high coefficient of determination (R(2)) (range: 0.86-0.98) indicated that the relationship between elastic modulus and torque can be accurately modeled by a linear regression over the entire range (0% to 100% of MVC). The changes in shear elastic modulus as a function of torque were highly repeatable. Lower R(2) values (0.89±0.13 for 1/16 of ROI) and significantly increased absolute errors were observed when the shear elastic modulus was averaged over smaller ROI, half, 1/4 and 1/16 of the full ROI) than the full ROI (mean size: 1.18±0.24cm(2)). It suggests that the ROI should be as large as possible for accurate measurement of muscle shear modulus. Copyright © 2015 Elsevier Ltd. All rights reserved.

  20. Electromyographic, cerebral and muscle hemodynamic responses during intermittent, isometric contractions of the biceps brachii at three submaximal intensities

    Directory of Open Access Journals (Sweden)

    Yagesh eBhambhani

    2014-06-01

    Full Text Available This study examined the electromyographic, cerebral and muscle hemodynamic responses during intermittent isometric contractions of biceps brachii at 20%, 40% and 60% of maximal voluntary contraction (MVC. Eleven volunteers completed two minutes of intermittent isometric contractions (12/min at an elbow angle of 90° interspersed with three minutes rest between intensities in systematic order. Surface electromyography (EMG was recorded from the right biceps brachii and near infrared spectroscopy (NIRS was used to simultaneously measure left prefrontal and right biceps brachii oxyhemoglobin (HbO2, deoxyhemoglobin (HHb and total hemoglobin (Hbtot. Transcranial Doppler ultrasound was used to measure middle cerebral artery velocity (MCAv bilaterally. Finger photoplethysmography was used to record beat-to-beat blood pressure and heart rate. EMG increased with force output from 20% to 60% MVC (P0.05. MCAv increased from rest to exercise but was not different among intensities (P>0.05. Force output correlated with the root mean square EMG and changes in muscle HbO2 (P0.05 at all three intensities. Force output declined by 8% from the 1st to the 24th contraction only at 60% MVC and was accompanied by systematic increases in RMS, cerebral HbO2 and Hbtot with a levelling off in muscle HbO2 and Hbtot. These changes were independent of alterations in mean arterial pressure. Since cerebral blood flow and oxygenation were elevated at 60% MVC, we attribute the development of fatigue to reduced muscle oxygen availability rather than impaired central n

  1. Electromyographic, cerebral, and muscle hemodynamic responses during intermittent, isometric contractions of the biceps brachii at three submaximal intensities

    Science.gov (United States)

    Bhambhani, Yagesh; Fan, Jui-Lin; Place, Nicolas; Rodriguez-Falces, Javier; Kayser, Bengt

    2014-01-01

    This study examined the electromyographic, cerebral and muscle hemodynamic responses during intermittent isometric contractions of biceps brachii at 20, 40, and 60% of maximal voluntary contraction (MVC). Eleven volunteers completed 2 min of intermittent isometric contractions (12/min) at an elbow angle of 90° interspersed with 3 min rest between intensities in systematic order. Surface electromyography (EMG) was recorded from the right biceps brachii and near infrared spectroscopy (NIRS) was used to simultaneously measure left prefrontal and right biceps brachii oxyhemoglobin (HbO2), deoxyhemoglobin (HHb), and total hemoglobin (Hbtot). Transcranial Doppler ultrasound was used to measure middle cerebral artery velocity (MCAv) bilaterally. Finger photoplethysmography was used to record beat-to-beat blood pressure and heart rate. EMG increased with force output from 20 to 60% MVC (P MVC (P MVC (P MVC (P > 0.05). MCAv increased from rest to exercise but was not different among intensities (P > 0.05). Force output correlated with the root mean square EMG and changes in muscle HbO2 (P 0.05) at all three intensities. Force output declined by 8% from the 1st to the 24th contraction only at 60% MVC and was accompanied by systematic increases in RMS, cerebral HbO2 and Hbtot with a leveling off in muscle HbO2 and Hbtot. These changes were independent of alterations in mean arterial pressure. Since cerebral blood flow and oxygenation were elevated at 60% MVC, we attribute the development of fatigue to reduced muscle oxygen availability rather than impaired central neuronal activation. PMID:24966837

  2. Correlation between architectural variables and torque in the erector spinae muscle during maximal isometric contraction.

    Science.gov (United States)

    Cuesta-Vargas, Antonio; González-Sánchez, Manuel

    2014-01-01

    This study analysed whether a significant relationship exists between the torque and muscle thickness and pennation angle of the erector spinae muscle during a maximal isometric lumbar extension with the lumbar spine in neutral position. This was a cross-sectional study in which 46 healthy adults performed three repetitions for 5 s of maximal isometric lumbar extension with rests of 90 s. During the lumbar extensions, bilateral ultrasound images of the erector spinae muscle (to measure pennation angle and muscle thickness) and torque were acquired. Reliability test analysis calculating the internal consistency (Cronbach's alpha) of the measure, correlation between pennation angle, muscle thickness and torque extensions were examined. Through a linear regression the contribution of each independent variable (muscle thickness and pennation angle) to the variation of the dependent variable (torque) was calculated. The results of the reliability test were: 0.976-0.979 (pennation angle), 0.980-0.980 (muscle thickness) and 0.994 (torque). The results show that pennation angle and muscle thickness were significantly related to each other with a range between 0.295 and 0.762. In addition, multiple regression analysis showed that the two variables considered in this study explained 68% of the variance in the torque. Pennation angle and muscle thickness have a moderate impact on the variance exerted on the torque during a maximal isometric lumbar extension with the lumbar spine in neutral position.

  3. Trunk muscle co-contraction increases during fatiguing, isometric, lateral bend exertions. Possible implications for spine stability.

    Science.gov (United States)

    Potvin, J R; O'Brien, P R

    1998-04-01

    Surface electromyographic activities were recorded from bilateral trunk muscles as test participants maintained a 50% maximum, voluntary, isometric, lateral bend contraction to volitional exhaustion. To challenge the trunk with a prolonged lateral bend task and observe the responses of the agonist and antagonist muscles to the resulting fatigue. Lateral bend exertions of the trunk have been identified as a risk factor for injury to spine tissues. However, little is known about the response of spine muscles to fatigue and the subsequent implications for spine stability, joint loading, and tissue injury. Surface electromyography provides a window on muscle loading and progressive fatigue. Eleven male participants performed a set of maximum lateral bend exertions at the start of the trial, then maintained an upright standing posture while resisting 50% of the maximum moment until volitional exhaustion, then performed another set of maximum contractions. All contractions were isometric. Measurements were made, throughout each contraction, of the lateral bend moment and abdominal and trunk extensor electromyographic activities at six bilateral surface electromyography sites. Electromyographic amplitude and mean power frequency were calculated with 500-millisecond segments recorded serially every 800 milliseconds. Mean values were calculated with data from the first and last 5% of the trial durations. Statistics determined if fatigue had a significant effect on maximum moment and the electromyographic statistics for each muscle site. Fatigue resulted in a significant decrease in maximum lateral bend moment and increase in moment variability. Decreases in mean power frequency, indicating fatigue, were observed in three agonists (the trunk extensors) and one antagonist muscle. Unfatigued agonist electromyographic amplitudes correlated well with the mechanical advantage of muscles to generate lateral bend moments. Unfatigued antagonist activities were low except for the

  4. Sustainable Markets Investment Briefings: Foreign investment contracts

    Energy Technology Data Exchange (ETDEWEB)

    Cotula, Lorenzo

    2007-08-15

    This is the fourth of a series of briefings which discuss the sustainable development issues raised by legal arrangements for the protection of foreign investment. The briefings are based on legal research by IIED and its partners. The goal is to provide accessible but accurate information for human rights, development and environmental organisations working on issues raised by foreign investment in low- and middle-income countries. Briefing 4 sets out some of the ways in which foreign investment contracts can impact on sustainable development.

  5. Evidence of skeletal muscle damage following electrically stimulated isometric muscle contractions in humans

    DEFF Research Database (Denmark)

    Mackey, Abigail; Bojsen-Moller, Jens; Qvortrup, Klaus

    2008-01-01

    It is unknown whether muscle damage at the level of the sarcomere can be induced without lengthening contractions. To investigate this, we designed a study where seven young, healthy men underwent 30 min of repeated electrical stimulated contraction of m. gastrocnemius medialis, with the ankle an...

  6. Functional connectivity between core and shoulder muscles increases during isometric endurance contractions in judo competitors

    DEFF Research Database (Denmark)

    Kawczyński, Adam; Samani, Afshin; Mroczek, Dariusz

    2015-01-01

    Purpose: The aim of this study was to assess the surface electromyogram (SEMG) changes within and between muscles of the torso and shoulder region during static endurance contraction in elite judokas. We hypothesized an increased functional connectivity of muscles from the shoulder and torso...... : We concluded that the increases in NMIs highlighted functional changes in the interplay between core and shoulder muscles during an endurance contraction in elite judokas....... endurance contraction consisting of bilateral arm abduction at 90°. The normalized mutual information (NMI) was computed between muscle pairs as an index indicating functional connectivity. Results: The NMIs increased significantly during endurance test for 10 of the 15 muscle pairs (P

  7. Inter-rectus distance in postpartum women can be reduced by isometric contraction of the abdominal muscles: a preliminary case-control study.

    Science.gov (United States)

    Pascoal, A G; Dionisio, S; Cordeiro, F; Mota, P

    2014-12-01

    To determine the effect of isometric contraction of the abdominal muscles on inter-rectus distance in postpartum women. Preliminary case-control study. Research laboratory. Ten postpartum women {mean age 30 [standard deviation (SD) 4] years; mean weight 58 (SD 7) kg; mean height 159 (SD 4) cm} and 10 nulliparous (control) women [mean age 28 (SD 2) years; mean weight 56 (SD 6) kg; mean height 160 (SD 6) cm]. Ultrasound images from the anterior abdominal wall were recorded at rest (supine position) and during an abdominal isometric contraction, with the subject actively performing an abdominal crunch (crook lying position). Two-way analysis of variance was used to compare the inter-rectus distance between groups (postpartum vs control) and between levels of abdominal muscle activation (rest vs isometric contraction). Inter-rectus distance 2cm above the level of the umbilicus. The inter-rectus distance was significantly greater in the postpartum group compared with the control group [14.7 (SD 3.1) mm vs 9.6 (SD 2.8) mm; mean difference 5.1mm; 95% confidence interval (CI) 3.4 to 6.8]. The inter-rectus distance was significantly lower during isometric contraction compared with rest [10.7 (SD 3.1) mm vs 13.4 (SD 3.1) mm; mean difference 2.8mm; 95% CI 1.2 to 4.5]. No interaction was found between group and muscle contraction. The inter-rectus distance was significantly higher in postpartum women compared with controls, and significantly lower during isometric contraction of the abdominal muscles (abdominal crunch) compared with rest. Copyright © 2014 Chartered Society of Physiotherapy. Published by Elsevier Ltd. All rights reserved.

  8. Auxotonic to isometric contraction transitioning in a beating heart causes myosin step-size to down shift.

    Directory of Open Access Journals (Sweden)

    Thomas P Burghardt

    Full Text Available Myosin motors in cardiac ventriculum convert ATP free energy to the work of moving blood volume under pressure. The actin bound motor cyclically rotates its lever-arm/light-chain complex linking motor generated torque to the myosin filament backbone and translating actin against resisting force. Previous research showed that the unloaded in vitro motor is described with high precision by single molecule mechanical characteristics including unitary step-sizes of approximately 3, 5, and 8 nm and their relative step-frequencies of approximately 13, 50, and 37%. The 3 and 8 nm unitary step-sizes are dependent on myosin essential light chain (ELC N-terminus actin binding. Step-size and step-frequency quantitation specifies in vitro motor function including duty-ratio, power, and strain sensitivity metrics. In vivo, motors integrated into the muscle sarcomere form the more complex and hierarchically functioning muscle machine. The goal of the research reported here is to measure single myosin step-size and step-frequency in vivo to assess how tissue integration impacts motor function. A photoactivatable GFP tags the ventriculum myosin lever-arm/light-chain complex in the beating heart of a live zebrafish embryo. Detected single GFP emission reports time-resolved myosin lever-arm orientation interpreted as step-size and step-frequency providing single myosin mechanical characteristics over the active cycle. Following step-frequency of cardiac ventriculum myosin transitioning from low to high force in relaxed to auxotonic to isometric contraction phases indicates that the imposition of resisting force during contraction causes the motor to down-shift to the 3 nm step-size accounting for >80% of all the steps in the near-isometric phase. At peak force, the ATP initiated actomyosin dissociation is the predominant strain inhibited transition in the native myosin contraction cycle. The proposed model for motor down-shifting and strain sensing involves ELC N

  9. Is the firing rate of motor units in different vastus medialis regions modulated similarly during isometric contractions?

    Science.gov (United States)

    Cabral, Hélio V; de Souza, Leonardo M L; Mello, Roger G T; Gallina, Alessio; de Oliveira, Liliam F; Vieira, Taian M

    2018-02-01

    Previous evidence suggests the fibers of different motor units reside within distinct vastus medialis (VM) regions. It remains unknown whether the activity of these motor units may be modulated differently. Herein we assess the discharge rate of motor units detected proximodistally from the VM to address this issue. Surface electromyograms (EMGs) were recorded proximally and distally from the VM while 10 healthy subjects performed isometric contractions. Single motor units were decomposed from surface EMGs. The smoothed discharge rates of motor units identified from the same and from different VM regions were then cross-correlated. During low-level contractions, the discharge rate varied more similarly for distal (cross-correlation peak; interquartile interval: 0.27-0.40) and proximal (0.28-0.52) than for proximodistal pairs of VM motor units (0.20-0.33; P = 0.006). The discharge rates of motor units from different proximodistal VM regions show less similarity in their variations than those of pairs of units either distally or proximally. Muscle Nerve 57: 279-286, 2018. © 2017 Wiley Periodicals, Inc.

  10. 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.

  11. Ultrasonographic analysis of dorsal neck muscles thickness changes induced by isometric contraction of shoulder muscles: A comparison between patients with chronic neck pain and healthy controls.

    Science.gov (United States)

    Karimi, Noureddin; Rezasoltani, Asghar; Rahnama, Leila; Noori-Kochi, Farhang; Jaberzadeh, Shapour

    2016-04-01

    Altered pattern of muscle activity is commonly seen with chronic neck pain (CNP). However, limited investigations have been done on dorsal neck muscles' activity pattern while performing upper limb tasks in patients with CNP. To investigate dorsal neck muscles' thickness changes during isometric contraction of shoulder muscles. Case-control study. This study investigated dorsal neck muscles' thickness changes during isometric contraction of shoulder muscles in 20 healthy participants (mean age 27 ± 4.37) and 17 patients with CNP (mean age 29 ± 5.50). Effects of isometric force of shoulder muscles on dorsal neck muscles' thickness changes were also evaluated. Significant muscle × group interaction was observed for the dorsal neck muscles thickness changes (p = 0.008) indicating different pattern of muscle activity in terms of changes in muscle thickness of two groups. Significant main effects of direction was observed (P = 0.003), with the abduction had the greatest impact on changing the dorsal neck muscles thickness. patients with CNP showed altered pattern of muscle thickness changes in comparison to healthy participants. Isometric abduction of shoulder muscles induced the greatest changes of dorsal neck muscles thickness among other force directions. Copyright © 2015 Elsevier Ltd. All rights reserved.

  12. A simulation study of the electromyographic volley at initiation of rapid isometric contractions in the first dorsal interosseous muscle.

    Science.gov (United States)

    Yamazaki, Y; Suzuki, M; Ohkuwa, T; Itoh, H

    1997-01-01

    Monopolar surface electromyograms (EMGs) of rapid isometric abduction of the first dorsal interosseous muscle (FDI) were initiated from an EMG volley that was characterized by a negative potential lasting over several tens of milliseconds. An EMG model was developed to study how the EMG volley was generated. EMGs were defined as the linear summations of surface-recorded action potential trains originating from single motor units (MUs). All action potential trains had the same discharge pattern but different recruitment thresholds, depending on the potential amplitude. Real action potentials in single MUs in FDI were recorded with a monopolar surface electrode, one of which was used as a prototype wave in simulation. The model predicted an initial negative potential comparable to that of the EMG volley observed in rapid contractions of FDI. Results from our simulation studies suggest that the EMG volley is caused by at least two independent factors: (1) the negative phase of the action potential is greater in area than the positive one, in which the effect is enhanced by the high discharge rate of many MUs; (2) many MUs are recruited within a short time in an orderly fashion starting from those with small action potentials to those with large ones.

  13. Feasibility of an Isometric Maximal Voluntary Contraction Test in Hematological Cancer Patients during Thrombocytopenia

    Directory of Open Access Journals (Sweden)

    Philipp Zimmer

    2013-01-01

    Full Text Available Introduction. Resistance training is rarely offered to hemato-oncological patients in the daily clinical routine due to its potential harmful impact on the cardiovascular system and the long periods of thrombocytopenia experienced by these patients. Therefore, it is important to determine a valid assessment to define and control resistance training. In this study, the feasibility of a maximal voluntary contraction (MVC test was investigated in hemato-oncological patients. This inexpensive assessment may be a practicable alternative to the one repetition maximum test which is currently described as the gold standard. Methods. 29 hemato-oncological patients with platelet counts between 30000/μL and 70000/μL were recruited for this pilot study. Complications like petechial bleedings, muscle convulsion, and pain were assessed using the Brief Pain Inventory before and 48 hours after the MVC test, which was performed unidirectionally for the quadriceps muscle. Results. We did not detect any statistically significant test-related exacerbations or pain development. Discussion. MVC testing seems to be a feasible method to control a resistance training program in hemato-oncological patients. Further studies need to extend their methods and, for example, compare the MVC test with the one repetition maximum test.

  14. Differences in cervical multifidus muscle thickness during isometric contraction of shoulder muscles: a comparison between patients with chronic neck pain and healthy controls.

    Science.gov (United States)

    Rahnama, Leila; Rezasoltani, Asghar; Zavieh, Minoo Khalkhali; NooriKochi, Farhang; Baghban, Alireza Akbarzadeh

    2015-01-01

    The purposes of this study were to (1) measure the thickness of cervical multifidus muscle (CMM) in different maximal voluntary contraction percentages of isometric contraction of shoulder muscles, (2) evaluate the differences of the CMM thickness in different directions of the shoulder movement, and (3) compare the changes in the CMM thickness of participants with neck pain and also of healthy individuals. Twenty healthy men (age, 27.45 ± 4.37 years; height, 177 ± 4.66 cm; weight, 72.85 ± 6.46 kg) and 20 men with chronic mechanical neck pain (age, 28.90 ± 5.53 years; height, 176 ± 5.98 cm; weight, 73.15 ± 7.82 kg) participated in the study. Both the right and left CMM thicknesses were measured using an ultrasound device while participants performed isometric contraction of shoulder muscles in 6 movement directions. In both groups, an increment of CMM thickness followed as the increase of isometric force (P pain participants (P = .03). Although no significant difference of CMM thickness was seen among the effects of the 6 force directions (P > .05), there was a significant difference of activity noted between the left and right sides (P = .047). The results of the present study indicate that isometric contraction of shoulder muscles caused an increase in the CMM thickness regardless of force direction. This increase was seen in both groups of healthy participants and patients with neck pain. However, less thickness changes were observed in participants with neck pain, which may be interpreted as reduced CMM activity in such people. Copyright © 2015 National University of Health Sciences. Published by Elsevier Inc. All rights reserved.

  15. Isometric rate of force development, maximum voluntary contraction, and balance in women with and without joint hypermobility.

    Science.gov (United States)

    Mebes, Christine; Amstutz, Astrid; Luder, Gere; Ziswiler, Hans-Ruedi; Stettler, Matthias; Villiger, Peter M; Radlinger, Lorenz

    2008-11-15

    To determine differences between hypermobile subjects and controls in terms of maximum strength, rate of force development, and balance. We recruited 13 subjects with hypermobility and 18 controls. Rate of force development and maximal voluntary contraction (MVC) during single leg knee extension of the right knee were measured isometrically for each subject. Balance was tested twice on a force plate with 15-second single-leg stands on the right leg. Rate of force development (N/second) and MVC (N) were extracted from the force-time curve as maximal rate of force development (= limit Deltaforce/Deltatime) and the absolute maximal value, respectively. The hypermobile subjects showed a significantly higher value for rate of force development (15.2% higher; P = 0.038, P = 0.453, epsilon = 0.693) and rate of force development related to body weight (16.4% higher; P = 0.018, P = 0.601, epsilon = 0.834) than the controls. The groups did not differ significantly in MVC (P = 0.767, P = 0.136, epsilon = 0.065), and MVC related to body weight varied randomly between the groups (P = 0.921, P = 0.050, epsilon = 0.000). In balance testing, the mediolateral sway of the hypermobile subjects showed significantly higher values (11.6% higher; P = 0.034, P = 0.050, epsilon = 0.000) than that of controls, but there was no significant difference (4.9% difference; P = 0.953, P = 0.050, epsilon = 0.000) in anteroposterior sway between the 2 groups. Hypermobile women without acute symptoms or limitations in activities of daily life have a higher rate of force development in the knee extensors and a higher mediolateral sway than controls with normal joint mobility.

  16. Neuromuscular function of the quadriceps muscle during isometric maximal, submaximal and submaximal fatiguing voluntary contractions in knee osteoarthrosis patients.

    Directory of Open Access Journals (Sweden)

    Anett Mau-Moeller

    Full Text Available Knee osteoarthrosis (KOA is commonly associated with a dysfunction of the quadriceps muscle which contributes to alterations in motor performance. The underlying neuromuscular mechanisms of muscle dysfunction are not fully understood. The main objective of this study was to analyze how KOA affects neuromuscular function of the quadriceps muscle during different contraction intensities.The following parameters were assessed in 20 patients and 20 healthy controls: (i joint position sense, i.e. position control (mean absolute error, MAE at 30° and 50° of knee flexion, (ii simple reaction time task performance, (iii isometric maximal voluntary torque (IMVT and root mean square of the EMG signal (RMS-EMG, (iv torque control, i.e. accuracy (MAE, absolute fluctuation (standard deviation, SD, relative fluctuation (coefficient of variation, CV and periodicity (mean frequency, MNF of the torque signal at 20%, 40% and 60% IMVT, (v EMG-torque relationship at 20%, 40% and 60% IMVT and (vi performance fatigability, i.e. time to task failure (TTF at 40% IMVT.Compared to the control group, the KOA group displayed: (i significantly higher MAE of the angle signal at 30° (99.3%; P = 0.027 and 50° (147.9%; P < 0.001, (ii no significant differences in reaction time, (iii significantly lower IMVT (-41.6%; P = 0.001 and tendentially lower RMS-EMG of the rectus femoris (-33.7%; P = 0.054, (iv tendentially higher MAE of the torque signal at 20% IMVT (65.9%; P = 0.068, significantly lower SD of the torque signal at all three torque levels and greater MNF at 60% IMVT (44.8%; P = 0.018, (v significantly increased RMS-EMG of the vastus lateralis at 20% (70.8%; P = 0.003 and 40% IMVT (33.3%; P = 0.034, significantly lower RMS-EMG of the biceps femoris at 20% (-63.6%; P = 0.044 and 40% IMVT (-41.3%; P = 0.028 and tendentially lower at 60% IMVT (-24.3%; P = 0.075 and (vi significantly shorter TTF (-51.1%; P = 0.049.KOA is not only associated with a deterioration of IMVT

  17. Training-specific functional, neural, and hypertrophic adaptations to explosive- vs. sustained-contraction strength training.

    Science.gov (United States)

    Balshaw, Thomas G; Massey, Garry J; Maden-Wilkinson, Thomas M; Tillin, Neale A; Folland, Jonathan P

    2016-06-01

    Training specificity is considered important for strength training, although the functional and underpinning physiological adaptations to different types of training, including brief explosive contractions, are poorly understood. This study compared the effects of 12 wk of explosive-contraction (ECT, n = 13) vs. sustained-contraction (SCT, n = 16) strength training vs. control (n = 14) on the functional, neural, hypertrophic, and intrinsic contractile characteristics of healthy young men. Training involved 40 isometric knee extension repetitions (3 times/wk): contracting as fast and hard as possible for ∼1 s (ECT) or gradually increasing to 75% of maximum voluntary torque (MVT) before holding for 3 s (SCT). Torque and electromyography during maximum and explosive contractions, torque during evoked octet contractions, and total quadriceps muscle volume (QUADSVOL) were quantified pre and post training. MVT increased more after SCT than ECT [23 vs. 17%; effect size (ES) = 0.69], with similar increases in neural drive, but greater QUADSVOL changes after SCT (8.1 vs. 2.6%; ES = 0.74). ECT improved explosive torque at all time points (17-34%; 0.54 ≤ ES ≤ 0.76) because of increased neural drive (17-28%), whereas only late-phase explosive torque (150 ms, 12%; ES = 1.48) and corresponding neural drive (18%) increased after SCT. Changes in evoked torque indicated slowing of the contractile properties of the muscle-tendon unit after both training interventions. These results showed training-specific functional changes that appeared to be due to distinct neural and hypertrophic adaptations. ECT produced a wider range of functional adaptations than SCT, and given the lesser demands of ECT, this type of training provides a highly efficient means of increasing function. Copyright © 2016 the American Physiological Society.

  18. Sustainability clauses in international supply chain contracts

    DEFF Research Database (Denmark)

    Peterkova, Katerina

    2014-01-01

    Our current society is not successful in mitigation of global social and environmental challenges. States lack legal tools, and sometimes also the will, to secure social and environmental interests transnationally and the existing soft and private regulation is criticized for its weak legitimacy...... of enforceable business contracts, SCCs are considered to overcome the heavily criticized softness of other CSR regulation and, therefore, to be more successful in fostering ethical behaviour of suppliers who are legally independent but often in economic and business terms dependent on the sourcing companies....... However, this hardening function is questionable face-to-face the lack of case law or another proof of SCCs’ formal enforcement. This article aims to shed a light on the question whether SCCs can be the efficient regulatory solution for global challenges we are looking for or whether they are yet another...

  19. Training-related changes in the EMG-moment relationship during isometric contractions: Further evidence of improved control of muscle activation in strength-trained men?

    Science.gov (United States)

    Amarantini, David; Bru, Bertrand

    2015-08-01

    The possibility of using electromyography (EMG) to track muscle activity has raised the question of its relationship with the effort exerted by the muscles around the joints. However, the EMG-moment relationship is yet to be fully defined, and increasing knowledge of this topic could contribute to research in motor control and to the development of EMG-based algorithms and devices. With regards the training-related adaptations at the peripheral and central level, the present study investigated the effect of strength training on EMG-moment relationship. Our aim was to clarify its nature and gain further understanding of how morphological and neural factors may affect its form. The EMG-moment relationship was determined during knee flexion and extension isometric contractions performed by strength-trained male athletes and untrained male participants. The results showed that strength training induced linearity of the EMG-moment relationship concomitantly with enhanced maximum force production capacity and decreased co-activation of knee agonist-antagonist muscle pair. These results clarified discordant results regarding the linear or curved nature of the EMG-moment in isometric conditions and suggested that the remarkable linearity of the EMG-moment found in trained participants could indicate improved control of muscle activation. Copyright © 2015 Elsevier Ltd. All rights reserved.

  20. Sustained maximal voluntary contraction produces independent changes in human motor axons and the muscle they innervate.

    Directory of Open Access Journals (Sweden)

    David A Milder

    Full Text Available The repetitive discharges required to produce a sustained muscle contraction results in activity-dependent hyperpolarization of the motor axons and a reduction in the force-generating capacity of the muscle. We investigated the relationship between these changes in the adductor pollicis muscle and the motor axons of its ulnar nerve supply, and the reproducibility of these changes. Ten subjects performed a 1-min maximal voluntary contraction. Activity-dependent changes in axonal excitability were measured using threshold tracking with electrical stimulation at the wrist; changes in the muscle were assessed as evoked and voluntary electromyography (EMG and isometric force. Separate components of axonal excitability and muscle properties were tested at 5 min intervals after the sustained contraction in 5 separate sessions. The current threshold required to produce the target muscle action potential increased immediately after the contraction by 14.8% (p<0.05, reflecting decreased axonal excitability secondary to hyperpolarization. This was not correlated with the decline in amplitude of muscle force or evoked EMG. A late reversal in threshold current after the initial recovery from hyperpolarization peaked at -5.9% at ∼35 min (p<0.05. This pattern was mirrored by other indices of axonal excitability revealing a previously unreported depolarization of motor axons in the late recovery period. Measures of axonal excitability were relatively stable at rest but less so after sustained activity. The coefficient of variation (CoV for threshold current increase was higher after activity (CoV 0.54, p<0.05 whereas changes in voluntary (CoV 0.12 and evoked twitch (CoV 0.15 force were relatively stable. These results demonstrate that activity-dependent changes in motor axon excitability are unlikely to contribute to concomitant changes in the muscle after sustained activity in healthy people. The variability in axonal excitability after sustained activity

  1. The effect of including a series of isometric conditioning contractions to the rowing warm-up on 1,000-m rowing ergometer time trial performance.

    Science.gov (United States)

    Feros, Simon A; Young, Warren B; Rice, Anthony J; Talpey, Scott W

    2012-12-01

    Rowing requires strength, power, and strength-endurance for optimal performance. A rowing-based warm-up could be enhanced by exploiting the postactivation potentiation (PAP) phenomenon, acutely enhancing power output at the beginning of a race where it is needed most. Minimal research has investigated the effects of PAP on events of longer duration (i.e. 1,000-m rowing). The purpose of this research was to investigate the effects of PAP on 1,000-m rowing ergometer performance through the use of 2 different warm-up procedures: (a) a rowing warm-up combined with a series of isometric conditioning contractions, known as the potentiated warm-up (PW), and (b) a rowing warm-up only (NW). The isometric conditioning contractions in the PW were performed by "pulling" an immovable handle on the rowing ergometer, consisting of 5 sets of 5 seconds (2 seconds at submaximal intensity, and 3 seconds at maximal intensity), with a 15-second recovery between sets. The 1,000-m rowing ergometer time trial was performed after each warm-up condition, whereby mean power output, mean stroke rate, and split time were assessed every 100 m. Ten Australian national level rowers served as the subjects and performed both conditions in a counterbalanced order on separate days. The PW reduced 1,000-m time by 0.8% (p > 0.05). The PW improved mean power output by 6.6% (p rowing warm-up enhance short-term rowing ergometer performance (especially at the start of a race) to a greater extent than a rowing warm-up alone.

  2. Experimental muscle pain changes the spatial distribution of upper trapezius muscle activity during sustained contraction.

    Science.gov (United States)

    Madeleine, Pascal; Leclerc, Fredéric; Arendt-Nielsen, Lars; Ravier, Philippe; Farina, Dario

    2006-11-01

    To investigate the effect of local excitation of nociceptive muscle afferents on the spatial distribution of muscle activity. Surface electromyographic (EMG) signals were recorded from the upper trapezius muscle of 10 healthy volunteers with a 5 x 13 electrode grid during 90-s isometric contractions before, during, 15 and 30 min after intramuscular injection of hypertonic (painful) or isotonic (non-painful) saline. From the multi-channel EMG recordings, two-dimensional maps of root mean square and mean power frequency were obtained. The centre of gravity of the root mean square map was used to quantify global changes in the spatial distribution of muscle activity. During sustained contractions, average root mean square increased, average mean frequency decreased and the centre of gravity moved cranially. During experimental muscle pain, compared to before injection, the average root mean square decreased and there was a caudal shift of the centre of gravity. Fifteen minutes after the painful injection the centre of gravity returned to its original position. Short-term dynamic reorganization of the spatial distribution of muscle activity occurred in response to nociceptive afferent input. The study furnishes an extension of the pain adaptation model indicating heterogeneous inhibition of muscle activity.

  3. Motor units in vastus lateralis and in different vastus medialis regions show different firing properties during low-level, isometric knee extension contraction.

    Science.gov (United States)

    de Souza, Leonardo Mendes Leal; Cabral, Hélio Veiga; de Oliveira, Liliam Fernandes; Vieira, Taian Martins

    2017-12-28

    Architectural differences along vastus medialis (VM) and between VM and vastus lateralis (VL) are considered functionally important for the patellar tracking, knee joint stability and knee joint extension. Whether these functional differences are associated with a differential activity of motor units between VM and VL is however unknown. In the present study, we, therefore, investigate neuroanatomical differences in the activity of motor units detected proximo-distally from VM and from the VL muscle. Nine healthy volunteers performed low-level isometric knee extension contractions (20% of their maximum voluntary contraction) following a trapezoidal trajectory. Surface electromyograms (EMGs) were recorded from VM proximal and distal regions and from VL using three linear adhesive arrays of eight electrodes. The firing rate and recruitment threshold of motor units decomposed from EMGs were then compared among muscle regions. Results show that VL motor units reached lower mean firing rates in comparison with VM motor units, regardless of their position within VM (P motor units (P = .997). Furthermore, no significant differences in the recruitment threshold were observed for all motor units analysed (P = .108). Our findings possibly suggest the greater potential of VL to generate force, due to its fibres arrangement, may account for the lower discharge rate observed for VL then either proximally or distally detected motor units in VM. Additionally, the present study opens new perspectives on the importance of considering muscle architecture in investigations of the neural aspects of motor behaviour. Copyright © 2017 Elsevier B.V. All rights reserved.

  4. Continuous monitoring of electromyography (EMG), mechanomyography (MMG), sonomyography (SMG) and torque output during ramp and step isometric contractions.

    Science.gov (United States)

    Guo, Jing-Yi; Zheng, Yong-Ping; Xie, Hong-Bo; Chen, Xin

    2010-11-01

    In this study we simultaneously collected ultrasound images, EMG, MMG from the rectus femoris (RF) muscle and torque signal from the leg extensor muscle group of nine male subjects (mean±SD, age=30.7±.4.9 years; body weight=67.0±8.4kg; height=170.4±6.9cm) during step, ramp increasing, and decreasing at three different rates (50%, 25% and 17% MVC/s). The muscle architectural parameters extracted from ultrasound imaging, which reflect muscle contractions, were defined as sonomyography (SMG) in this study. The cross-sectional area (CSA) and aspect ratio between muscle width and thickness (width/thickness) were extracted from ultrasound images. The results showed that the CSA of RF muscles decreased by 7.25±4.07% when muscle torque output changed from 0% to 90% MVC, and the aspect ratio decreased by 41.66±7.96%. The muscle contraction level and SMG data were strongly correlated (R(2)=0.961, P=0.003, for CSA and R(2)=0.999, PEMG RMS in ramp increasing was 8.25±4.00% higher than step (P=0.002). The normalized MMG RMS of step contraction was significantly lower than ramp increasing and decreasing, with averaged differences of 12.22±3.37% (P=0.001) and 12.06±3.37% (P=0.001), respectively. The results of this study demonstrated that the CSA and aspect ratio, i.e., SMG signals, can provide useful information about muscle contractions. They may therefore complement EMG and MMG for studying muscle activation strategies under different conditions. Crown Copyright © 2010. Published by Elsevier Ltd. All rights reserved.

  5. Assessment of force and fatigue in isometric contractions of the upper trapezius muscle by surface EMG signal and perceived exertion scale.

    Science.gov (United States)

    Troiano, Amedeo; Naddeo, Francesco; Sosso, Erik; Camarota, Gianfranco; Merletti, Roberto; Mesin, Luca

    2008-08-01

    Quantifying muscle force and fatigue is important in designing ergonomic work stations, in planning appropriate work-rest patterns, and in preventing/assessing the progress of disorders. In 14 subjects (seven males, seven females), muscle force and fatigue were estimated by subjective perception (based on Borg scale CR10) and objective indexes extracted from surface electromyogram (EMG). The experimental protocol consisted of an isometric task selective for the upper trapezius muscle at different force levels (10-80% of maximal voluntary contraction--MVC, in steps of 10%MVC) and one fatiguing contraction (constant force level at 50%MVC until exhaustion). Surface EMG signals were detected by a two-dimensional (2D) array of electrodes placed half way between C7 and the acromion. The following variables were calculated from EMG signals: muscle fibre conduction velocity (CV), root mean square value (RMS), mean frequency of the power spectrum (MNF), fractal dimension (FD), and entropy. All detected signals were also used to build topographical maps of RMS. Both subjective and objective indications of force and fatigue can provide information on exerted force and endurance time (ET). In particular, Borg ratings, RMS, and entropy were significantly related to force, and the rate of change of CV, MNF, FD, and Borg ratings were predictive of the endurance time. Moreover, significant differences were found in Borg ratings between males and females. The correlation coefficient of pairs of topographical maps of RMS was high (of the order of 0.8). This reflects a characteristic spatial-temporal recruitment of upper trapezius motor units that is not affected by force levels or fatigue.

  6. Effect of myofascial release technique on pain, disability, maximum isometric contraction of the extensor muscles, and pressure pain threshold in patients with chronic nonspecific neck pain: Double blinded randomized clinical trial

    OpenAIRE

    Hasan Namvar; Gholamreza olyaei; Behrouz Attarbashi Moghadam; Mohammad Hosseinifar

    2016-01-01

    The impact of myofascial release technique alone has not been investigated in the patients with non-specific chronic neck pain. Thus, the aim of this study was to investigate the impacts of myofascial release technique on pain, disability, the maximum contraction of isometric extensor muscles of neck and pressure pain threshold in the patient with non-specific chronic neck pain compared with control group. In this clinical, randomized, double-blind trial, the patients with non-specific chr...

  7. Optimal Normalization Tests for Muscle Activation of the Levator Scapulae, Pectoralis Minor, and Rhomboid Major: An Electromyography Study Using Maximum Voluntary Isometric Contractions.

    Science.gov (United States)

    Castelein, Birgit; Cagnie, Barbara; Parlevliet, Thierry; Danneels, Lieven; Cools, Ann

    2015-10-01

    To identify maximum voluntary isometric contraction (MVIC) test positions for the deeper-lying scapulothoracic muscles (ie, levator scapulae, pectoralis minor, rhomboid major), and to provide a standard set of a limited number of test positions that generate an MVIC in all scapulothoracic muscles. Cross-sectional study. Physical and rehabilitation medicine department. Healthy subjects (N=21). Not applicable. Mean peak electromyographic activity from levator scapulae, pectoralis minor, and rhomboid major (investigated with fine-wire electromyography) and from upper trapezius, middle trapezius, lower trapezius, and serratus anterior (investigated with surface electromyography) during the performance of 12 different MVICs. The results indicated that various test positions generated similar high mean electromyographic activity and that no single test generated maximum activity for a specific muscle in all subjects. The results of this study support using a series of test positions for normalization procedures rather than a single exercise to increase the likelihood of recruiting the highest activity in the scapulothoracic muscles. A standard set of 5 test positions was identified as being sufficient for generating an MVIC of all scapulothoracic muscles: seated T, seated U 135°, prone T-thumbs up, prone V-thumbs up, and supine V-thumbs up. A standard set of test positions for normalization of scapulothoracic electromyographic data that also incorporates the levator scapulae, pectoralis minor, and rhomboid major muscles is 1 step toward a more comprehensive understanding of normal and abnormal muscle function of these muscles and will help to standardize the presentation of scapulothoracic electromyographic muscle activity. Copyright © 2015 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.

  8. Effect of lower extremity functional electrical stimulation pulsed isometric contractions on arm cycling peak oxygen uptake in spinal cord injured individuals.

    Science.gov (United States)

    Brurok, Berit; Tørhaug, Tom; Karlsen, Trine; Leivseth, Gunnar; Helgerud, Jan; Hoff, Jan

    2013-03-01

    To compare peak oxygen uptake (VO2peak) between: (i) functional electrical stimulation lower extremity pulsed isometric muscle contractions combined with arm cycling (FES iso hybrid), (ii) functional electrical stimulation cycling combined with arm cycling (FES hybrid cycling), and (iii) arm cycling exercise (ACE) in individuals with spinal cord injury with level of injury above and below T6. Cross-over repeated measures design. METHODS/PARTICIPANTS: Individuals with spinal cord injury (n = 15) with level of injury between C4 and T12, were divided into groups; above (spinal cord injury - high, n = 8) and below (spinal cord injury - low, n = 7) T6 level. On separate days, VO2peak was compared between: (i) ACE, (ii) FES iso hybrid, and (iii) FES hybrid cycling. In the SCI-high group, FES iso hybrid increased VO2peak (17.6 (standard deviation (SD) 5.0) to 23.6 (SD 3.6) ml/kg/min; p = 0.001) and ventilation (50.4 (SD 20.8) to 58.2 (SD 20.7) l/min; p = 0.034) more than ACE. Furthermore, FES hybrid cycling resulted in a 6.8 ml/kg/min higher VO2peak (p = 0.001) and an 11.0 litres/minute (p = 0.001) higher ventilation. ACE peak workload was 10.5 W (p = 0.001) higher during FES hybrid cycling compared with ACE. In the spinal cord injury - low group, no significant differences were found between the modalities. VO2peak increased when ACE was combined with FES iso hybrid or FES hybrid cycling in persons with spinal cord injury above the T6 level. Portable FES may serve as a less resource-demanding alternative to stationary FES cycling, and may have important implications for exercise prescription for spinal cord injury.

  9. Effect of myofascial release technique on pain, disability, maximum isometric contraction of the extensor muscles, and pressure pain threshold in patients with chronic nonspecific neck pain: Double blinded randomized clinical trial

    Directory of Open Access Journals (Sweden)

    Hasan Namvar

    2016-07-01

    Full Text Available The impact of myofascial release technique alone has not been investigated in the patients with non-specific chronic neck pain. Thus, the aim of this study was to investigate the impacts of myofascial release technique on pain, disability, the maximum contraction of isometric extensor muscles of neck and pressure pain threshold in the patient with non-specific chronic neck pain compared with control group. In this clinical, randomized, double-blind trial, the patients with non-specific chronic neck pain have been entered the study by the available sampling method and have been located randomly into two groups of myofascial release therapy group, and control group. Pressure pain threshold, pain intensity, disability and isometric power of neck extensor muscles before and after intervention were registered through pressure algometer, visual analogue scale, neck disability index, and pressure biofeedback. The treatment was performed for 4 sessions and each session for 20 minutes. The paired t-tests and independent t-test were used for within group and between group comparison respectively. Comparing the mean of pain intensity, pressure pain threshold, neck disability index in the intervention group compared with control group showed significant reduction (P0.05. Myofascial Release is one of the effective manual therapy techniques in reducing pain, disability, improving the isometric extension strength of neck in patients with nonspecific chronic neck pain.

  10. Higher Neuromuscular Manifestations of Fatigue in Dynamic than Isometric Pull-Up Tasks in Rock Climbers

    Directory of Open Access Journals (Sweden)

    Boccia Gennaro

    2015-09-01

    Full Text Available Neuromuscular assessment of rock climbers has been mainly focused on forearm muscles in the literature. We aimed to extend the body of knowledge investigating on two other upper limb muscles during sport-specific activities in nine male rock climbers. We assessed neuromuscular manifestations of fatigue recording surface electromyographic signals from brachioradialis and teres major muscles, using multi-channel electrode arrays. Participants performed two tasks until volitional exhaustion: a sequence of dynamic pull-ups and an isometric contraction sustaining the body at half-way of a pull-up (with the elbows flexed at 90°. The tasks were performed in randomized order with 10 minutes of rest in between. The normalized rate of change of muscle fiber conduction velocity was calculated as the index of fatigue. The time-to-task failure was significantly shorter in the dynamic (31 ±10 s than isometric contraction (59 ±19 s. The rate of decrease of muscle fiber conduction velocity was found steeper in the dynamic than isometric task both in brachioradialis (isometric: −0.2 ±0.1%/s; dynamic: −1.2 ±0.6%/s and teres major muscles (isometric: −0.4±0.3%/s; dynamic: −1.8±0.7%/s. The main finding was that a sequence of dynamic pull-ups lead to higher fatigue than sustaining the body weight in an isometric condition at half-way of a pull-up. Furthermore, we confirmed the possibility to properly record physiological CV estimates from two muscles, which had never been studied before in rock climbing, in highly dynamic contractions.

  11. [Muscle exercise after anterior cruciate ligament reconstruction of the knee--Part II: The development of the exercise method by simultaneous isometric contraction of the quadriceps and the hamstrings, and its biomechanics].

    Science.gov (United States)

    Yasuda, K; Sasaki, T; Shirado, O; Yagi, T; Monji, J

    1985-12-01

    An attempt was made to investigate the stress of the ACL in the simultaneous isometric contraction (IMC) of the quadriceps and the hamstrings by means of analysis of two-dimensional models, and to estimate electromyographically the forces of those muscles in that contraction. The anterior drawer force (ADF) in the simultaneous IMC decreased as the flexion angle of the knee increased. The average value of the angles, where the ADF became zero, was 7.4 degrees. The integrated EMGs of the quadriceps and the hamstrings in the simultaneous maximum IMC were equal to 30-60% of those in separate maximum IMC. In the early stage of the rehabilitation after the ACL reconstruction, the simultaneous IMC of the quadriceps and the hamstrings is useful as one of the muscle exercise method, because that can be performed at the knee position near the full extension and can generate sufficient muscle force for exercise.

  12. Towards sustainable infrastructure development through integrated contracts : Experiences with inclusiveness in Dutch infrastructure projects

    NARCIS (Netherlands)

    Lenferink, Sander; Tillema, Taede; Arts, Jos

    Current complex society necessitates finding inclusive arrangements for delivering sustainable road infrastructure integrating design, construction and maintenance stages of the project lifecycle. In this article we investigate whether linking stages by integrated contracts can lead to more

  13. Contractions

    Science.gov (United States)

    ... body for labor and delivery. Labor contractions signal the beginning of childbirth. What causes contractions? Braxton-Hicks (false ... of your last menstrual period.) Labor contractions signal the beginning of childbirth. These contractions come at regular intervals, ...

  14. [Muscle exercise after the anterior cruciate ligament reconstruction of the knee--Part I: The force given to the anterior cruciate ligament by separate isometric contraction of the quadriceps or the hamstrings].

    Science.gov (United States)

    Yasuda, K; Sasaki, T; Shirado, O; Yagi, T; Monji, J

    1985-12-01

    An attempt was made to investigate the force of the anterior cruciate ligament (ACL) in separate isometric contraction (IMC) of the quadriceps and the hamstrings by means of the analysis of two-dimensional models. In IMC of the quadriceps, the average value of the anterior drawer force (ADF) was equal to 14% of the quadriceps tension at the knee flexion of 5 degrees. The ADF decreased as the flexion angle increased. The average value of the angles, where the ADF became zero, was 45.3 degrees, and the standard deviation was 12.5 degrees. In IMC of the hamstrings, the posterior drawer force was given at the every flexion angle. In the early stage of the rehabilitation after the ACL reconstruction, the quadriceps exercise by IMC should be performed at the knee flexion of more than 70 degrees (average + 1.96 X S.D.). The hamstrings exercise by IMC can be carried out regardless of flexion angle.

  15. The effect of short-term isometric muscle contraction and the Valsalva maneuver on systemic and pulmonary hemodynamics in patients with severe heart failure.

    Science.gov (United States)

    Soucek, Miroslav; Frana, Petr; Kara, Tomas; Sitar, Jan; Halamek, Josef; Jurak, Pavel; Rihacek, Ivan; Spinarova, Lenka; Oral, Ivo

    2009-06-01

    Chronic heart failure is characterized by high mortality, frequent hospitalization, and reduced quality of life. Patients with severe heart failure are often in very poor physical condition, they are unable to take part in the usual exercise programs, and therefore need an individual approach. To assess the systemic and pulmonary hemodynamic responses to maximum voluntary contraction of the lower extremity muscles (MVC-LEM) with persistent physiologic breathing, the Valsalva maneuver, and the combination of Valsalva with MVC-LEM. Seventeen patients with severe heart failure (ejection fraction 20%) were exposed to 3 types of load for a period of 10 seconds: 1) MVC-LEM with persistent physiologic breathing, 2) the Valsalva maneuver, and 3) a combination of MVC-LEM with the Valsalva maneuver. During each measurement, a continuous, time-synchronized record was taken of the electrocardiogram, and the pulmonary and systemic blood pressures. There were slight changes in the heart rate and systemic blood pressure when comparing resting versus MVC-LEM values. There were much greater and significant changes (P maximum voluntary contraction of the muscles of the lower extremities with persistent physiologic breathing did not have an abnormal effect on the systemic and pulmonary hemodynamics in patients with severe chronic heart failure. The Valsalva maneuver caused significantly higher hemodynamic changes in the systemic and pulmonary system with possible negative effects. 2009 Wiley Periodicals, Inc.

  16. Sustained inhibition of rat myometrial gap junctions and contractions by lindane

    Directory of Open Access Journals (Sweden)

    Grindatti Carmen M

    2003-10-01

    Full Text Available Abstract Background Gap junctions increase in size and abundance coincident with parturition, forming an intercellular communication network that permits the uterus to develop the forceful, coordinated contractions necessary for delivery of the fetus. Lindane, a pesticide used in the human and veterinary treatment of scabies and lice as well as in agricultural applications, inhibits uterine contractions in vitro, inhibits myometrial gap junctions, and has been associated with prolonged gestation length in rats. The aim of the present study was to investigate whether brief exposures to lindane would elicit sustained inhibition of rat uterine contractile activity and myometrial gap junction intercellular communication. Methods To examine effects on uterine contraction, longitudinal uterine strips isolated from late gestation (day 20 rats were exposed to lindane in muscle baths and monitored for changes in spontaneous phasic contractions during and after exposure to lindane. Lucifer yellow dye transfer between myometrial cells in culture was used to monitor gap junction intercellular communication. Results During a 1-h exposure, 10 micro M and 100 micro M lindane decreased peak force and frequency of uterine contraction but 1 micro M lindane did not. After removal of the exposure buffer, contraction force remained significantly depressed in uterine strips exposed to 100 micro M lindane, returning to less than 50% basal levels 5 h after cessation of lindane exposure. In cultured myometrial myocytes, significant sustained inhibition of Lucifer yellow dye transfer was observed 24 h after lindane exposures as brief as 10 min and as low as 0.1 micro M lindane. Conclusion Brief in vitro exposures to lindane have long-term effects on myometrial functions that are necessary for parturition, inhibiting spontaneous phasic contractions in late gestation rat uterus and gap junction intercellular communication in myometrial cell cultures.

  17. Sex differences in variances of multi-channel surface electromyography distribution of the vastus lateralis muscle during isometric knee extension in young adults.

    Science.gov (United States)

    Nishikawa, Yuichi; Watanabe, Kohei; Takahashi, Tetsuya; Hosomi, Naohisa; Orita, Naoya; Mikami, Yukio; Maruyama, Hirofumi; Kimura, Hiroaki; Matsumoto, Masayasu

    2017-03-01

    The aim of the present study was to compare spatial electromyographic potential distribution during force production between healthy young female and male using multi-channel surface electromyography (multi-SEMG). Thirty healthy subjects (15 females) performed sustained isometric knee extension at 10% maximal voluntary contraction (MVC) task for 120 s. Multi-SEMG signals from the vastus lateralis muscle were detected and the modified entropy, coefficient of variation (CV), and correlation coefficient determined. The modified entropy and CV showed significant interaction and difference between females and males at all time points during the 10% MVC task. The correlation coefficient in females was significantly lower at 90 and 120 s than that of males. The multi-SEMG potential distribution pattern in females showed more varied motor unit recruitment during sustained low-intensity isometric contraction than that of males. Variations in motor unit recruitment may result from recruitment and/or de-recruitment of motor units.

  18. Evaluation of electromyographic activity and heart rate responses to isometric exercise. The role played by muscular mass and type

    Directory of Open Access Journals (Sweden)

    E. Silva

    1999-01-01

    Full Text Available The purpose of the present study was to examine the relationship between the electromyographic (EMG activity and heart rate (HR responses induced by isometric exercise performed by knee extension (KE and flexion (KF in men. Fifteen healthy male subjects, 21 ± 1.3 years (mean ± SD, were submitted to KE and KF isometric exercise tests at 100% of maximal voluntary contraction (MVC. The exercises were performed with one leg (right or left and with two legs simultaneously, for 10 s in the sitting position with the hip and knee flexed at 90o. EMG activity (root mean square values and HR (beats/min were recorded simultaneously both at rest and throughout the sustained contraction. The HR responses to isometric exercise in KE and KF were similar when performed with one and two legs. However, the HR increase was always significantly higher in KE than KF (P0.05 and KF (r = 0.15, P>0.05 contractions were not significant. These results suggest that the predominant mechanism responsible for the larger increase in HR response to KE as compared to KF in our study could be dependent on qualitative and quantitative differences in the fiber type composition found in each muscle group. This mechanism seems to demand a higher activation of motor units with a corresponding increase in central command to the cardiovascular centers that modulate HR control.

  19. Effects of electromyostimulation versus voluntary isometric training on elbow flexor muscle strength.

    Science.gov (United States)

    Colson, Serge S; Martin, Alain; Van Hoecke, Jacques

    2009-10-01

    The purpose of this study was to determine whether 7 weeks of standardized (same number and duration of repetitions, sets and rest strictly identical) electromyostimulation training of the elbow flexor muscles would induce strength gains equivalent to those of voluntary isometric training in isometric, eccentric and concentric contractions. Twenty-five males were randomly assigned to an electromyostimulated group (EMS, n=9), a voluntary isometric group (VOL, n=8), or a control group (CON, n=8). Maximal voluntary isometric, eccentric and concentric strength, electromyographic (EMG) activity of the biceps and triceps brachii muscles, elbow flexor muscle activation (twitch interpolation technique) and contractile properties were assessed before and after the training period. The main findings were that the isometric torque gains of EMS were greater than those of VOL after the training period (Pelectromyostimulation training would be more efficient than voluntary isometric training to improve both isometric and dynamic strength.

  20. The influence of aging on the isometric torque sharing patterns among the plantar flexor muscles.

    Science.gov (United States)

    Oliveira, Liliam F; Verneque, Debora; Menegaldo, Luciano L

    2017-01-01

    Physiological cross-sectional area (PCSA) reduction of the triceps surae (TS) muscles during aging suggests a proportional loss of torque among its components: soleus, medial and lateral gastrocnemii. However, direct measurements of muscle forces in vivo are not feasible. The purpose of this paper was to compare, between older and young women, isometric ankle joint torque sharing patterns among TS muscles and tibialis anterior (TA). An EMG-driven model was used for estimating individual muscle torque contributions to the total plantar flexor torque, during sustained contractions of 10% and 40% of maximum voluntary contraction (MVC). Relative individual muscle contributions to the total plantar flexion torque were similar between older and young women groups, for both intensities, increasing from LG, MG to SOL. Muscle strength (muscle torque/body mass) was significantly greater for all TS components in 40% MVC contractions. Increased TA activation was observed in 10% of MVC for older people. Despite the reduced maximum isometric torque and muscle strength, the results suggest small variations of ankle muscle synergies during the aging process.

  1. The isometric torque at which knee-extensor muscle reoxygenation stops.

    NARCIS (Netherlands)

    de Ruiter, C.J.; Goudsmit, J.F.; Tricht, J.A.; de Haan, A.

    2007-01-01

    PURPOSE: We investigated the knee-extensor torque at which reoxygenation (inflow of arterial blood) during an isometric contraction stopped, whether this torque depended on maximal torque capacity (MTC), and whether there were differences among the synergists. METHODS: Isometric knee-extension

  2. Leg dominancy in relation to fast isometric torque production and squat jump height

    NARCIS (Netherlands)

    de Ruiter, C.J.; de Korte, A.; Schreven, S.; de Haan, A.

    2010-01-01

    We hypothesized that maximal unilateral isometric knee extensor torque, the rate of torque development during maximally fast isometric contractions and unilateral squat jump performance would be better with the dominant than non-dominant leg. Limb dominancy was established using the step up, balance

  3. Reduced Voluntary Activation During Brief and Sustained Contractions of a Hand Muscle in Secondary-Progressive Multiple Sclerosis Patients.

    Science.gov (United States)

    Wolkorte, Ria; Heersema, Dorothea J; Zijdewind, Inge

    2016-05-01

    Secondary-progressive multiple sclerosis (SPMS) patients have structural cortical damage resulting in increased compensatory cortical activity during (submaximal) performance. However, functional effects of changed cortical output are difficult to measure. The interpolated-twitch technique allows for measurement of voluntary activation (VA) necessary for force production. This study aimed to determine VA, force, and muscle fatigue during brief and sustained contractions in SPMS patients. Because fatigue effects are not confined to the motor system, we additionally examined fatiguing effects on cognitive performance. Twenty-five SPMS and 25 sex-, age-, and education-matched participants performed brief (5 seconds) and sustained (2 minutes) maximal index finger abductions. To evaluate VA, double-pulse twitches were evoked before, during, and after contractions. Additionally, data were compared with data obtained in relapsing-remitting multiple sclerosis (RRMS) patients. Subjects also performed choice-reaction time tasks before and after the sustained contraction. During brief contractions, VA (85% vs 94%,P= .004) and force (25 N vs 32 N,P= .011) were lower for SPMS patients than controls. During sustained contractions, VA (P= .001) was also lower, resulting in greater force decline (73% vs 63%,P< .001) and reduced peripheral fatigue (19% vs 50%,P< .001). Comparisons with RRMS resulted in lower VA, greater force decline, and greater estimated central fatigue in SPMS. SPMS patients were slower (P< .001) and made more errors (P< .001) than controls, but neither group reduced their performance after the sustained contraction. SPMS patients had lower VA than RRMS patients and controls. The importance of voluntary activation for muscle force and fatigability warrants targeted rehabilitation strategies. © The Author(s) 2015.

  4. Differential contributions of ankle plantarflexors during submaximal isometric muscle action

    DEFF Research Database (Denmark)

    Masood, Tahir; Bojsen-Møller, Jens; Kalliokoski, Kari K

    2014-01-01

    The objective of this study was to investigate the relative contributions of superficial and deep ankle plantarflexors during repetitive submaximal isometric contractions using surface electromyography (SEMG) and positron emission tomography (PET). Myoelectric signals were obtained from twelve....... The findings of this study provide valuable reference for studies where individual muscle contributions are estimated using models and simulations....

  5. Isometric Tremor Irregularity, Torque Steadiness and Rate of Force Development in Parkinson's Disease

    DEFF Research Database (Denmark)

    Rose, Martin Høyer; Løkkegaard, Annemette; Sonne-Holm, Stig

    2013-01-01

    We investigated lower-extremity isometric tremor Approximate Entropy (irregularity), torque steadiness and rate of force development (RFD) and their associations to muscle activation strategy during isometric knee extensions in patients with Parkinson's disease (PD). Thirteen male patients...... that both knee isometric tremor Approximate Entropy and torque steadiness clearly differentiate between patients with PD and healthy controls. Furthermore, severely compromised RFD was found in patients with PD and was associated with decreased agonist muscle activation....... with idiopathic PD and 15 neurologically healthy matched controls performed isometric maximal contractions (extension/flexion) as well as steady submaximal and powerful isometric knee extensions. The patients with PD showed decreased isometric tremor irregularity. Torque steadiness was reduced in PD...

  6. A modified isometric test to evaluate blood pressure control with ...

    African Journals Online (AJOL)

    Blood pressure at rest is not predictive of roundthe- clock values. Blood pressure should therefore be measured during effort to evaluate hypertension and its response to treatment. The effect of sustained-release verapamil (240 mg taken once a day) on blood pressure at rest and during isometric effort was therefore ...

  7. Cortical and spinal mechanisms of task failure of sustained submaximal fatiguing contractions.

    Directory of Open Access Journals (Sweden)

    Petra S Williams

    Full Text Available In this and the subsequent companion paper, results are presented that collectively seek to delineate the contribution that supraspinal circuits have in determining the time to task failure (TTF of sustained submaximal contractions. The purpose of this study was to compare adjustments in supraspinal and spinal excitability taken concurrently throughout the performance of two different fatigue tasks with identical mechanical demands but different TTF (i.e., force-matching and position-matching tasks. On separate visits, ten healthy volunteers performed the force-matching or position-matching task at 15% of maximum strength with the elbow flexors to task failure. Single-pulse transcranial magnetic stimulation (TMS, paired-pulse TMS, paired cortico-cervicomedullary stimulation, and brachial plexus electrical stimulation were delivered in a 6-stimuli sequence at baseline and every 2-3 minutes throughout fatigue-task performance. Contrary to expectations, the force-matching task TTF was 42% shorter (17.5 ± 7.9 min than the position-matching task (26.9 ± 15.11 min; p0.05. Therefore, failure occurred after a similar mean decline in motorneuron excitability developed (p0.10 and an index of upstream excitation of the motor cortex remained constant (p>0.40. Together, these results suggest that as fatigue develops prior to task failure, the increase in corticospinal excitability observed in relationship to the decrease in spinal excitability results from a combination of decreasing intracortical inhibition with constant levels of intracortical facilitation and upstream excitability that together eventually fail to provide the input to the motor cortex necessary for descending drive to overcome the spinal cord resistance, thereby contributing to task failure.

  8. Cortical and Spinal Mechanisms of Task Failure of Sustained Submaximal Fatiguing Contractions

    Science.gov (United States)

    Williams, Petra S.; Hoffman, Richard L.; Clark, Brian C.

    2014-01-01

    In this and the subsequent companion paper, results are presented that collectively seek to delineate the contribution that supraspinal circuits have in determining the time to task failure (TTF) of sustained submaximal contractions. The purpose of this study was to compare adjustments in supraspinal and spinal excitability taken concurrently throughout the performance of two different fatigue tasks with identical mechanical demands but different TTF (i.e., force-matching and position-matching tasks). On separate visits, ten healthy volunteers performed the force-matching or position-matching task at 15% of maximum strength with the elbow flexors to task failure. Single-pulse transcranial magnetic stimulation (TMS), paired-pulse TMS, paired cortico-cervicomedullary stimulation, and brachial plexus electrical stimulation were delivered in a 6-stimuli sequence at baseline and every 2–3 minutes throughout fatigue-task performance. Contrary to expectations, the force-matching task TTF was 42% shorter (17.5±7.9 min) than the position-matching task (26.9±15.11 min; pmuscle fatigue (p = 0.59). There were no task-specific differences for the total amount or rate of change in the neurophysiologic outcome variables over time (p>0.05). Therefore, failure occurred after a similar mean decline in motorneuron excitability developed (p0.10) and an index of upstream excitation of the motor cortex remained constant (p>0.40). Together, these results suggest that as fatigue develops prior to task failure, the increase in corticospinal excitability observed in relationship to the decrease in spinal excitability results from a combination of decreasing intracortical inhibition with constant levels of intracortical facilitation and upstream excitability that together eventually fail to provide the input to the motor cortex necessary for descending drive to overcome the spinal cord resistance, thereby contributing to task failure. PMID:24667484

  9. Enhancing Economic Sustainability by Markdown Money Supply Contracts in the Fashion Industry: China vs U.S.A.

    OpenAIRE

    Bin Shen; Tsan-Ming Choi; Chris Kwan-Yu Lo

    2015-01-01

    Supply chain contracts, such as the markdown money policy (MMP), are commonly adopted in the fashion industry. In this paper, we explore how fashion companies can use MMP to enhance economic sustainability from the cross-cultural perspective. We conduct case studies on two fashion firms (suppliers), one from China and one from U.S.A., that are adopting MMP in their respective supply chains. Via semi-structured interviews with staff members and some public data searching of the target companie...

  10. Whole body oxygen uptake and evoked torque during subtetanic isometric electrical stimulation of the quadriceps muscles in a single 30-minute session.

    Science.gov (United States)

    Minogue, Conor M; Caulfield, Brian M; Lowery, Madeleine M

    2014-09-01

    To evaluate the time course of fatigue in torque output and oxygen uptake during isometric subtetanic neuromuscular electrical stimulation (NMES) to facilitate the design of NMES-based rehabilitation protocols that can accumulate a defined aerobic exercise volume within a given time period. Single-arm intervention study with within-subject comparisons. University research laboratory. Volunteer sample of healthy men (N=11; mean age, 34.2 ± 11.5 y; range, 19-53 y; body mass, 79.1 ± 11.7 kg; range, 58-100 kg). A single 30-minute session of continuous bilateral isometric quadriceps NMES at 4 Hz evoking a mean twitch amplitude of 12% of the maximum voluntary contraction. Whole body oxygen consumption rate (V˙o2), and evoked torque were measured simultaneously throughout. Mean increment in V˙o2 was 596 ± 238 mL/min, and average exercise intensity during the session was 3 ±.47 metabolic equivalents. The V˙o2 and torque declined slowly at a rate of -.54%±.31% and -.47%±.57% per minute, respectively. Despite having a higher incremental V˙o2, the observed fatigue rate was considerably less than that previously reported during intermittent isometric tetanic stimulation, suggesting that subtetanic isometric NMES is more sustainable for exercise interventions aimed at accumulating a therapeutic aerobic exercise volume. Copyright © 2014 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.

  11. Electromyographic examination of selected muscle activation during isometric core exercises.

    Science.gov (United States)

    Oliver, Gretchen D; Stone, Audrey J; Plummer, Hillary

    2010-11-01

    The purpose of the current study was to quantitatively examine the muscle activations of 3 common isometric core exercises (abdominal bridge, single-leg abdominal bridge, and superman) along with a newly introduced isometric exercise (flying squirrel) and determine if muscle activations differed among the exercises. The design was a comparison study. An athletic training classroom laboratory was where all data collections occurred. Thirty healthy collegiate graduate students (age, 23.4 ± 1.4 year; height, 171.3 ± 10.3 cm; mass, 73.3 ± 16.2 kg), regardless of sex, consented to participate. The independent variable was the muscle selected. The main outcome measures or dependent variables were the muscle activation reported as percent of maximum voluntary isometric contraction during each exercise. Results revealed that the multifidi produced the greatest muscle activity in all exercises, and the single-leg abdominal bridge exercise produced greater muscle activation than the general abdominal bridge exercise (P exercises may be a part of a core stability program. In addition, these findings may be incorporated into an isometric core exercise program to supplement a currently implemented isometric core exercise program.

  12. A Model for Sustainable Building Energy Efficiency Retrofit (BEER) Using Energy Performance Contracting (EPC) Mechanism for Hotel Buildings in China

    Science.gov (United States)

    Xu, Pengpeng

    Hotel building is one of the high-energy-consuming building types, and retrofitting hotel buildings is an untapped solution to help cut carbon emissions contributing towards sustainable development. Energy Performance Contracting (EPC) has been promulgated as a market mechanism for the delivery of energy efficiency projects. EPC mechanism has been introduced into China relatively recently, and it has not been implemented successfully in building energy efficiency retrofit projects. The aim of this research is to develop a model for achieving the sustainability of Building Energy Efficiency Retrofit (BEER) in hotel buildings under the Energy Performance Contracting (EPC) mechanism. The objectives include: • To identify a set of Key Performance Indicators (KPIs) for measuring the sustainability of BEER in hotel buildings; • To identify Critical Success Factors (CSFs) under EPC mechanism that have a strong correlation with sustainable BEER project; • To develop a model explaining the relationships between the CSFs and the sustainability performance of BEER in hotel building. Literature reviews revealed the essence of sustainable BEER and EPC, which help to develop a conceptual framework for analyzing sustainable BEER under EPC mechanism in hotel buildings. 11 potential KPIs for sustainable BEER and 28 success factors of EPC were selected based on the developed framework. A questionnaire survey was conducted to ascertain the importance of selected performance indicators and success factors. Fuzzy set theory was adopted in identifying the KPIs. Six KPIs were identified from the 11 selected performance indicators. Through a questionnaire survey, out of the 28 success factors, 21 Critical Success Factors (CSFs) were also indentified. Using the factor analysis technique, the 21 identified CSFs in this study were grouped into six clusters to help explain project success of sustainable BEER. Finally, AHP/ANP approach was used in this research to develop a model to

  13. Bilateral movements increase sustained extensor force in the paretic arm.

    Science.gov (United States)

    Kang, Nyeonju; Cauraugh, James H

    2018-04-01

    Muscle weakness in the extensors poststroke is a common motor impairment. Unfortunately, research is unclear on whether bilateral movements increase extensor force production in the paretic arm. This study investigated sustained force production while stroke individuals maximally extended their wrist and fingers on their paretic arm. Specifically, we determined isometric force production in three conditions: (a) unilateral paretic arm, (b) unilateral nonparetic arm, and (c) bilateral (both arms executing the same movement simultaneously). Seventeen chronic stroke patients produced isometric sustained force by executing wrist and fingers extension in unilateral and bilateral contraction conditions. Mean force, force variability (coefficient of variation), and signal-to-noise ratio were calculated for each contraction condition. Analysis of two-way (Arm × Type of Condition: 2 × 2; Paretic or Nonparetic Arm × Unilateral or Bilateral Conditions) within-subjects ANOVAs revealed that the bilateral condition increased sustained force in the paretic arm, but reduced sustained force in the nonparetic arm. Further, although the paretic arm exhibited more force variability and less signal-to-noise ratio than the nonparetic arm during a unilateral condition, there were no differences when participants simultaneously executed isometric contractions with both arms. Our unique findings indicate that bilateral contractions transiently increased extensor force in the paretic arm. Implications for Rehabilitation Bilateral movements increased isometric wrsit extensor force in paretic arms and redcued force in nonparetic arms versus unilateral movements. Both paretic and nonparetic arms produced similar force variability and signal-to-noise ratio during bilateral movements. Increased sustained force in the paretic arm during the bilateral condition indicates that rehabilitation protocols based on bilateral movements may be beneficial for functional recovery.

  14. ISOMETRIC EXERCISE AND ITS EFFECT ON BLOOD PRESSURE AND HEART RATE, BEFORE AND AFTER TRAINING IN YOUNG HEALTHY MALES

    Directory of Open Access Journals (Sweden)

    Mohammed

    2015-05-01

    Full Text Available INTRODUCTION: Isometric exercise is a normal part of everyday activities and many occupational tasks. Preventive services are important as they give physicians an opportunity and responsibility to promote regular physical activity, reduc e high blood pressure, and help in weight control. Physical inactivity is recognized as a risk factor for coronary artery disease. Regular aerobic physical activity increases exercise capacity and plays a role in both primary and secondary prevention of ca rdiovascular disease. OBJECTIVE: To assess the effects of isometric handgrip training on Blood pressure and Heart rate in healthy young males in the age group of 18 - 22 years. MATERIALS AND METHOD : Study subjects consisted of 30 healthy adult males in the age group of 18 - 22 yrs. Age and sex matched adults who were not active in sports or in physical activities constituted the control group (n=30. Blood pressure and heart rate were recorded and eval uated after a defined protocol of handgrip sustained static (isometric contractions performed with the handgrip dynamometer at Rest and Post Exercise. BP and HR were recorded with the help of automated blood pressure monitor and power lab 8/30 series inst rument available in the Department of Physiology , Navodaya Medical college, Raichur. RESULTS: There was no change in Resting Blood pressure and Heart rate between the subject and control group before the training sessions. There was significant decrease in resting Blood pressure and Heart rate in trained subject group when compared to untrained control group after 5 weeks of training sessions. CONCLUSION : Isometric hand grip training is effective in lowering arterial pressure in normotensive subjects. Isome tric training may be an effective intervention in the prevention and treatment of hypertension

  15. Quantitative sensory response of the SCM muscle on sustained low level activation simulating co-contractions during bruxing.

    Science.gov (United States)

    Eberhard, Lydia; Terebesi, Sophia; Giannakopoulos, Nikolaos Nikitas; Hellmann, Daniel; Schindler, Hans-Jürgen; Schmitter, Marc; Pfau, Doreen

    2017-11-10

    Bruxism is discussed as an etiological factor in the pathogenesis of orofacial and cervical pain. As the sternocleidomastoid muscle (SCM) is co-activated during clenching, our aim was to investigate, whether the muscle loading leads to peripheral or central sensitizations. In twenty-one healthy female volunteers, somatosensory profiles of the SCM were recorded according to the test battery of the German Research Network on Neuropathic Pain (DFNS) prior to and after an isometric muscle exercise. QST comprised thermal and mechanical stimuli. A submaximal activation of the SCM (15% MVC) was kept for 10min in sitting position. In separate test sessions one month apart, one sham and one verum experiment were conducted in randomized order. During the muscle loading, the parameters cold detection threshold (CDT), mechanical pain sensitivity (MPS) and pressure pain treshold (PPT) were tested and experimental pain recorded by visual analogoue scales (VAS). All test sessions were performed during the follicular phase of the menstrual cycle (day 5), to avoid effects on pain perception. Data were analyzed with Repeated Measures ANOVA (SPSS 22.0) RESULTS: No significant changes were found during or after (sham) loading except for stimulus-response-function (SR, P=0.01) and PPT (P=0.02) in the sham test. No effect was observed in the verum experiment (P=0.12 up to 1.0). Prolonged low level contraction of the SCM does not evoke painful sensitization. In contrast, submaximal muscle activation seems to have a protective effect corresponding to a training effect preventing sensitization. Copyright © 2017. Published by Elsevier Ltd.

  16. Muscle Activation Pattern During Isometric Ab Wheel Rollout Exercise in Different Shoulder Angle-Positions

    OpenAIRE

    Marchetti, Paulo Henrique; Schoenfeld, Brad J.; Silva, Josinaldo Jarbas da; Guiselini, Mauro Antonio; Freitas, Fabio Sisconeto de; Pecoraro, Silvio Luiz; Gomes,Willy Andrade; Lopes,Charles Ricardo

    2015-01-01

    OBJECTIVE: To investigate muscle activation of the shoulder extensors and trunk stabilizers by surface electromyography (sEMG) activity during the isometric Ab Wheel Rollout exercise in different shoulder joint positions. METHOD: We recruited 8 young, healthy, resistance trained men (age: 25 ± 3 years, height: 178 ± 5 cm, and total body mass: 81 ± 2 kg). All subjects performed two sets of 10 sec. maximal isometric contractions of the Ab Wheel Rollout exercise keeping the knees fixed on the f...

  17. Energetics of contraction.

    Science.gov (United States)

    Barclay, C J

    2015-04-01

    Muscles convert energy from ATP into useful work, which can be used to move limbs and to transport ions across membranes. The energy not converted into work appears as heat. At the start of contraction heat is also produced when Ca(2+) binds to troponin-C and to parvalbumin. Muscles use ATP throughout an isometric contraction at a rate that depends on duration of stimulation, muscle type, temperature and muscle length. Between 30% and 40% of the ATP used during isometric contraction fuels the pumping Ca(2+) and Na(+) out of the myoplasm. When shortening, muscles produce less force than in an isometric contraction but use ATP at a higher rate and when lengthening force output is higher than the isometric force but rate of ATP splitting is lower. Efficiency quantifies the fraction of the energy provided by ATP that is converted into external work. Each ATP molecule provides 100 zJ of energy that can potentially be converted into work. The mechanics of the myosin cross-bridge are such that at most 50 zJ of work can be done in one ATP consuming cycle; that is, the maximum efficiency of a cross-bridge is ∼50%. Cross-bridges in tortoise muscle approach this limit, producing over 90% of the possible work per cycle. Other muscles are less efficient but contract more rapidly and produce more power. © 2015 American Physiological Society.

  18. Enhancing Economic Sustainability by Markdown Money Supply Contracts in the Fashion Industry: China vs U.S.A.

    Directory of Open Access Journals (Sweden)

    Bin Shen

    2015-12-01

    Full Text Available Supply chain contracts, such as the markdown money policy (MMP, are commonly adopted in the fashion industry. In this paper, we explore how fashion companies can use MMP to enhance economic sustainability from the cross-cultural perspective. We conduct case studies on two fashion firms (suppliers, one from China and one from U.S.A., that are adopting MMP in their respective supply chains. Via semi-structured interviews with staff members and some public data searching of the target companies, we find that the cultural factors, such as power distance and collectivism/individualism, affect contract selection, contract management, supplier–retailer leadership, and supplier–retailer relationship. We use the Hofstede’s national cultural dimensions theory to explain our insights. Specifically, in China, a country with a relatively high degree of power distance and collectivism, the companies tend to care more about the group interest and loyalty. The Chinese fashion companies are more willing to play the leading role in managing the relationships with their retailers, and offer MMP to them. In the U.S.A., a country with a relatively low degree of power distance and individualism, the companies are more likely to emphasize their own interest in trading. In fact, we find that American fashion suppliers tend to bargain with their retailers, and they are less willing to proactively provide the markdown money as a sponsor. Finally, managerial implications are provided, and several future challenges on MMP are examined.

  19. The effect of sustained low-intensity contractions on supraspinal fatigue in human elbow flexor muscles

    DEFF Research Database (Denmark)

    Søgaard, Karen; Gandevia, Simon C; Todd, Gabrielle

    2006-01-01

    several minutes while MVC torque only returned to approximately 85% baseline. The resting twitch showed no recovery. Thus, as well as fatigue in the muscle, the prolonged low-force contraction produced progressive central fatigue, and some of this impairment of the subjects' ability to drive the muscle......Subjects quickly fatigue when they perform maximal voluntary contractions (MVCs). Much of the loss of force is from processes within muscle (peripheral fatigue) but some occurs because voluntary activation of the muscle declines (central fatigue). The role of central fatigue during submaximal...... stimulation (TMS) was followed by stimulation of either brachial plexus or the motor nerve of biceps brachii. After nerve stimulation, a resting twitch was also evoked before subjects resumed the 15% MVC. Perceived effort, elbow flexion torque and surface EMG from biceps, brachioradialis and triceps were...

  20. Effects of muscle pain induced by glutamate injections during sustained clenching on the contraction pattern of masticatory muscles.

    Science.gov (United States)

    Michelotti, Ambrosina; Cioffi, Iacopo; Rongo, Roberto; Borrelli, Roberta; Chiodini, Paolo; Svensson, Peter

    2014-01-01

    To evaluate the contraction pattern of masticatory muscles during sustained clenching tasks with or without experimental pain induced by glutamate injection into the masseter muscle. It was hypothesized that acute muscle pain could induce compensatory changes in the electromyographic (EMG) activity of the masticatory muscles. Fifteen volunteers (seven males, mean age ± SD = 29.7 ± 1.1 years; eight females, mean age ± SD = 23.5 ± 1.2 years) were recruited in a crossover experimental study. All subjects participated in two randomized 20-minute experimental sessions. Each subject was asked to clench at 25% of the maximum voluntary contraction (MVC). After 10 minutes, isotonic saline or glutamate was injected in random order into the right masseter. EMG activity (root mean square [RMS] and mean power frequency [MPF]) was assessed in the masseter and anterior temporalis muscles on both sides. Pain and fatigue were assessed by 0-10 numeric rating scales (NRS) every minute. Differences between conditions (isotonic saline vs glutamate) for all the outcome parameters were analyzed by using a mixed effect model. The EMG activity of the masticatory muscles and pain and fatigue scores were not dependent on isotonic saline/glutamate injection (all P > .05). The RMS in the temporalis and masseter muscles increased with time (right masseter P = 0.001, left masseter P = .004, right temporalis P = .22, left temporalis P = .006), whereas the MPF decreased (right masseter P = .0001, left masseter P muscles during a sustained clenching task. This finding strongly suggests the adaptive capacity of the stomatognathic system in the presence of acute nociceptive inputs.

  1. Pelvic floor muscle training decreases hip adductors isometric peak torque in incontinent women: an exploratory study

    Directory of Open Access Journals (Sweden)

    Grasiéla Nascimento Correia

    Full Text Available INTRODUCTION: The pelvic floor muscle (PFM training is the most common treatment for urinary incontinence (UI, however many women performed the contraction of PFM with associated contraction of abdominal, gluteus and hip adductors muscles. OBJECTIVE: To assess the effects of pelvic floor muscle (PFM training on isometric and isokinetic hip adductors peak torque (PT among women suffering from urinary incontinence (UI. MATERIALS AND METHODS: It is a longitudinal and prospective exploratory study. This study included 15 physically active women aged 45 years old and over, who presented complaints of UI. The PFM function (digital evaluation and perineometry, isometric and isokinetic hip adductors PT and one hour pad test were performed before and after treatment. The PFM training was performed in group, one hour once a week for 12 sessions. RESULTS: Significant improvement of PFM function and pressure level (p = 0.003, and significant decrease of hip adductors isometric PT and one-hour pad test, were found post-treatment. Moderate negative correlations between PFM contraction pressure and hip adductors isokinetic PT for dominant side (DS (r = -0.62; p = 0.03 and non-dominant side (NDS (r = -0.64; p = 0.02; and between PFM fast fibers contraction and hip adductors isometric PT for DS (r = -0.60; p = 0.03 and NDS (r = -0.59; p = 0.04 were also found. CONCLUSIONS: The PFM training decreased hip adductors PT and improved PFM functions and UI.

  2. Force levels in uni- and bimanual isometric tasks affect variability measures differently throughout lifespan.

    NARCIS (Netherlands)

    Smits-Engelsman, B.C.M.; Galen, G.P. van; Duysens, J.E.J.

    2004-01-01

    Ninety-four participants (age 5-93 years) performed isometric force production tasks at five different levels of their maximum voluntary contraction (MVC) with either one or two index fingers. Research questions were whether variability measures in the bimanual task condition were different compared

  3. Force levels in uni- and bimanual isometric tasks affect variability measures differently throughout lifespan

    NARCIS (Netherlands)

    Smits-Engelsman, B.C.M.; Galen, G.P. van; Duysens, J.E.J.

    2004-01-01

    Ninety-four participants (age 5-93 years) performed isometric force production tasks at five different levels of their maximum voluntary contraction (MVC) with either one or two index fingers. Research questions were whether variability measures in the bimanual task condition were different compared

  4. Fast unilateral isometric knee extension torque development and bilateral jump height.

    NARCIS (Netherlands)

    C.J. de Ruiter; M.F. Bobbert; Dr. D.M. van Leeuwen; A.J. Heijblom; A. de Haan

    2006-01-01

    PURPOSE: We hypothesized that the initial rate (first 40 ms) of unilateral knee extensor torque development during a maximally fast isometric contraction would depend on the subjects' ability for fast neural activation and that it would predict bilateral jumping performance. METHODS: Nine males

  5. Fast unilateral isometric knee extension torque development and bilateral jump height.

    NARCIS (Netherlands)

    de Ruiter, C.J.; Leeuwen, D.; Heijblom, A.; Bobbert, M.F.; de Haan, A.

    2006-01-01

    Purpose: We hypothesized that the initial rate (first 40 ms) of unilateral knee extensor torque development during a maximally fast isometric contraction would depend on the subjects' ability for fast neural activation and that it would predict bilateral jumping performance. Methods: Nine males

  6. Effect of vastus lateralis fatigue on load sharing between quadriceps femoris muscles during isometric knee extensions.

    Science.gov (United States)

    Bouillard, Killian; Jubeau, Marc; Nordez, Antoine; Hug, François

    2014-02-01

    The present study aimed to investigate the effects of selective fatigue (i.e., one muscle of the quadriceps) on load sharing strategies during submaximal knee extensions. Shear wave elastography was used to measure muscle shear elastic modulus, as this is considered to be an index of individual muscle force. Sixteen participants attended two experimental sessions that each involved six 10-s knee extensions at 20% of maximal voluntary contraction (MVC) followed by a sustained submaximal isometric knee extension at 20% of MVC, until task failure (Tlim). Between the 10-s contractions and Tlim, participants were required to rest (5 min) for the control session or underwent 5 min of electromyostimulation (EMS) on vastus lateralis (EMS session). Compared with the control session, vastus lateralis shear elastic modulus values were significantly lower after EMS considering both the start of Tlim (54.6 ± 11.8 vs. 68.4 ± 19.2 kPa; P = 0.011) and the entire Tlim contraction (59.0 ± 14.0 vs. 74.4 ± 20.3 kPa; P = 0.019). However, no significant differences were observed for the other recorded muscles (vastus medialis and rectus femoris; both P = 1), i.e., different patterns of changes were found between participants. In conclusion, this study demonstrates that prefatiguing a single agonist muscle does not lead to a consistent redistribution of load sharing among the quadriceps muscles between individuals. These results suggest that the central nervous system does not use a common principle among individuals to control load sharing when neuromuscular fatigue occurs.

  7. The antihypertensive effects of aerobic versus isometric handgrip resistance exercise.

    Science.gov (United States)

    Ash, Garrett I; Taylor, Beth A; Thompson, Paul D; MacDonald, Hayley V; Lamberti, Lauren; Chen, Ming-Hui; Farinatti, Paulo; Kraemer, William J; Panza, Gregory A; Zaleski, Amanda L; Deshpande, Ved; Ballard, Kevin D; Mujtaba, Mohammadtokir; White, C Michael; Pescatello, Linda S

    2017-02-01

    Aerobic exercise reduces blood pressure (BP) on average 5-7 mmHg among those with hypertension; limited evidence suggests similar or even greater BP benefits may result from isometric handgrip (IHG) resistance exercise. We conducted a randomized controlled trial investigating the antihypertensive effects of an acute bout of aerobic compared with IHG exercise in the same individuals. Middle-aged adults (n = 27) with prehypertension and obesity randomly completed three experiments: aerobic (60% peak oxygen uptake, 30 min); IHG (30% maximum voluntary contraction, 4 × 2 min bilateral); and nonexercise control. Study participants were assessed for carotid-femoral pulse wave velocity pre and post exercise, and left the laboratory wearing an ambulatory BP monitor. SBP and DBP were lower after aerobic versus IHG (4.8 ± 1.8/3.1 ± 1.3 mmHg, P = 0.01/0.04) and control (5.6 ± 1.8/3.6 ± 1.3 mmHg, P = 0.02/0.04) over the awake hours, with no difference between IHG versus control (P = 0.80/0.83). Pulse wave velocity changes following acute exercise did not differ by modality (aerobic increased 0.01 ± 0.21 ms, IHG decreased 0.06 ± 0.15 ms, control increased 0.25 ± 0.17 ms, P > 0.05). A subset of participants then completed either 8 weeks of aerobic or IHG training. Awake SBP was lower after versus before aerobic training (7.6 ± 3.1 mmHg, P = 0.02), whereas sleep DBP was higher after IHG training (7.7 ± 2.3 mmHg, P = 0.02). Our findings did not support IHG as antihypertensive therapy but that aerobic exercise should continue to be recommended as the primary exercise modality for its immediate and sustained BP benefits.

  8. Age-related differences in muscle fatigue vary by contraction type: a meta-analysis.

    Science.gov (United States)

    Avin, Keith G; Law, Laura A Frey

    2011-08-01

    During senescence, despite the loss of strength (force-generating capability) associated with sarcopenia, muscle endurance may improve for isometric contractions. The purpose of this study was to perform a systematic meta-analysis of young versus older adults, considering likely moderators (ie, contraction type, joint, sex, activity level, and task intensity). A 2-stage systematic review identified potential studies from PubMed, CINAHL, PEDro, EBSCOhost: ERIC, EBSCOhost: Sportdiscus, and The Cochrane Library. Studies reporting fatigue tasks (voluntary activation) performed at a relative intensity in both young (18-45 years of age) and old (≥ 55 years of age) adults who were healthy were considered. Sample size, mean and variance outcome data (ie, fatigue index or endurance time), joint, contraction type, task intensity (percentage of maximum), sex, and activity levels were extracted. Effect sizes were (1) computed for all data points; (2) subgrouped by contraction type, sex, joint or muscle group, intensity, or activity level; and (3) further subgrouped between contraction type and the remaining moderators. Out of 3,457 potential studies, 46 publications (with 78 distinct effect size data points) met all inclusion criteria. A lack of available data limited subgroup analyses (ie, sex, intensity, joint), as did a disproportionate spread of data (most intensities ≥ 50% of maximum voluntary contraction). Overall, older adults were able to sustain relative-intensity tasks significantly longer or with less force decay than younger adults (effect size=0.49). However, this age-related difference was present only for sustained and intermittent isometric contractions, whereas this age-related advantage was lost for dynamic tasks. When controlling for contraction type, the additional modifiers played minor roles. Identifying muscle endurance capabilities in the older adult may provide an avenue to improve functional capabilities, despite a clearly established decrement in

  9. Changes in the tibialis anterior tendon moment arm from rest to maximum isometric dorsiflexion: in vivo observations in man.

    Science.gov (United States)

    Maganaris, C N; Baltzopoulos, V; Sargeant, A J

    1999-11-01

    In the present study, we examined the hypothesis that the tibialis anterior tendon moment arm increases during maximum isometric dorsiflexion as compared with rest. In musculoskeletal modelling applications, moment arms from passive muscles at rest are assumed representative of those measured during isometric muscle contraction. The validity of this assumption is questionable in musculotendon actuators enclosed by retinacular systems as in tibialis anterior. Sagittal-plane magnetic resonance images of the right ankle were taken in six subjects at rest and during maximum isometric dorsiflexion at six ankle angles between dorsiflexion and plantarflexion having the body placed in the supine position and the knee flexed at 90 degrees. Instant centres of rotation in the tibio-talar joint, tibialis anterior tendon action lines and moment arms were identified in the sagittal plane at ankle angles of -15 degrees, 0 degrees,+15 degrees and +30 degrees at rest and during maximum isometric dorsiflexion. At any given ankle angle, the tibialis anterior tendon moment arm during maximum isometric dorsiflexion increased by 0.9-1.5 cm (Pdorsiflexion is invalid. Erroneous tendon forces, muscle stresses and joint moments by as much as 30% would be calculated using resting tibialis anterior tendon moment arms in the moment equilibrium equation around the ankle joint during maximum isometric dorsiflexion. A substantial increase in the tibialis anterior tendon moment arm occurs from rest to maximum isometric dorsiflexion. This needs to be taken into consideration when using planimetric musculoskeletal modelling for analysing maximal static ankle dorsiflexion loads.

  10. Relation between Peak Power Output in Sprint Cycling and Maximum Voluntary Isometric Torque Production.

    Science.gov (United States)

    Kordi, Mehdi; Goodall, Stuart; Barratt, Paul; Rowley, Nicola; Leeder, Jonathan; Howatson, Glyn

    2017-08-01

    From a cycling paradigm, little has been done to understand the relationships between maximal isometric strength of different single joint lower body muscle groups and their relation with, and ability to predict PPO and how they compare to an isometric cycling specific task. The aim of this study was to establish relationships between maximal voluntary torque production from isometric single-joint and cycling specific tasks and assess their ability to predict PPO. Twenty male trained cyclists participated in this study. Peak torque was measured by performing maximum voluntary contractions (MVC) of knee extensors, knee flexors, dorsi flexors and hip extensors whilst instrumented cranks measured isometric peak torque from MVC when participants were in their cycling specific position (ISOCYC). A stepwise regression showed that peak torque of the knee extensors was the only significant predictor of PPO when using SJD and accounted for 47% of the variance. However, when compared to ISOCYC, the only significant predictor of PPO was ISOCYC, which accounted for 77% of the variance. This suggests that peak torque of the knee extensors was the best single-joint predictor of PPO in sprint cycling. Furthermore, a stronger prediction can be made from a task specific isometric task. Copyright © 2017 Elsevier Ltd. All rights reserved.

  11. Influences of Fascicle Length During Isometric Training on Improvement of Muscle Strength.

    Science.gov (United States)

    Tanaka, Hiroki; Ikezoe, Tome; Umehara, Jun; Nakamura, Masatoshi; Umegaki, Hiroki; Kobayashi, Takuya; Nishishita, Satoru; Fujita, Kosuke; Araki, Kojiro; Ichihashi, Noriaki

    2016-11-01

    Tanaka, H, Ikezoe, T, Umehara, J, Nakamura, M, Umegaki, H, Kobayashi, T, Nishishita, S, Fujita, K, Araki, K, and Ichihashi, N. Influences of fascicle length during isometric training on improvement of muscle strength. J Strength Cond Res 30(11): 3249-3255, 2016-This study investigated whether low-intensity isometric training would elicit a greater improvement in maximum voluntary contraction (MVC) at the same fascicle length, rather than the joint angle, adopted during training. Sixteen healthy women (21.8 ± 1.5 years) were randomly divided into an intervention group and a control group. Before (Pre) and after (Post) training, isometric plantarflexion MVCs were measured every 10° through the range of ankle joint position from 20° dorsiflexion to 30° plantarflexion (i.e., 6 ankle angles). Medial gastrocnemius fascicle length was also measured at each position, using B-mode ultrasound under 3 conditions of muscle activation: at rest, 30%MVC at respective angles, and MVC. Plantarflexion resistance training at an angle of 20° plantarflexion was performed 3 days a week for 4 weeks at 30%MVC using 3 sets of twenty 3-second isometric contractions. Maximum voluntary contraction in the intervention group increased at 0 and 10° plantarflexion (0°; Pre: 81.2 ± 26.5 N·m, Post: 105.0 ± 21.6 N·m, 10°; Pre: 63.0 ± 23.6 N·m, Post: 81.3 ± 20.3 N·m), which was not the angle used in training (20°). However, the fascicle length adopted in training at 20° plantarflexion and 30%MVC was similar to the value at 0 or 10° plantarflexion at MVC. Low-intensity isometric training at a shortened muscle length may be effective for improving MVC at a lengthened muscle length because of specificity of the fascicle length than the joint angle.

  12. Hand-grip isometric strength in judo

    Directory of Open Access Journals (Sweden)

    Juan G Bonitch-Góngora

    2014-02-01

    Full Text Available The grip is an important technical and tactical aspect through which the judokas dominate the adversary, hindering the application of appropriate techniques and favoring their own attack. The judokas must have high levels of isometric force and endurance to this type of force on the gripping muscles of the forearms, as one of the key aspects for success. This article reviews the grip muscular strength and endurance profiles of judokas of different groups (gender, age and competitive level. In general, the peak isometric strength of elite judokas has not changed in the last 40 years and is similar to that reached by non-elite judokas or even registered in large populations. This indicate that the evaluation of the isometric hand grip endurance may be a more relevant parameter than the peak isometric force in judokas, as during the bouts the grip must be maintained for relatively long periods of time and the maximum force cannot be maintained for long. However there are few studies on the ability to resist successive isometric handgrip stress in judokas.

  13. Can Conservation Contracts Co-exist with Change? Payment for Ecosystem Services in the Context of Adaptive Decision-Making and Sustainability

    Science.gov (United States)

    Hayes, Tanya; Murtinho, Felipe; Cárdenas Camacho, Luis Mario; Crespo, Patricio; McHugh, Sarah; Salmerón, David

    2015-01-01

    This paper considers the ability of payment for ecosystem services (PES) programs to operate in the context of dynamic and complex social-ecological systems. Drawing on the experiences of two different PES programs in Latin America, we examine how PES institutions fit with the tenets of adaptive decision-making for sustainable resource management. We identify how the program goals and the connection to the market influence the incentive structure, information gathering, learning and feedback processes, and the structure of decision-making rights, specifically the ability to make and modify resource-use rules. Although limited in their generalizability, findings from the two case studies suggest a tension between the contractual model of PES and adaptive decision-making in natural resource systems. PES programs are not inherently decentralized, flexible management tools, as PES contracts tend to restrict decision-making rights and offer minimal flexibility mechanisms to change resource-use practices over the duration of the contract period. Furthermore, PES design and flexibility is heavily dependent on the goals and mission of the buyer and the respective market. If PES is to facilitate sustainable resource management, greater attention is needed to assess how the institutional design of the PES contracts influence the motivation and capacity of participants and program officers alike to adaptively manage the respective resource systems.

  14. Army Corps of Engineers and Gulf Region Division contingency contracting in Iraq/Afghanistan: sustaining civilian voluntary workforce

    OpenAIRE

    Brosch, Paige; Wigfall, Henry; Clemons, Travis

    2008-01-01

    Joint Applied Project The objective of this project is to describe, analyze, and recommend the strategy and process of using an Army volunteer civilian contracting deployable workforce in Iraq and Afghanistan particularly in terms of the U S. Army Corps of Engineers (USACE) accomplishing the contingency contracting mission, and completing the construction portion of the reconstruction efforts. The Corps has been extensively involved in the nation building effort in Iraq/Afghanistan usi...

  15. The Contracting Support Brigade: Is It Capable of Sustaining Tempo and Combat Power in the Operational Environment

    Science.gov (United States)

    2015-05-21

    Veldhuizen, CPT Roy Faulkner , CPT Nate Miatech, MSG Kelvin Barton, and MSG Chester Montgomery. I conclude these acknowledgments by breaking protocol. However...Support: Cultural Change Needed to Improve How DOD Plans for and Manages Operational Contract Support, by William M. Solis. GAO-10-829T, 2010. Accessed...Operational Contract Support Enabler-Joint Contingency Acquisition Support Office (JCASO), by William E. Gortney. Washington, DC: CJCS, 2011.

  16. Effect of submaximal isometric wrist extension training on grip strength.

    Science.gov (United States)

    Shimose, Ryota; Matsunaga, Atsuhiko; Muro, Masuo

    2011-03-01

    Gripping force is produced by co-contraction of forearm flexors and extensors. Activation of extensors is important for stabilizing the wrist during gripping. However, forearm muscle function is complicated and the neurophysiological mechanism responsible for the gain in gripping force is unclear. Therefore, the purpose of this study was to investigate whether increasing forearm extensor activation with isometric wrist extension training has an effect on gripping force. Thirteen healthy subjects participated in this study. Maximal voluntary contraction of gripping was measured using a piezosensor (MVC(grip)) and EMG of forearm muscles at every wrist angle (from 70° flexion to 80° extension with 10° intervals) were measured simultaneously at baseline, 4 weeks, and 8 weeks after training. Training consisted of 30 repetitions equal to 70% MVC of isometric wrist extension for 8 weeks (5/week) on the right side. Gripping force was measured on both sides using a grip dynamometer without wrist angle restriction. Gripping force, EMG, maximal wrist extension force, and wrist angle-gripping force curve were investigated after training. After training, maximal wrist extension force increased significantly. Gripping force on the trained side also increased significantly. The training changed wrist angle at peak of MVC(grip). EMG activation of forearm extensors increased and that of flexors decreased during gripping. These results suggest that wrist extension training leads to an increase in gripping force and changes the balance of EMG activation between forearm flexors and extensors during gripping. Therefore, this training method should be useful as a therapeutic strategy for increasing grip strength.

  17. Avaliação da inibição recíproca em humanos durante contrações isométricas dos músculos tibial anterior e sóleo Assessment of reciprocal inhibition in humans during isometric contractions of the tibialis anterior and soleus muscles

    Directory of Open Access Journals (Sweden)

    José Eduardo Pompeu

    2009-09-01

    Full Text Available Os objetivos do presente trabalho foram: (1 desenvolver um método para estimar o grau de inibição recíproca (IR entre músculos antagonistas em humanos (sóleo e tibial anterior e (2 comparar os níveis de IR no repouso, na dorsiflexão (DF e na flexão plantar (FP. Participaram nove sujeitos saudáveis com idade entre 20 e 30 anos, quatro homens e cinco mulheres. Os sujeitos permaneceram sentados numa cadeira com o pé direito apoiado e fixo num pedal acoplado a um torquímetro; as medições foram feitas no repouso e durante contração isométrica dos músculos dorsiflexores e flexores plantares do tornozelo. A onda H do músculo sóleo foi captada por eletrodos de superfície. O reflexo H (RH "teste" do músculo sóleo foi medido aplicando-se um estímulo na fossa poplítea (nervo tibial. O reflexo H "condicionado" foi obtido pelo pareamento de dois estímulos: o primeiro aplicado sobre a cabeça da fíbula e o segundo, na fossa poplítea, após 1 a 3 ms.. As amplitudes pico-a-pico dos RH teste e condicionado foram utilizadas para o cálculo da IR. Os valores de IR foram: 16,41%±8,68 no repouso; 21,94%±5,39 na DF e 3,12%±11,84 na FP. Foi constatada menor inibição recíproca na FP quando comparada às demais condições (pThe purposes of the present study were (1 to develop a method to estimate the level of reciprocal inhibition (RI between antagonist (soleus and anterior tibial muscles in humans, and (2 to compare RI levels during rest, dorsiflexion (DF and plantar flexion (PF. Nine healthy subjects (four men, five women aged between 20 and 30 years were assessed. Each subject remained seated with his/her right foot strapped to a rigid foot plate coupled to a torquemeter; measurements were taken at rest and during isometric contraction of the ankle dorsiflexor and plantar flexor muscles. The soleus muscle H-wave was captured by surface electrodes. A "test" H- reflex was elicited by a stimulus (electrical pulse to the popliteal fossa

  18. Isometric relaxation of rat myocardium at end-systolic fiber length.

    Science.gov (United States)

    Wiegner, A W; Bing, S H

    1978-12-01

    In a "physiologically sequenced" contraction (PSC), which loads the isolated muscle preparation in a manner which approximates that of the intact heart, isometric relaxation precedes isotonic relaxation and occurs at minimum ("end-systolic") length. We studied the effects of inital muscle length, load, temperature, calcium, and isoproterenol on the isometric relaxation phase of physiologically sequenced contractions to define the determinants of the rate of isometric relaxation of rat left ventricular myocardium. At the baseline temperature (28 degrees C), relaxation was found to be nonexponential, and the maximum rate of decline of force (-dF/dtmax) was used to evaluate changes in relaxation. Three factors, shortening, end-systolic length, and total load, were examined as possible mechanical determinants of -dF/dtmax. We found that -dF/dtmax is linearly related to end-systolic muscle length for lengths below 94% of Lmax; -dF/dtmax is also strongly related to total load for lightly loaded contractions, but peaks at loads of approximately 80% of peak developed force and declines thereafter. Shortening is poorly correlated with -dF/dtmax. The slope of the linear portion of the relation between -dF/dtmax and end-systolic length appears to be independent of muscle-loading conditions and sensitive to factors known to alter relaxation.

  19. [Reliability and validity of the analysis of hand grip and pinch force in isometric and isokinetic conditions].

    Science.gov (United States)

    Benaglia, P G; Franchignoni, F; Ferriero, G; Zebellin, G; Sartorio, F

    1999-01-01

    Strength measurement of the hand grip is at the core of most protocols of functional assessment of the upper limb and in rehabilitation plays a major role in the analysis of treatment efficacy and patients' occupational ability. The aims of this study were to: a) verify the repeatability of strength measurements made during performance of the hand grip and three types of pinch, carried out under isometric and isokinetic conditions; b) compare maximal isometric strength with the corresponding isokinetic value for each of the manoeuvres studied; c) investigate the correlations between the strength expressed in the different manoeuvres, under both isometric and isokinetic conditions. We studied 14 voluntary subjects over three sessions conducted at 48-hr intervals, employing a computerized isokinetic dynamometer Lido WorkSet equipped with device N(o) 21 for the study of pinch (lateral pinch, pulp pinch, chuck pinch) and device N(o) 52 for the grip study. Isometric contractions resulted stronger than isokinetic ones, and the hand grip was found to be the manoeuvre able to produce most strength. The repeatability of each strength measurement test over the three days was high (Intraclass Correlation Coefficients: 0.89-0.93). Correlations between the isometric and isokinetic performance for each of the manoeuvres examined were always high (Pearson's r coefficients: 0.89-0.95) as were those between the different manoeuvres, whether performed in isometric or isokinetic modality (r: 0.60-0.94).

  20. The effects of isometric resistance training on stretch reflex induced tremor in the knee extensor muscles.

    Science.gov (United States)

    Durbaba, Rade; Cassidy, Angela; Budini, Francesco; Macaluso, Andrea

    2013-06-15

    This study examines the effect of 4 wk of high-intensity isometric resistance training on induced tremor in knee extensor muscles. Fourteen healthy volunteers were assigned to either the training group (n = 7) or the nontraining control group (n = 7). Induced tremor was assessed by measuring force fluctuations during anisometric contractions against spring loading, whose compliance was varied to allow for preferential activation of the short or long latency stretch reflex components. Effects of high-intensity isometric resistance training on induced tremor was assessed under two contraction conditions: relative force matching, where the relative level of activity was equal for both pre- and post-training sessions, set at 30% maximum voluntary contraction (MVC), and absolute force matching, where the level of activity was set to 30% pretrained MVC. The training group experienced a 26.5% increase in MVC in contrast to the 0.8% for the control group. For relative force-matching contractions, induced tremor amplitude and frequency did not change in either the training or control group. During absolute force-matching contractions, induced tremor amplitude was decreased by 37.5% and 31.6% for the short and long components, respectively, with no accompanying change in frequency, for the training group. No change in either measure was observed in the control group for absolute force-matching contractions. The results are consistent with high-intensity isometric resistance training induced neural changes leading to increased strength, coupled with realignment of stretch reflex automatic gain compensation to the new maximal force output. Also, previous reported reductions in anisometric tremor following strength training may partly be due to changed stretch reflex behavior.

  1. ANODAL TRANSCRANIAL DIRECT CURRENT STIMULATION (TDCS) INCREASES ISOMETRIC STRENGTH OF SHOULDER ROTATORS MUSCLES IN HANDBALL PLAYERS.

    Science.gov (United States)

    Hazime, Fuad Ahmad; da Cunha, Ronaldo Alves; Soliaman, Renato Rozenblit; Romancini, Ana Clara Bezerra; Pochini, Alberto de Castro; Ejnisman, Benno; Baptista, Abrahão Fontes

    2017-06-01

    Weakness of the rotator cuff muscles can lead to imbalances in the strength of shoulder external and internal rotators, change the biomechanics of the glenohumeral joint and predispose an athlete to injury. Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation technique that has demonstrated promising results in a variety of health conditions. However few studies addressed its potential approach in the realm of athletics. The purpose of this study was to investigate if transcranial direct current stimulation (tDCS) technique increases the isometric muscle strength of shoulder external and internal rotators in handball athletes. Randomized, double-blind, placebo-controlled, crossover study. Eight female handball players aged between 17 and 21 years (Mean=19.65; SD=2.55) with 7.1 ± 4.8 years of experience in training, participating in regional and national competitions were recruited. Maximal voluntary isometric contraction (MVIC) of shoulder external and internal rotator muscles was evaluated during and after 30 and 60 minutes post one session of anodal and sham current (2mA; 0.057mA/cm2) with a one-week interval between stimulations. Compared to baseline, MVIC of shoulder external and internal rotators significantly increased after real but not sham tDCS. Between-group differences were observed for external and internal rotator muscles. Maximal voluntary isometric contraction of external rotation increased significantly during tDCS, and 30 and 60 minutes post-tDCS for real tDCS compared to that for sham tDCS. For internal rotation MVIC increased significantly during and 60 minutes post-tDCS. The results indicate that transcranial direct current stimulation temporarily increases maximal isometric contractions of the internal and external rotators of the shoulder in handball players. 2.

  2. Isometric handgrip does not elicit cardiovascular overload or post-exercise hypotension in hypertensive older women.

    Science.gov (United States)

    Olher, Rafael dos Reis Vieira; Bocalini, Danilo Sales; Bacurau, Reury Frank; Rodriguez, Daniel; Figueira, Aylton; Pontes, Francisco Luciano; Navarro, Francisco; Simões, Herbert Gustavo; Araujo, Ronaldo Carvalho; Moraes, Milton Rocha

    2013-01-01

    Arterial hypertension is a serious health problem affecting mainly the elderly population. Recent studies have considered both aerobic and resistance exercises as a non-pharmacological aid for arterial hypertension treatment. However, the cardiovascular responses of the elderly to isometric resistance exercise (eg, isometric handgrip [IHG]) have not yet been documented. The purpose of this study was to investigate cardiovascular responses to different intensities of isometric exercise, as well as the occurrence of post-isometric exercise hypotension in hypertensive elderly people under antihypertensive medication treatment. Twelve women volunteered to participate in the study after a maximal voluntary contraction test (MVC) and standardization of the intervention workload consisting of two sessions of IHG exercise performed in four sets of five contractions of a 10-second duration. Sessions were performed both at 30% of the MVC and 50% of the MVC, using a unilateral IHG protocol. Both intensities were compared with a control session without exercise. Systolic blood pressure (SBP) and diastolic blood pressure (DBP) at rest (R), during peak exercise (PE), and after 5, 10, 15, 30, 45, and 60 minutes of post-exercise recovery were evaluated. No significant changes were observed after isometric exercise corresponding to 30% MVC for either SBP (R: 121 ± 10; PE: 127 ± 14; 5 min: 125 ± 13; 10 min: 123 ± 12; 15 min: 122 ± 11; 30 min: 124 ± 11; 45 min: 124 ± 10; 60 min: 121 ± 10 mmHg) or DBP (R: 74 ± 9; PE: 76 ± 6; 5 min: 74 ± 5; 10 min: 72 ± 8; 15 min: 72 ± 5; 30 min: 72 ± 8; 45 min: 73 ± 6; 60 min: 75 ± 7 mmHg). Similarly, the 50% MVC did not promote post-isometric exercise hypotension for either SBP (R: 120 ± 7; PE: 125 ± 11; 5 min: 120 ± 9; 10 min: 122 ± 9; 15 min: 121 ± 11; 30 min: 121 ± 9; 45 min: 121 ± 9; 60 min: 120 ± 7 mmHg) or DBP (R: 72 ± 8; PE: 78 ± 7; 5 min: 72 ± 7; 10 min: 72 ± 8; 15 min: 71 ± 7; 30 min: 72 ± 8; 45 min: 75 ± 10

  3. Force variability during isometric wrist flexion in highly skilled and sedentary individuals.

    Science.gov (United States)

    Salonikidis, Konstantinos; Amiridis, Ioannis G; Oxyzoglou, Nikolaos; de Villareal, Eduardo Saez Saez; Zafeiridis, Andreas; Kellis, Eleftherios

    2009-12-01

    The association of expertness in specific motor activities with a higher ability to sustain a constant application of force, regardless of muscle length, has been hypothesized. Ten highly skilled (HS group) young tennis and handball athletes and 10 sedentary (S group) individuals performed maximal and submaximal (5, 10, 20, 50, and 75% of the MVC) isometric wrist flexions on an isokinetic dynamometer (Kin-Com, Chattanooga). The wrist joint was fixed at five different angles (230, 210, 180, 150, and 1300). For each position the percentages of the maximal isometric force were calculated and participants were asked to maintain the respective force level for 5 s. Electromyographic (EMG) activation of the Flexor Carpi Ulnaris and Extensor Digitorum muscles was recorded using bipolar surface electrodes. No significant differences were observed in maximal isometric strength between HS and S groups. Participants of HS group showed significantly (P wrist angles. The CV and SD values remained unaltered regardless of wrist angle. No difference in normalized agonist and antagonist EMG activity was observed between the two groups. It is concluded that long-term practice could be associated with decreased isometric force variability independently from muscular length and coactivation of the antagonist muscles.

  4. Endothelium-Independent Hypoxic Contraction Is Prevented Specifically by Nitroglycerin via Inhibition of Akt Kinase in Porcine Coronary Artery

    Directory of Open Access Journals (Sweden)

    Huixia Liu

    2016-01-01

    Full Text Available Objective. Hypoxia-induced sustained contraction of porcine coronary artery is endothelium-independent and mediated by PI3K/Akt/Rho kinase. Nitroglycerin (NTG is a vasodilator used to treat angina pectoris and acute heart failure. The present study was to determine the role of NTG in hypoxia-induced endothelium-independent contraction and the underlying mechanism. Methods and Results. Organ chamber technique was used to measure the isometric vessel tension of isolated porcine coronary arteries. Protein levels of phosphorylated and total Akt were determined by western blot. A sustained contraction of porcine coronary arteries induced by hypoxia was significantly reduced by NTG but not by isoproterenol. This contraction was also inhibited by DETA NONOate, 8-Br-cGMP, which can be reversed by ODQ, and Rp-8-Br-PET-cGMPS. The restored contraction was blocked by LY294002. The reduction of Akt-p at Ser-473 by NTG, DETA NONOate, and 8-Br-cGMP was significantly inhibited by ODQ, PKG-I. The decrease in Akt-p level by NTG and 8-Br-cGMP was prevented by calyculin A but not by okadaic acid. Conclusions. These results demonstrated that the endothelium-independent sustained hypoxic vasoconstriction can be prevented by NTG and that the inhibition of PI3K/Akt signaling pathway may be involved.

  5. Efeitos na medida do ângulo Q com a contração isométrica voluntária máxima do músculo quadricipital Efectos en la medida del ángulo Q con la contracción isométrica voluntária máxima del musculo cuadricipital Effects in the Q angle measurement with maximal voluntary isometric contraction of the quadriceps muscle

    Directory of Open Access Journals (Sweden)

    A.C.G. Belchior

    2006-02-01

    examination situations, having the quadriceps relaxed and in a maximal voluntary isometric contraction (MVIC through radiographic measurement, aiming to contribute to the assessment and treatment of patients with patelofemoral disorder (PFD. Through the standard radiological method twenty 21 years old mean women (40 knees were assessed. All individuals were positioned supine using a U-podalic stabilizer, having their lower limbs relaxed, using a plumb film on the anterior tuberosity of the tibia. For the statistical analysis, the averages for the asymptomatic and symptomatic groups in a relaxed and MVIC status, as well as the Student's t-test with p < 0.05 significance level were used. The mean values to the Q angle compared to the asymptomatic group were 17.15º on relaxation, and 14.5º on MVIC, while the asymptomatic group presented 21.45º, and 15.8º, respectively. The results in the equality analysis between the symptomatic and asymptomatic groups on the relaxed status attained a p = 0.004, and to the maximal voluntary isometric contraction, p = 0.29. Considering the data attained in the present study, it can be verified that in a relaxing status, there is a difference between the value of the Q angle among symptomatic and asymptomatic individuals, being found a higher value in the FPD bearers, while in a maximal isometric contraction of the quadriceps muscle no statistical difference was found in the present study, with a reduction in the angle in both groups.

  6. Enhanced Phenylephrine Contractions in Rabbit Carotid Arteries ...

    African Journals Online (AJOL)

    Carotid arteries were isolated from rabbits and cut into 2mm rings, suspended in 20ml organ baths and bubbled with 95% O2, 5% CO2 and isometric ... There were no significant differences in PE contractions following exposure to intact erythrocytes and ghosts from subjects with different Hb genotypes; however, exposure ...

  7. Response of Coagulation Indices to Two Types of Exercise of Eccentric and Isometric in Male Bodybuilding Athletes

    Directory of Open Access Journals (Sweden)

    Maryam Azimpour

    2016-05-01

    Full Text Available Abstract Background and Objectives: Although activation of blood coagulation system in response to physical activity has been identified to some extent, but the contribution of eccentric activity in comparison with isometric activity as resistance exercise, is not clear yet. Therefore, this research was carried out with the purpose of investigating the effect of one session of eccentric and isometric resistance exercise on some coagulation factors in male bodybuilders. Methods: In this semi-experimental study, 28 volunteers were randomly selected from male bodybuilders and divided into two experimental groups and one control group. One of the experimental groups performed eccentric exercise [controlled return (extension of the elbow flexion movement involving an eccentric contraction] and another group performed isometric exercises (holding barbell while flexing elbows at 45 degrees. In order to assess coagulation indices, blood sampling was performed 15 minutes before and immediately after the exercise. Results: Thromboplastin and prothrombin times did not significantly change immediately after the exercise, but the number of platelets significantly increased in both isometric and eccentric types of exercise immediately after the exercise. Conclusion: The results of isometric and eccentric acute resistance exercise showed that the exercise had no negative impact on blood coagulation factors, and increased coagulation system activity reflects the increased number of platelets. The difference between the results of researches carried out in this direction can be resulted from the difference between the exercise protocols, methods and measurement time, and level of preparedness of the participants in the research.

  8. Unusual Wrist Tremor: Unilateral Isometric Tremor?

    Science.gov (United States)

    Zesiewicz, Theresa; Vu, Tuan; Carranza, Michael A.; Appelbaum, Rachel; Snyder, Madeline; Staffetti, Joseph S.; Allison, Kevin G.; Shimberg, William R.; Louis, Elan D.

    2014-01-01

    Background Tremors may be difficult to classify. Case Report An 83-year-old male presented with an unusual left wrist tremor. The tremor could be reproducibly elicited by making a fist or carrying a weighted object (e.g., a shopping bag, bottle of water) of approximately 1 lb or more, and it intensified with heavier weights. The tremor was difficult to classify, although it shared features with isometric tremor. Discussion This specific presentation of tremor has not been reported previously. We hope that the detailed description we provide will aid other neurologists who encounter this or similar tremors in their clinics. PMID:24455450

  9. Roughly isometric minimal immersions into Riemannian manifolds

    DEFF Research Database (Denmark)

    Markvorsen, Steen

    . In this talk we will mainly be concerned with {\\em{minimal}} isometric immersions of such geometrized approximations $(G, g)$ of $X$ into Riemannian manifolds $N$ with bounded curvature. When such an immersion exists, we will call it an $X$-web in $N$. Such webs admit a natural 'geometric' extension...... of the intrinsic combinatorial discrete Laplacian, and we will show that they share several analytic and geometric properties with their smooth (minimal submanifold) counterparts in $N$. The intrinsic properties thus obtained may hence serve as roughly invariant descriptors for the original metric space $X$....

  10. Isometric Reflection Vectors and Characterizations of Hilbert Spaces

    Directory of Open Access Journals (Sweden)

    Donghai Ji

    2014-01-01

    Full Text Available A known characterization of Hilbert spaces via isometric reflection vectors is based on the following implication: if the set of isometric reflection vectors in the unit sphere SX of a Banach space X has nonempty interior in SX, then X is a Hilbert space. Applying a recent result based on well-known theorem of Kronecker from number theory, we improve this by substantial reduction of the set of isometric reflection vectors needed in the hypothesis.

  11. No Critical Peripheral Fatigue Threshold during Intermittent Isometric Time to Task Failure Test with the Knee Extensors.

    Science.gov (United States)

    Froyd, Christian; Beltrami, Fernando G; Millet, Guillaume Y; Noakes, Timothy D

    2016-01-01

    It has been proposed that group III and IV muscle afferents provide inhibitory feedback from locomotor muscles to the central nervous system, setting an absolute threshold for the development of peripheral fatigue during exercise. The aim of this study was to test the validity of this theory. Thus, we asked whether the level of developed peripheral fatigue would differ when two consecutive exercise trials were completed to task failure. Ten trained sport students performed two exercise trials to task failure on an isometric dynamometer, allowing peripheral fatigue to be assessed 2 s after maximal voluntary contraction (MVC) post task failure. The trials, separated by 8 min, consisted of repeated sets of 10 × 5-s isometric knee extension followed by 5-s rest between contractions. In each set, the first nine contractions were performed at a target force at 60% of the pre-exercise MVC, while the 10th contraction was a MVC. MVC and evoked force responses to supramaximal electrical femoral nerve stimulation on relaxed muscles were assessed during the trials and at task failure. Stimulations at task failure consisted of single stimulus (SS), paired stimuli at 10 Hz (PS10), paired stimuli at 100 Hz (PS100), and 50 stimuli at 100 Hz (tetanus). Time to task failure for the first trial (12.84 ± 5.60 min) was longer (P fatigue. The present data therefore question the existence of a critical peripheral fatigue threshold during intermittent isometric exercise to task failure with the knee extensors.

  12. Relationship between force fluctuation in the plantar flexor and sustainable time for single-leg standing.

    Science.gov (United States)

    Oshita, Kazushige; Yano, Sumio

    2010-01-01

    The purpose of this study was to investigate the relationships between force fluctuation during isometric plantar flexion and the sustainable time for single-leg standing. Fourteen healthy males (21+/-1 years) performed unilateral (preferred leg) force matching tasks and single-leg quiet standing. Force matching tasks were performed to maintain isometric plantar flexion for 15 s at levels corresponding to 10% and 20% maximal voluntary contraction (MVC) with the visual feedback of force. Force fluctuation during force matching tasks was quantified as the standard deviation of force. Sustainable time for single-leg quiet standing was performed to maintain a single-leg quiet standing barefoot on a platform using the preferred leg with their eyes closed. Force fluctuation was significantly greater in 20% MVC task compared to 10% MVC task. The sustainable time for single-leg quiet standing was strongly correlated with force fluctuation in 20% MVC task (r=-0.56, p=0.04). However, it was not related to force fluctuation in 10% MVC task (r=0.19, p=0.52) or MVC value (r=0.13, p=0.65). These results suggest that a specificity of contraction intensity is observed between force steadiness and the posture stability during single-leg quiet standing; force steadiness during 20% MVC plantar flexion is one of the important components for posture stability during single-leg quiet standing.

  13. The Advantages of Normalizing Electromyography to Ballistic Rather than Isometric or Isokinetic Tasks.

    Science.gov (United States)

    Suydam, Stephen M; Manal, Kurt; Buchanan, Thomas S

    2017-07-01

    Isometric tasks have been a standard for electromyography (EMG) normalization stemming from anatomic and physiologic stability observed during contraction. Ballistic dynamic tasks have the benefit of eliciting maximum EMG signals for normalization, despite having the potential for greater signal variability. It is the purpose of this study to compare maximum voluntary isometric contraction (MVIC) to nonisometric tasks with increasing degrees of extrinsic variability, ie, joint range of motion, velocity, rate of contraction, etc., to determine if the ballistic tasks, which elicit larger peak EMG signals, are more reliable than the constrained MVIC. Fifteen subjects performed MVIC, isokinetic, maximum countermovement jump, and sprint tasks while EMG was collected from 9 muscles in the quadriceps, hamstrings, and lower leg. The results revealed the unconstrained ballistic tasks were more reliable compared to the constrained MVIC and isokinetic tasks for all triceps surae muscles. The EMG from sprinting was more reliable than the constrained cases for both the hamstrings and vasti. The most reliable EMG signals occurred when the body was permitted its natural, unconstrained motion. These results suggest that EMG is best normalized using ballistic tasks to provide the greatest within-subject reliability, which beneficially yield maximum EMG values.

  14. Physiological tremor (8-12Hz component) in isometric force control.

    Science.gov (United States)

    Novak, Thomas; Newell, Karl M

    2017-02-22

    The experiment investigated the influence of physiological tremor (8-12Hz band) on the variability of isometric force control as a function of force level and hand dominance. Subjects were instructed to match a constant force level target line on a computer screen and minimize error in a uni-manual isometric finger abduction task at 5%, 25%, 45%, 65%, and 85% of their maximal voluntary contraction (MVC). The experimental protocol was performed independently with the left and right hands in separate blocks of performance. Tremor amplitude was enhanced at an increasing rate with increments of force level and was correlated with both performance outcome (Root mean square error - RMSE) and time-dependent regularity (Sample Entropy) of the force signal. No significant findings in force variability (dispersion or irregularity) were found between the dominant and non-dominant hands. Physiological tremor has a small but direct influence on the dispersion and time dependent structure of the variability of isometric force control but its relative influence on force amplitude decreases with increments of force level. Copyright © 2017 Elsevier B.V. All rights reserved.

  15. Isometric knee-extensor torque development and jump height in volleyball players.

    Science.gov (United States)

    de Ruiter, C J; Vermeulen, Gido; Toussaint, Huub M; de Haan, Arnold

    2007-08-01

    The goal of the present study was to determine the contribution of the intrinsic muscle properties and muscle activation of the knee extensors to the maximal rate of unilateral isometric torque development and to relate both factors to maximal bilateral jumping performance in experienced jumpers. On the basis of previous studies, we hypothesized that maximal rate of torque development during maximal effort isometric contractions and jump height would depend on the subjects' ability for maximal muscle activation rather than on the muscle's contractile properties. Eleven male elite volleyball players (20 +/- 2 yr, means +/- SD) performed squat jumps starting from a 120 degrees knee angle (SJ120; full extension = 180 degrees ) and countermovement jumps. In addition, maximal voluntary and electrically evoked unilateral isometric knee-extension torque development (120 degrees angle) was obtained. Torque time integral for the first 40 ms after torque onset (TTI40) and (time to) maximal rate of torque development (MRTD) were calculated. Muscle activation was quantified using surface EMG. Voluntary TTI40 was significantly related to the preceding EMG (r2 = 0.83) and negatively related to the time to MRTD (r2 = 0.64). Voluntary MRTD and TTI40 were not related to their respective values obtained during electrical stimulation (r2 speed. However, unexpectedly, only the latter could predict jump performance in skilled jumpers.

  16. Muscle activity of the erector spinae during Pilates isometric exercises on and off Swiss Ball.

    Science.gov (United States)

    Paz, G; Maia, M; Santiago, F; Lima, V; Miranda, H

    2014-10-01

    The purpose of this study was to investigate the muscle activity of the Erector spinae (ES) during Pilates isometric exercises on and off Swiss ball. Fifteen women (22.9±2.1years, 171.7±4.7 cm, 65.7±5.3 kg and 11.2±3.2% of body fat) with previous Pilates experience (1±0.9 years) participated as subjects in this study. In the first test session, the anthropometric data and maximal voluntary contraction (MVC) was measured. In the second test session, three isometric exercises were conducted on and off the Swiss ball: back extension (BE), back extension with elbows flexed (BTF) and back extension with elbows extended (BTE). During all exercises, average integrated electromyography (IEMG) from ES muscle was collected and analyzed. A one-way ANOVA with repeated measures followed by Bonferroni post hoc was adopted to compare the muscle activity (PSwiss ball, respectively. Significant differences were observed for the ES activity during BTE exercise when compared to BTF and BT on and off Swiss ball, respectively. The Swiss ball may not provide a potential effect on ES activity during Pilates isometric exercises with similar posture when compared to stable surfaces. Therefore, the combination of BT, BTF and BTE exercises may be an interesting alternative to provide progressive increases in the ES activity.

  17. Shoulder muscular activity during isometric three-point kneeling exercise on stable and unstable surfaces.

    Science.gov (United States)

    de Araújo, Rodrigo Cappato; de Andrade, Rodrigo; Tucci, Helga Tatiana; Martins, Jaqueline; de Oliveira, Anamaria Siriani

    2011-08-01

    The purpose of this study was to determine if performing isometric 3-point kneeling exercises on a Swiss ball influenced the isometric force output and EMG activities of the shoulder muscles when compared with performing the same exercises on a stable base of support. Twenty healthy adults performed the isometric 3-point kneeling exercises with the hand placed either on a stable surface or on a Swiss ball. Surface EMG was recorded from the posterior deltoid, pectoralis major, biceps brachii, triceps brachii, upper trapezius, and serratus anterior muscles using surface differential electrodes. All EMG data were reported as percentages of the average root mean square (RMS) values obtained in maximum voluntary contractions for each muscle studied. The highest load value was obtained during exercise on a stable surface. A significant increase was observed in the activation of glenohumeral muscles during exercises on a Swiss ball. However, there were no differences in EMG activities of the scapulothoracic muscles. These results suggest that exercises performed on unstable surfaces may provide muscular activity levels similar to those performed on stable surfaces, without the need to apply greater external loads to the musculoskeletal system. Therefore, exercises on unstable surfaces may be useful during the process of tissue regeneration.

  18. Isokinetic and isometric muscle strength combined with transcutaneous electrical muscle stimulation in primary fibromyalgia syndrome

    DEFF Research Database (Denmark)

    Jacobsen, Søren; Wildschiødtz, Gordon; Danneskiold-Samsøe, B

    1991-01-01

    with superimposed transcutaneous electrical stimulation. The examination protocol was repeated after 1 h of resting. Isokinetic and isometric muscle strength was found to be, respectively, 45% (p = 0.0001) and 44% (p = 0.0001) lower in the patient group compared to the healthy subjects. The frequency...... of superimposed twitches was 65% in the patient group and 15% in the control group (p = 0.003). Patients with primary fibromyalgia have a lower maximum voluntary muscle strength than expected. The increased presence of superimposed electrically elicited twitches during maximum voluntary contraction indicates...

  19. The Adaptive Range of 1/f Isometric Force Production

    Science.gov (United States)

    Sosnoff, Jacob J.; Valantine, Andrew D.; Newell, Karl M.

    2009-01-01

    The adaptive range of 1/f dynamics in isometric force output was investigated. Participants produced isometric force to targets with predictable demands (constant and sinusoidal) and 1/f noise waveforms (white, pink, brown, and black) that also varied in the frequency bandwidth represented in the force signal (0-4 Hz, 0-8 Hz, and 0-12 Hz). The…

  20. Differences in Contraction-Induced Hemodynamics and Surface EMG in Duchenne Muscular Dystrophy.

    Science.gov (United States)

    Van Ginderdeuren, Eva; Caicedo, Alexander; Taelmans, Joachim; Goemans, Nathalie; van den Hauwe, Marlen; Naulaers, Gunnar; Van Huffel, Sabine; Buyse, Gunnar

    2016-01-01

    Duchenne muscular dystrophy (DMD) is the most common and devastating type of muscular dystrophy worldwide. In this study we have investigated the potential of the combined use of non-invasive near-infrared spectroscopy (NIRS) and surface electromyography (sEMG) to assess contraction-induced changes in oxygenation and myoelectrical activity, respectively in the biceps brachii of eight DMD patients aged 9-12 years and 11 age-matched healthy controls. Muscle tissue oxygenation index (TOI), oxyhemoglobin (HbO2), and sEMG signals were continuously measured during a sustained submaximal contraction of 60% maximal voluntary isometric contraction, and post-exercise recovery period. Compared to controls, DMD subjects showed significantly smaller changes in TOI during the contraction. In addition, during the reoxygenation phase some dynamic parameters extracted from the HbO2 measurements were significantly different between the two groups, some of which were correlated with functional performances on a 6-min walking test. In conclusion, non-invasive continuous monitoring of skeletal muscle oxygenation by NIRS is feasible in young children, and significant differences in contraction-induced deoxygenation and reoxygenation patterns were observed between healthy controls and DMD children.

  1. Unusual Wrist Tremor: Unilateral Isometric Tremor?

    Directory of Open Access Journals (Sweden)

    Theresa A. Zesiewicz

    2014-01-01

    Full Text Available Background: Tremors may be difficult to classify.Case Report: An 83‐year‐old male presented with an unusual left wrist tremor. The tremor could be reproducibly elicited by making a fist or carrying a weighted object (e.g., a shopping bag, bottle of water of approximately 1 lb or more, and it intensified with heavier weights. The tremor was difficult to classify, although it shared features with isometric tremor.Discussion: This specific presentation of tremor has not been reported previously. We hope that the detailed description we provide will aid other neurologists who encounter this or similar tremors in their clinics.

  2. Comparison of blood pressure and heart rate responses to isometric exercise and passive muscle stretch in humans.

    Science.gov (United States)

    Baum, K; Selle, K; Leyk, D; Essfeld, D

    1995-01-01

    The responses of mean arterial blood pressure (BPa) and heart rate (fc) to isometric contraction and passive stretch were compared in seven healthy male subjects at identical external forces. They were investigated in the sitting position with the hip and knee joint flexed to 90 degrees. Each subject performed two tests, separated by a day, in which the stimuli were applied in random order. After 5 min of rest they performed either 10-min static plantar flexion of one calf (200 N) or 10 min of passive calf muscle stretch at the same load. After 5-min rest, the second stimulus was applied for a further 10 min followed by 5-min rest. The second test was identical except for the sequence of the stimuli. The BPa was measured by a noninvasive and continuous method. Contraction of the vastus lateralis, gastrocnemius lateralis, and soleus muscles were determined by the myo-electric activity (electromyogram, EMG) by means of surface electrodes. The EMG activity of the vastus lateralis muscle remained at resting values throughout the experiments. Increases in EMG activity could only be detected for the triceps surae muscles during isometric contraction. During the initial 2 min of stimulation the BPa and fc responses to active contraction and passive stretch were comparable. Thereafter, both parameters showed significantly higher values during contraction. It was concluded that mechanical stress may have contributed to the early response of BPa during both passive stretch and voluntary contraction but that chemical stimuli were needed to maintain the peripheral cardiovascular drive.

  3. β-alanine supplementation improves isometric endurance of the knee extensor muscles.

    Science.gov (United States)

    Sale, Craig; Hill, Chester A; Ponte, James; Harris, Roger C

    2012-06-14

    We examined the effect of four weeks of β-alanine supplementation on isometric endurance of the knee extensors at 45% maximal voluntary isometric contraction (MVIC). Thirteen males (age 23 ± 6 y; height 1.80 ± 0.05 m; body mass 81.0 ± 10.5 kg), matched for pre-supplementation isometric endurance, were allocated to either a placebo (n = 6) or β-alanine (n = 7; 6.4 g·d-1 over 4 weeks) supplementation group. Participants completed an isometric knee extension test (IKET) to fatigue, at an intensity of 45% MVIC, before and after supplementation. In addition, two habituation tests were completed in the week prior to the pre-supplementation test and a further practice test was completed in the week prior to the post-supplementation test. MVIC force, IKET hold-time, and impulse generated were recorded. IKET hold-time increased by 9.7 ± 9.4 s (13.2%) and impulse by 3.7 ± 1.3 kN·s-1 (13.9%) following β-alanine supplementation. These changes were significantly greater than those in the placebo group (IKET: t(11) = 2.9, p ≤0.05; impulse: t(11) = 3.1, p ≤ 0.05). There were no significant changes in MVIC force in either group. Four weeks of β-alanine supplementation at 6.4 g·d-1 improved endurance capacity of the knee extensors at 45% MVIC, which most likely results from improved pH regulation within the muscle cell as a result of elevated muscle carnosine levels.

  4. β-alanine supplementation improves isometric endurance of the knee extensor muscles

    Directory of Open Access Journals (Sweden)

    Sale Craig

    2012-06-01

    Full Text Available Abstract Background We examined the effect of four weeks of β-alanine supplementation on isometric endurance of the knee extensors at 45% maximal voluntary isometric contraction (MVIC. Methods Thirteen males (age 23 ± 6 y; height 1.80 ± 0.05 m; body mass 81.0 ± 10.5 kg, matched for pre-supplementation isometric endurance, were allocated to either a placebo (n = 6 or β-alanine (n = 7; 6.4 g·d-1 over 4 weeks supplementation group. Participants completed an isometric knee extension test (IKET to fatigue, at an intensity of 45% MVIC, before and after supplementation. In addition, two habituation tests were completed in the week prior to the pre-supplementation test and a further practice test was completed in the week prior to the post-supplementation test. MVIC force, IKET hold-time, and impulse generated were recorded. Results IKET hold-time increased by 9.7 ± 9.4 s (13.2% and impulse by 3.7 ± 1.3 kN·s-1 (13.9% following β-alanine supplementation. These changes were significantly greater than those in the placebo group (IKET: t(11 = 2.9, p ≤0.05; impulse: t(11 = 3.1, p ≤ 0.05. There were no significant changes in MVIC force in either group. Conclusion Four weeks of β-alanine supplementation at 6.4 g·d-1 improved endurance capacity of the knee extensors at 45% MVIC, which most likely results from improved pH regulation within the muscle cell as a result of elevated muscle carnosine levels.

  5. Isometric handgrip does not elicit cardiovascular overload or post-exercise hypotension in hypertensive older women

    Directory of Open Access Journals (Sweden)

    Olher RR

    2013-06-01

    Full Text Available Rafael dos Reis Vieira Olher,1,2,* Danilo Sales Bocalini,3,* Reury Frank Bacurau,4 Daniel Rodriguez,5 Aylton Figueira Jr,5 Francisco Luciano Pontes Jr,4 Francisco Navarro,6 Herbert Gustavo Simões,1 Ronaldo Carvalho Araujo,7 Milton Rocha Moraes8 1Universidade Católica de Brasília, Distrito Federal, 2Universidade Gama Filho, Rio de Janeiro, 3Universidade Nove de Julho (UNINOVE, São Paulo, 4Universidade de São Paulo – Escola de Artes, Ciências e Humanidades, São Paulo, 5Universidade São Judas Tadeu (USJT, São Paulo, Brazil, 6Universidade Federal do Maranhão, Maranhão, 7Universidade de São Paulo, Instituto de Ciências Biomédicas, São Paulo, 8Universidade Federal de São Paulo – Escola Paulista de Medicina, São Paulo, Brazil *These authors contributed equally to this work Background: Arterial hypertension is a serious health problem affecting mainly the elderly population. Recent studies have considered both aerobic and resistance exercises as a non-pharmacological aid for arterial hypertension treatment. However, the cardiovascular responses of the elderly to isometric resistance exercise (eg, isometric handgrip [IHG] have not yet been documented. Objective: The purpose of this study was to investigate cardiovascular responses to different intensities of isometric exercise, as well as the occurrence of post-isometric exercise hypotension in hypertensive elderly people under antihypertensive medication treatment. Patients and methods: Twelve women volunteered to participate in the study after a maximal voluntary contraction test (MVC and standardization of the intervention workload consisting of two sessions of IHG exercise performed in four sets of five contractions of a 10-second duration. Sessions were performed both at 30% of the MVC and 50% of the MVC, using a unilateral IHG protocol. Both intensities were compared with a control session without exercise. Systolic blood pressure (SBP and diastolic blood pressure (DBP at rest

  6. Acute effects of whole-body vibration on peak isometric torque, muscle twitch torque and voluntary muscle activation of the knee extensors.

    Science.gov (United States)

    Jordan, M; Norris, S; Smith, D; Herzog, W

    2010-06-01

    The purpose of this investigation was to compare the acute effects of whole-body vibration (WBV) with a static squat on resting muscle twitch torque, peak isometric torque and voluntary muscle activation of the knee extensors during an isometric maximal voluntary contraction (MVC). Twenty-four healthy, strength-trained males were recruited for this randomized, cross-over design investigation. The WBV treatment consisted of three sets of 60 s of vibration (30 Hz, +/-4 mm) while standing in a semi-squat position. Voluntary muscle activation, peak isometric torque during MVC and resting muscle twitch torque (RTT) through percutaneous femoral nerve stimulation were obtained before and following the treatment. Change in peak isometric torque, voluntary muscle activation and the RTT were calculated as the difference between pre- and post-treatment values. There was no observable post-activation potentiation of muscle twitch torque or enhancement in voluntary muscle activation or peak isometric torque. However, decreases in the peak isometric torque (P=0.0094) and voluntary muscle activation (P=0.0252) were significantly smaller post WBV interventions compared with the control treatment. Based on the current data, it is unclear whether or not this was attributable to the effects of WBV but further research into this possibility is warranted.

  7. Maximal isometric strength of the cervical musculature in 100 healthy volunteers

    DEFF Research Database (Denmark)

    Jordan, A; Mehlsen, J; Bülow, P M

    1999-01-01

    A descriptive study involving maximal isometric strength measurements of the cervical musculature.......A descriptive study involving maximal isometric strength measurements of the cervical musculature....

  8. Relaxant effect of U0126 in hemolysate-, oxyhemoglobin-, and bloody cerebrospinal fluid-induced contraction in rabbit basilar artery.

    Science.gov (United States)

    Zubkov, A Y; Rollins, K S; McGehee, B; Parent, A D; Zhang, J H

    2001-01-01

    It has been suggested that mitogen-activated protein kinase (MAPK) is involved in cerebral vasospasm after subarachnoid hemorrhage. The present study was undertaken to explore the inhibitory effect of U0126, a novel MAPK inhibitor, in the contraction of the rabbit basilar artery by 3 spasmogens: hemolysate, oxyhemoglobin, and bloody cerebrospinal fluid (CSF) from patients with vasospasm. The contraction and relaxation of rabbit basilar arteries were measured by isometric tension. MAPK immunoprecipitation was assessed by Western blot analysis. (1) Pretreatment of the rabbit basilar arteries with U0126 reduced contractions to hemolysate, oxyhemoglobin, or bloody CSF applied subsequently. (2) In the absence of endothelial cells, U0126 produced an inhibitory effect similar to the contractions induced by hemolysate, oxyhemoglobin, or bloody CSF. (3) U0126 relaxed the sustained contraction induced by hemolysate, oxyhemoglobin, or bloody CSF. (4) Hemolysate, oxyhemoglobin, and bloody CSF enhanced MAPK immunoprecipitation. (5) U0126 reduced MAPK immunoprecipitation induced by hemolysate, oxyhemoglobin, and bloody CSF. (6) Hemolysate, oxyhemoglobin, and bloody CSF significantly increased MAPK activity in the rabbit basilar artery. (7) U0126 abolished the effect of hemolysate, oxyhemoglobin, or bloody CSF on MAPK activation. This study demonstrated a role of MAPK in the contraction of rabbit basilar arteries by hemolysate, oxyhemoglobin, and bloody CSF. MAPK inhibitor U0126 may be useful in the treatment of cerebral vasospasm.

  9. Isometric muscle fatigue of the paravertebral and upper extremity muscles after whiplash injury.

    Science.gov (United States)

    Rastovic, Pejana; Gojanovic, Marija Definis; Berberovic, Marina; Pavlovic, Marko; Lesko, Josip; Galic, Gordan; Pandza, Maja

    2017-01-01

    Whiplash-associated disorders (WAD) result from injury of neck structures that most often occur during traffic accidents as a result of rapid acceleration-deceleration. The dominant symptoms manifest in the musculoskeletal system and include increased fatigue. Because of the frequency of whiplash injuries, a simple, cheap and useful diagnostic tool is needed to differentiate whiplash injury from healthy patients or those faking symptoms. To determine muscle fatigue in patients with whiplash injury in six body positions. Analytical cross-sectional study. Emergency center, university hospital. We studied patients with whiplash injury from vehicular traffic accidents who presented to the emergency center within 6 hours of sustaining the injury. We determined whiplash injury grade according to the Quebec Task Force (QTF) classification and measured isometric muscle endurance in six different body positions. Control subjects for each patient were matched by age, gender and anthropomorphic characteristics. Cut-off values were determined to distinguish patients with whiplash injury from controls and for determination of injury grade . QTF grade, time to muscle fatigue in seconds. From September 2013 to September 2016, we enrolled 75 patients with whiplash injury and 75 matching control subjects. In all six positions, the patients with whiplash injury felt muscle fatigue faster than equivalent controls (P muscle fatigue decreased with increasing injury grades in all six positions. Assignment to the patient or control group and to injury grade could be predicted with more than 90% accuracy on the basis of time to muscle fatigue. The most efficient position was the highest injury grade, by which 99.9% of the patients were accurately categorized. Isometric muscle endurance correlated with whiplash injury grade in all six positions (P muscle endurance and the appearance of isometric muscle fatigue during testing can be a useful indicator of whiplash injury and grade. The size

  10. Strength Recovery Following Rhythmic or Sustained Exercise as a Function of Time.

    Science.gov (United States)

    Kearney, Jay T.

    The relative rates of strength recovery subsequent to bouts of rhythmic or sustained isometric exercise were investigated. The 72 undergraduates who served as subjects were tested seven times within the framework of a repeated measures design. Each testing session involved two bouts of either rhythmic or sustained isometric exercise separated by a…

  11. Profitability Implications of Sustainable Contracting

    Science.gov (United States)

    2006-08-01

    Office Properties Trust Financial Services Goldman Sachs Group Inc. Financial Services Merrill Lynch & Co. Inc. Financial Services Coca - Cola Co. Food...of this study should not be imparted directly onto construction contractors. 43 LIST OF REFERENCES 1. Articulating the Business and Ethical Arguments...zero loss- making projects, zero work place accidents, zero environmental incidents and zero ethical breaches. They were selected as a green conaktrf

  12. 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 ...

  13. Isometric and dynamic strength and neuromuscular attributes as predictors of vertical jump performance in 11- to 13-year-old male athletes.

    Science.gov (United States)

    McKinlay, Brandon John; Wallace, Phillip J; Dotan, Raffy; Long, Devon; Tokuno, Craig; Gabriel, David A; Falk, Bareket

    2017-09-01

    In explosive contractions, neural activation is a major factor in determining the rate of torque development, while the latter is an important determinant of jump performance. However, the contribution of neuromuscular activation and rate of torque development to jump performance in children and youth is unclear. The purpose of this study was to examine the relationships between the rate of neuromuscular activation, peak torque, rate of torque development, and jump performance in young male athletes. Forty-one 12.5 ± 0.5-year-old male soccer players completed explosive, unilateral isometric and dynamic (240°/s) knee extensions (Biodex System III), as well as countermovement-, squat-, and drop-jumps. Peak torque (pT), peak rate of torque development (pRTD), and rate of vastus lateralis activation (Q30) during the isometric and dynamic contractions were examined in relation to attained jump heights. Isometric pT and pRTD were strongly correlated (r = 0.71) but not related to jump performance. Dynamic pT and pRTD, normalized to body mass, were significantly related to jump height in all 3 jumps (r = 0.38-0.66, p jump performance, while isometric contractions are not. These findings have implications in the choice of training and assessment methods for young athletes.

  14. A randomized controlled trial comparing home-based isometric handgrip exercise versus endurance training for blood pressure management.

    Science.gov (United States)

    Goessler, Karla Fabiana; Buys, Roselien; VanderTrappen, Dieter; Vanhumbeeck, Lise; Cornelissen, Veronique Ann

    2018-02-02

    Aerobic endurance exercise (AEX) is an effective treatment in the prevention and management of high blood pressure (BP). Growing evidence suggests potential benefits from isometric handgrip (IHG) exercise, which may promote similar or even larger reductions in BP than AEX. We compared the effects of home-based AEX and home-based IHG on BP. Sixty healthy individuals (31 men; mean age, 33.1 years; mean BP, 126.9 ± 1.6/84.7 ± 1.1 mm Hg) were randomized to IHG, AEX, or a control group. Both exercise interventions were performed in the home environment. The IHG group performed daily 4 × 2 minutes sustained grips at 30% of maximal volitional contraction. Participants in the AEX group were advised to perform at least 150 min/wk of aerobic exercise at moderate intensity. Outcome measurements were assessed at baseline and 8 weeks of follow-up. Compared with the control group, AEX resulted in a larger reduction in ambulatory BP; both AEX and IHG exercise tended to induce larger reductions in office systolic BP, and office diastolic BP was significantly more reduced after AEX but not IHG exercise. Responses to training were not significantly different between both the exercise interventions. Eight weeks of home-based AEX results in significant reductions in both ambulatory BP and office BP in healthy adults, whereas IHG reduces only office BP. Copyright © 2018 American Society of Hypertension. Published by Elsevier Inc. All rights reserved.

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

    Directory of Open Access Journals (Sweden)

    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.

  16. Surface electromyogram analysis of the direction of isometric torque generation by the first dorsal interosseous muscle

    Science.gov (United States)

    Zhou, Ping; Suresh, Nina L.; Zev Rymer, William

    2011-06-01

    The objective of this study was to determine whether a novel technique using high density surface electromyogram (EMG) recordings can be used to detect the directional dependence of muscle activity in a multifunctional muscle, the first dorsal interosseous (FDI). We used surface EMG recordings with a two-dimensional electrode array to search for inhomogeneous FDI activation patterns with changing torque direction at the metacarpophalangeal joint, the locus of action of the FDI muscle. The interference EMG distribution across the whole FDI muscle was recorded during isometric contraction at the same force magnitude in five different directions in the index finger abduction-flexion plane. The electrode array EMG activity was characterized by contour plots, interpolating the EMG amplitude between electrode sites. Across all subjects the amplitude of the flexion EMG was consistently lower than that of the abduction EMG at the given force. Pattern recognition methods were used to discriminate the isometric muscle contraction tasks with a linear discriminant analysis classifier, based on the extraction of two different feature sets of the surface EMG signal: the time domain (TD) feature set and a combination of autoregressive coefficients and the root mean square amplitude (AR+RMS) as a feature set. We found that high accuracies were obtained in the classification of different directions of the FDI muscle isometric contraction. With a monopolar electrode configuration, the average overall classification accuracy from nine subjects was 94.1 ± 2.3% for the TD feature set and 95.8 ± 1.5% for the AR+RMS feature set. Spatial filtering of the signal with bipolar electrode configuration improved the average overall classification accuracy to 96.7 ± 2.7% for the TD feature set and 98.1 ± 1.6% for the AR+RMS feature set. The distinct EMG contour plots and the high classification accuracies obtained from this study confirm distinct interference EMG pattern distributions as a

  17. Relationships between rapid isometric torque characteristics and vertical jump performance in division I collegiate American football players: influence of body mass normalization.

    Science.gov (United States)

    Thompson, Brennan J; Ryan, Eric D; Sobolewski, Eric J; Smith, Doug B; Akehi, Kazuma; Conchola, Eric C; Buckminster, Tyler

    2013-10-01

    The purpose of the present study was to examine the relationships between absolute and body mass-normalized rapid isometric torque variables and vertical jump (VJ) performance of the leg extensors and flexors in elite National Collegiate Athletic Association Division I Football Bowl Subdivision collegiate American football players. Thirty-one players performed isometric maximal voluntary contractions of the leg extensor and flexor muscle groups and a countermovement VJ. Rate of torque development (RTD) and the contractile impulse (IMPULSE) were determined from 0 to 30, 0 to 50, 0 to 100, and 0 to 200 milliseconds from the onset of muscular contraction. The relationships between absolute and normalized rapid torque variables and VJ performance were assessed using correlation coefficients (r). There were no significant correlations (p > 0.05) observed between the absolute rapid torque variables and VJ performance, except for leg flexion RTD at 0-200 milliseconds (p = 0.024). All normalized rapid torque variables of the leg extensors and flexors were significantly correlated to VJ performance (p ≤ 0.001-0.026). These findings indicated that normalizing rapid torque variables to body mass improves the relationships between isometric rapid torque variables and VJ performance and normalized leg extension and flexion are both similarly related to VJ performance. Strength and conditioning professionals may use these findings in an attempt to identify and monitor dynamic sport performance. Furthermore, future studies examining the relationship between dynamic on the field performances and laboratory-based isometric strength testing may consider including normalized rapid torque variables.

  18. Isometric hip and knee torque measurements as an outcome measure in robot assisted gait training.

    Science.gov (United States)

    Galen, Sujay S; Clarke, Celia J; McLean, Alan N; Allan, David B; Conway, Bernard A

    2014-01-01

    Strength changes in lower limb muscles following robot assisted gait training (RAGT) in subjects with incomplete spinal cord injury (ISCI) has not been quantified using objective outcome measures. To record changes in the force generating capacity of lower limb muscles (recorded as peak voluntary isometric torque at the knee and hip), before, during and after RAGT in both acute and subacute/chronic ISCI subjects using a repeated measures study design. Eighteen subjects with ISCI participated in this study (Age range: 26-63 years mean age = 49.3 ± 11 years). Each subject participated in the study for a total period of eight weeks, including 6 weeks of RAGT using the Lokomat system (Hocoma AG, Switzerland). Peak torques were recorded in hip flexors, extensors, knee flexors and extensors using torque sensors that are incorporated within the Lokomat. All the tested lower limb muscle groups showed statistically significant (p torques in the acute subjects. Comparison between the change in peak torque generated by a muscle and its motor score over time showed a non-linear relationship. The peak torque recorded during isometric contractions provided an objective outcome measure to record changes in muscle strength following RAGT.

  19. Cerebral mechanisms underlying the effects of music during a fatiguing isometric ankle-dorsiflexion task.

    Science.gov (United States)

    Bigliassi, Marcelo; Karageorghis, Costas I; Nowicky, Alexander V; Orgs, Guido; Wright, Michael J

    2016-10-01

    The brain mechanisms by which music-related interventions ameliorate fatigue-related symptoms during the execution of fatiguing motor tasks are hitherto under-researched. The objective of the present study was to investigate the effects of music on brain electrical activity and psychophysiological measures during the execution of an isometric fatiguing ankle-dorsiflexion task performed until the point of volitional exhaustion. Nineteen healthy participants performed two fatigue tests at 40% of maximal voluntary contraction while listening to music or in silence. Electrical activity in the brain was assessed by use of a 64-channel EEG. The results indicated that music downregulated theta waves in the frontal, central, and parietal regions of the brain during exercise. Music also induced a partial attentional switching from associative thoughts to task-unrelated factors (dissociative thoughts) during exercise, which led to improvements in task performance. Moreover, participants experienced a more positive affective state while performing the isometric task under the influence of music. © 2016 Society for Psychophysiological Research.

  20. Isometric force development in human horizontal eye muscles and pulleys during saccadic eye movements.

    Science.gov (United States)

    Lennerstrand, Gunnar; Bolzani, Roberto; Benassi, Mariagrazia; Tian, Suna; Schiavi, Costantino

    2009-11-01

    The connective tissue elements forming the check ligaments and portals of the human eye muscles have recently been ascribed with a pulley function. Active positioning of the pulleys over orbital layer contraction during eye movements has been suggested. Other studies have instead demonstrated fibrous tissue connections between all parts of the muscle and the pulleys. We aimed to compare the isometric force developed at the muscle tendon and at the pulleys of the horizontal eye muscles, and to investigate which eye muscle structures might exert force on the pulleys. Isometric force development was recorded from the lateral and medial rectus muscles in six patients operated for strabismus under topical anaesthesia. Two strain gauge probes were used, each attached with 5-0 silk sutures either to the muscle tendon or to the pulley. The eye muscles were activated by horizontal saccadic eye movements in steps from 30 degrees in the off-direction to 30 degrees in the on-direction of the muscles. The forces developed at the tendon and pulley were almost identical with respect to amplitude and other parameters. No differences were found in forces developed at the pulleys of the medial and lateral rectus muscles. The results support the presence of fibrous tissue connections between all eye muscle fibres and pulley structures, rather than orbital fibre control of the pulley.

  1. Isometric exercises reduce temporal summation of pressure pain in humans

    DEFF Research Database (Denmark)

    Vaegter, H B; Handberg, G; Graven-Nielsen, T

    2015-01-01

    BACKGROUND: Aerobic and isometric exercises are known to decrease pain sensitivity. The effect of different types of exercise on central mechanisms such as temporal summation of pain (TSP) is less clear. This study hypothesized that both aerobic and isometric exercises would increase pressure pain...... tolerance (PTT) and reduce TSP with greater effects after higher-intensity exercises. METHODS: One hundred thirty-six healthy subjects (18-65 years; 68 women) participated in two randomized crossover experiments with trials on two different days. PTT and TSP were assessed before and after bicycling...... and a non-exercise condition (experiment 1), and after low- and high-intensity bicycling and low- and high-intensity isometric arm and leg exercises with the dominant arm/leg (experiment 2). PTT and TSP were assessed before and after each exercise condition on the non-dominant arm and leg by computer...

  2. EFFECT OF ISOMETRIC QUADRICEPS STRENGTHENING EXERCISE AT MULTIPLE ANGLES IN KNEE JOINT AMONG NORMAL ADULTS

    Directory of Open Access Journals (Sweden)

    JibiPaul

    2014-04-01

    Full Text Available Introduction: Strengthening exercises have been routinely used in persons with orthopaedic problems and athletes to increase force production or minimize muscle imbalance and joint injuries.Many studies have reported that isometric contractions can rapidly increases strength in quadriceps muscle. Objective: Objective of the study was to find out the effect of isometric strengthening exercise on strength of quadriceps at 45 and 90 degree of knee joint and also to compare the effect of strengthening exercise on strength of quadriceps at multiple angles of knee joint among control and experimental group. Methodology: This was a ccomparative experimental study with forty female healthy subjects from physiotherapy department of KPJ Healthcare University College, Malaysia. Convenient sampling method used to select the samples. The subjects were selected by inclusion criteria and randomly divided equally in to two with 20 subjects in each group. Isometric strengthening exercise and squatting exercise were given as intervention program for eight weeks respectively for experimental and control group. Pre and post data of quadriceps muscle strength measured were collected separately at 45 and 90 degree of knee joint using goniometry during resisted extension of knee in multi gym. Result: In experimental group Pre –Post statistical analysis found significant effect in increase of quadriceps strength at 45 and 90 degree with P<0.0001.****In control group quadriceps pre-post statistical analysis found no significant effect in increase of quadriceps strength at 45 and 90 degree with P<0.083NS and P<0.055 NS respectively. Comparative study between experimental and control groups for quadriceps strength at 90 degree of knee joint found significant effect in increase of quadriceps strength with P< 0.001.*** Comparative study between experimental and control groups for quadriceps strength at 45 degree of knee joint found significant effect in increase of

  3. Spontaneous contractility of human placental vessels in vitro axipetal and isometric recording.

    Science.gov (United States)

    Gonzalez Panizza, V H; Benedetti, W L; Alvarez, H

    1980-01-01

    In vitro contractility of isolated cylindrical segments of chorial arteries and veins from 40 human term placentas was studied. Contractility was recorded by an isometrical and axipetal method. Spontaneous contractility was observed in 75% of the arteries and in 45% of veins. In both types of vessels, contractility was similar and characterized by development of tonic circumferential tension, between 100 and 200 mg/mm. Clonic activity consisting of rhythmic contractions with an average frequency between 0.7 and 0.9/min and an average intensity of 5--40 mg/min was superimposed. Vasoconstrictor drugs (PGF2 alpha, histamine and adrenaline) increase tonic tension without modifying the frequency of clonic activity. It is suggested that spontaneous contractility may be the expression of myogenic excitability related to the regulation of fetal placental blood flow.

  4. Regular physical exercise improves cardiac autonomic and muscle vasodilatory responses to isometric exercise in healthy elderly

    Directory of Open Access Journals (Sweden)

    Sarmento AO

    2017-06-01

    Full Text Available Adriana de Oliveira Sarmento,1–3 Amilton da Cruz Santos,1,4 Ivani Credidio Trombetta,2,5 Marciano Moacir Dantas,1 Ana Cristina Oliveira Marques,1,4 Leone Severino do Nascimento,1,4 Bruno Teixeira Barbosa,1,2 Marcelo Rodrigues Dos Santos,2 Maria do Amparo Andrade,3 Anna Myrna Jaguaribe-Lima,3,6 Maria do Socorro Brasileiro-Santos1,3,4 1Laboratory of Physical Training Studies Applied to Health, Department of Physical Education, Federal University of Paraiba, João Pessoa, Brazil; 2Unit of Cardiovascular Rehabilitation and Exercise Physiology – Heart Institute (InCor/HC-FMUSP, University of São Paulo, São Paulo, Brazil; 3Graduate Program in Physiotherapy, Federal University of Pernambuco, Recife, Brazil; 4Associate Graduate Program in Physical Education UPE/UFPB, João Pessoa, Brazil; 5Graduate Program in Medicine, Universidade Nove de Julho (UNINOVE, São Paulo, Brazil; 6Department of Morphology and Animal Physiology, Federal Rural University of Pernambuco, Recife, Brazil Abstract: The objective of this study was to evaluate cardiac autonomic control and muscle vasodilation response during isometric exercise in sedentary and physically active older adults. Twenty healthy participants, 10 sedentary and 10 physically active older adults, were evaluated and paired by gender, age, and body mass index. Sympathetic and parasympathetic cardiac activity (spectral and symbolic heart rate analysis and muscle blood flow (venous occlusion plethysmography were measured for 10 minutes at rest (baseline and during 3 minutes of isometric handgrip exercise at 30% of the maximum voluntary contraction (sympathetic excitatory maneuver. Variables were analyzed at baseline and during 3 minutes of isometric exercise. Cardiac autonomic parameters were analyzed by Wilcoxon and Mann–Whitney tests. Muscle vasodilatory response was analyzed by repeated-measures analysis of variance followed by Tukey’s post hoc test. Sedentary older adults had higher cardiac

  5. Comparison between the effects of 4 different electrical stimulation current waveforms on isometric knee extension torque and perceived discomfort in healthy women.

    Science.gov (United States)

    Dantas, Lucas Ogura; Vieira, Amilton; Siqueira, Aristides Leite; Salvini, Tania Fatima; Durigan, João Luiz Quagliotti

    2015-01-01

    We studied the effects of different neuromuscular electrical stimulation (NMES) currents, 2 kHz-frequency alternating currents (KACs, Russian and Aussie) and 2 pulsed currents (PCs), on isometric knee extension torque and discomfort level, both in isolation and combined, with maximum voluntary contraction (MVC). Twenty-one women (age 21.6 ± 2.5 years) were studied. We evaluated torque evoked by NMES or NMES combined with maximum voluntary contraction of the quadriceps muscle of healthy women. Discomfort level was measured using a visual analog pain scale. Despite comparable levels of discomfort, evoked torque was lower for Russian current compared with the other modalities (Russian 50.8%, Aussie 71.7%, PC500 76.9%, and PC200 70.1%; P Russian current for inducing isometric knee extension torque. This information is important in guiding decision making with regard to NMES protocols for muscle strengthening. © 2014 Wiley Periodicals, Inc.

  6. Effects of fatiguing constant versus alternating intensity intermittent isometric muscle actions on maximal torque and neuromuscular responses.

    Science.gov (United States)

    Smith, C M; Housh, T J; Hill, E C; Cochrane, K C; Jenkins, N Dm; Schmidt, R J; Johnson, G O

    2016-12-14

    To determine the effects of constant versus alternating applications of torque during fatiguing, intermittent isometric muscle actions of the leg extensors on maximal voluntary isometric contraction (MVIC) torque and neuromuscular responses. Sixteen subjects performed two protocols, each consisting of 50 intermittent isometric muscle actions of the leg extensors with equal average load at a constant 60% MVIC or alternating 40 then 80% (40/80%) MVIC with a work-to-rest ratio of 6-s on and 2-s off. MVIC torque as well as electromyographic signals from the vastus lateralis (VL), vastus medialis (VM), and rectus femoris (RF) and mechanomyographic signals from the VL were recorded pretest, immediately posttest, and 5-min posttest. The results indicated that there were no time-related differences between the 60% MVIC and 40/80% MVIC protocols. The MVIC torque decreased posttest (22 to 26%) and remained depressed 5-min posttest (9%). There were decreases in electromyographic frequency (14 to 19%) and mechanomyographic frequency (23 to 24%) posttest that returned to pretest levels 5-min posttest. There were no changes in electromyographic amplitude and mechanomyogrpahic amplitude. These findings suggested that these neuromuscular parameters did not track the fatigue-induced changes in MVIC torque after 5-min of recovery.

  7. Analysis of muscle fatigue induced by isometric vibration exercise at varying frequencies.

    Science.gov (United States)

    Mischi, M; Rabotti, C; Cardinale, M

    2012-01-01

    An increase in neuromuscular activity, measured by electromyography (EMG), is usually observed during vibration exercise. The underlying mechanisms are however unclear, limiting the possibilities to introduce and exploit vibration training in rehabilitation programs. In this study, a new training device is used to perform vibration exercise at varying frequency and force, therefore enabling the analysis of the relationship between vibration frequency and muscle fatigue. Fatigue is estimated by maximum voluntary contraction measurement, as well as by EMG mean-frequency and conduction-velocity analysis. Seven volunteers performed five isometric contractions of the biceps brachii with a load consisting of a baseline of 80% of their maximum voluntary contraction (MVC), with no vibration and with a superimposed 20, 30, 40, and 50 Hz vibrational force of 40 N. Myoelectric and mechanical fatigue were estimated by EMG analysis and by assessment of the MVC decay, respectively. A dedicated motion artifact canceler, making use of accelerometry, is proposed to enable accurate EMG analysis. Use of this canceler leads to better interpolation of myoelectric fatigue trends and to better correlation between mechanical and myoelectric fatigue. In general, our results suggest vibration at 30 Hz to be the most fatiguing exercise. These results contribute to the analysis of vibration exercise and motivate further research aiming at improved training protocols.

  8. Isometric knee extensor fatigue following a Wingate test: peripheral and central mechanisms.

    Science.gov (United States)

    Fernandez-del-Olmo, M; Rodriguez, F A; Marquez, G; Iglesias, X; Marina, M; Benitez, A; Vallejo, L; Acero, R M

    2013-02-01

    Central and peripheral fatigue have been explored during and after running or cycling exercises. However, the fatigue mechanisms associated with a short maximal cycling exercise (30 s Wingate test) have not been investigated. In this study, 10 volunteer subjects performed several isometric voluntary contractions using the leg muscle extensors before and after two bouts of cycling at 25% of maximal power output and two bouts of Wingate tests. Transcranial magnetic stimulation (TMS) and electrical motor nerve stimulation (NM) were applied at rest and during the voluntary contractions. Maximal voluntary contraction (MVC), voluntary activation (VA), twitch amplitude evoked by electrical nerve stimulation, M wave and motor potential evoked by TMS (MEP) were recorded. MVC, VA and twitch amplitude evoked at rest by NM decreased significantly after the first and second Wingate tests, indicating central and peripheral fatigue. MVC and VA, but not the twitch amplitude evoked by NM, recovered before the second Wingate test. These results suggest that the Wingate test results in a decrease in MVC associated with peripheral and central fatigue. While the peripheral fatigue is associated with an intramuscular impairment, the central fatigue seems to be the main reason for the Wingate test-induced impairment of MVC. © 2011 John Wiley & Sons A/S.

  9. Analysis of maximal isometric force and EMG signal in lower limb exercise. 10.5007/1980-0037.2011v13n6p429

    OpenAIRE

    Cleiton Silva Correa; Bruna Gonçalves Cordeiro da Silva; Cristine Lima Alberton; Eurico Nestor Wilhelm Neto; Antonio Carlos de Moraes; Claudia Silveira Lima; Ronei Silveira Pinto

    2011-01-01

    The aim of this study was to compare maximal isometric force (MIF) and the electrical activity of the vastus medialis, vastus lateralis, rectus femoris, gluteus maximus and biceps femoris long head muscles between maximal voluntary contractions (MVC) performed at different joint angles, and to identify the most suitable positions to normalize the electromyography (EMG) signals from each of these muscles when they are activated under dynamic conditions. Ten men ranging in age from 20 to 30 yea...

  10. Mechanomyography-Based Wearable Monitor of Quasi-Isometric Muscle Fatigue for Motor Neural Prostheses.

    Science.gov (United States)

    Krueger, Eddy; Popović-Maneski, Lana; Nohama, Percy

    2018-02-01

    A motor neural prosthesis based on surface functional electrical stimulation (sFES) can restore functional movement (e.g., standing, walking) in patients with a spinal cord injury (SCI). sFES generates muscle contractions in antigravity muscles and allows balance-assisted standing. This induced standing has several benefits, such as improved cardiovascular function, decreased incidence of urinary infections, reduced joint contractures, and muscle atrophy. The duration of sFES assisted standing is limited due to the quick onset of muscle fatigue. Currently, there is no method available to reliably estimate real-time muscle fatigue during sFES. Simply monitoring the M-wave changes is not suitable due to the high signal disturbances that arise during multi-channel electrical stimulation. Mechanomyography (MMG) is immune to electrical stimulation artifacts and can be used to detect subtle vibrations on the surface of the skin related to activation of the underlying muscle's motor units (MU). The aim of this study was to develop a method for detecting muscle fatigue brought on by sFES. The method was tested in three different heads of the quadriceps muscle in SCI patients during electrically elicited quasi-isometric contraction. Six spinal cord-injured male volunteers, with no voluntary control of the quadriceps muscle participated in the study. Electrical bursts of voltage-controlled monophasic square pulses at frequencies of 1 kHz (50% duty cycle) at 50 Hz (15% duty cycle) were used to generate thigh muscle contractions that controlled the knee joint in the sagittal plane. The pulse amplitudes were set to position the knee joint at a 5° angle from the horizontal plane and when the knee angle dropped to 20° (e.g., the quadriceps were unable to hold the lower leg in the desired position), the test was terminated. Two data segments lasting 10 s each, at the beginning and end of each test, were analyzed. The muscle contraction was assessed by MMG sensors positioned on

  11. Bed rest attenuates sympathetic and pressor responses to isometric exercise in antigravity leg muscles in humans.

    Science.gov (United States)

    Kamiya, Atsunori; Michikami, Daisaku; Shiozawa, Tomoki; Iwase, Satoshi; Hayano, Junichiro; Kawada, Toru; Sunagawa, Kenji; Mano, Tadaaki

    2004-05-01

    Although spaceflight and bed rest are known to cause muscular atrophy in the antigravity muscles of the legs, the changes in sympathetic and cardiovascular responses to exercises using the atrophied muscles remain unknown. We hypothesized that bed rest would augment sympathetic responses to isometric exercise using antigravity leg muscles in humans. Ten healthy male volunteers were subjected to 14-day 6 degrees head-down bed rest. Before and after bed rest, they performed isometric exercises using leg (plantar flexion) and forearm (handgrip) muscles, followed by 2-min postexercise muscle ischemia (PEMI) that continues to stimulate the muscle metaboreflex. These exercises were sustained to fatigue. We measured muscle sympathetic nerve activity (MSNA) in the contralateral resting leg by microneurography. In both pre- and post-bed-rest exercise tests, exercise intensities were set at 30 and 70% of the maximum voluntary force measured before bed rest. Bed rest attenuated the increase in MSNA in response to fatiguing plantar flexion by approximately 70% at both exercise intensities (both P antigravity leg muscles.

  12. Effects of Jaw Clenching and Jaw Alignment Mouthpiece Use on Force Production During Vertical Jump and Isometric Clean Pull.

    Science.gov (United States)

    Allen, Charles R; Fu, Yang-Chieh; Cazas-Moreno, Vanessa; Valliant, Melinda W; Gdovin, Jacob R; Williams, Charles C; Garner, John C

    2018-01-01

    Allen, CR, Fu, Y-C, Cazas-Moreno, V, Valliant, MW, Gdovin, JR, Williams, CC, and Garner, JC. Effects of jaw clenching and jaw alignment mouthpiece use on force production during vertical jump and isometric clean pull. J Strength Cond Res 32(1): 237-243, 2018-This study examined the effects of jaw clenching, a self-adapted, jaw-repositioning mouthpiece on force production during maximum countermovement vertical jump and maximum isometric midthigh clean pull assessments in an attempt to determine any ergogenic effect attributable to clenching, jaw-repositioning mouthpiece use, or the combination of both. Thirty-six male subjects performed vertical jump and isometric clean pull assessments from a force platform under various mouthpiece and clench conditions. A 3 × 2 (mouthpiece × clench) repeated-measures analysis of variance was conducted to analyze each of the following force production variables for both assessments: peak force, normalized peak force, and rate of force development. In addition, jump height was analyzed for the vertical jump. Results revealed improvements in peak force (F1,35 = 15.84, p ≤ 0.001, (Equation is included in full-text article.)= 0.31), normalized peak force (F1,35 = 16.28, p ≤ 0.001, (Equation is included in full-text article.)= 0.32), and rate of force development (F1,35 = 12.89, p = 0.001, (Equation is included in full-text article.)= 0.27) during the isometric clean pull assessment when participants maximally clenched their jaw, regardless of mouthpiece condition. There were no statistically significant differences in jump height, peak force, normalized peak force, or rate of force development during the vertical jump for any treatment condition. This study supports previous research demonstrating that the implementation of remote voluntary contractions such as jaw clenching can lead to concurrent activation potentiation and a resulting ergogenic effect during activities involving and requiring high-force production.

  13. Probing disorder in isometric pyrochlore and related complex oxides.

    Science.gov (United States)

    Shamblin, Jacob; Feygenson, Mikhail; Neuefeind, Joerg; Tracy, Cameron L; Zhang, Fuxiang; Finkeldei, Sarah; Bosbach, Dirk; Zhou, Haidong; Ewing, Rodney C; Lang, Maik

    2016-05-01

    There has been an increased focus on understanding the energetics of structures with unconventional ordering (for example, correlated disorder that is heterogeneous across different length scales). In particular, compounds with the isometric pyrochlore structure, A2B2O7, can adopt a disordered, isometric fluorite-type structure, (A, B)4O7, under extreme conditions. Despite the importance of the disordering process there exists only a limited understanding of the role of local ordering on the energy landscape. We have used neutron total scattering to show that disordered fluorite (induced intrinsically by composition/stoichiometry or at far-from-equilibrium conditions produced by high-energy radiation) consists of a local orthorhombic structural unit that is repeated by a pseudo-translational symmetry, such that orthorhombic and isometric arrays coexist at different length scales. We also show that inversion in isometric spinel occurs by a similar process. This insight provides a new basis for understanding order-to-disorder transformations important for applications such as plutonium immobilization, fast ion conduction, and thermal barrier coatings.

  14. Development of isometric force and force control in children

    NARCIS (Netherlands)

    Smits-Engelsman, B.C.M.; Westenberg, Y.; Duysens, J.E.J.

    2004-01-01

    Fifty-six children between 5 and 12 years of age and 15 adults performed a task (pressing on a lever with the index finger of the preferred hand), in which a force had to be maintained constant at five levels with on-line visual feedback. Since this is a simple isometric task, the hypothesis is that

  15. Development of isometric force and force control in children.

    NARCIS (Netherlands)

    Smits-Engelsman, B.C.M.; Westenberg, Y.; Duysens, J.E.J.

    2003-01-01

    Fifty-six children between 5 and 12 years of age and 15 adults performed a task (pressing on a lever with the index finger of the preferred hand), in which a force had to be maintained constant at five levels with on-line visual feedback. Since this is a simple isometric task, the hypothesis is that

  16. Comparative effects of pilates and isometric exercises on pain ...

    African Journals Online (AJOL)

    Objectives: Knee osteoarthritis is the most common disease of the knee joint and a growing public health problem with physical disability, preventing performance of daily activities. The purpose of this study was to compare the effect of isometric and Pilates exercise on pain, functional disability and range of motion in ...

  17. Cylindrical symmetry locally isometric $AdS_{4}$ spacetime

    CERN Document Server

    Ahmed, Faizuddin; Sarma, Debojit; Myrzakulov, Ratbay

    2016-01-01

    We present a maximally symmetric vacuum spacetime, which is locally isometric anti- de Sitter, admitting closed timelike curves appear after a definite instant of time i.e., a time-machine spacetime. The spacetime is regular, free-from curvature singularities and an $4D$ extension of the Misner space in curved spacetime with identical causality violating properties.

  18. Isometric coactions of compact quantum groups on compact ...

    Indian Academy of Sciences (India)

    isometry group' in Rieffel's framework, we might expect it to be compact. Therefore, we gather some information on compact quantum groups and compact quantum metric spaces together with other preliminary notions in the second section. Next, we introduce our notion of isometric coactions in the third section. We show in ...

  19. Isometric coactions of compact quantum groups on compact ...

    Indian Academy of Sciences (India)

    We propose a notion of isometric coaction of a compact quantum group on a compact quantum metric space in the framework of Rieffel, where the metric structure is given by a Lipnorm. Within this setting we study the problem of the existence of a quantum isometry group.

  20. A modified isometric test to evaluate blood pressure control with ...

    African Journals Online (AJOL)

    SAMJ. VOL 83. NOV 1993. A modified isometric test to evaluate blood pressure control with once-daily slow-release verapamil. A. CANTOR, H. GILUTZ, T. MEYER. Abstract Blood pressure at rest is not predictive of round- the-clock values. Blood pressure should therefore be measured during effort to evaluate hypertension.

  1. Polymorphic Contracts

    Science.gov (United States)

    Belo, João Filipe; Greenberg, Michael; Igarashi, Atsushi; Pierce, Benjamin C.

    Manifest contracts track precise properties by refining types with predicates - e.g., {x : Int |x > 0 } denotes the positive integers. Contracts and polymorphism make a natural combination: programmers can give strong contracts to abstract types, precisely stating pre- and post-conditions while hiding implementation details - for example, an abstract type of stacks might specify that the pop operation has input type {x :α Stack |not ( empty x )} . We formalize this combination by defining FH, a polymorphic calculus with manifest contracts, and establishing fundamental properties including type soundness and relational parametricity. Our development relies on a significant technical improvement over earlier presentations of contracts: instead of introducing a denotational model to break a problematic circularity between typing, subtyping, and evaluation, we develop the metatheory of contracts in a completely syntactic fashion, omitting subtyping from the core system and recovering it post facto as a derived property.

  2. 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

  3. 48 CFR 923.103 - Contract clauses.

    Science.gov (United States)

    2010-10-01

    ... 48 Federal Acquisition Regulations System 5 2010-10-01 2010-10-01 false Contract clauses. 923.103... Contract clauses. Insert the clause at 952.223-78, Sustainable Acquisition Program, or its Alternate I, in all contracts under which the contractor operates Government-owned facilities or Government-owned...

  4. Contract out

    Energy Technology Data Exchange (ETDEWEB)

    Walker, S. (Independent Editorial and Technical Services, Oxford (United Kingdom))

    1999-05-01

    Mining companies opt to offer all or part of their operations out to contract mainly to reduce risk. Contract mining has been most popular in the Southern Hemisphere over the last 15 years, with some exceptions - contractors were often employed in the UK's opencast coal sector and some US coal operators have made extensive use of contract mining. The article discusses the pros and cons of outsourcing, giving examples of contracted out work in Australia (by Thiess Contractors) the USA (Morrison Knudsen), and the UK (Kie Mining). The author comments that successful contracting can only be achieved where both parties know where they stand and have a good working relationship. 2 photos.

  5. Effects of calcium antagonists on K(+)-induced contraction in isolated aorta from diabetic and age-matched control rats

    NARCIS (Netherlands)

    Heijnis, J. B.; van Zwieten, P. A.

    1993-01-01

    The effects of nifedipine, verapamil and diltiazem on K(+)-induced contraction were investigated in isolated aortic rings from diabetic and age-matched control rats. Six weeks after streptozotocin injection there was no significant difference between the maximum isometric contraction to KCl (80

  6. Electromyographic response of global abdominal stabilizers in response to stable- and unstable-base isometric exercise.

    Science.gov (United States)

    Atkins, Stephen J; Bentley, Ian; Brooks, Darrell; Burrows, Mark P; Hurst, Howard T; Sinclair, Jonathan K

    2015-06-01

    Core stability training traditionally uses stable-base techniques. Less is known as to the use of unstable-base techniques, such as suspension training, to activate core musculature. This study sought to assess the neuromuscular activation of global core stabilizers when using suspension training techniques, compared with more traditional forms of isometric exercise. Eighteen elite level, male youth swimmers (age, 15.5 ± 2.3 years; stature, 163.3 ± 12.7 cm; body mass, 62.2 ± 11.9 kg) participated in this study. Surface electromyography (sEMG) was used to determine the rate of muscle contraction in postural musculature, associated with core stability and torso bracing (rectus abdominus [RA], external obliques [EO], erector spinae [ES]). A maximal voluntary contraction test was used to determine peak amplitude for all muscles. Static bracing of the core was achieved using a modified "plank" position, with and without a Swiss ball, and held for 30 seconds. A mechanically similar "plank" was then held using suspension straps. Analysis of sEMG revealed that suspension produced higher peak amplitude in the RA than using a prone or Swiss ball "plank" (p = 0.04). This difference was not replicated in either the EO or ES musculature. We conclude that suspension training noticeably improves engagement of anterior core musculature when compared with both lateral and posterior muscles. Further research is required to determine how best to activate both posterior and lateral musculature when using all forms of core stability training.

  7. Electromyographic assessment of muscle fatigue during isometric vibration training at varying frequencies.

    Science.gov (United States)

    Mischi, M; Rabotti, C; Cardinale, M

    2010-01-01

    Resistance exercise is essential to improve or maintain muscle performance. Vibration training has been suggested as an alternative option for muscle conditioning, aiming especially at improving muscle strength and power. Several studies link the effects of vibration training to enhanced neuromuscular stimulation, measured by electromyography (EMG) and typically ascribed to involuntary reflex mechanisms. However, the underlying mechanisms are still unclear, limiting the use of vibration training. This paper proposes additional methods to analyze the mechanisms involved in vibration training. A dedicated measurement setup was realized to relate vibration parameters to muscle fatigue in the biceps brachii. Fatigue is estimated by EMG mean frequency and conduction velocity assessments as well as by maximum voluntary contraction (MVC) force measurements. A modified maximum likelihood algorithm is proposed for the conduction velocity estimation based on high-density EMG recording. Five volunteers performed four isometric contractions of 50 s at 80% MVC with no vibration (control) and with superimposed vibration at 20, 30, and 40 Hz. Fatigue was estimated from the decay of force, EMG mean frequency, and EMG conduction velocity. 30-Hz vibrations represented the most fatiguing stimulus. Our preliminary results also show a better correlation between force and conduction velocity decay than between force and mean frequency decay, indicating the former as a better EMG indicator of fatigue. The proposed methods provide important advancements for the analysis of vibration exercise and guidance towards the definition of optimal training protocols.

  8. Isometric multipliers of a vector valued Beurling algebra on a ...

    Indian Academy of Sciences (India)

    Abstract. Let (S, ω) be a weighted abelian semigroup, let Mω(S) be the semigroup of ω-bounded multipliers of S, and let A be a strictly convex commutative Banach algebra with identity. It is shown that T is an onto isometric multiplier of l1(S,ω, A) if and only if there exists an invertible σ ∈ Mω(S), a unitary point a ∈ A, and a k ...

  9. Exoskeletal chitin scales isometrically with body size in terrestrial insects.

    Science.gov (United States)

    Lease, Hilary M; Wolf, Blair O

    2010-06-01

    The skeletal system of animals provides the support for a variety of activities and functions. For animals such as mammals, which have endoskeletons, research has shown that skeletal investment (mass) scales with body mass to the 1.1 power. In this study, we ask how exoskeletal investment in insects scales with body mass. We measured the body mass and mass of exoskeletal chitin of 551 adult terrestrial insects of 245 species, with dry masses ranging from 0.0001 to 2.41 g (0.0002-6.13 g wet mass) to assess the allometry of exoskeletal investment. Our results showed that exoskeletal chitin mass scales isometrically with dry body mass across the Insecta as M(chitin) = a M(dry) (b), where b = 1.03 +/- 0.04, indicating that both large and small terrestrial insects allocate a similar fraction of their body mass to chitin. This isometric chitin-scaling relationship was also evident at the taxonomic level of order, for all insect orders except Coleoptera. We additionally found that the relative exoskeletal chitin investment, indexed by the coefficient, a, varies with insect life history and phylogeny. Exoskeletal chitin mass tends to be proportionally less and to increase at a lower rate with mass in flying than in nonflying insects (M(flying insect chitin) = -0.56 x M(dry) (0.97); M(nonflying insect chitin) = -0.55 x M(dry) (1.03)), and to vary with insect order. Isometric scaling (b = 1) of insect exoskeletal chitin suggests that the exoskeleton in insects scales differently than support structures of most other organisms, which have a positive allometry (b > 1) (e.g., vertebrate endoskeleton, tree secondary tissue). The isometric pattern that we document here additionally suggests that exoskeletal investment may not be the primary limit on insect body size.

  10. Causes of excitation-induced muscle cell damage in isometric contractions: mechanical stress or calcium overload?

    DEFF Research Database (Denmark)

    Fredsted, Anne; Gissel, Hanne; Madsen, Klavs

    2007-01-01

    Prolonged or unaccustomed exercise leads to muscle cell membrane damage, detectable as release of the intracellular enzyme lactic acid dehydrogenase (LDH). This is correlated to excitation-induced influx of Ca2+, but it cannot be excluded that mechanical stress contributes to the damage. We here ...

  11. A comparison of two gluteus maximus EMG maximum voluntary isometric contraction positions

    OpenAIRE

    Bret Contreras; Andrew D. Vigotsky; Brad J. Schoenfeld; Chris Beardsley; John Cronin

    2015-01-01

    Background. The purpose of this study was to compare the peak electromyography (EMG) of the most commonly-used position in the literature, the prone bent-leg (90°) hip extension against manual resistance applied to the distal thigh (PRONE), to a novel position, the standing glute squeeze (SQUEEZE). Methods. Surface EMG electrodes were placed on the upper and lower gluteus maximus of thirteen recreationally active females (age = 28.9 years; height = 164 cm; body mass = 58.2 kg), before three m...

  12. Aspects of isometric contractions and static balance in women with symptomatic and asymptomatic joint hypermobility.

    OpenAIRE

    Mueller Mebes C; Luder G; Schmid S; Stettler M; Stutz U; Ziswiler HR; Radlinger L

    2016-01-01

    Objective: The aim of the current study was to identify the differences in strength balance and muscle activity between women with normal mobility and those with generalized joint hypermobility (GJH) with and without symptoms. Methods: A total of 195 women 67 normomobile (NM) and 128 hypermobile (HM) were included in this explorative cross sectional study whereby 56 were classified as symptomatically hypermobile (HM s) and 47 as asymptomatically hypermobile (HM as). Peak force (Fmax) and rate...

  13. EMG-force relations during isometric contractions of the first dorsal interosseous muscle after stroke.

    Science.gov (United States)

    Zhou, Ping; Li, Xiaoyan; Rymer, William Zev

    2013-01-01

    This study examines the electromyogram (EMG)-force relations observed in the first dorsal interosseous (FDI) muscle of hemiparetic stroke survivors. Fourteen stroke subjects were instructed to perform different levels of index finger abduction using their paretic and contralateral hands, respectively. Surface EMG and force signals were recorded from the FDI muscle. The EMG-force relation was constructed using linear regression of the EMG amplitude and force measurements. We found that there were diverse changes in the slope of the EMG-force relations in paretic muscles compared with contralateral muscles, with significant increases and decreases being observed relative to the contralateral side. Regression analysis did not verify strong correlations between the ratio of paretic and contralateral muscle EMG-force slopes and any clinical parameters. These findings suggest that there appear to be different types of processes (eg, motor unit control property changes, muscle fiber atrophy, spinal motoneuron degeneration, muscle fiber reinnervation, etc) at work post stroke that may impact the EMG-force relations and that may be present in varying degree in any given stroke survivor.

  14. Motor unit firing behaviour of soleus muscle in isometric and dynamic contractions

    DEFF Research Database (Denmark)

    Kallio, Jouni; Søgaard, Karen; Avela, Janne

    2013-01-01

    Understanding the detailed control of human locomotion and balance can be improved, when individual motor units can be isolated and their firing rates followed in natural movement of large, fuctionally important muscles. For this reason the present study investigated the motor unit discharge rate...

  15. Improved identification of dystonic cervical muscles via abnormal muscle activity during isometric contractions

    NARCIS (Netherlands)

    De Bruijn, E.; Nijmeijer, S. W. R.; Forbes, P. A.; Koelman, J. H. T. M.; van der Helm, F. C. T.; Tijssen, M. A. J.; Happee, R.

    2015-01-01

    Background: The preferred treatment for cervical dystonia (CD) is injection of botulinum toxin in the dystonic muscles. Unfortunately, in the absence of reliable diagnostic methods it can be difficult to discriminate dystonic muscles from healthy muscles acting in compensation. We investigated if

  16. Improved identification of dystonic cervical muscles via abnormal muscle activity during isometric contractions

    NARCIS (Netherlands)

    de Bruijn, E.; Nijmeijer, S. W. R.; Forbes, P. A.; Koelman, J. H. T. M.; van der Helm, F. C. T.; Tijssen, M. A. J.; Happee, R.

    2015-01-01

    The preferred treatment for cervical dystonia (CD) is injection of botulinum toxin in the dystonic muscles. Unfortunately, in the absence of reliable diagnostic methods it can be difficult to discriminate dystonic muscles from healthy muscles acting in compensation. We investigated if dystonic

  17. Changes in Systolic Blood Pressure during Isometric Contractions of Different Size Muscle Groups.

    Science.gov (United States)

    1979-05-01

    gree in Physical Therapy at the May, 1 1979 graduation Thesisee hIi supervisor I M:embere;Am I - IN Copyrigh-l tzy J07 A. BUCK All !Piahts Peserved...Arthritis, gout , amoutation, sciatica, back pain or otrer disorder of the muscles, bones, or joints? I I- 4 102 Ř-DICA1- HISTOPY rOHRM(conttd.) 11...L.P.T., PhD. Joe A. Buck, L.P.T. I, --------------------------------- , hereby certify that I have bean told by L.R. Amundsen or of the physical therapy

  18. The influence of isometric preload on power expressed during bench press in strength-trained men.

    Science.gov (United States)

    Bartolomei, Sandro; Fukuda, David H; Hoffman, Jay R; Stout, Jeffrey R; Merni, Franco

    2017-03-01

    The purpose of this study was to compare the power expressed during the bench press exercise in resistance-trained men following different pre-activation conditions. Twenty-two trained men (age 24.1 ± 1.7 years, height 178.6 ± 6.1 cm, body mass 81.1 ± 10.6 kg) completed a maximal effort bench press (1-RM) test (100.0 kg ± 8.1 kg). In a subsequent assessment, each participant performed concentric bench press movements with loads of 20%, 30%, 40% and 50% of their 1-RM preceded by either a concentric contraction (CC), a low isometric preload (LIP; 70% 1-RM) or a high isometric preload (HIP; 100% 1-RM) conditions. All movements were performed in a Smith machine with a settable quick-release device. Participants performed all three conditions in randomized fashion. Results indicated that power outputs during the bench press exercise following HIP were significantly (p < 0.05) greater than CC at 20% 1-RM (+9%), 30% 1-RM (+16%) and 40% 1-RM (+14%), and LIP at 20% 1-RM (+4%), 30% 1-RM (+20%) and 40% 1-RM (+15%). No differences were found between conditions at 50% 1-RM. Area under the force-power curve with HIP was greater (p < 0.05) than with CC and LIP. In conclusion, results of this study indicate that the use of a HIP (100% 1-RM) in trained participants results in significantly greater power output during the concentric phase of a multi-joint exercise when compared to standard concentric movement.

  19. EMG analysis of shoulder muscle fatigue during resisted isometric shoulder elevation.

    Science.gov (United States)

    Minning, Stephen; Eliot, Colin A; Uhl, Tim L; Malone, Terry R

    2007-04-01

    The purpose of this study was to determine if a difference existed in the rate of fatigue of select shoulder muscles during isometric shoulder elevation and if the measured rate of fatigue was consistent from day to day. Shoulder muscle fatigue has been associated with alterations in joint mechanics and possibly contributes to shoulder dysfunction. While research exists, there is limited information on an objective and reliable measure of shoulder fatigue. Sixteen asymptomatic subjects were evaluated. The subjects held a weight equivalent to 60% of his/her Maximum Voluntary Isometric Contraction (MVIC) while elevating in the scapular plane. Surface electrodes were applied to collect electromyographic activity from the upper trapezius, middle deltoid, serratus anterior, and lower trapezius muscles while the arm was held at 90 degrees elevation. Data collection ceased when the subject was no longer able to maintain 90 degrees of elevation. The subject then rested and a second trial performed. One week later, the two-trial procedure was repeated. A significant interaction of trial x day x muscle was found for the rate of fatigue. Post hoc analysis revealed that the rate of fatigue of the middle deltoid was significantly greater than the other muscles tested. The intraday reliability was good for all muscles but interday reliability was poor except for the middle deltoid. This study suggests that the middle deltoid appears to fatigue faster than the other shoulder muscles tested at the selected level of shoulder elevation. This should be considered in designing a rehabilitation program to develop a sequence that does not overly fatigue the middle deltoid.

  20. Double-leg isometric exercise training in older men

    Directory of Open Access Journals (Sweden)

    Baross AW

    2013-01-01

    Full Text Available Anthony W Baross,1 Jonathan D Wiles,2 Ian L Swaine21Sport and Exercise Science, University of Northampton, Northampton, UK; 2Sport and Exercise Science, Canterbury Christ Church University, Canterbury, Kent, UKAbstract: Double-leg isometric training has been demonstrated to reduce resting blood pressure in young men when using electromyographic activity (EMG to regulate exercise intensity. This study assessed this training method in healthy older (45–60 years. men. Initially, 35 older men performed an incremental isometric exercise test to determine the linearity of the heart rate versus percentage peak EMG (%EMGpeak and systolic blood pressure versus %EMGpeak relationship. Thereafter, 20 participants were allocated to a training or control group. The training group performed three double-leg isometric sessions per week for 8 weeks, at 85% of peak heart rate. The training resulted in a significant reduction in resting systolic (11 ± 8 mmHg, P < 0.05 and mean arterial (5 ± 7 mmHg, P < 0.05 blood pressure. There was no significant change in resting systolic blood pressure for the control group or diastolic blood pressure in either group (all P > 0.05. These findings show that this training method, used previously in young men, is also effective in reducing resting systolic and mean arterial blood pressure in older men.Keywords: electromyography, resting blood pressure, heart rate

  1. Fatigue and recovery from dynamic contractions in men and women differ for arm and leg muscles.

    Science.gov (United States)

    Senefeld, Jonathon; Yoon, Tejin; Bement, Marie Hoeger; Hunter, Sandra K

    2013-09-01

    Whether there is a gender difference in fatigue and recovery from maximal velocity fatiguing contractions and across muscles is not understood. Sixteen men and 19 women performed 90 isotonic contractions at maximal voluntary shortening velocity (maximal velocity concentric contractions, MVCC) with the elbow flexor and knee extensor muscles (separate days) at a load equivalent to 20% maximal voluntary isometric contraction (MVIC). Power (from MVCCs) decreased similarly for men and women for both muscles (P > 0.05). Men and women had similar declines in MVIC of elbow flexors, but men had greater reductions in knee extensor MVIC force and MVIC electromyogram activity than women (P muscle fatigue often observed during isometric tasks was diminished during fast dynamic contractions for upper and lower limb muscles. Copyright © Published 2013 by Wiley Periodicals, Inc. This article is a US Government wmusork and, as such, is in the public domain in the United States of America.

  2. Isometric hip muscle strength in posttraumatic below-knee amputees

    Directory of Open Access Journals (Sweden)

    Jandrić Slavica

    2007-01-01

    Full Text Available Background/Aim. Traumas and war injuries, next to chronic occlusive artery disease and diabetes mellitus-derived complications, are the most frequent cause of the lower limbs amputation. They affect mostly younger population that need a higher level of activities as compared with the elderly. Medical rehabilitation is very significant for the muscle performance improvement in this population providing their social reintegration. The aim of this study was to investigate the effect of below-knee amputation on the hip isometric muscle strength and effect of rehabilitation on improvement of hip muscle strength in below-knee amputees, secondary to war wounding. Methods. Forty below-knee amputees (after war wounding, average age 35.6±10.6 years, that were included in primary rehabilitation program with prosthetics, were examined. Objective parameters were used to evaluate therapeutical effects. Isometric muscle strength of hip flexors, extensors, abductors and adductors was measured by dynamometer and expressed in Newton (N at admission, control and discharge for each patient. Average length of the treatment was 51 ± 34.1 days. Results. For isometric hip flexors (t = - 1.99346, p < 0.05, extensors (t = -4.629073, p < 0.001, abductors (t = -4.9408, p < 0.001 and adductors (t = -2.00228, p < 0.05, muscle strength was significantly less on the amputated than on nonamputated side. The highest differences in muscle strength between amputated and nonamputated limbs were noted for hip abductors (26.6% and extensors (23.3%. There was significant improvement of mean values of strength for all examined hip muscles after rehabilitation and prosthetics for both legs in comparison to beginning of the therapy. The hip abductor on the amputated side was for 19.4% weaker after rehabilitation in comparison to the nonamputated limb. Conclusion. Decreases of isometric muscle strength in all examined hip muscles were observed, more in the amputated limb. Rehabilitation

  3. Learning contracts

    Directory of Open Access Journals (Sweden)

    Nena Mijoč

    2006-12-01

    Full Text Available There are four different expressions to describe the method of learning, which increases the efficiency of adult learning. The article explains the translation of »learning contract« into Slovene as a method in adult learning area, which came in use in USA in 1970, also in organizations offering formal education. In the period of lifelong learning, when everyone is supposed to be able to learn efficiently from different sources it is even more important to have the skills to plan our learning. Learning contract develops these competencies and has already become established in organizations, which support learning processes. Learning contract is slowly gaining ground also to the area of formal education. Learning contract is an agreement in writing between two people, where one of them offers advice, the other undertakes the learning process. How do we prepare the agreement, who is responsible for its preparation and execution? Learning contract in writing explains objectives, techniques, strategies and how the learning process will be assessed. At the same time, learning is also limited in time. It is a strong motivational took, since it comprises needs of an individual and is adapted to the interests and learning style of a particular individual. This is especially suitable method for acquiring competencies, for field work and experiential learning at work. Learning contract is very suitable and efficient also for independent academical studies, especially when combined with the method of discussion.

  4. 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...

  5. Influence of obstructive sleep apnea syndrome in the fluctuation of the submaximal isometric torque of knee extensors in patients with early-grade osteoarthritis

    Science.gov (United States)

    Silva, Andressa; Mello, Marco T.; Serrão, Paula R.; Luz, Roberta P.; Bittencourt, Lia R.; Mattiello, Stela M.

    2015-01-01

    OBJECTIVE: The aim of this study was to investigate whether obstructive sleep apnea (OSA) alters the fluctuation of submaximal isometric torque of the knee extensors in patients with early-grade osteoarthritis (OA). METHOD: The study included 60 male volunteers, aged 40 to 70 years, divided into four groups: Group 1 (G1) - Control (n=15): without OA and without OSA; Group 2 (G2) (n=15): with OA and without OSA; Group 3 (G3) (n=15): without OA and with OSA; and Group 4 (G4) (n=15) with OA and with OSA. Five patients underwent maximal isometric contractions of 10 seconds duration each, with the knee at 60° of flexion to determine peak torque at 60°. To evaluate the fluctuation of torque, 5 submaximal isometric contractions (50% of maximum peak torque) of 10 seconds each, which were calculated from the standard deviation of torque and coefficient of variation, were performed. RESULTS: Significant differences were observed between groups for maximum peak torque, while G4 showed a lower value compared with G1 (p=0.005). Additionally, for the average torque exerted, G4 showed a lower value compared to the G1 (p=0.036). However, no differences were found between the groups for the standard deviation (p=0.844) and the coefficient of variation (p=0.143). CONCLUSION: The authors concluded that OSA did not change the parameters of the fluctuation of isometric submaximal torque of knee extensors in patients with early-grade OA. PMID:26443974

  6. EMG parameters and EEG α Index change at fatigue period during different types of muscle contraction

    Science.gov (United States)

    Zhang, Li; Zhou, Bin; Song, Gaoqing

    2011-03-01

    The purpose of this study is to measure and analyze the characteristics in change of EMG and EEG parameters at muscle fatigue period in participants with different exercise capacity. Twenty participants took part in the tests. They were divided into two groups, Group A (constant exerciser) and Group B (seldom-exerciser). MVC dynamic and 1/3 isometric exercises were performed; EMG and EEG signals were recorded synchronously during different type of muscle contraction. Results indicated that values of MVC, RMS and IEMG in Group A were greater than Group B, but isometric exercise time was shorter than the time of dynamic exercise although its intensity was light. Turning point of IEMG and α Index occurred synchronously during constant muscle contraction of isometric or dynamic exercise. It is concluded that IEMG turning point may be an indication to justify muscle fatigue. Synchronization of EEG and EMG reflects its common characteristics on its bio-electric change.

  7. Computation and Evaluation of Features of Surface Electromyogram to Identify the Force of Muscle Contraction and Muscle Fatigue

    OpenAIRE

    Sridhar P. Arjunan; Kumar, Dinesh K.; Ganesh Naik

    2014-01-01

    The relationship between force of muscle contraction and muscle fatigue with six different features of surface electromyogram (sEMG) was determined by conducting experiments on thirty-five volunteers. The participants performed isometric contractions at 50%, 75%, and 100% of their maximum voluntary contraction (MVC). Six features were considered in this study: normalised spectral index (NSM5), median frequency, root mean square, waveform length, normalised root mean square (NRMS), and increas...

  8. Novel Roles for Kv7 Channels in Shaping Histamine-Induced Contractions and Bradykinin-Dependent Relaxations in Pig Coronary Arteries

    Science.gov (United States)

    Chen, Xingjuan; Li, Wennan; Hiett, S. Christopher; Obukhov, Alexander G.

    2016-01-01

    Voltage-gated Kv7 channels are inhibited by agonists of Gq-protein-coupled receptors, such as histamine. Recent works have provided evidence that inhibition of vascular Kv7 channels may trigger vessel contractions. In this study, we investigated how Kv7 activity modulates the histamine-induced contractions in “healthy” and metabolic syndrome (MetS) pig right coronary arteries (CAs). We performed isometric tension and immunohistochemical studies with domestic, lean Ossabaw, and MetS Ossabaw pig CAs. We found that neither the Kv7.2/Kv7.4/Kv7.5 activator ML213 nor the general Kv7 inhibitor XE991 altered the tension of CA rings under preload, indicating that vascular Kv7 channels are likely inactive in the preloaded rings. Conversely, ML213 potently dilated histamine-pre-contracted CAs, suggesting that Kv7 channels are activated during histamine applications and yet partially inhibited by histamine. Immunohistochemistry analysis revealed strong Kv7.4 immunostaining in the medial and intimal layers of the CA wall, whereas Kv7.5 immunostaining intensity was strong in the intimal but weak in the medial layers. The medial Kv7 immunostaining was significantly weaker in MetS Ossabaw CAs as compared to lean Ossabaw or domestic CAs. Consistently, histamine-pre-contracted MetS Ossabaw CAs exhibited attenuated ML213-dependent dilations. In domestic pig CAs, where medial Kv7 immunostaining intensity was stronger, histamine-induced contractions spontaneously decayed to ~31% of the peak amplitude within 4 minutes. Oppositely, in Ossabaw CAs, where Kv7 immunostaining intensity was weaker, the histamine-induced contractions were more sustained. XE991 pretreatment significantly slowed the decay rate of histamine-induced contractions in domestic CAs, supporting the hypothesis that increased Kv7 activity correlates with a faster rate of histamine-induced contraction decay. Alternatively, XE991 significantly decreased the amplitude of bradykinin-dependent dilations in pre-contracted

  9. 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...

  10. Some Extensions of Banach's Contraction Principle in Complete Cone Metric Spaces

    Directory of Open Access Journals (Sweden)

    Raja P

    2008-01-01

    Full Text Available Abstract In this paper we consider complete cone metric spaces. We generalize some definitions such as -nonexpansive and -uniformly locally contractive functions -closure, -isometric in cone metric spaces, and certain fixed point theorems will be proved in those spaces. Among other results, we prove some interesting applications for the fixed point theorems in cone metric spaces.

  11. CONTRACTION CHARACTERISTICS AND MYOSIN HEAVY-CHAIN COMPOSITION OF RABBIT MASSETER MOTOR UNITS

    NARCIS (Netherlands)

    KWA, SHS; WEIJS, WA; JUCH, PJW

    1. We studied isometric twitch peak force (TPF) and twitch contraction time (TCT) of 249 motor units of the masseter muscle in 41 rabbits after extracellular electrical stimulation of single trigeminal motoneurons in the brain stem. In 41 of these units we determined the amount of tension decrease

  12. A survey on dilations of projective isometric representations

    Directory of Open Access Journals (Sweden)

    Tania-Luminiţa Costache

    2009-01-01

    Full Text Available In this paper we present Laca-Raeburn's dilation theory of projective isometric representations of a semigroup to projective isometric representations of a group [M.Laca and I.Raeburn, Proc. Amer. Math. Soc., 1995] and Murphy's proof of a dilation theorem more general than that proved by Laca and Raeburn. Murphy applied the theory which involves positive definite kernels and their Kolmogorov decompositions to obtain the Laca-Raeburn dilation theorem [G.J. Murphy, Proc. Amer. Math.Soc., 1997]. We also present Heo's dilation theorems for projective representations, which generalize Stinespring dilation theorem for covariant completely positive maps and generalize to Hilbert C*-modules the Naimark-Sz-Nagy characterization of positive definite functions on groups [J.Heo, J.Math.Anal.Appl., 2007]. In the last part of the paper it is given the dilation theory obtained in [G.J. Murphy, Proc. Amer. Math.Soc., 1997] in the case of unitary operator-valued multipliers [Un Cig Ji, Young Yi Kim and Su Hyung Park, J. Math. Anal. Appl., 2007].

  13. Comparative study of maximum isometric grip strength in different sports

    Directory of Open Access Journals (Sweden)

    Noé Gomes Borges Junior

    2009-06-01

    Full Text Available The objective of this study was to compare maximum isometric grip strength (Fmaxbetween different sports and between the dominant (FmaxD and non-dominant (FmaxND hand. Twenty-nine male aikido (AI, jiujitsu (JJ, judo (JU and rowing (RO athletes and 21non-athletes (NA participated in the study. The hand strength test consisted of maintainingmaximum isometric grip strength for 10 seconds using a hand dynamometer. The position of the subjects was that suggested by the American Society of Hand Therapy. Factorial 2X5 ANOVA with Bonferroni correction, followed by a paired t test and Tukey test, was used for statistical analysis. The highest Fmax values were observed for the JJ group when using the dominant hand,followed by the JU, RO, AI and NA groups. Variation in Fmax could be attributed to handdominance (30.9%, sports modality (39.9% and the interaction between hand dominance andsport (21.3%. The present results demonstrated significant differences in Fmax between the JJ and AI groups and between the JJ and NA groups for both the dominant and non-dominant hand. Significant differences in Fmax between the dominant and non-dominant hand were only observed in the AI and NA groups. The results indicate that Fmax can be used for comparisonbetween different sports modalities, and to identify differences between the dominant and nondominanthand. Studies involving a larger number of subjects will permit the identification of differences between other modalities.

  14. One Point Isometric Matching with the Heat Kernel

    KAUST Repository

    Ovsjanikov, Maks

    2010-09-21

    A common operation in many geometry processing algorithms consists of finding correspondences between pairs of shapes by finding structure-preserving maps between them. A particularly useful case of such maps is isometries, which preserve geodesic distances between points on each shape. Although several algorithms have been proposed to find approximately isometric maps between a pair of shapes, the structure of the space of isometries is not well understood. In this paper, we show that under mild genericity conditions, a single correspondence can be used to recover an isometry defined on entire shapes, and thus the space of all isometries can be parameterized by one correspondence between a pair of points. Perhaps surprisingly, this result is general, and does not depend on the dimensionality or the genus, and is valid for compact manifolds in any dimension. Moreover, we show that both the initial correspondence and the isometry can be recovered efficiently in practice. This allows us to devise an algorithm to find intrinsic symmetries of shapes, match shapes undergoing isometric deformations, as well as match partial and incomplete models efficiently. Journal compilation © 2010 The Eurographics Association and Blackwell Publishing Ltd.

  15. Acute Improvement of Vertical Jump Performance After Isometric Squats Depends on Knee Angle and Vertical Jumping Ability.

    Science.gov (United States)

    Tsoukos, Athanasios; Bogdanis, Gregory C; Terzis, Gerasimos; Veligekas, Panagiotis

    2016-08-01

    Tsoukos, A, Bogdanis, GC, Terzis, G, and Veligekas, P. Acute improvement of vertical jump performance after isometric squats depends on knee angle and vertical jumping ability. J Strength Cond Res 30(8): 2250-2257, 2016-This study examined the acute effects of maximum isometric squats at 2 different knee angles (90 or 140°) on countermovement jump (CMJ) performance in power athletes. Fourteen national-level male track and field power athletes completed 3 main trials (2 experimental and 1 control) in a randomized and counterbalanced order 1 week apart. Countermovement jump performance was evaluated using a force-plate before and 15 seconds, 3, 6, 9, and 12 minutes after 3 sets of 3 seconds maximum isometric contractions with 1-minute rest in between, from a squat position with knee angle set at 90 or 140°. Countermovement jump performance was improved compared with baseline only in the 140° condition by 3.8 ± 1.2% on the 12th minute of recovery (p = 0.027), whereas there was no change in CMJ height in the 90° condition. In the control condition, there was a decrease in CMJ performance over time, reaching -3.6 ± 1.2% (p = 0.049) after 12 minutes of recovery. To determine the possible effects of baseline jump performance on subsequent CMJ performance, subjects were divided into 2 groups ("high jumpers" and "low jumpers"). The baseline CMJ values of "high jumpers" and "low jumpers" differed significantly (CMJ: 45.1 ± 2.2 vs. 37.1 ± 3.9 cm, respectively, p = 0.001). Countermovement jump was increased only in the "high jumpers" group by 5.4 ± 1.4% (p = 0.001) and 7.4 ± 1.2% (p = 0.001) at the knee angles of 90 and 140°, respectively. This improvement was larger at the 140° angle (p = 0.049). Knee angle during isometric squats and vertical jumping ability are important determinants of the acute CMJ performance increase observed after a conditioning activity.

  16. Gluteal muscle activation during the isometric phase of squatting exercises with and without a Swiss ball.

    Science.gov (United States)

    Barton, Christian J; Kennedy, Aedin; Twycross-Lewis, Richard; Woledge, Roger; Malliaras, Peter; Morrissey, Dylan

    2014-02-01

    Growing evidence supports hip muscle activation and strengthening exercise prescription to prevent and treat various lower limb injuries. Common prescriptions include single-legged and double-legged squatting, with and without a Swiss ball. We aimed to establish the effect of varying forms of squatting exercises on gluteal muscle activation. Observational laboratory study. Nineteen (11 male) healthy participants (28.4 +/- 2.7 years old) were compared using one-way repeated measures analysis of variance. Surface electromyography (EMG) measures of gluteus medius (GMed) and gluteus maximus (GMax) during the isometric phase of single-legged and double-legged squatting, with and without a Swiss ball. A greater percentage of maximal voluntary contraction (%MVC) during single-legged squatting was found compared to double-legged squatting for GMed (42 versus 9%MVC, p Swiss ball increased GMax activity (42 versus 35%MVC, p = 0.026) and demonstrated a trend toward increased GMed activity (46 versus 42%MVC, p = 0.075) during the single-legged squat. These results indicate single-legged squatting may be more appropriate than double-legged squatting to facilitate strength gains of GMed and GMax. Additionally, the Swiss ball may be a useful adjunct to target gluteal muscle strengthening during single-legged squatting. Copyright © 2013 Elsevier Ltd. All rights reserved.

  17. Electromyographic response of global abdominal stabilisers in response to stable- and unstable-base isometric exercise.

    Science.gov (United States)

    Atkins, Stephen

    2014-12-24

    Core stability training traditionally uses stable base techniques. Less is known as to the use of unstable base techniques, such as suspension training, to activate core musculature. This study sought to assess the neuromuscular activation of global core stabilisers when using suspension training techniques, compared to more traditional forms of isometric exercise. Eighteen elite level, male youth swimmers (Age 15.5yrs ± 2.3yrs; Stature - 163.3cm ± 12.7cm; Body Mass 62.2kg ± 11.9 kg) participated in the current study. Surface electromyography (sEMG) was used to determine the rate of muscle contraction in postural musculature, associated with core stability and torso bracing (rectus abdominus-RA, external oblique's-EO, erector spinae-ES). A maximal voluntary contraction (MVC) test was used to determine peak amplitude for all muscles. Static bracing of the core was achieved using a modified 'plank' position, with and without a Swiss ball, and held for 30 seconds. A mechanically similar 'plank' was then held using suspension straps. Analysis of sEMG revealed that suspension produced higher peak amplitude in the RA than using a prone or Swiss Ball 'plank' (p=0.04). This difference was not replicated in either the EO or ES musculature. We conclude that suspension training noticeably improves engagement of anterior core musculature when compared to both lateral and posterior muscles. Further research is required to determine how best to activate both posterior and lateral musculature when using all forms of core stability training.

  18. 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

  19. Neural and non-neural control of skin blood flow during isometric handgrip exercise in the heat stressed human

    DEFF Research Database (Denmark)

    Shibasaki, M.; Rasmussen, P.; Secher, Niels H.

    2009-01-01

    as an absence of sweating and cutaneous vasodilatation during a whole-body heat stress. Upon this confirmation, adenosine was perfused through one of the microdialysis probes to increase skin blood flow similar to that of the unblocked site. After internal temperature increased approximately 0.7 degrees C......During heat stress, isometric handgrip (IHG) exercise causes cutaneous vasoconstriction, but it remains controversial whether neural mechanisms are responsible for this observation. The objective of this study was to test the hypothesis that cutaneous vasoconstriction during IHG exercise in heat......, subjects performed 2 min of IHG exercise at 35% of maximal voluntary contraction using the non-blocked arm. IHG exercise significantly decreased CVC at the unblocked site (82.3 +/- 5.7 to 70.9 +/- 5.4%max, P = 0.005, means +/- S.E.M.) and the adenosine treated site of the blocked arm (75.2 +/- 7.2 to 68...

  20. Dynamic optimization of stimulation frequency to reduce isometric muscle fatigue using a modified Hill-Huxley model.

    Science.gov (United States)

    Doll, Brian D; Kirsch, Nicholas A; Bao, Xuefeng; Dicianno, Brad E; Sharma, Nitin

    2017-08-18

    Optimal frequency modulation during functional electrical stimulation (FES) may minimize or delay the onset of FES-induced muscle fatigue. An offline dynamic optimization method, constrained to a modified Hill-Huxley model, was used to determine the minimum number of pulses that would maintain a constant desired isometric contraction force. Six able-bodied participants were recruited for the experiments, and their quadriceps muscles were stimulated while they sat on a leg extension machine. The force-time (F-T) integrals and peak forces after the pulse train was delivered were found to be statistically significantly greater than the force-time integrals and peak forces obtained after a constant frequency train was delivered. Experimental results indicated that the optimized pulse trains induced lower levels of muscle fatigue compared with constant frequency pulse trains. This could have a potential advantage over current FES methods that often choose a constant frequency stimulation train. Muscle Nerve, 2017. © 2017 Wiley Periodicals, Inc.

  1. It wears me out just imagining it! Mental imagery leads to muscle fatigue and diminished performance of isometric exercise.

    Science.gov (United States)

    Graham, Jeffrey D; Sonne, Michael W L; Bray, Steven R

    2014-12-01

    The purpose of this study was to investigate the aftereffects of self-generated mental imagery of an effortful task on physical self-control endurance and muscle fatigue. Participants performed two isometric handgrip endurance trials (50% of maximum contraction) separated by either an imagery manipulation or a quiet rest period. The imagery group showed greater negative changes in endurance performance from trial 1 to trial 2 (p=.003, d=0.87) and increased muscle activation at baseline (p=.01, d=0.73) and at 25% (p=.03, d=0.61) of the second endurance trial compared to controls. We conclude that imagined performance of an effortful task depletes self-control strength and contributes to muscle fatigue. Copyright © 2014 Elsevier B.V. All rights reserved.

  2. Intramuscular pressure, tissue oxygenation, and muscle fatigue of the multifidus during isometric extension in elite rowers with low back pain.

    Science.gov (United States)

    Dehner, Christoph; Schmelz, Andreas; Völker, Hans-Ullrich; Pressmar, Jochen; Elbel, Martin; Kramer, Michael

    2009-11-01

    Chronic low back pain (LBP) has been reported with a high incidence in elite rowers. It results in less effective training, long interruptions in training, and a drop in performance. The authors hypothesized that exercise-induced LBP in rowers is caused by a chronic functional compartment syndrome (CFCS) of the multifidus muscle. Controlled clinical trial. The rowers were tested in their training camp. The control group was tested at a university hospital. 14 volunteer elite rowers complaining of LBP and 16 healthy volunteer amateur athletes. Intramuscular pressure (IMP), tissue oxygenation pressure (pO2), and median frequency (MF) shift in the electromyographic power density spectrum during isometric fatiguing extension at 60% of maximum voluntary contraction. At the beginning (controls 186.6 mm Hg vs rowers 60.2 mm Hg, P = .002) and the end (controls 224.1 mm HG vs rowers 77.1 mm Hg, P pain generation during exercise in elite rowers.

  3. Obtaining maximum muscle excitation for normalizing shoulder electromyography in dynamic contractions.

    Science.gov (United States)

    Hodder, Joanne N; Keir, Peter J

    2013-10-01

    Muscle specific maximal voluntary isometric contractions (MVIC) are commonly used to elicit reference amplitudes to normalize electromyographic signals (EMG). It has been questioned whether this is appropriate for normalizing EMG from dynamic contractions. This study compares EMG amplitude when shoulder muscle activity from dynamic contractions is normalized to isometric and isokinetic maximal excitation as well as a hybrid approach currently used in our laboratory. Anterior, middle and posterior deltoid, upper and lower trapezius, pectoralis major, latissimus dorsi and infraspinatus were monitored during (1) manually resisted MVICs, and (2) maximum voluntary dynamic concentric contractions (MVDC) on an isokinetic dynamometer. Dynamic contractions were performed (a) at 30°/s about the longitudinal, frontal and sagittal axes of the shoulder, and (b) during manual bi-rotation of a tilted wheel at 120°/s. EMG from the wheel task was normalized to the maximum excitation from (i) the muscle specific MVIC, (ii) from any MVIC (MVICALL), (iii) for any MVDC, (iv) from any exertion (maximum experimental excitation, MEE). Mean EMG from the wheel task was up to 45% greater when normalized to muscle specific isometric contractions (method i) than when normalized to MEE (method iv). Seventy-five percent of MEE's occurred during MVDCs. This study presents an 20 useful and effective process for obtaining the greatest excitation from the shoulder muscles when normalizing dynamic efforts. Copyright © 2013 Elsevier Ltd. All rights reserved.

  4. Acute effects of prolonged intermittent low-intensity isometric warm-up schemes on jump, sprint, and agility performance in collegiate soccer players.

    Science.gov (United States)

    Pojskić, H; Pagaduan, J C; Babajić, F; Užičanin, E; Muratović, M; Tomljanović, M

    2015-06-01

    The aim of the present study was to compare the effects of different warm-up interventions on jump, sprint and agility performance in collegiate soccer players. Twenty-one healthy male college soccer players (age: 20.14 ± 1.65 years; body height: 179.9 ± 8.34 cm; body mass: 74.4 ± 13.0 kg; % body fat: 9.45 ± 4.8) participated in the study. Subjects underwent four different randomized warm-up protocols separated by at least 48 hours. The warm-up schemes were: 1. no conditioning contraction protocol (NCC); 2. dynamic stretching (DS); 3. prolonged intermittent low-intensity isometric exercise (ST); and, 4. ST with an additional external load equal to 30% of body weight (ST + 30% BW). All interventions were preceded by a general warm-up. Results from one-way repeated measures ANOVA demonstrated a significant difference in countermovement jump (CMJ) at F(3,60) = 10.2, ηρ(2) = 0.337, p agility performance was also observed; F(3, 60) = 24.1, ηρ(2)= 0.546, p agility was observed in DS, ST and ST + 30% BW. In conclusion, a prolonged intermittent low-intensity isometric protocol using bodyweight only showed similar benefits with dynamic stretching in countermovement jump performance. When the same isometric condition with additional load equal to 30% of bodyweight was applied, effects in speed and agility were similar to dynamic stretching.

  5. Acute response to a 2-minute isometric exercise test predicts the blood pressure-lowering efficacy of isometric resistance training in young adults

    OpenAIRE

    Somani, Yasina B.; Baross, Anthony W.; Brook, Robert D.; Milne, Kevin J.; McGowan, Cheri L.; Swaine, Ian L.

    2017-01-01

    Background:\\ud \\ud This work aimed to explore whether different forms of a simple isometric exercise test could be used to predict the blood pressure (BP)-lowering efficacy of different types of isometric resistance training (IRT) in healthy young adults. In light of the emphasis on primary prevention of hypertension, identifying those with normal BP who will respond to IRT is important. Also, heightened BP reactivity increases hypertension risk, and as IRT reduces BP reactivity in patients w...

  6. Spatial EMG potential distribution pattern of vastus lateralis muscle during isometric knee extension in young and elderly men.

    Science.gov (United States)

    Watanabe, Kohei; Kouzaki, Motoki; Merletti, Roberto; Fujibayashi, Mami; Moritani, Toshio

    2012-02-01

    The aim of the present study was to compare spatial electromyographic (EMG) potential distribution during force production between elderly and young individuals using multi-channel surface EMG (SEMG). Thirteen elderly (72-79years) and 13 young (21-27years) healthy male volunteers performed ramp submaximal contraction during isometric knee extension from 0% to 65% of maximal voluntary contraction. During contraction, multi-channel EMG was recorded from the vastus lateralis muscle. To evaluate alteration in heterogeneity and pattern in spatial EMG potential distribution, coefficient of variation (CoV), modified entropy and correlation coefficients with initial torque level were calculated from multi-channel SEMG at 5% force increment. Increase in CoV and decrease in modified entropy of RMS with increase of exerted torque were significantly smaller in elderly group (pchannel SEMG pattern in elderly individual reflects neuromuscular activation strategy regulated predominantly by clustering of similar type of muscle fibers in aged muscle. Copyright © 2011 Elsevier Ltd. All rights reserved.

  7. Synchronization of muscular oscillations between two subjects during isometric interaction

    Directory of Open Access Journals (Sweden)

    Laura V. Schaefer

    2014-09-01

    Full Text Available Muscles oscillate with a frequency around 10 Hz. But what happens with myofascial oscillations, if two neuromuscular systems interact? The purpose of this study was to examine this question, initially, on the basis of a case study. Oscillations of the triceps brachii muscles of two subjects were determined through mechanomyography (MMG during isometric interaction. The MMG-signals were analyzed concerning the interaction of the two subjects with algorithms of nonlinear dynamics. In this case study it could be shown, that the muscles of both neuromuscular systems also oscillate with the known frequency (here 12 Hz during interaction. Furthermore, both subjects were able to adapt their oscillations against each other. This adjustment induced a significant ( < .05 coherent behavior, which was characterized by a phase shifting of approximately 90°. The authors draw the conclusion, that the complementary neuromuscular partners potentially have the ability of mutual synchronization.

  8. Acute effect of different stretching methods on isometric muscle strength

    Directory of Open Access Journals (Sweden)

    Gabriel Vasconcellos de Lima Costa e Silva

    2014-03-01

    This study investigated the acute effect of static stretching methods (SS and proprioceptive neuromuscular facilitation (PNF on the static muscle strength (SMS. Eleven young male subjects with strength training experience, performed 3 tests with a 48h interval between them, randomly selected, where each one subject carried out all procedures: a hand grip without stretching; b hand grip preceded by static stretching of wrist flexors muscles; c hand grip preceded by PNF stretching of wrist flexors muscles. The Shapiro-Wilk test verified the normality of data, and a one-way ANOVA with repeated measures, followed by Tukey’s post hoc test, evaluated the differences between the groups. The significance was set at p 0.05. In conclusion, both stretching methods had caused negative effects on isometric strength, reducing its levels.

  9. Dynamic Variability of Isometric Action Tremor in Precision Pinching

    Directory of Open Access Journals (Sweden)

    Tim Eakin

    2012-01-01

    Full Text Available Evolutionary development of isometric force impulse frequencies, power, and the directional concordance of changes in oscillatory tremor during performance of a two-digit force regulation task was examined. Analyses compared a patient group having tremor confounding volitional force regulation with a control group having no neuropathological diagnosis. Dependent variables for tremor varied temporally and spatially, both within individual trials and across trials, across individuals, across groups, and between digits. Particularly striking findings were magnitude increases during approaches to cue markers and shifts in the concordance phase from pinching toward rigid sway patterns as the magnitude increased. Magnitudes were significantly different among trace line segments of the task and were characterized by differences in relative force required and by the task progress with respect to cue markers for beginning, reversing force change direction, or task termination. The main systematic differences occurred during cue marker approach and were independent of trial sequence order.

  10. Synchronization of muscular oscillations between two subjects during isometric interaction

    Directory of Open Access Journals (Sweden)

    Laura V. Schaefer

    2014-05-01

    Full Text Available Muscles oscillate with a frequency around 10 Hz. But what happens with myofascial oscillations, if two neuromuscular systems interact? The purpose of this study was to examine this question, initially, on the basis of a case study. Oscillations of the triceps brachii muscles of two subjects were determined through mechanomyography (MMG during isometric interaction. The MMG-signals were analyzed concerning the interaction of the two subjects with algorithms of nonlinear dynamics. In this case study it could be shown, that the muscles of both neuromuscular systems also oscillate with the known frequency (here 12 Hz during interaction. Furthermore, both subjects were able to adapt their oscillations against each other. This adjustment induced a significant ( < .05 coherent behavior, which was characterized by a phase shifting of approximately 90°. The authors draw the conclusion, that the complementary neuromuscular partners potentially have the ability of mutual synchronization.

  11. [ISOMETRIC RETRACTION AND THE INVISIBLE PROCESSES OF NERVE CELLS].

    Science.gov (United States)

    Sotnikov, O S; Vasyagina, N Yu; Krasnova, T V

    2015-01-01

    Recently, a large number of physiological studies on stress and hibernation had described an unusual morphological phenomenon of the rapid disappearance and reapperance of apical dendrites of pyramidal neurons of the hippocampus, prefrontal cortex and other parts of the brain. In this article an attempt is maid to explain this phenomenon on the basis of morphological analysis of natural elastic properties of neuroplasm and structural kinetics of partially preserved processes of the living isolated neurons. The neuroplasm displacement with its bidirectional flow was identified in the processes. A new physiological phenomenon is described--the isometric retraction of nerve cell processes, during which the neuroplasm fluxes were directed to the opposite sides, leading to abrupt thinning of middle parts of the processes and to a thickening of both ends. It is suggested that the extremely attenuated processes can reach the submicroscopic sizes, becoming invisible in the light microscope. The repeated reversible "disappearance" and "appearance" of the processes was demonstrated supravitally in the culture of neurons and of C-1300 neuroblastoma cells. Reduction of the diameter of the processes to a limit of their visibility was demonstrated by the example of their natural stretching. The same effect was observed in the areas between the reversible varicosities of the processes. These areas became extremely thin, and then invisible. Becoming thinner, the processes were capable of sharp extension. A review of the available literature and our own data allow to conclude that the phenomenon of the disappearance of the apical dendrites was due to their isometric retraction, which lead to the emergence of "invisible processes".

  12. Comparative study of maximum isometric grip strength in different sports

    Directory of Open Access Journals (Sweden)

    Noé Gomes Borges Junior

    2009-01-01

    Full Text Available http://dx.doi.org/10.5007/1980-0037.2009v11n3p292   The objective of this study was to compare maximum isometric grip strength (Fmaxbetween different sports and between the dominant (FmaxD and non-dominant (FmaxND hand. Twenty-nine male aikido (AI, jiujitsu (JJ, judo (JU and rowing (RO athletes and 21non-athletes (NA participated in the study. The hand strength test consisted of maintainingmaximum isometric grip strength for 10 seconds using a hand dynamometer. The position of the subjects was that suggested by the American Society of Hand Therapy. Factorial 2X5 ANOVA with Bonferroni correction, followed by a paired t test and Tukey test, was used for statistical analysis. The highest Fmax values were observed for the JJ group when using the dominant hand,followed by the JU, RO, AI and NA groups. Variation in Fmax could be attributed to handdominance (30.9%, sports modality (39.9% and the interaction between hand dominance andsport (21.3%. The present results demonstrated significant differences in Fmax between the JJ and AI groups and between the JJ and NA groups for both the dominant and non-dominant hand. Significant differences in Fmax between the dominant and non-dominant hand were only observed in the AI and NA groups. The results indicate that Fmax can be used for comparisonbetween different sports modalities, and to identify differences between the dominant and nondominanthand. Studies involving a larger number of subjects will permit the identification of differences between other modalities.

  13. Development, validity and reliability of a new pressure air biofeedback device (PAB) for measuring isometric extension strength of the lumbar spine.

    Science.gov (United States)

    Pienaar, Andries W; Barnard, Justhinus G

    2017-04-01

    This study describes the development of a new portable muscle testing device, using air pressure as a biofeedback and strength testing tool. For this purpose, a pressure air biofeedback device (PAB®) was developed to measure and record the isometric extension strength of the lumbar multifidus muscle in asymptomatic and low back pain (LBP) persons. A total of 42 subjects (age 47.58 years, ±18.58) participated in this study. The validity of PAB® was assessed by comparing a selected measure, air pressure force in millibar (mb), to a standard criterion; calibrated weights in kilograms (kg) during day-to-day tests. Furthermore, clinical trial-to-trial and day-to-day tests of maximum voluntary isometric contraction (MVIC) of L5 lumbar multifidus were done to compare air pressure force (mb) to electromyography (EMG) in microvolt (μV) and to measure the reliability of PAB®. A highly significant relationship were found between air pressure output (mb) and calibrated weights (kg). In addition, Pearson correlation calculations showed a significant relationship between PAB® force (mb) and EMG activity (μV) for all subjects (n = 42) examined, as well as for the asymptomatic group (n = 24). No relationship was detected for the LBP group (n = 18). In terms of lumbar extension strength, we found that asymptomatic subjects were significantly stronger than LBP subjects. The results of the PAB® test differentiated between LBP and asymptomatic subject's lumbar isometric extension strength without any risk to the subjects and also indicate that the lumbar isometric extension test with the new PAB® device is reliable and valid.

  14. Retractable Contracts

    Directory of Open Access Journals (Sweden)

    Franco Barbanera

    2016-02-01

    Full Text Available In calculi for modelling communication protocols, internal and external choices play dual roles. Two external choices can be viewed naturally as dual too, as they represent an agreement between the communicating parties. If the interaction fails, the past agreements are good candidates as points where to roll back, in order to take a different agreement. We propose a variant of contracts with synchronous rollbacks to agreement points in case of deadlock. The new calculus is equipped with a compliance relation which is shown to be decidable.

  15. Distinct profiles of neuromuscular fatigue during muscle contractions below and above the critical torque in humans.

    Science.gov (United States)

    Burnley, Mark; Vanhatalo, Anni; Jones, Andrew M

    2012-07-01

    Whether the transition in fatigue processes between "low-intensity" and "high-intensity" contractions occurs gradually, as the torque requirements are increased, or whether this transition occurs more suddenly at some identifiable "threshold", is not known. We hypothesized that the critical torque (CT; the asymptote of the torque-duration relationship) would demarcate distinct profiles of central and peripheral fatigue during intermittent isometric quadriceps contractions (3-s contraction, 2-s rest). Nine healthy men performed seven experimental trials to task failure or for up to 60 min, with maximal voluntary contractions (MVCs) performed at the end of each minute. The first five trials were performed to determine CT [~35-55% MVC, denoted severe 1 (S1) to severe 5 (S5) in ascending order], while the remaining two trials were performed 10 and 20% below the CT (denoted CT-10% and CT-20%). Dynamometer torque and the electromyogram of the right vastus lateralis were sampled continuously. Peripheral and central fatigue was determined from the fall in potentiated doublet torque and voluntary activation, respectively. Above CT, contractions progressed to task failure in ~3-18 min, at which point the MVC did not differ from the target torque (S1 target, 88.7 ± 4.3 N·m vs. MVC, 89.3 ± 8.8 N·m, P = 0.94). The potentiated doublet fell significantly in all trials, and voluntary activation was reduced in trials S1-S3, but not trials S4 and S5. Below CT, contractions could be sustained for 60 min on 17 of 18 occasions. Both central and peripheral fatigue developed, but there was a substantial reserve in MVC torque at the end of the task. The rate of global and peripheral fatigue development was four to five times greater during S1 than during CT-10% (change in MVC/change in time S1 vs. CT-10%: -7.2 ± 1.4 vs. -1.5 ± 0.4 N·m·min(-1)). These results demonstrate that CT represents a critical threshold for neuromuscular fatigue development.

  16. Rho A and the Rho kinase pathway regulate fibroblast contraction: Enhanced contraction in constitutively active Rho A fibroblast cells

    Energy Technology Data Exchange (ETDEWEB)

    Nobe, Koji, E-mail: kojinobe@pharm.showa-u.ac.jp [Department of Pharmacology, School of Pharmaceutical Sciences, Showa University, Tokyo (Japan); Nobe, Hiromi [Department of Pharmacology, School of Pharmaceutical Sciences, Showa University, Tokyo (Japan); Department of Physical Therapy, Bunkyo-Gakuin University (Japan); Yoshida, Hiroko [Department of Pharmacology, School of Pharmaceutical Sciences, Showa University, Tokyo (Japan); Kolodney, Michael S. [Dermatology Division, Department of Medicine, UCLA, Los Angeles, CA (United States); Paul, Richard J. [Department of Molecular and Cellular Physiology, University of Cincinnati College of Medicine, Cincinnati, OH (United States); Honda, Kazuo [Department of Pharmacology, School of Pharmaceutical Sciences, Showa University, Tokyo (Japan)

    2010-08-20

    Research highlights: {yields} Mechanisms of fibroblast cell contraction in collagen matrix. {yields} Assessed an isometric force development using 3D-reconstituted-fibroblast fiber. {yields} Constitutively active Rho A induced the over-contraction of fibroblast cells. {yields} Rho A and Rho kinase pathway has a central role in fibroblast cell contraction. -- Abstract: Fibroblast cells play a central role in the proliferation phase of wound healing processes, contributing to force development. The intracellular signaling pathways regulating this non-muscle contraction are only partially understood. To study the relations between Rho A and contractile responses, constitutively active Rho A (CA-Rho A) fibroblast cells were reconstituted into fibers and the effects of calf serum (CS) on isometric force were studied. CS-induced force in CA-Rho A fibroblast fibers was twice as large as that in wild type (NIH 3T3) fibroblast fibers. During this response, the translocation of Rho A from the cytosol to the membrane was detected by Rho A activity assays and Western blot analysis. Pre-treatment with a Rho specific inhibitor (C3-exoenzyme) suppressed translocation as well as contraction. These results indicate that Rho A activation is essential for fibroblast contraction. The Rho kinase inhibitor ( (Y27632)) inhibited both NIH 3T3 and CA-Rho A fibroblast fiber contractions. Activation of Rho A is thus directly coupled with Rho kinase activity. We conclude that the translocation of Rho A from the cytosol to the membrane and the Rho kinase pathway can regulate wound healing processes mediated by fibroblast contraction.

  17. The effects of 16 months of angle-specific isometric strengthening exercises in midrange on torque of the knee extensor muscles in osteoarthritis of the knee: a case study.

    Science.gov (United States)

    Marks, R

    1994-08-01

    Although often advocated for arthritis rehabilitation, several studies conducted on healthy subjects have demonstrated conflicting results as to whether isometric strengthening exercises performed at one joint angle can result in strength gains at other angles. The objective of this study was to determine whether midrange strength training of the quadriceps surrounding an osteoarthritic knee would increase strength in this part of the range of motion as well at other knee angles. The midrange position was chosen because the subject, a 57-year-old female with a 2-year history of moderately severe osteoarthritis of the left knee, had greatest weakness in this position. The training occurred three times per week for 16 months using a resistance training program of three sets of two maximal isometric contractions at a knee angle of 60 degrees. The dependent variable of maximal isometric knee extensor torque was recorded on an isokinetic dynamometer at knee angles of 90, 60, and 30 degrees at 6 weeks, 1 year, and 16 months. These data demonstrated a progressive torque increase at all angles over the 16-month period, with a steeper slope at the training angle. Contrary to the specificity of training concept, angle-specific strengthening in midrange may be sufficient to strengthen the extensors surrounding an osteoarthritic knee through a wide range of motion. Mid-range isometric strengthening exercises might thus prove useful in the rehabilitation of patients with knee osteoarthritis who are unable to exercise their weakened quadriceps at other angles due to pain or swelling.

  18. Acute Response to a 2-Minute Isometric Exercise Test Predicts the Blood Pressure-Lowering Efficacy of Isometric Resistance Training in Young Adults.

    Science.gov (United States)

    Somani, Yasina B; Baross, Anthony W; Brook, Robert D; Milne, Kevin J; McGowan, Cheri L; Swaine, Ian L

    2018-02-09

    This work aimed to explore whether different forms of a simple isometric exercise test could be used to predict the blood pressure (BP)-lowering efficacy of different types of isometric resistance training (IRT) in healthy young adults. In light of the emphasis on primary prevention of hypertension, identifying those with normal BP who will respond to IRT is important. Also, heightened BP reactivity increases hypertension risk, and as IRT reduces BP reactivity in patients with hypertension, it warrants further investigation in a healthy population. Forty-six young men and women (24 ± 5 years; 116 ± 10/ 68 ± 8 mm Hg) were recruited from 2 study sites: Windsor, Canada (n = 26; 13 women), and Northampton, United Kingdom (n = 20; 10 women). Resting BP and BP reactivity to an isometric exercise test were assessed prior to and following 10 weeks of thrice weekly IRT. Canadian participants trained on a handgrip dynamometer (isometric handgrip, IHG), while participants in the UK trained on an isometric leg extension dynamometer (ILE). Men and women enrolled in both interventions demonstrated significant reductions in systolic BP (P exercise test appears to be a viable tool to identify individuals who may respond to traditional IRT prescription.

  19. 41 CFR 102-76.50 - What is sustainable development?

    Science.gov (United States)

    2010-07-01

    ... and Construction Sustainable Development § 102-76.50 What is sustainable development? Sustainable... 41 Public Contracts and Property Management 3 2010-07-01 2010-07-01 false What is sustainable development? 102-76.50 Section 102-76.50 Public Contracts and Property Management Federal Property Management...

  20. Isometric evaluation of rotator cuff muscles in volleyball athletes.

    Science.gov (United States)

    Martelli, G; Ciccarone, G; Grazzini, G; Signorini, M; Urgelli, S

    2013-06-01

    The aim of the present study was to evaluate, in a group of semi-professional volleyball players, the function of the rotator cuff muscles with a new specific device. We have studied 30 asymptomatic volleyball players, 15 females and 15 males, all right handed central or lateral spikers, with some specific functional tests. Every subject was evaluated by some common clinical tests to detect shoulder range of motion (ROM) and rotator cuff muscles strength in both sides. Athletes were also submitted to an isometric bilateral shoulder strength test, with a specific upper limb dynamometer (Dynatorq), in three different positions: 1) arm 0° abducted; 2) arm 90° abducted and 90° external rotation, to try to reproduce the spike gesture; 3) arm behind the thorax, as a simulation of clinical lift-off test. All clinical and instrumental data were collected in male and female groups and, in each group, comparisons between dominant and non dominant shoulders. Our data show in all athletes an initial postero-superior impingement with significant weakness of the subscapularis muscle in the dominant shoulder. In all overhead athletes, and in particular in volleyball spikers, a pre-clinical diagnosis of lack of strength of the subscapularis muscle in the dominant side, before the occurrence of pain or discomfort signs, could be an important diagnostic aspect to avoid or delay the back-retraction of the joint capsule of the shoulder.

  1. Effects of one-night sleep deprivation on selective attention and isometric force in adolescent karate athletes.

    Science.gov (United States)

    Ben Cheikh, Ridha; Latiri, Imed; Dogui, Mohamed; Ben Saad, Helmi

    2017-06-01

    Most of the available literature related to aspects of sleep deprivation is primarily focused on memory and learning, and studies regarding its effects on selective attention and/or physical performance are scarce. Moreover, the available literature includes general population or people involved in team sports (e.g. volleyball). However, only few studies were performed on athletes involved in combat sports (e.g. karate). The aim of the present study was to determine the effects of a total one-night sleep deprivation (1NSD) on activation and inhibition processes of selective attention and on maximal isometric force in karate athletes. Twelve young karate athletes (mean age 16.9±0.8 years) were enrolled. The protocol consists of two successive sessions: a normal night's sleep (NNS) and a total 1NSD. After each night, athletes performed selective attention and muscle strength tests during the same following three times (T) of the day: T1NNS or T11NSD: 8-9 a.m.; T2NNS or T21NSD: 12 a.m.-1 p.m.; T3NNS or T31NSD: 4-5 p.m. Activation (simple [SRT] and choice reaction times [CRT]) and inhibition (negative priming) processes were evaluated using Superlab v. 4.5 software (Cedrus Corporation, San Pedro, CA, USA). Maximal force and maximal force time (MFT) of brachial biceps isometric contraction were evaluated (Ergo System®, Globus, Codognè, Italy). A non-parametric test was used to evaluate the sessions (NNS vs. SND for the same time period) and time (T1NNS vs. 1NSD) effects. All athletes completed all tests after a NNS. Twelve, eleven and four athletes completed all tests at T11NSD, T21NSD and T31NSD, respectively. As for sessions effects, no statistically significant difference was found. As for time effects, a significant increase in SRT at T21NSD vs. T1NNS (345±47 vs. 317±33 ms, respectively), a significant increase in MFT at T21NSD vs. T1NNS (2172±260 vs.1885±292 ms, respectively), and no significant changes in CRT and negative priming reaction time or MFT data

  2. Task-Dependent Intermuscular Motor Unit Synchronization between Medial and Lateral Vastii Muscles during Dynamic and Isometric Squats.

    Directory of Open Access Journals (Sweden)

    Maurice Mohr

    Full Text Available Motor unit activity is coordinated between many synergistic muscle pairs but the functional role of this coordination for the motor output is unclear. The purpose of this study was to investigate the short-term modality of coordinated motor unit activity-the synchronized discharge of individual motor units across muscles within time intervals of 5ms-for the Vastus Medialis (VM and Lateralis (VL. Furthermore, we studied the task-dependency of intermuscular motor unit synchronization between VM and VL during static and dynamic squatting tasks to provide insight into its functional role.Sixteen healthy male and female participants completed four tasks: Bipedal squats, single-leg squats, an isometric squat, and single-leg balance. Monopolar surface electromyography (EMG was used to record motor unit activity of VM and VL. For each task, intermuscular motor unit synchronization was determined using a coherence analysis between the raw EMG signals of VM and VL and compared to a reference coherence calculated from two desynchronized EMG signals. The time shift between VM and VL EMG signals was estimated according to the slope of the coherence phase angle spectrum.For all tasks, except for singe-leg balance, coherence between 15-80Hz significantly exceeded the reference. The corresponding time shift between VM and VL was estimated as 4ms. Coherence between 30-60Hz was highest for the bipedal squat, followed by the single-leg squat and the isometric squat.There is substantial short-term motor unit synchronization between VM and VL. Intermuscular motor unit synchronization is enhanced for contractions during dynamic activities, possibly to facilitate a more accurate control of the joint torque, and reduced during single-leg tasks that require balance control and thus, a more independent muscle function. It is proposed that the central nervous system scales the degree of intermuscular motor unit synchronization according to the requirements of the movement

  3. The effects of imagery on fast isometric knee extensor torque development

    NARCIS (Netherlands)

    de Ruiter, C.J.; Hutter, R.I.; Icke, C; Groen, B; Gemmink, A; Smilde, H; de Haan, A.

    2012-01-01

    We hypothesized that imagery training would improve fast onset of neuromuscular activation and thereby fast knee extensor isometric torque development. Forty young healthy participants not involved in strength training, were assigned to one of four groups: physical training, imagery training,

  4. Contracting as a Science

    Science.gov (United States)

    2012-04-30

    neoclassical theory to be classified as financial, physical, legal, human, organizational, informational, and relational. Each firm will have some...social science theories applicable to contracting research, identify a contracting paradigm (or paradigms) and potential contracting theories and...principles, examine the nature of contracting research and practice, and present thoughts and ideas toward a general theory of contracting which, hopefully

  5. Effects of intra-set rest on the ability to repeat work at maximal isometric strength.

    Science.gov (United States)

    García Manso, Juan M; Valverde, Teresa; Arrones, Luis; Navarro-Valdivielso, Manuel; Martin Dantas, Estélio H; Da Silva-Grigoletto, Marzo E

    2016-03-01

    The aim of this paper was to analyze how the rest between interval repetitions in intra-set training (at maximal isometric loads) could affect the ability to repeat maximal contractions in subjects with different levels of performance and different experience in strength development work. Twenty subjects were divided randomly into two different groups depending on their sport characteristics: ten subjects were trained in strength development work (Group Strenght--23.1±4.6 years; 172.0±5.3 cm; 79.9±12.1 kg; 2175.6±490.8 N; 46.9±4.9 mL/kg.min), and ten subjects were trained in endurance work (Group Endurance--21.3±4.5 years; 172.4±4.1 cm; 60.0±4.6 kg; 815.5±206.5 N; 67.4±4.9 mL/kg.min). To assess the ability to repeat maximal efforts, 20 repetitions of 5 seconds were performed in a half-squat position, with 1 minute of rest between repetitions. For both groups, four different phases were observed in the Interval Maximal Force test during the 20-repetition assessment: potentiation, maintenance, moderate loss, and significant loss. For the GE, the loss in maximum strength capacity began in the fourth repetition (GS4th: 3.4%, ns, Effect Size: 0.09 vs. GE3th: 1.6%; ns; ES: 0.06) and reached a statistically significant value in the twelfth repetition (GS12th: 12.7%, P=0.03, ES: 0.35 vs. GE7th: 12.5%; P=0.01; ES: 0.49). The number of repetitions at which the strength began to decrease depended on the subject's sport characteristic and performance level. This study shows how an appropriate intra-set rest inclusion can significantly increase the work performed in every set without changing the muscle contraction characteristics, thus delaying muscle fatigue and maintaining the desired training objective.

  6. EFFICACY OF POST ISOMETRIC RELAXATION VERSUS STATIC STRECHING IN SUBJECTS WITH CHRONIC NON SPECIFIC NECK PAIN

    OpenAIRE

    P Haritha; Shanthi, C; Madhavi, K.

    2015-01-01

    Background: Neck pain is a common problem within our society. Upper trapezius sternocleidomastoid and the levator scapulae are the most common postural muscles that tends to get shorten leading to restricted neck mobility. There is lack of evidence to allow conclusions to be drawn about the effectiveness of post isometric relaxation when compared with static stretching exercises. The aim is to find out the effectiveness of Post isometric relaxation Versus Static stretching in the subjects wit...

  7. Validation and Reliability of a Novel Test of Upper Body Isometric Strength

    Directory of Open Access Journals (Sweden)

    Bellar David

    2015-09-01

    Full Text Available The purpose of the present investigation was to examine the association of a novel test of upper body isometric strength against a 1RM bench press measurement. Forty college age adults (n = 20 female, n = 20 male; age 22.8 ± 2.8 years; body height 171.6 ± 10.8 cm; body mass 73.5 ± 16.3 kg; body fat 23.1 ± 5.4% volunteered for the present investigation. The participants reported to the lab on three occasions. The first visit included anthropometric measurements and familiarization with both the upper body isometric test and bench press exercise. The final visits were conducted in a randomized order, with one being a 1RM assessment on the bench press and the other consisting of three trials of the upper body isometric assessment. For the isometric test, participants were positioned in a “push-up” style position while tethered (stainless steel chain to a load cell (high frequency anchored to the ground. The peak isometric force was consistent across all three trials (ICC = 0.98 suggesting good reliability. Multiple regression analysis was completed with the predictors: peak isometric force, gender, against the outcome variable 1RM bench press. The analysis resulted in a significant model (r2 = 0.861, p≤0.001 with all predictor variables attaining significance in the model (p<0.05. Isometric peak strength had the greatest effect on the model (Beta = 5.19, p≤0.001. Results from this study suggest that the described isometric upper body strength assessment is likely a valid and reliable tool to determine strength. Further research is warranted to gather a larger pool of data in regard to this assessment.

  8. Isometric multipliers of Lp (G, X) Lp (G, X) Lp (G, X)

    Indian Academy of Sciences (India)

    We use the characterization of isometries of L p ( G , X ) onto itself to characterize the isometric, invertible, left multipliers of L p ( G , X ) for 1 ≤ < ∞, ≠ 2, under the assumption that is not the l p -direct sum of two non-zero subspaces. In fact we prove that if is an isometric left multiplier of L p ( G , X ) onto itself then ...

  9. Direct measurement of Vorticella contraction force by micropipette deflection.

    Science.gov (United States)

    France, Danielle; Tejada, Jonathan; Matsudaira, Paul

    2017-02-01

    The ciliated protozoan Vorticella convallaria is noted for its exceptionally fast adenosine triphosphate-independent cellular contraction, but direct measurements of contractile force have proven difficult given the length scale, speed, and forces involved. We used high-speed video microscopy to image live Vorticella stalled in midcontraction by deflection of an attached micropipette. Stall forces correlate with both distance contracted and the resting stalk length. Estimated isometric forces range from 95 to 177 nanonewtons (nN), or 1.12 nN·μm-1 of the stalk. Maximum velocity and work are also proportional to distance contracted. These parameters constrain proposed biochemical/physical models of the contractile mechanism. © Published 2017. This article is a U.S. Government work and is in the public domain in the USA.

  10. Isometric Tunnel Placement in Ulnar Collateral Ligament Reconstruction with Single CT Scan

    Directory of Open Access Journals (Sweden)

    Erica Kholinne

    2017-01-01

    Full Text Available Background. Isometric tunnel placement for anterior bundle of the medial collateral ligament (MCL reconstruction is mandatory for successful surgery. Purpose. This study aimed to demonstrate a useful method for identifying isometric tunnel placement using a single computed tomography (CT scan. Study Design. Descriptive Laboratory Study. Methods. Five normal elbows were scanned at 4 different flexion angles at 45° increment. Three-dimensional models were analyzed using 2 different approaches: single and multiple CT scans methods. Ligament footprints in the humerus and the ulna were registered. Ligament length and isometric points were defined. The locations of the isometric points were imported into both methods to be compared. Results. There was no significant difference between 2 methods in calculating the length in every zone. There was also no significant difference in determining isometric ligament’s origin point, which is located approximately 18.2±4.0 mm and 18.4±2.9 mm for single and multiple CT, respectively, measured inferolaterally from medial epicondyle. Conclusions. A solid preoperative plan is critical when predicting tunnel locations due to the difficulty in finding isometric points and the individuality of optimal bone tunnel locations. Using single CT scan, optimal locations can be predicted with the same accuracy as a multiple CT scans with less radiation exposure.

  11. Relationships between Isometric Force-Time Characteristics and Dynamic Performance

    Directory of Open Access Journals (Sweden)

    Thomas Dos’Santos

    2017-09-01

    Full Text Available The purpose of this study was to explore the relationships between isometric mid-thigh pull (IMTP force-time characteristics (peak force and time-specific force vales (100–250 ms and dynamic performance and compare dynamic performance between stronger and weaker athletes. Forty-three athletes from different sports (rowing, soccer, bicycle motocross, and hockey performed three trials of the squat jump (SJ, countermovement jump (CMJ, and IMTP, and performed a one repetition maximum power clean (PC. Reactive strength index modified (RSImod was also calculated from the CMJ. Statistically significant large correlations between IMTP force-time characteristics and PC (ρ = 0.569–0.674, p < 0.001, and moderate correlations between IMTP force-time characteristics (excluding force at 100 ms and RSImod (ρ = 0.389–0.449, p = 0.013–0.050 were observed. Only force at 250 ms demonstrated a statistically significant moderate correlation with CMJ height (ρ = 0.346, p = 0.016 and no statistically significant associations were observed between IMTP force-time characteristics and SJ height. Stronger athletes (top 10 demonstrated statistically significantly greater CMJ heights, RSImods, and PCs (p ≤ 0.004, g = 1.32–1.89 compared to weaker (bottom 10 athletes, but no differences in SJ height were observed (p = 0.871, g = 0.06. These findings highlight that the ability to apply rapidly high levels of force in short time intervals is integral for PC, CMJ height, and reactive strength.

  12. An analysis of the training and development of the contract specialist 1102 interns

    OpenAIRE

    Jones, Pamela; Pettygrue, Valerie

    2010-01-01

    Joint Applied Project This thesis analyzed the U.S. Army Contracting Command (ACC) training and development programs for contract specialists (1102s). Involvement in two wars has generated unintended consequences in the contracting community, which may be adversely affecting the Army's ability to meet and sustain its contracting responsibilities, e.g., an expanding contracting mission accompanied by substantial attrition of experienced contracting professionals. The study analyzed 11...

  13. Mechanomyography and Torque during FES-Evoked Muscle Contractions to Fatigue in Individuals with Spinal Cord Injury

    Science.gov (United States)

    Mohamad, Nor Zainah; Hamzaid, Nur Azah; Abdul Wahab, Ahmad Khairi; Hasnan, Nazirah

    2017-01-01

    A mechanomyography muscle contraction (MC) sensor, affixed to the skin surface, was used to quantify muscle tension during repetitive functional electrical stimulation (FES)-evoked isometric rectus femoris contractions to fatigue in individuals with spinal cord injury (SCI). Nine persons with motor complete SCI were seated on a commercial muscle dynamometer that quantified peak torque and average torque outputs, while measurements from the MC sensor were simultaneously recorded. MC-sensor-predicted measures of dynamometer torques, including the signal peak (SP) and signal average (SA), were highly associated with isometric knee extension peak torque (SP: r = 0.91, p torque (SA: r = 0.89, p muscle torques (SP; ρC = 0.91) and average muscle torques (SA; ρC = 0.89) with the equivalent dynamometer measures, over a range of FES current amplitudes. The relationship of dynamometer torques and predicted MC torques during repetitive FES-evoked muscle contraction to fatigue were moderately associated (SP: r = 0.80, p muscle mechanomyography sensor was an accurate proxy for electrically-evoked muscle contraction torques when directly measured during isometric dynamometry in individuals with SCI. The novel application of the MC sensor during FES-evoked muscle contractions suggested its possible application for real-world tasks (e.g., prolonged sit-to-stand, stepping,) where muscle forces during fatiguing activities cannot be directly measured. PMID:28708068

  14. A Systematic Review of Isometric Lingual Strength-Training Programs in Adults With and Without Dysphagia.

    Science.gov (United States)

    McKenna, Victoria S; Zhang, Bin; Haines, Morgan B; Kelchner, Lisa N

    2017-05-17

    This systematic review summarizes the effects of isometric lingual strength training on lingual strength and swallow function in adult populations. Furthermore, it evaluates the designs of the reviewed studies and identifies areas of future research in isometric lingual strength training for dysphagia remediation. A comprehensive literature search of 3 databases and additional backward citation search identified 10 studies for inclusion in the review. The review reports and discusses the isometric-exercise intervention protocols, pre- and postintervention lingual-pressure data (maximum peak pressures and lingual-palatal pressures during swallowing), and oropharyngeal swallowing measures such as penetration-aspiration scales, oropharyngeal residue and duration, lingual volumes, and quality-of-life assessments. Studies reported gains in maximum peak lingual pressures following isometric lingual strength training for both healthy adults and select groups of individuals with dysphagia. However, due to the variability in study designs, it remains unclear whether strength gains generalize to swallow function. Although isometric lingual strength training is a promising intervention for oropharyngeal dysphagia, the current literature is too variable to confidently report specific therapeutic benefits. Future investigations should target homogenous patient populations and use randomized controlled trials to determine the efficacy of this treatment for individuals with dysphagia.

  15. Relationship between lower extremity isometric muscle strength and standing balance in patients with multiple sclerosis.

    Science.gov (United States)

    Citaker, Seyit; Guclu-Gunduz, Arzu; Yazici, Gokhan; Bayraktar, Deniz; Nazliel, Bijen; Irkec, Ceyla

    2013-01-01

    Muscle strength and standing balance decrease in patients with Multiple Sclerosis (MS). The aim of the present study was to investigate the relationship between the lower extremity isometric muscle strength and standing balance in patients with MS. Forty-seven patients with MS and 10 healthy volunteers were included. Neurological disability level was assessed using Expanded Disability Status Scale (EDSS). Isometric strength of seven lower extremity muscles (hip flexor-extensor-abductor-adductor, knee flexor-extensor, and ankle dorsal flexor) was assessed using hand-held dynamometer. Duration of static one-leg standing balance was measured using digital chronometer. Hip flexor-extensor-abductor-adductor, knee flexor-extensor, and ankle dorsal flexor isometric muscle strength, and duration of one-leg standing balance were decreased in patients with MS when compared with controls (p leg standing balance in patients with MS. All assessed lower extremity isometric muscle strength (except ankle dorsal flexor) was related with EDSS. Hip flexor-extensor-abductor-adductor, knee flexor-extensor, and ankle dorsal flexor isometric muscle strength decreases in ambulatory MS patients. Lower extremity muscle weakness and neurological disability level are related with imbalance in MS population. Hip and knee region muscles weakness increases the neurological disability level. For the better balance and decrease neurological disability level whole lower extremity muscle strengthening should be included in rehabilitation programs.

  16. EFFECTS OF COMMERCIAL CONTRACT

    OpenAIRE

    Ana-Maria Florea; Constantin Giurca

    2014-01-01

    The contract is a legal instrument used to organize economic and social life. International trade agreement has certain features in order to ensure the international exchange of goods and services between the Contracting Parties. In terms of commercial contract, there is a foreign origin element, that gives the parties the right to determine the law to govern the contract. A fundamental aspect of commercial contract, in addition to that of determining the law applicable to judicial report est...

  17. Cross-Activation of the Motor Cortex during Unilateral Contractions of the Quadriceps

    Science.gov (United States)

    Hendy, Ashlee M.; Chye, Lilian; Teo, Wei-Peng

    2017-01-01

    Transcranial magnetic stimulation (TMS) studies have demonstrated that unilateral muscle contractions in the upper limb produce motor cortical activity in both the contralateral and ipsilateral motor cortices. The increase in excitability of the corticomotor pathway activating the resting limb has been termed “cross-activation”, and is of importance due to its involvement in cross-education and rehabilitation. To date, very few studies have investigated cross-activation in the lower limb. Sixteen healthy participants (mean age 29 ± 9 years) took part in this study. To determine the effect of varying contraction intensities in the lower limb, we investigated corticomotor excitability and intracortical inhibition of the right rectus femoris (RF) while the left leg performed isometric extension at 0%, 25%, 50%, 75% and 100% of maximum force output. Contraction intensities of 50% maximal force output and greater produced significant cross-activation of the corticomotor pathway. A reduction in silent period duration was observed during 75% and 100% contractions, while the release of short-interval intracortical inhibition (SICI) was only observed during maximal (100%) contractions. We conclude that increasing isometric contraction intensities produce a monotonic increase in cross-activation, which was greatest during 100% force output. Unilateral training programs designed to induce cross-education of strength in the lower limb should therefore be prescribed at the maximal intensity tolerable. PMID:28824401

  18. Cross-Activation of the Motor Cortex during Unilateral Contractions of the Quadriceps

    Directory of Open Access Journals (Sweden)

    Ashlee M. Hendy

    2017-08-01

    Full Text Available Transcranial magnetic stimulation (TMS studies have demonstrated that unilateral muscle contractions in the upper limb produce motor cortical activity in both the contralateral and ipsilateral motor cortices. The increase in excitability of the corticomotor pathway activating the resting limb has been termed “cross-activation”, and is of importance due to its involvement in cross-education and rehabilitation. To date, very few studies have investigated cross-activation in the lower limb. Sixteen healthy participants (mean age 29 ± 9 years took part in this study. To determine the effect of varying contraction intensities in the lower limb, we investigated corticomotor excitability and intracortical inhibition of the right rectus femoris (RF while the left leg performed isometric extension at 0%, 25%, 50%, 75% and 100% of maximum force output. Contraction intensities of 50% maximal force output and greater produced significant cross-activation of the corticomotor pathway. A reduction in silent period duration was observed during 75% and 100% contractions, while the release of short-interval intracortical inhibition (SICI was only observed during maximal (100% contractions. We conclude that increasing isometric contraction intensities produce a monotonic increase in cross-activation, which was greatest during 100% force output. Unilateral training programs designed to induce cross-education of strength in the lower limb should therefore be prescribed at the maximal intensity tolerable.

  19. Effect of Knee Joint Angle and Contraction Intensity on Hamstrings Coactivation.

    Science.gov (United States)

    Wu, Rui; Delahunt, Eamonn; Ditroilo, Massimiliano; Lowery, Madeleine M; DE Vito, Giuseppe

    2017-08-01

    This study investigated the effect of knee joint angle and contraction intensity on the coactivation of the hamstring muscles (when acting as antagonists to the quadriceps) in young and older individuals of both sexes. A total of 25 young (24 ± 2.6 yr) and 26 older (70 ± 2.5 yr) healthy men and women participated. Maximal voluntary isometric contraction of the knee extensors and flexors was assessed at two knee joint angles (90° and 60°, 0° = full extension). At each angle, participants performed submaximal contractions of the knee extensors (20%, 50%, and 80% maximal voluntary isometric contraction), whereas surface EMG was simultaneously acquired from the vastus lateralis and biceps femoris muscles to assess the level (EMG root-mean-square) of agonist activation and antagonist coactivation. Subcutaneous adipose tissue in the areas corresponding to surface EMG electrode placements was measured via ultrasonography. The contractions performed at 90° knee flexion demonstrated higher levels of antagonist coactivation (all P knee flexion. Furthermore, after controlling for subcutaneous adipose tissue, older participants exhibited a higher level of antagonist coactivation at 60° knee flexion compared with young participants (P knee joint angle and contraction intensity and 2) subcutaneous adipose tissue may affect the measured coactivation level likely because of a cross-talk effect. Antagonist coactivation may play a protective role in stabilizing the knee joint and maintaining constant motor output.

  20. EMGD-FE: an open source graphical user interface for estimating isometric muscle forces in the lower limb using an EMG-driven model

    Science.gov (United States)

    2014-01-01

    Background This paper describes the “EMG Driven Force Estimator (EMGD-FE)”, a Matlab® graphical user interface (GUI) application that estimates skeletal muscle forces from electromyography (EMG) signals. Muscle forces are obtained by numerically integrating a system of ordinary differential equations (ODEs) that simulates Hill-type muscle dynamics and that utilises EMG signals as input. In the current version, the GUI can estimate the forces of lower limb muscles executing isometric contractions. Muscles from other parts of the body can be tested as well, although no default values for model parameters are provided. To achieve accurate evaluations, EMG collection is performed simultaneously with torque measurement from a dynamometer. The computer application guides the user, step-by-step, to pre-process the raw EMG signals, create inputs for the muscle model, numerically integrate the ODEs and analyse the results. Results An example of the application’s functions is presented using the quadriceps femoris muscle. Individual muscle force estimations for the four components as well the knee isometric torque are shown. Conclusions The proposed GUI can estimate individual muscle forces from EMG signals of skeletal muscles. The estimation accuracy depends on several factors, including signal collection and modelling hypothesis issues. PMID:24708668

  1. EMGD-FE: an open source graphical user interface for estimating isometric muscle forces in the lower limb using an EMG-driven model.

    Science.gov (United States)

    Menegaldo, Luciano Luporini; de Oliveira, Liliam Fernandes; Minato, Kin K

    2014-04-04

    This paper describes the "EMG Driven Force Estimator (EMGD-FE)", a Matlab® graphical user interface (GUI) application that estimates skeletal muscle forces from electromyography (EMG) signals. Muscle forces are obtained by numerically integrating a system of ordinary differential equations (ODEs) that simulates Hill-type muscle dynamics and that utilises EMG signals as input. In the current version, the GUI can estimate the forces of lower limb muscles executing isometric contractions. Muscles from other parts of the body can be tested as well, although no default values for model parameters are provided. To achieve accurate evaluations, EMG collection is performed simultaneously with torque measurement from a dynamometer. The computer application guides the user, step-by-step, to pre-process the raw EMG signals, create inputs for the muscle model, numerically integrate the ODEs and analyse the results. An example of the application's functions is presented using the quadriceps femoris muscle. Individual muscle force estimations for the four components as well the knee isometric torque are shown. The proposed GUI can estimate individual muscle forces from EMG signals of skeletal muscles. The estimation accuracy depends on several factors, including signal collection and modelling hypothesis issues.

  2. Peripheral Vascular Resistance Impairment during Isometric Physical Exercise in Normotensive Offspring of Hypertensive Parents

    Directory of Open Access Journals (Sweden)

    Natália Portela

    Full Text Available Abstract Background: A family history of hypertension is associated with vascular and autonomic abnormalities, as well as an impaired neurohemodynamic response to exercise. Objective: To test the hypothesis that normotensive individuals with a family history of hypertension present an impaired peripheral vascular resistance response to exercise. Methods: The study included 37 normotensive volunteers of both sexes who were sedentary, eutrophic, and nonsmokers, comprising 23 with (FH+; 24 ± 3 years and 14 without (FH-; 27 ± 5 years a family history of hypertension. Blood pressure, heart rate (DIXTAL®, forearm blood flow (Hokanson®, and peripheral vascular resistance were simultaneously measured for 3 minutes during rest and, subsequently, for 3 minutes during an isometric exercise at 30% of maximal voluntary contraction (Jamar®. Results: At rest, the FH+ and FH- groups present similar mean blood pressure (83 ± 7 versus 83 ± 5 mmHg, p = 0.96, heart rate (69 ± 8 bpm versus 66 ± 7 bpm, p = 0.18, forearm blood flow (3 ± 1 mL/min/100 mL versus 2.7 ± 1 mL/min/100 mL, p = 0.16, and peripheral vascular resistance (30 ± 9 units versus 34±9 units, p = 0.21, respectively. Both groups showed a significant and similar increase in mean blood pressure (∆ = 15 ± 7 mmHg versus 14 ± 7 mmHg, p = 0.86, heart rate (∆ = 12 ± 8 bpm versus 13 ± 7 bpm, p = 0.86, and forearm blood flow (∆ = 0.8 ± 1.2 mL/min/100 mL versus 1.4 ± 1.1 mL/min/100 mL, p = 0.25, respectively, during exercise. However, individuals in the FH+ group showed no reduction in peripheral vascular resistance during exercise, which was observed in the FH- group (∆ = -0.4 ± 8.6 units versus -7.2 ± 6.3 units, p = 0.03. Conclusion: Normotensive individuals with a family history of hypertension present an impaired peripheral vascular resistance response to exercise.

  3. An isometric muscle force estimation framework based on a high-density surface EMG array and an NMF algorithm

    Science.gov (United States)

    Huang, Chengjun; Chen, Xiang; Cao, Shuai; Qiu, Bensheng; Zhang, Xu

    2017-08-01

    Objective. To realize accurate muscle force estimation, a novel framework is proposed in this paper which can extract the input of the prediction model from the appropriate activation area of the skeletal muscle. Approach. Surface electromyographic (sEMG) signals from the biceps brachii muscle during isometric elbow flexion were collected with a high-density (HD) electrode grid (128 channels) and the external force at three contraction levels was measured at the wrist synchronously. The sEMG envelope matrix was factorized into a matrix of basis vectors with each column representing an activation pattern and a matrix of time-varying coefficients by a nonnegative matrix factorization (NMF) algorithm. The activation pattern with the highest activation intensity, which was defined as the sum of the absolute values of the time-varying coefficient curve, was considered as the major activation pattern, and its channels with high weighting factors were selected to extract the input activation signal of a force estimation model based on the polynomial fitting technique. Main results. Compared with conventional methods using the whole channels of the grid, the proposed method could significantly improve the quality of force estimation and reduce the electrode number. Significance. The proposed method provides a way to find proper electrode placement for force estimation, which can be further employed in muscle heterogeneity analysis, myoelectric prostheses and the control of exoskeleton devices.

  4. Shoulder muscle isometric strength and active range of motion in patients with frozen shoulder syndrome after manipulation under anesthesia.

    Science.gov (United States)

    Sokk, Jelena; Gapeyeva, Helena; Ereline, Jaan; Merila, Mati; Pääsuke, Mati

    2012-01-01

    Frozen shoulder syndrome (FSS) causes pain and restriction of movement in the shoulder. The aim was to assess changes in shoulder muscle isometric maximal voluntary contraction (MVC) force and active range of motion (AROM) in patients with frozen shoulder syndrome (FSS) after manipulation under general anesthesia (MUA). In total, 18 patients with FSS (9 women and 9 men) with a mean age of 53.6 years (SD, 9.7) participated in this study. MVC force of shoulder flexors, adductors, and internal and external rotators was measured by a handheld dynamometer. AROM in the same directions was measured goniometrically. The patients were screened according to the intensity of pain by day and at night. The data were collected before MUA and 1 and 6 months after MUA. A significant reduction in MVC force and AROM was noted before MUA in the involved extremity as compared with the uninvolved extremity (P0.05), whereas AROM of flexion and external rotation remained significantly reduced (Pshoulder pain by day and at night was recorded 1 and 6 months after MUA (Pshoulder muscle MVC force for the involved extremity did not differ significantly as compared with the uninvolved extremity, whereas the shoulder AROM in flexion and external rotation remained lower.

  5. Between-day reliability of electromechanical delay of selected neck muscles during performance of maximal isometric efforts

    Directory of Open Access Journals (Sweden)

    Almosnino Sivan

    2009-09-01

    Full Text Available Abstract Background The purpose of this study was to assess the between-day reliability of the electromechanical delay (EMD of selected neck muscles during the performance of maximal isometric contractions in five different directions. Methods Twenty-one physically active males participated in two testing sessions separated by seven to eight days. Using a custom-made fixed frame dynamometer, cervical force and surface electromyography (EMG were recorded bilaterally from the splenius capitis, upper trapezius and sternocleidomastoid muscles during the performance of efforts in extension, flexion, left and right lateral bending, and protraction. The EMD was extracted using the Teager-Kaiser Energy Operator. Reliability indices calculated for each muscle in each testing direction were: the difference in scores between the two testing sessions and corresponding 95% confidence intervals, the standard error of measurement (SEM and intra-class correlation coefficients (ICC. Results EMD values showed no evidence of systematic difference between the two testing sessions across all muscles and testing directions. The SEM for extension, flexion and lateral bending efforts ranged between 2.5 ms to 4.8 ms, indicating a good level of measurement precision. For protraction, SEM values were higher and considered to be imprecise for research and clinical purposes. ICC values for all muscles across all testing directions ranged from 0.23 to 0.79. Conclusion EMD of selected neck muscles can be measured with sufficient precision for the assessment of neck muscle function in an athletic population in the majority of directions tested.

  6. Characteristics of the Motor Units during Sternocleidomastoid Isometric Flexion among Patients with Mechanical Neck Disorder and Asymptomatic Individuals.

    Science.gov (United States)

    Yang, Chia-Chi; Su, Fong-Chin; Yang, Po-Ching; Lin, Hwai-Ting; Guo, Lan-Yuen

    2016-01-01

    Mechanical neck disorder is a widespread and non-neurological musculoskeletal condition resulting from modern lifestyles. Presently, the fundamental electrophysiological properties of the motor units of the sternocleidomastoid muscles and the characteristics of the short-term synchronization of the motor unit in patients with neck pain are ambiguous. This study therefore aims to clarify the fundamental electrophysiological properties of the motor units of the sternocleidomastoid muscles in patients with mechanical neck disorder and in asymptomatic individuals. We further investigated whether alterations in the degree of motor unit short-term synchronization occur. The surface electrophysiological signals of the bilateral sternal heads of the sternocleidomastoid muscles of twelve patients with mechanical neck disorder and asymptomatic individuals were detected at 25% of the maximum voluntary contraction during cervical isometric flexion and then decomposed into individual motor unit action potential trains. We found that the patients with mechanical neck disorder showed significantly higher initial and mean firing rates of the sternocleidomastoid muscles and displayed substantially lower motor unit short-term synchronization values compared with the asymptomatic subjects. Consequently, these convincing findings support the assertion that patients with mechanical neck disorder display altered neuromuscular control strategies, such as the reinforcement of motor unit recruitment firing rates in the sternocleidomastoid muscles. The motor units of these patients also revealed neural recruitment strategies with relatively poor efficiency when executing the required motor tasks.

  7. Characteristics of the Motor Units during Sternocleidomastoid Isometric Flexion among Patients with Mechanical Neck Disorder and Asymptomatic Individuals.

    Directory of Open Access Journals (Sweden)

    Chia-Chi Yang

    Full Text Available Mechanical neck disorder is a widespread and non-neurological musculoskeletal condition resulting from modern lifestyles. Presently, the fundamental electrophysiological properties of the motor units of the sternocleidomastoid muscles and the characteristics of the short-term synchronization of the motor unit in patients with neck pain are ambiguous. This study therefore aims to clarify the fundamental electrophysiological properties of the motor units of the sternocleidomastoid muscles in patients with mechanical neck disorder and in asymptomatic individuals. We further investigated whether alterations in the degree of motor unit short-term synchronization occur. The surface electrophysiological signals of the bilateral sternal heads of the sternocleidomastoid muscles of twelve patients with mechanical neck disorder and asymptomatic individuals were detected at 25% of the maximum voluntary contraction during cervical isometric flexion and then decomposed into individual motor unit action potential trains. We found that the patients with mechanical neck disorder showed significantly higher initial and mean firing rates of the sternocleidomastoid muscles and displayed substantially lower motor unit short-term synchronization values compared with the asymptomatic subjects. Consequently, these convincing findings support the assertion that patients with mechanical neck disorder display altered neuromuscular control strategies, such as the reinforcement of motor unit recruitment firing rates in the sternocleidomastoid muscles. The motor units of these patients also revealed neural recruitment strategies with relatively poor efficiency when executing the required motor tasks.

  8. [Comparison of the effectiveness of isokinetic vs isometric therapeutic exercise in patients with osteoarthritis of knee].

    Science.gov (United States)

    Rosa, Uganet Hernández; Velásquez Tlapanco, Jorge; Lara Maya, Catalina; Villarreal Ríos, Enrique; Martínez González, Lidia; Vargas Daza, Emma Rosa; Galicia Rodríguez, Liliana

    2012-01-01

    Osteoarthritis is a chronic joint disease; isometric exercise leads to the development of mechanical work and isokinetic exercise leads to better joint mobility. To compare the effectiveness of isometric versus isokinetic therapeutic exercises in patients with knee osteoarthritis. Quasiexperimental study in a population of 45 to 75 year old patients with a diagnosis of knee osteoarthritis. Group 1 (experimental) was put under isokinetic exercises and group 2 (control) under isometric exercises. The sample size was of 33 patients per group; the allocation to the experimentation or control group was nonrandom, but stratified by degrees of knee osteoarthritis. The effectiveness of the exercise was measured in three dimensions: muscle strength, joint range and pain. The intervention lasted eight weeks and the physical activity was carried out every third day. The statistical analysis included averages, standard deviation, percentage, Chi square test, z test for two populations, t test for two independent populations and twin t test. The analysis of muscle strength comparing the categories independently demonstrates differences at 8 weeks; 33.3% of the isokinetic exercise is in the normal category and 15.2% in the isometric exercise (p= 0.04). There was not difference of joint range between groups, despite finding a stage I range in 100.0% of the isokinetic group and 97.0% in the isometric (p> 0.05) group. Pain was milder in the isokinetic exercise group at 8 weeks (p= 0.01) Isokinetic exercises have a greater effectiveness than isometric exercises for muscle strength and pain in patients with knee osteoarthritis. However, other studies with randomized designs are needed. Copyright © 2011 Elsevier España, S.L. All rights reserved.

  9. Validity of an Isometric Midthigh Pull Dynamometer in Male Youth Athletes.

    Science.gov (United States)

    Till, Kevin; Morris, Rhys; Stokes, Keith; Trewartha, Grant; Twist, Craig; Dobbin, Nick; Hunwicks, Richard; Jones, Ben

    2017-11-16

    Till, K, Morris, R, Stokes, K, Trewartha, G, Twist, C, Dobbin, N, Hunwicks, R, and Jones, B. Validity of an isometric midthigh pull dynamometer in male youth athletes. J Strength Cond Res XX(X): 000-000, 2017-The purpose of this study was to investigate the validity of an isometric midthigh pull dynamometer against a criterion measure (i.e., 1,000-Hz force platform) for assessing muscle strength in male youth athletes. Twenty-two male adolescent (age 15.3 ± 0.5 years) rugby league players performed 4 isometric midthigh pull efforts (i.e., 2 on the dynamometer and 2 on the force platform) separated by 5-minute rest in a randomized and counterbalanced order. Mean bias, typical error of estimate (TEE), and Pearson correlation coefficient for peak force (PF) and peak force minus body weight (PFBW) from the force platform were validated against peak force from the dynamometer (DynoPF). When compared with PF and PFBW, mean bias (with 90% confidence limits) for DynoPF was very large (-32.4 [-34.2 to -30.6] %) and moderate (-10.0 [-12.8 to -7.2] %), respectively. The TEE was moderate for both PF (8.1 [6.3-11.2] %) and PFBW (8.9 [7.0-12.4]). Correlations between DynoPF and PF (r 0.90 [0.79-0.95]) and PFBW (r 0.90 [0.80-0.95]) were nearly perfect. The isometric midthigh pull assessed using a dynamometer underestimated PF and PFBW obtained using a criterion force platform. However, strong correlations between the dynamometer and force platform suggest that a dynamometer provides an appropriate alternative to assess isometric midthigh pull strength when a force platform is not available. Therefore, practitioners can use an isometric midthigh pull dynamometer to assess strength in the field with youth athletes but should be aware that it underestimates peak force.

  10. Ensuring sustained user quality in buildings. Success contracting with functional tendering of the building services equipment guarantees quality for 15 years; Nutzerqualitaet in Gebaeuden dauerhaft sicherstellen. Erfolgscontracting mit funktionaler Ausschreibung ermoeglicht eine 15-jaehrige Garantie auf die Gebaeudetechnik

    Energy Technology Data Exchange (ETDEWEB)

    Milles, Uwe

    2012-07-01

    Until now, buildings regularly require more energy and provide less user quality in practice than was to be expected from the installed technology during the planning. That has structural reasons. The naerco research project has investigated this aspect and developed the success contracting concept: pre-defined energy and quality parameters are contracted out as part of a function-based tender. A contractor guarantees their realisation for 15 years. The contractual process also includes continual control of the agreed values and a bonus-malus system.

  11. Muscle Shear Moduli Changes and Frequency of Alternate Muscle Activity of Plantar Flexor Synergists Induced by Prolonged Low-Level Contraction

    Directory of Open Access Journals (Sweden)

    Ryota Akagi

    2017-09-01

    Full Text Available During prolonged low-level contractions, synergist muscles are activated in an alternating pattern of activity and silence called as alternate muscle activity. Resting muscle stiffness is considered to increase due to muscle fatigue. Thus, we investigated whether the difference in the extent of fatigue of each plantar flexor synergist corresponded to the difference in the frequency of alternate muscle activity between the synergists using muscle shear modulus as an index of muscle stiffness. Nineteen young men voluntarily participated in this study. The shear moduli of the resting medial and lateral gastrocnemius muscles (MG and LG and soleus muscle (SOL were measured using shear wave ultrasound elastography before and after a 1-h sustained contraction at 10% peak torque during maximal voluntary contraction of isometric plantar flexion. One subject did not accomplish the task and the alternate muscle activity for MG was not found in 2 subjects; therefore, data for 16 subjects were used for further analyses. The magnitude of muscle activation during the fatiguing task was similar in MG and SOL. The percent change in shear modulus before and after the fatiguing task (MG: 16.7 ± 12.0%, SOL: −4.1 ± 13.9%; mean ± standard deviation and the alternate muscle activity during the fatiguing task (MG: 33 [20–51] times, SOL: 30 [17–36] times; median [25th–75th percentile] were significantly higher in MG than in SOL. The contraction-induced change in shear modulus (7.4 ± 20.3% and the alternate muscle activity (37 [20–45] times of LG with the lowest magnitude of muscle activation during the fatiguing task among the plantar flexors were not significantly different from those of the other muscles. These results suggest that the degree of increase in muscle shear modulus induced by prolonged contraction corresponds to the frequency of alternate muscle activity between MG and SOL during prolonged contraction. Thus, it is likely that, compared with

  12. 48 CFR 970.5223-7 - Sustainable acquisition program.

    Science.gov (United States)

    2010-10-01

    ... Management, and Executive Order 13514, Federal Leadership in Environmental, Energy, and Economic Performance... Leadership in High Performance and Sustainable Buildings (Guiding Principles) shall be achieved through... SUPPLEMENTARY REGULATIONS DOE MANAGEMENT AND OPERATING CONTRACTS Solicitation Provisions and Contract Clauses...

  13. Comparison of kinematics of ACL-deficient and healthy knees during passive flexion and isometric leg press.

    Science.gov (United States)

    Esfandiarpour, Fateme; Shakourirad, Ali; Talebian Moghaddam, Saeed; Olyaei, Gholamreza; Eslami, Abouzar; Farahmand, Farzam

    2013-12-01

    Studying the kinematics of the ACL deficient (ACLD) knees, during different physiological activities and muscle contraction patterns, can improve our understanding of the joint's altered biomechanics due to ACL deficiency as well as the efficacy and safety of the rehabilitations exercises. Twenty-five male volunteers, including 11 normal and 14 unilateral ACLD subjects, participated in this study. The kinematics of the injured knees of the ACLD subjects was compared with their intact knees and the healthy group during passive flexion and isometric leg press with the knees flexed from full extension to 45° flexion, with 15° intervals. An accurate registration algorithm was used to obtain the three dimensional kinematical parameters, from magnetic resonance images. The ACL deficiency mainly altered the tibial anterior translation, and to some extent its internal rotation, with the change in other parameters not significant. During leg press, the anterior translation of the ACLD knees was significantly larger than that of the normal knees at 30° flexion, but not at 45°. Comparison of the anterior translations of the ACLD knees during leg press with that of the passive flexion revealed improved consistency (CVs changed from 1.2 and 4.0 to 0.6 and 0.6, at 30° and 45° flexion, respectively), but considerable larger translations (means increased by 6.2 and 4.9mm, at 30° and 45° flexion, respectively). The simultaneous contraction of the quadriceps and hamstrings during leg press, although reduces the knee laxity, cannot compensate for the loss of the ACL to restore the normal kinematics of the joint, at least during early flexion. Copyright © 2012 Elsevier B.V. All rights reserved.

  14. 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.

  15. Effects of asymmetric dynamic and isometric liftings on strength/force and rating of perceived exertion.

    Science.gov (United States)

    Hattori, Y; Ono, Y; Shimaoka, M; Hiruta, S; Kamijima, M; Shibata, E; Ichihara, G; Ando, S; Villaneuva, M B; Takeuchi, Y

    1996-06-01

    A laboratory study was undertaken to determine the postural and physical characteristics and subjective stress during dynamic lifting of a usual load (10 kg) compared with during isometric lifting. The authors also aimed to clarify the effects of asymmetric lifting on these parameters. The subjects were thirteen male college students. They were asked to lift a box weighing 10 kg. They performed sixteen different lifting tasks from the floor to a height of 71 cm, involving a combination of three independent factors: two lifting modes (isometric lifting and dynamic lifting), four lifting angles in relation to the sagittal plane (sagittal plane, right 45 degree, right 90 degree and left 90 degree planes) and two lifting postures (squat and stoop). For each lifting task, strengths or forces and ground reaction forces were measured. At the end of each task, the authors asked the subjects to rate their perceived exertion (RPE) during lifting at ten sites of the body. Angle factor had a significant effect on isometric strengths and dynamic peak forces. Isometric strengths during the maximum 3 s were highest in lifting in the right 45 degree plane, followed by that in the sagittal plane, while those in the right 90 degree and left 90 degree planes were the lowest. However, peak forces in dynamic lifting were the highest in the lifting in the sagittal plane, followed by that in the right 45 degree plane, while those in the right 90 degree and left 90 degree planes were the lowest. Postural factor had a significant effect on height at peak force, which is higher in squat lifting than in stoop lifting. RPEs for the left arm, the backs and the right whole body in isometric lifting were significantly higher than in dynamic lifting of 10 kg. There were remarkably high RPEs for the ipsilateral thigh to the box in right 90 degree and left 90 degree planes during both isometric and dynamic liftings. Locations of the resultant force consisting of three component forces on the force

  16. Cilnidipine but not amlodipine suppresses sympathetic activation elicited by isometric exercise in hypertensive patients.

    Science.gov (United States)

    Koike, Yumi; Kawabe, Tetsuya; Nishihara, Kanami; Iwane, Naomi; Hano, Takuzo

    2015-01-01

    Pupillometry was used to evaluate the effects of the calcium channel blockers cilnidipine (CL) and amlodipine (AM) on changes in autonomic nervous activity induced by isometric exercise in patients with hypertension. After handgrip exercise, the velocity of miosis increased in both the CL and AM groups. However, the velocity of mydriasis increased in only the AM group. Velocity slopes of miosis and mydriasis were smaller in the CL group than in the AM group. The low-to-high frequency ratio obtained from pulse wave analysis increased in only the AM group. Sympathetic activation elicited by isometric exercise was suppressed more effectively by CL than by AM.

  17. Phase-contrast MRI reveals mechanical behavior of superficial and deep aponeuroses in human medial gastrocnemius during isometric contraction

    National Research Council Canada - National Science Library

    Ryuta Kinugasa; Dongsuk Shin; Junichiro Yamauchi; Chandan Mishra; John A. Hodgson; V. Reggie Edgerton; Shantanu Sinha

    2008-01-01

    The behavior of the entire medial gastrocnemius (MG) superficial and deep aponeurosis structure was investigated with velocity-encoded phase-contrast, spin-tag, and three-dimensional morphometric magnetic resonance imaging...

  18. 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.

  19. Schistosomiasis differentially affects vasoconstrictor responses: up-regulation of 5-HT receptor-mediated aorta contraction

    Directory of Open Access Journals (Sweden)

    Suellen D'Arc dos Santos Oliveira

    2011-06-01

    Full Text Available Schistosomiasis, classified by the World Health Organization as a neglected tropical disease, is an intravascular parasitic disease associated to a chronic inflammatory state. Evidence implicating inflammation in vascular dysfunction continues to mount, which, broadly defined, reflects a failure in the control of intracellular Ca2+ and consequently, vascular contraction. Therefore, we measured aorta contraction induced by 5-hydroxytryptamine (5-HT and endothelin-1 (ET-1, two important regulators of vascular contraction. Isometric aortic contractions were determined in control and Schistosoma mansoni-infected mice. In the infected animals, 5-HT induced a 50% higher contraction in relation to controls and we also observed an increased contraction in response to Ca2+ mobilisation from sarcoplasmic reticulum. Nevertheless, Rho kinase inhibition reduced the contraction in response to 5-HT equally in both groups, discarding an increase of the contractile machinery sensitivity to Ca2+. Furthermore, no alteration was observed for contractions induced by ET-1 in both groups. Our data suggest that an immune-vascular interaction occurs in schistosomiasis, altering vascular contraction outside the mesenteric portal system. More importantly, it affects distinct intracellular signalling involved in aorta contraction, in this case increasing 5-HT receptor signalling.

  20. Contingency Contracting Customer Guide

    Science.gov (United States)

    1996-12-01

    deployed contracting officer to train individual customers on the process, the customer support guide provides the necessary explanations without...straining valuable manpower resources. The Contracting Deployment Customer Guide aids the customer in contingency situations and addresses purchase requests

  1. 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.

  2. 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.

  3. Reduced modulation of pain in older adults following isometric and aerobic exercise

    Science.gov (United States)

    Naugle, Kelly M.; Naugle, Keith E.; Riley, Joseph L.

    2016-01-01

    Laboratory based studies show that acute aerobic and isometric exercise reduces sensitivity to painful stimuli in young healthy individuals, indicative of a hypoalgesic response. However, little is known regarding the effect of aging on exercise-induced hypoalgesia (EIH). The purpose of this study was to examine age differences in EIH following submaximal isometric exercise, and moderate and vigorous aerobic exercise. Healthy older and younger adults completed one training session and four testing sessions consisting of either a submaximal isometric handgrip exercise, vigorous or moderate intensity stationary cycling, or quiet rest (control). The following measures were taken pre and post exercise/quiet rest: 1) pressure pain thresholds (PPTs), 2) suprathreshold pressure pain ratings, 3) pain ratings during 30-s of prolonged noxious heat stimulation, and 3) temporal summation of heat pain. The results revealed age differences in EIH following isometric and aerobic exercise, with younger adults experiencing greater EIH compared to older adults. The age differences in EIH varied across pain induction techniques and exercise type. These results provide evidence for abnormal pain modulation following acute exercise in older adults. PERSPECTIVE This article enhances our understanding of the influence of a single bout of exercise on pain sensitivity and perception in healthy older compared to younger adults. This knowledge could potentially help clinicians optimize exercise as a method of pain management. PMID:26993959

  4. Reduced Modulation of Pain in Older Adults After Isometric and Aerobic Exercise.

    Science.gov (United States)

    Naugle, Kelly M; Naugle, Keith E; Riley, Joseph L

    2016-06-01

    Laboratory-based studies show that acute aerobic and isometric exercise reduces sensitivity to painful stimuli in young healthy individuals, indicative of a hypoalgesic response. However, little is known regarding the effect of aging on exercise-induced hypoalgesia (EIH). The purpose of this study was to examine age differences in EIH after submaximal isometric exercise and moderate and vigorous aerobic exercise. Healthy older and younger adults completed 1 training session and 4 testing sessions consisting of a submaximal isometric handgrip exercise, vigorous or moderate intensity stationary cycling, or quiet rest (control). The following measures were taken before and after exercise/quiet rest: 1) pressure pain thresholds, 2) suprathreshold pressure pain ratings, 3) pain ratings during 30 seconds of prolonged noxious heat stimulation, and 4) temporal summation of heat pain. The results revealed age differences in EIH after isometric and aerobic exercise, with younger adults experiencing greater EIH compared with older adults. The age differences in EIH varied across pain induction techniques and exercise type. These results provide evidence for abnormal pain modulation after acute exercise in older adults. This article enhances our understanding of the influence of a single bout of exercise on pain sensitivity and perception in healthy older compared with younger adults. This knowledge could help clinicians optimize exercise as a method of pain management. Copyright © 2016 American Pain Society. Published by Elsevier Inc. All rights reserved.

  5. Effect of trunk inclination on isometric extensor and flexor torque of ...

    African Journals Online (AJOL)

    A Cybex 6000, dynamometer Trunk extension / flexion unit was used to measure maximal voluntary isometric strength of the lumbar flexor and extensor muscles at 0, 23, 46, 69 and 92 degrees of trunk flexion. ANOVA with post-hoc testing was applied to the flexion and extension data. Alpha was set at p < 0.05. Significant ...

  6. Isometric knee-extensor torque development and jump height in volleyball players

    NARCIS (Netherlands)

    de Ruiter, C.J.; Vermeulen, G.; Toussaint, H.M.; de Haan, A.

    2007-01-01

    PURPOSE: The goal of the present study was to determine the contribution of the intrinsic muscle properties and muscle activation of the knee extensors to the maximal rate of unilateral isometric torque development and to relate both factors to maximal bilateral jumping performance in experienced

  7. Effects of isometric quadriceps strength training at different muscle lengths on dynamic torque production.

    Science.gov (United States)

    Noorkõiv, Marika; Nosaka, Kazunori; Blazevich, Anthony J

    2015-01-01

    This study aims to (1) determine whether isometric training at a short vs. long quadriceps muscle length affects concentric torque production; (2) examine the relationship between muscle hypertrophy and concentric torque; and (3) determine whether changes in fascicle length are associated with changes in concentric torque. Sixteen men performed isometric training at a short (SL, n = 8) or a long muscle length (LL, n = 8). Changes in maximal concentric torque were measured at 30, 60, 90, 120, 180, 240 and 300 rad · s(-1). The relationships between the changes in concentric torque, cross-sectional area, volume and fascicle length were tested. Concentric torque increased significantly after training only in LL and at angular velocities of 30 and 120 rad · s(-1) by 12-13% (P Muscle size increased in LL only, the changes were correlated (r = 0.73-0.93, P torque. Vastus lateralis (VL) fascicle length increased in both groups (5.4 ± 4.9%, P = 0.001) but the change was not correlated with changes in concentric torque in either group. Isometric training-induced increases in muscle size and concentric torque were best elicited by training at long muscle lengths. These results highlight a clear muscle length dependence of isometric training on dynamic torque production.

  8. How isometric are the medial patellofemoral, superficial medial collateral, and lateral collateral ligaments of the knee?

    Science.gov (United States)

    Victor, Jan; Wong, Pius; Witvrouw, Eric; Sloten, Jos Vander; Bellemans, Johan

    2009-10-01

    Ligament isometry is a cornerstone in the description of normal knee function and thorough knowledge is mandatory for successful repair of torn ligaments. This study was undertaken to validate a novel experimental model for the study of ligament strains and to determine the length changes in the superficial medial collateral, lateral collateral, and medial patellofemoral ligaments. Descriptive laboratory study. Passive motions and loaded squats of 12 cadaveric specimens were performed while controlling ankle load and optically tracking the motion of the bones. Preexperiment and postexperiment computed axial tomography scans allow the transformation of rigid body motion to relative motion of relevant anatomic landmarks on the femur, tibia, and patella. The superficial medial collateral ligament is a near-isometric ligament with a strain of less than 2%. The ligament is a little more slack in midflexion (30 degrees to 50 degrees ) and in deep flexion, but length changes are not significant (P > .05). The lateral collateral ligament behaves near isometric (tension from the collateral ligaments (P superficial medial collateral ligament is a near-isometric ligament with no significant length changes. The medial patellofemoral ligament behaves differently in its cranial and caudal parts. In knees with chronic medial collateral ligament insufficiency, isometric repair of the superficial medial collateral ligament can be attempted. A medial patellofemoral ligament reconstruction with a double fixation on the medial patellar border is supported. The cranial bundle should be tightened at full extension and the caudal bundle at 30 degrees of knee flexion.

  9. The Relationship Between Maximum Isometric Strength and Ball Velocity in the Tennis Serve

    Directory of Open Access Journals (Sweden)

    Baiget Ernest

    2016-12-01

    Full Text Available The aims of this study were to analyze the relationship between maximum isometric strength levels in different upper and lower limb joints and serve velocity in competitive tennis players as well as to develop a prediction model based on this information. Twelve male competitive tennis players (mean ± SD; age: 17.2 ± 1.0 years; body height: 180.1 ± 6.2 cm; body mass: 71.9 ± 5.6 kg were tested using maximum isometric strength levels (i.e., wrist, elbow and shoulder flexion and extension; leg and back extension; shoulder external and internal rotation. Serve velocity was measured using a radar gun. Results showed a strong positive relationship between serve velocity and shoulder internal rotation (r = 0.67; p < 0.05. Low to moderate correlations were also found between serve velocity and wrist, elbow and shoulder flexion – extension, leg and back extension and shoulder external rotation (r = 0.36 – 0.53; p = 0.377 – 0.054. Bivariate and multivariate models for predicting serve velocity were developed, with shoulder flexion and internal rotation explaining 55% of the variance in serve velocity (r = 0.74; p < 0.001. The maximum isometric strength level in shoulder internal rotation was strongly related to serve velocity, and a large part of the variability in serve velocity was explained by the maximum isometric strength levels in shoulder internal rotation and shoulder flexion.

  10. The effects of imagery training on fast isometric knee extensor torque development

    NARCIS (Netherlands)

    de Ruiter, Cornelis J.; Hutter, Vana; Icke, Chris; Groen, Bart; Gemmink, Anne; Smilde, Hiltsje; de Haan, Arnold

    2012-01-01

    We hypothesized that imagery training would improve the fast onset of neuromuscular activation and thereby fast knee extensor isometric torque development. Forty young healthy participants, not involved in strength training, were assigned to one of four groups: physical training, imagery training,

  11. Effects of age and content of augmented feedback on learning an isometric force-production task

    NARCIS (Netherlands)

    van Dijk, Henk; Mulder, Theo; Hermens, Hermie J.

    2007-01-01

    This study addressed the interaction between age and the informational content of feedback on learning an isometric force-production task. Healthy men and women (30 young adults: 20 to 35 years; 30 older adults: 55 to 70 years) were randomly assigned to a certain type of feedback: knowledge of

  12. Efficacy of Interactive Whiteboard on Psychomotor Skills Achievement of Students in Isometric and Orthographic Projection

    Science.gov (United States)

    Gambari, Isiaka A.; Balogun, Sherifat A.; Alfa, Ahmadu S.

    2014-01-01

    This paper discusses importance of technology education and evidences of declining performance of junior secondary school students in basic technology subject. Potentials on interactive whiteboard (IWB) as one of the new technologies to meet the challenges of the 21st century are also discussed. The efficacy of IWB for teaching Isometric and…

  13. Isometric muscle strength and mobility capacity in children with cerebral palsy

    NARCIS (Netherlands)

    Dallmeijer, Annet J.; Rameckers, Eugene A.; Houdijk, Han; de Groot, Sonja; Scholtes, Vanessa A.; Becher, Jules G.

    2017-01-01

    Purpose: To determine the relationship between isometric leg muscle strength and mobility capacity in children with cerebral palsy (CP) compared to typically developing (TD) peers. Method: Participants were 62 children with CP (6-13 years), able to walk with (n=10) or without (n=52) walking aids,

  14. Isometric behavior of the reconstructed medial patellofemoral ligament using two different femoral pulleys: a cadaveric study.

    Science.gov (United States)

    Triantafillopoulos, Ioannis K; Panagopoulos, Andreas; van Niekerk, Louw

    2007-09-01

    Several techniques have been described for reconstructing the medial patellofemoral ligament (MPFL). However, the anatomy of the medial patellar retinaculum and the isometry of both intact and reconstructed MPFL remain controversial. The purpose of this study was to investigate the isometric behavior of the reconstructed MPFL when two different pulleys are used for the reconstruction. Eight anatomical knees were dissected and the medial patellar retinaculum and MPFL were studied. A pilot technique for the reconstruction of the MPFL using a semitendinosus autograft was developed. A "dynamic" femoral fixation was chosen which utilized two different pulleys: the medial intermuscular septum (MIS) at the adductor's tendon insertion and the posterior third of the medial collateral ligament (MCL). The isometric behavior of the reconstructed MPFL and the stability of both pulleys were investigated. The MPFL was a thickened, band-like condensation of the superficial MPR layer extending from the MFE to the medial border of the patella. The reconstructed MPFL demonstrated the most isometric behavior when the MCL was used as a pulley. The average difference in graft length during knee flexion from 0 degrees to 90 degrees when the MCL or MIS were used as a pulley was 1 mm and 4 mm, respectively. The MIS pulley was more stable but less isometric than the MCL pulley. "Dynamic" MPFL reconstruction with a semitendinosus tendon autograft can restore patellofemoral stability without excessive soft-tissue dissection or implantation of hardware at the medial epicondyle, which can lead to symptoms of its own.

  15. Age-related decreases in motor unit discharge rate and force control during isometric plantar flexion

    DEFF Research Database (Denmark)

    Kallio, J; Søgaard, Karen; Avela, J

    2012-01-01

    Aging is related to multiple changes in muscle physiology and function. Previous findings concerning the effects of aging on motor unit discharge rate (DR) and fluctuations in DR and force are somewhat contradictory. Eight YOUNG and nine OLD physically active males performed isometric ramp (RECR)...

  16. Isometric elbow extensors strength in supine- and prone-lying positions.

    Science.gov (United States)

    Abdelzaher, Ibrahim E; Ababneh, Anas F; Alzyoud, Jehad M

    2013-01-01

    The purpose of this study was to compare isometric strength of elbow extensors measured in supine- and prone-lying positions at elbow flexion angles of 45 and 90 degrees. Twenty-two male subjects under single-blind procedures participated in the study. Each subject participated in both supine-lying and prone-lying measuring protocols. Calibrated cable tensiometer was used to measure isometric strength of the right elbow extensors and a biofeedback electromyography was used to assure no substitution movements from shoulder girdle muscles. The mean values of isometric strength of elbow extensors measured from supine-lying position at elbow flexion angles of 45 and 90 degrees were 11.1  ±  4.2 kg and 13.1  ±  4.6 kg, while those measured from prone-lying position were 9.9  ±  3.6 kg and 12  ±  4.2 kg, respectively. There is statistical significant difference between the isometric strength of elbow extensors measured from supine-lying position at elbow flexion angles of 45 and 90 degrees compared to that measured from prone-lying position (p  lying starting position is better than prone-lying starting position.

  17. Effects of age and content of augmented feedback on learning an isometric force-production task

    NARCIS (Netherlands)

    van Dijk, H; Mulder, T.; Hermens, Hermanus J.

    This study addressed the interaction between age and the informational content of feedback on learning an isometric force-production task. Healthy men and women (30 young adults: 20 to 35 years; 30 older adults: 55 to 70 years) were randomly assigned to a certain type of feedback: knowledge of

  18. ISOMETRIC GLUTEUS MEDIUS MUSCLE TORQUE AND FRONTAL PLANE PELVIC MOTION DURING RUNNING

    Directory of Open Access Journals (Sweden)

    Evie N. Burnet

    2009-06-01

    Full Text Available The objective of this study was to investigate the relationship between isometric GM torque and the degree of frontal plane pelvic drop during running. Twenty-one healthy, recreational runners (9 males, 12 females who ran 8.05 km or more per week were obtained from a sample of convenience. GM maximal isometric torque was collected prior to the run. Subjects then ran on a treadmill for 30 minutes while bilateral three-dimensional pelvic kinematic data were collected for 10 seconds at each 2 minute increment. Left side pelvic drop showed a slight increase (effect size = 0.61; while, the right side pelvic drop remained stable (effect size = 0.18. Pearson's Correlations showed no relationship between GM isometric torque and frontal plane pelvic drop for any of the data collection periods during the 30-minute run. These results suggest that isometric GM torque was a poor predictor of frontal plane pelvic drop. One should question whether a dynamic rather than static measure of GM strength would be more appropriate. Future research is needed to identify dynamic strength measures that would better predict biomechanical components of running gait

  19. Correlation between maximum isometric strength variables and specific performance of Brazilian military judokas

    Directory of Open Access Journals (Sweden)

    Michel Moraes Gonçalves

    2017-06-01

    Full Text Available It was our objective to correlate specific performance in the Special Judo Fitness Test (SJFT and the maximum isometric handgrip (HGSMax, scapular traction (STSMax and lumbar traction (LTSMax strength tests in military judo athletes. Twenty-two military athletes from the judo team of the Brazilian Navy Almirante Alexandrino Instruction Centre, with average age of 26.14 ± 3.31 years old, and average body mass of 83.23 ± 14.14 kg participated in the study. Electronic dynamometry tests for HGSMax, STSMax and LTSMax were conducted. Then, after approximately 1 hour-interval, the SJFT protocol was applied. All variables were adjusted to the body mass of the athletes. Pearson correlation coefficient for statistical analysis was used. The results showed moderate negative correlation between the SJFT index and STSMax (r= -0.550, p= 0.008, strong negative correlations between the SJFT index and HGSMax (r= -0.706, p< 0.001, SJFT index and LTSMax (r= -0.721; p= 0.001, besides the correlation between the sum of the three maximum isometric strength tests and the SJFT index (r= -0.786, p< 0.001. This study concludes that negative correlations occur between the SJFT index and maximum isometric handgrip, shoulder and lumbar traction strength and the sum of the three maximum isometric strength tests in military judokas.

  20. Contracting for Public Services

    DEFF Research Database (Denmark)

    Greve, Carsten

    strategic purchasing understanding markets communicating the contracting decision designing and drafting the contract the role of the consumer the regulation of service provision Illustrated throughout with practitioner case-studies from a range of OECD countries, this book presents an important new...... theoretical ‘contract management model' and a ‘mature contract model', and explores the mechanisms, formal rules and informal norms that influence the way governments contract for public services. This book is essential reading for all students of public management and all public service managers....

  1. Isometric muscle strength and mobility capacity in children with cerebral palsy.

    Science.gov (United States)

    Dallmeijer, Annet J; Rameckers, Eugene A; Houdijk, Han; de Groot, Sonja; Scholtes, Vanessa A; Becher, Jules G

    2017-01-01

    To determine the relationship between isometric leg muscle strength and mobility capacity in children with cerebral palsy (CP) compared to typically developing (TD) peers. Participants were 62 children with CP (6-13 years), able to walk with (n = 10) or without (n = 52) walking aids, and 47 TD children. Isometric muscle strength of five muscle groups of the leg was measured using hand-held dynamometry. Mobility capacity was assessed with the 1-min walk, the 10-m walk, sit-to-stand, lateral-step-up and timed-stair tests. Isometric strength of children with CP was reduced to 36-82% of TD. When adjusted for age and height, the percentage of variance in mobility capacity that was explained by isometric strength of the leg muscles was 21-24% (walking speed), 25% (sit-to-stand), 28% (lateral-step-up) and 35% (timed-stair) in children with CP. Hip abductors and knee flexors had the largest contribution to the explained variance, while knee extensors showed the weakest correlation. Weak or no associations were found between strength and mobility capacity in TD children. Isometric strength, especially hip abductor and knee flexor strength, is moderately related to mobility capacity in children with CP, but not in TD children. To what extent training of these muscle groups will lead to better mobility capacity needs further study. Implications for Rehabilitation Strength training in children with cerebral palsy (CP) may be targeted more specifically at hip abductors and knee flexors. The moderate associations imply that large improvements in mobility capacity may not be expected when strength increases.

  2. EFFICACY OF POST ISOMETRIC RELAXATION VERSUS STATIC STRECHING IN SUBJECTS WITH CHRONIC NON SPECIFIC NECK PAIN

    Directory of Open Access Journals (Sweden)

    P.Haritha

    2015-12-01

    Full Text Available Background: Neck pain is a common problem within our society. Upper trapezius sternocleidomastoid and the levator scapulae are the most common postural muscles that tends to get shorten leading to restricted neck mobility. There is lack of evidence to allow conclusions to be drawn about the effectiveness of post isometric relaxation when compared with static stretching exercises. The aim is to find out the effectiveness of Post isometric relaxation Versus Static stretching in the subjects with chronic nonspecific neck pain. To evaluate the effectiveness of post isometric relaxation technique on pain by using Visual analoge scale, range of motion by using Universal Goniometry, and functional disability by using Neck Disability Index in chronic nonspecific neck pain. Methods: A convenient sample of thirty seven subjects was diagnosed with nonspecific neck pain was randomly allocated to one of the two treatment groups on the basis of the inclusion criteria. The experimental group (n=15 received three sessions of post isometric relaxation technique for trapezius, sternocleidomastoid and the levator scapulae and control group (n=15 received the three sessions of static stretching for trapezius, sternocliedomastiod and levator scapulae for four weeks. Results: Non parametric tests demonstrated a statistically significant difference with experimental group showing greater improvement in ROM, VAS, and NDI than the control group and significant difference within the group also. Conclusion: This study concluded and the results reflected that post isometric relaxation technique group had better improvement in reduction of pain, improvement in the range of motion, and increased neck functional activities than the static stretching group.

  3. Effects of isotonic and isometric exercises with mist sauna bathing on cardiovascular, thermoregulatory, and metabolic functions

    Science.gov (United States)

    Iwase, Satoshi; Kawahara, Yuko; Nishimura, Naoki; Nishimura, Rumiko; Sugenoya, Junichi; Miwa, Chihiro; Takada, Masumi

    2014-08-01

    To clarify the effects of isometric and isotonic exercise during mist sauna bathing on the cardiovascular function, thermoregulatory function, and metabolism, six healthy young men (22 ± 1 years old, height 173 ± 4 cm, weight 65.0 ± 5.0 kg) were exposed to a mist sauna for 10 min at a temperature of 40 °C, and relative humidity of 100 % while performing or not performing ˜30 W of isometric or isotonic exercise. The effect of the exercise was assessed by measuring tympanic temperature, heart rate, systolic and diastolic blood pressure, chest sweat rate, chest skin blood flow, and plasma catecholamine and cortisol, glucose, lactate, and free fatty acid levels. Repeated measures ANOVA showed no significant differences in blood pressure, skin blood flow, sweat rate, and total amount of sweating. Tympanic temperature increased more during isotonic exercise, and heart rate increase was more marked during isotonic exercise. The changes in lactate indicated that fatigue was not very great during isometric exercise. The glucose level indicated greater energy expenditure during isometric exercise. The free fatty acid and catecholamine levels indicated that isometric exercise did not result in very great energy expenditure and stress, respectively. The results for isotonic exercise of a decrease in lactate level and an increase in plasma free fatty acid level indicated that fatigue and energy expenditure were rather large while the perceived stress was comparatively low. We concluded that isotonic exercise may be a more desirable form of exercise during mist sauna bathing given the changes in glucose and free fatty acid levels.

  4. 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.

  5. Adaptive strength gains in dystrophic muscle exposed to repeated bouts of eccentric contraction

    Science.gov (United States)

    Call, Jarrod A.; Eckhoff, Michael D.; Baltgalvis, Kristen A.; Warren, Gordon L.

    2011-01-01

    The objective of this study was to determine the functional recovery and adaptation of dystrophic muscle to multiple bouts of contraction-induced injury. Because lengthening (i.e., eccentric) contractions are extremely injurious for dystrophic muscle, it was considered that repeated bouts of such contractions would exacerbate the disease phenotype in mdx mice. Anterior crural muscles (tibialis anterior and extensor digitorum longus) and posterior crural muscles (gastrocnemius, soleus, and plantaris) from mdx mice performed one or five repeated bouts of 100 electrically stimulated eccentric contractions in vivo, and each bout was separated by 10–18 days. Functional recovery from one bout was achieved 7 days after injury, which was in contrast to a group of wild-type mice, which still showed a 25% decrement in electrically stimulated isometric torque at that time point. Across bouts there was no difference in the immediate loss of strength after repeated bouts of eccentric contractions for mdx mice (−70%, P = 0.68). However, after recovery from each bout, dystrophic muscle had greater torque-generating capacity such that isometric torque was increased ∼38% for both anterior and posterior crural muscles at bout 5 compared with bout 1 (P muscles excised from in vivo-tested hindlimbs 14–18 days after bout 5 had greater specific force than contralateral control muscles (12.2 vs. 10.4 N/cm2, P = 0.005) and a 20% greater maximal relaxation rate (P = 0.049). Additional adaptations due to the multiple bouts of eccentric contractions included rapid recovery and/or sparing of contractile proteins, enhanced parvalbumin expression, and a decrease in fiber size variability. In conclusion, eccentric contractions are injurious to dystrophic skeletal muscle; however, the muscle recovers function rapidly and adapts to repeated bouts of eccentric contractions by improving strength. PMID:21960659

  6. Effects of contract-relax vs static stretching on stretch-induced strength loss and length-tension relationship

    DEFF Research Database (Denmark)

    Balle, S S; Magnusson, S P; McHugh, M P

    2015-01-01

    The purpose of this study was to determine the acute effects of contract-relax stretching (CRS) vs static stretching (SS) on strength loss and the length-tension relationship. We hypothesized that there would be a greater muscle length-specific effect of CRS vs SS. Isometric hamstring strength...... loss compared with SS. These results support the use of SS for stretching the hamstrings....

  7. New staff contract policy

    CERN Multimedia

    HR Department

    2006-01-01

    Following discussion at TREF and on the recommendation of the Finance Committee, Council approved a new staff contract policy, which became effective on 1 January 2006. Its application is covered by a new Administrative Circular No. 2 (Rev. 3) 'Recruitment, appointment and possible developments regarding the contractual position of staff members'. The revised circular replaces the previous Circulars No. 9 (Rev. 3) 'Staff contracts' and No. 2 (Rev. 2) 'Guidelines and procedures concerning recruitment and probation period for staff members'. The main features of the new contract policy are as follows: The new policy provides chances for long-term employment for all staff recruits staying for four years without distinguishing between those assigned to long-term or short-term activities when joining CERN. In addition, it presents a number of simplifications for the award of ICs. There are henceforth only 2 types of contract: Limited Duration (LD) contracts for all recruitment and Indefinite Contracts (IC) for...

  8. Ultrasound elastography-based assessment of the elasticity of the supraspinatus muscle and tendon during muscle contraction.

    Science.gov (United States)

    Muraki, Takayuki; Ishikawa, Hiroaki; Morise, Shuhei; Yamamoto, Nobuyuki; Sano, Hirotaka; Itoi, Eiji; Izumi, Shin-ichi

    2015-01-01

    Although elasticity of the supraspinatus muscle and tendon is a useful parameter to represent the conditions of the supraspinatus muscle and tendon, assessment of the elasticity in clinical settings has not been established. The purpose of this study was to determine the elasticity of the supraspinatus muscle belly and tendon under different muscle contraction conditions using ultrasound real-time tissue elastography (RTE). Twenty-three healthy individuals participated in this study. Ultrasound RTE was used for elasticity measurements of the muscle belly and tendon of the supraspinatus muscle. The elasticity was defined as the ratio of strain in the tissues to that in an acoustic coupler (reference). A greater ratio indicated that the tissue was softer. Measurements were performed with study subjects in the lateral decubitus position at 10° of shoulder abduction under conditions of (1) no contraction, (2) isometric contraction without a weight, and (3) isometric contraction with a 1-kg weight. The intraclass correlation coefficient (ICC1,3) of 3 measurements under each condition ranged from 0.931 to 0.998, showing high intraobserver reliability. Strain ratios for both the supraspinatus muscle belly and tendon significantly decreased with increases in muscle contraction (P elasticity of the supraspinatus muscle belly and tendon that accompany varying levels of muscle contraction in clinical practice. Copyright © 2015 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.

  9. Selective muscle contraction during plantarflexion is incompatible with maximal voluntary torque assessment.

    Science.gov (United States)

    Turpin, Nicolas A; Costes, Antony; Villeger, David; Watier, Bruno

    2014-08-01

    Large variations in maximal voluntary torque are reported in the literature during isometric plantarflexion contractions. We propose that these differences, which could reach 40 % across similar studies, could be explained by differences in the instructions provided, and notably by instructions as to favoring or not multi-joint contractions. Sixteen participants were placed on an isokinetic ergometer in 3 different positions, supine, prone and seated, with the ankle in the neutral position, and instructed to create maximal force on the footplate by conforming to instructions that favored either isolated (ISOL) or multi-joint (ALL) isometric contractions. Torque, foot kinematics and the electromyographic activity of seven muscles of the lower limb have been recorded. Joint torques were greater in ALL compared to ISOL (p muscles that do not span over the ankle joint significantly influenced the measured joint torque. Nevertheless, the observed gains in torque were associated with greater plantarflexor muscles activation, showing that the ISOL condition may have induced a form of inhibition of these muscles. The results of this study suggest that using isolated contractions, hence constrained testing protocols, cannot provide optimal conditions for MVC testing, notably for plantarflexor muscles, which seem to be extremely sensitive to such constrained conditions.

  10. Relative changes with contraction in the central excitability state of the tibialis anterior and calf muscles.

    Science.gov (United States)

    Fisher, M A

    1980-01-01

    F responses were recorded from the surface of the tibialis muscle and medial aspect of the soleus muscle in 14 normal subjects. The persistence (that is the fraction of measurable F responses found with a series of supramaximal stimuli) and average F amplitudes (measured peak-to-peak and based on at least five F responses) were determined both at rest and with isometric contraction with the ankle maintained at 90 degrees. Although the persistence at rest was significantly less in the tibialis anterior soleus than the (p less than 0.001), no significant difference was found with the muscles contracted. This was associated with a significant increase in both average F amplitudes and average F amplitude/direct motor response ratios in the tibialis anterior in comparison to the soleus. In four of the subjects, studies were also performed when the H reflex in the soleus muscle was eliminated by thigh compression. Comparable changes in both F response persistence and average F amplitude were found with and without an H reflex. These data indicate that, in contrast to the situation at rest, with isometric contraction the "central excitatory state" of the tibialis anterior is at least as great as in its antagonist antigravity muscles and that this is not due simply to increased large fiber reflex input associated with agonist contraction. PMID:7373321

  11. Contracting in crisis intervention.

    Science.gov (United States)

    Nelson, Z P; Mowry, D D

    1976-01-01

    The use of contracts in the social services is an important area that needs to be looked at. This paper is concerned specifically with the use of contracts in one particular part of social services: crisis intervention. Contracts that define the working relationship between the client and mental health counselor can be beneficial for both when they attempt to solve the problems that contributed to the crisis situation. There are five benefits to be gained from the use of contracts in crisis intervention and they are briefly discussed.

  12. Smart contracts sobre Bitcoin

    OpenAIRE

    Andreu Alemany, Josep Miquel

    2016-01-01

    El present treball final de màster realitza una introducció als smart contracts. El treball introdueix el concepte de contracte intel·ligent, els seus usos i alguns exemples existents. Seguidament proporciona les nocions necessàries de les transaccions del protocol Bitcoin per poder implementar un contracte intel·ligent, usant la blockchain que ofereix el protocol. Per últim, s'explica la implementació d'un contracte intel·ligent usant bitcoin: un canal de micropagaments. El presente traba...

  13. Assessment of factors that impact on the viability of contract farming ...

    African Journals Online (AJOL)

    This research analyses factors that affect the viability of contract farming in the Zimbabwean maize and soya sector. The objective was to analyse how sustainability factors (social, ethical, environmental and economic factors) were integrated to ensure the viability and sustainability of contract ventures. A sample of 70 ...

  14. Improvements in Force Variability and Structure from Vision- to Memory-Guided Submaximal Isometric Knee Extension in Subacute Stroke.

    Science.gov (United States)

    Chow, John W; Stokic, Dobrivoje S

    2017-11-02

    We examined changes in variability, accuracy, frequency composition, and temporal regularity of force signal from vision-guided to memory-guided force-matching tasks in 17 subacute stroke and 17 age-matched healthy subjects. Subjects performed a unilateral isometric knee extension at 10%, 30%, and 50% of peak torque (MVC) for 10 s (3 trials each). Visual feedback was removed at the 5s-mark in the first 2 trials (feedback withdrawal), and 30 s after the second trial the subjects were asked to produce the target force without visual feedback (force recall). The coefficient of variation and constant error were used to quantify force variability and accuracy. Force structure was assessed by the median frequency, relative spectral power in the 0-3 Hz band, and sample entropy of the force signal. At 10% MVC, the force signal in subacute stroke subjects became steadier, more broadband, and temporally more irregular after the withdrawal of visual feedback, with progressively larger error at higher contraction levels. Also, the lack of modulation in the spectral frequency at higher force levels with visual feedback persisted in both the withdrawal and recall conditions. In terms of changes from the visual feedback condition, the feedback withdrawal produced a greater difference between the paretic, non-paretic, and control legs than the force recall. The overall results suggest improvements in force variability and structure from vision- to memory-guided force control in subacute stroke despite decreased accuracy. Different sensory-motor memory retrieval mechanisms seem to be involved in the feedback withdrawal and force recall conditions, which deserves further studies.

  15. Modular Organization of Exploratory Force Development Under Isometric Conditions in the Human Arm.

    Science.gov (United States)

    Roh, Jinsook; Lee, Sang Wook; Wilger, Kevin D

    2018-01-31

    Muscle coordination of isometric force production can be explained by a smaller number of modules. Variability in force output, however, is higher during exploratory/transient force development phases than force maintenance phase, and it is not clear whether the same modular structure underlies both phases. In this study, eight neurologically-intact adults isometrically performed target force matches in 54 directions at hands, and electromyographic (EMG) data from eight muscles were parsed into four sequential phases. Despite the varying degree of motor complexity across phases (significant between-phase differences in EMG-force correlation, angular errors, and between-force correlations), the number/composition of motor modules were found equivalent across phases, suggesting that the CNS systematically modulated activation of the same set of motor modules throughout sequential force development.

  16. Novel Use of the Nintendo Wii Board for Measuring Isometric Lower Limb Strength

    DEFF Research Database (Denmark)

    Gronbech Jorgensen, Martin; Andersen, Stig; Ryg, Jesper

    BACKGROUND: Portable, low-cost, objective and reproducible assessment of muscle strength in the lower limbs is important as it allows clinicians to precisly track progression of patients undergoing rehabilitation. The Nintendo Wii Balance Board (WBB) is portable, inexpensive, durable, available...... worldwide, and may serve the above function. OBJECTIVE: The purpose of the study was to evaluate (1) reproducibility and (2) concurrent validity of the WBB for measuring isometric muscle strength in the lower limb. METHODS: A custom hardware and software was developed to utilize the WBB for assessment...... the difference and the mean. CONCLUSIONS: A high relative and an acceptable absolute reproducibility combined with a good validity was found for the novel method using the WBB for measuring isometric lower limb strength in older adults. Further research using the WBB for assessing lower limb strength should...

  17. Acute effects of prolonged intermittent low-intensity isometric warm-up schemes on jump, sprint, and agility performance in collegiate soccer players

    Directory of Open Access Journals (Sweden)

    Haris Pojskic

    2015-02-01

    Full Text Available The aim of the present study was to compare the effects of different warm-up interventions on jump, sprint and agility performance in collegiate soccer players. Twenty-one healthy male college soccer players (age: 20.14 ± 1.65 years; body height: 179.9 ± 8.34 cm; body mass: 74.4 ± 13.0 kg; % body fat: 9.45 ± 4.8 participated in the study. Subjects underwent four different randomized warm-up protocols separated by at least 48 hours. The warm-up schemes were: 1. no conditioning contraction protocol (NCC; 2. dynamic stretching (DS; 3. prolonged intermittent low-intensity isometric exercise (ST; and, 4. ST with an additional external load equal to 30% of body weight (ST + 30% BW. All interventions were preceded by a general warm-up. Results from one-way repeated measures ANOVA demonstrated a significant difference in countermovement jump (CMJ at F(3,60 = 10.2, ηρ 2 = 0.337, p < 0.01. Post hoc analysis revealed a significant difference in CMJ performance in DS when compared to NCC and ST + 30% BW. No significant difference in CMJ was observed between DS and ST. CMJ scores in NCC, ST, and ST + 30% BW were non-significant. There was a significant difference in speed; F(3, 60 = 6.61, ηρ 2 = 0.248, p < 0.01. Post hoc analysis revealed significantly better time in DS than NCC and ST. However, no difference in speed was observed between DS and ST + 30% BW. Similarly, speed was similar in NCC, ST and ST + 30% BW. A significant difference in agility performance was also observed; F(3, 60 = 24.1, ηρ 2 = 0.546, p < 0.01. Post hoc analysis revealed significantly greater performance gains in DS than NCC. No significant difference in agility was observed in DS, ST and ST + 30% BW. In conclusion, a prolonged intermittent low-intensity isometric protocol using bodyweight only showed similar benefits with dynamic stretching in countermovement jump performance. When the same isometric condition with additional load equal to 30% of bodyweight was applied

  18. Cervical isometric strength and range of motion of elite rugby union players: a cohort study

    OpenAIRE

    Hamilton, David F.; Gatherer, Don

    2014-01-01

    BACKGROUND: Head and neck injury is relatively common in Rugby Union. Despite this, strength and range-of-motion characteristics of the cervical spine are poorly characterised. The aim of this study was to provide data on the strength and range-of-motion of the cervical spine of professional rugby players to guide clinical rehabilitation.METHODS: A cohort study was performed evaluating 27 players from a single UK professional rugby club. Cervical isometric strength and range-of-motion were as...

  19. Effect of slow rhythmic voluntary breathing pattern on isometric handgrip among health care students

    OpenAIRE

    Rajajeyakumar M, Janitha A, Madanmohan, Balachander J

    2014-01-01

    Introduction: Hand grip strength is a widely used test in experimental and epidemiologicalstudies. The measure of hand grip strength is influenced by several factors, including age; gender; different angle of the shoulder, elbow, forearm, and wrist; and posture.So we planned to study theeffect of slow voluntary breathing exercise (Savitri Pranayam) onthe various strengths of isometric hand grip (IHG) amongyoung health care students.Methods: The present study was conducted on 60 volunteers 17-...

  20. An Investigation Into the Relationship Between Maximum Isometric Strength and Vertical Jump Performance.

    Science.gov (United States)

    Thomas, Christopher; Jones, Paul A; Rothwell, James; Chiang, Chieh Y; Comfort, Paul

    2015-08-01

    Research has demonstrated a clear relationship between dynamic strength and vertical jump (VJ) performance; however, the relationship of isometric strength and VJ performance has been studied less extensively. The aim of this study was to determine the relationship between isometric strength and performance during the squat jump (SJ) and countermovement jump (CMJ). Twenty-two male collegiate athletes (mean ± SD; age = 21.3 ± 2.9 years; height = 175.63 ± 8.23 cm; body mass = 78.06 ± 10.77 kg) performed isometric midthigh pulls (IMTPs) to assess isometric peak force (IPF), maximum rate of force development, and impulse (IMP) (I100, I200, and I300). Force-time data, collected during the VJs, were used to calculate peak velocity, peak force (PF), peak power (PP), and jump height. Absolute IMTP measures of IMP showed the strongest correlations with VJ PF (r = 0.43-0.64; p ≤ 0.05) and VJ PP (r = 0.38-0.60; p ≤ 0.05). No statistical difference was observed in CMJ height (0.33 ± 0.05 m vs. 0.36 ± 0.05 m; p = 0.19; ES = -0.29) and SJ height performance (0.29 ± 0.06 m vs. 0.33 ± 0.05 m; p = 0.14; ES = -0.34) when comparing stronger to weaker athletes. The results of this study illustrate that absolute IPF and IMP are related to VJ PF and PP but not VJ height. Because stronger athletes did not jump higher than weaker athletes, dynamic strength tests may be more practical methods of assessing the relationships between relative strength levels and dynamic performance in collegiate athletes.

  1. Effect of long-term isometric training on core/torso stiffness.

    Science.gov (United States)

    Lee, Benjamin C Y; McGill, Stuart M

    2015-06-01

    Although core stiffness enhances athletic performance traits, controversy exists regarding the effectiveness of isometric vs. dynamic core training methods. This study aimed to determine whether long-term changes in stiffness can be trained, and if so, what is the most effective method. Twenty-four healthy male subjects (23 ± 3 years; 1.8 ± 0.06 m; 77.5 ± 10.8 kg) were recruited for passive and active stiffness measurements before and after a 6-week core training intervention. Twelve subjects (22 ± 2 years; 1.8 ± 0.08 m; 78.3 ± 12.3 kg) were considered naive to physical and core exercise. The other 12 subjects (24 ± 3 years; 1.8 ± 0.05 m; 76.8 ± 9.7 kg) were Muay Thai athletes (savvy). A repeated-measures design compared core training methods (isometric vs. dynamic, with a control group) and subject training experience (naive vs. savvy) before and after a 6-week training period. Passive stiffness was assessed on a "frictionless" bending apparatus and active stiffness assessed through a quick release mechanism. Passive stiffness increased after the isometric training protocol. Dynamic training produced a smaller effect, and as expected, there was no change in the control group. Active stiffness did not change in any group. Comparisons between subject and training groups did not reveal any interactions. Thus, an isometric training approach was superior in terms of enhancing core stiffness. This is important since increased core stiffness enhances load bearing ability, arrests painful vertebral micromovements, and enhances ballistic distal limb movement. This may explain the efficacy reported for back and knee injury reduction.

  2. The Effect of Long Term Isometric Training on Core/Torso Stiffness.

    Science.gov (United States)

    Lee, Benjamin; McGill, Stuart

    2015-03-23

    While core stiffness enhances athletic performance traits controversy exists regarding the effectiveness of isometric vs dynamic core training methods. This study aimed to determine if long term changes in stiffness can be trained, and if so, what is the most effective method. Twenty four healthy male subjects (23 ± 3 years, 1.8 ± 0.06 m, 77.5 ± 10.8 kg) were recruited for passive and active stiffness measurements before and after a six week core training intervention. Twelve subjects (22 ± 2 years, 1.8 ± 0.08 m, 78.3 ± 12.3 kg) were considered naïve to physical and core exercise. The other twelve subjects (24 ± 3 years, 1.8 ± 0.05 m, 76.8 ± 9.7 kg) were Muay Thai athletes (savvy). A repeated measures design compared core training methods (Isometric vs. Dynamic, with a Control group) and subject training experience (naïve vs. savvy) before and after a six week training period. Passive stiffness was assessed on a 'frictionless' bending apparatus and active stiffness assessed via a quick release mechanism. Passive stiffness increased following the isometric training protocol. Dynamic training produced a smaller effect and as expected there was no change in the Control group. Active stiffness did not change in any group. Comparisons between subject and training groups did not reveal any interactions. Thus, an isometric training approach was superior in terms of enhancing core stiffness. This is important since increased core stiffness enhances load bearing ability, arrests painful vertebral micromovements and enhances ballistic distal limb movement. This may explain the efficacy reported for back and knee injury reduction.

  3. Isometric force production parameters during normal and experimental low back pain conditions

    Directory of Open Access Journals (Sweden)

    Blouin Jean-Sébastien

    2005-02-01

    Full Text Available Abstract Background The control of force and its between-trial variability are often taken as critical determinants of motor performance. Subjects performed isometric trunk flexion and extension forces without and with experiment pain to examine if pain yields changes in the control of trunk forces. The objective of this study is to determine if experimental low back pain modifies trunk isometric force production. Methods Ten control subjects participated in this study. They were required to exert 50 and 75% of their isometric maximal trunk flexion and extension torque. In a learning phase preceding the non painful and painful trials, visual and verbal feedbacks were provided. Then, subjects were asked to perform 10 trials without any feedback. Time to peak torque, time to peak torque variability, peak torque variability as well as constant and absolute error in peak torque were calculated. Time to peak and peak dF/dt were computed to determine if the first peak of dF/dt could predict the peak torque achieved. Results Absolute and constant errors were higher in the presence of a painful electrical stimulation. Furthermore, peak torque variability for the higher level of force was increased with in the presence of experimental pain. The linear regressions between peak dF/dt, time to peak dF/dt and peak torque were similar for both conditions. Experimental low back pain yielded increased absolute and constant errors as well as a greater peak torque variability for the higher levels of force. The control strategy, however, remained the same between the non painful and painful condition. Cutaneous pain affects some isometric force production parameters but modifications of motor control strategies are not implemented spontaneously. Conclusions It is hypothesized that adaptation of motor strategies to low back pain is implemented gradually over time. This would enable LBP patients to perform their daily tasks with presumably less pain and more

  4. Reference values for isometric muscle force among workers for the Netherlands: a comparison of reference values

    OpenAIRE

    Schans, van der, D.A.; Soer, Remko; Krijnen, W.P.; Reneman, Michiel; Douma, K.W.

    2014-01-01

    Background: Muscle force is important for daily life and sports and can be measured with a handheld dynamometer. Reference values are employed to quantify a subject’s muscle force. It is not unambiguous whether reference values can be generalized to other populations. Objectives in this study were; first to confirm the reliability of the utilization of hand-held dynamometers for isometric strength measurement; second to determine reference values for a population of Dutch workers; third to co...

  5. The reliability of a handheld dynamometer in measuring maximal isometric neck strength

    OpenAIRE

    Vannebo, Katrine Tranaas

    2015-01-01

    Neck pain is the fourth leading cause of disability worldwide, and is a burden to both the affected individual and the society. Several studies have documented decreased neck strength in patients with chronic neck pain. However, there is a need for a practical and reliable device to measure neck strength in clinical practice. The main objective of this study was to determine the reliability of a handheld dynamometer in measuring maximal isometric neck strength in flexion, extension and latera...

  6. Isometric force production in experienced fighter pilots during +3 Gz centrifuge acceleration.

    Science.gov (United States)

    Guardiera, Simon; Bock, Otmar; Pongratz, Hans; Krause, Wolfgang

    2007-11-01

    Previously, we have shown that naïve subjects produce exaggerated isometric forces when exposed to increased acceleration (+Gz) for the first time. The present study investigates whether +G,-experienced PA-200 Tornado pilots show similar deficits. Experiments were conducted in the stationary (+1 Gz) or rotating (+3 Gz) gondola of a human-rated centrifuge. With their dominant hand, seven pilots produced visually prescribed forces of specific direction and magnitude using an isometric joystick. In practice trials, subjects received continuous visual feedback about their performance, while in test trials they did not. Peak forces during test trials were significantly higher in +3 Gz than in +1 Gz, although this increase of about 25% referring to the +1 Gz value was somewhat smaller in pilots than in nonpilot controls (increase of about 36%). Since pilots' responses were exaggerated in +3 Gz, it seems that frequent exposure to varying +Gz levels is not sufficient for a profound adaptation of force-producing mechanisms to +3 Gz. In consequence, pilots' performance on isometric tasks could be compromised during flight maneuvers in +Gz.

  7. Comparison of Maximal Lingual Pressure Generation During Isometric Gross and Fine Sensorimotor Tasks in Healthy Adults.

    Science.gov (United States)

    Rogus-Pulia, Nicole; Churness, Kim; Hind, Jacqueline; Gangnon, Ronald; Banaszynski, Kelsey; Robbins, JoAnne

    2015-10-01

    To (1) compare 2 distinct isometric lingual press tasks, fine sensorimotor versus gross sensorimotor, at multiple sensor locations in relation to age and sex; and (2) provide a normative data set using a lingual-strengthening device. Cohort study. University. Healthy men and women (N=71; age range, 21-82y) recruited from the community. Participants were stratified by age and sex and divided into 3 age groups. Participants completed, in random order, 2 isometric tasks: (1) fine sensorimotor: tongue press maximally and discreetly against each of 5 sensors; and (2) gross sensorimotor: tongue press maximally against all 5 sensors simultaneously. Primary outcome was maximum isometric pressure in hectopascals (hPa). Secondary outcomes were time to reach peak pressure (s) and pressure gradient (hPa/s). Maximum pressures were significantly lower in those of older age for both fine and gross sensorimotor lingual tasks (Psensorimotor task generating higher pressures at the front sensor for all age groups. However, the gross sensorimotor task generated faster maximum pressures at all sensor locations for all age groups. For both sensorimotor tasks, subjects of older age as a whole generated less steep pressure gradients (Psensorimotor task may be more beneficial for targeting timing as a biomechanical parameter during therapy, and the fine sensorimotor task may be more beneficial for targeting strength. Copyright © 2015 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.

  8. Relative contribution of trunk muscles to the stability of the lumbar spine during isometric exertions.

    Science.gov (United States)

    Cholewicki, Jacek; VanVliet, James J

    2002-02-01

    To compare the relative contribution of various trunk muscles to the stability of the lumbar spine. Quantification of spine stability with a biomechanical model. Modern low back rehabilitation techniques focus on muscles that stabilize the lumbar spine. However, the relative contribution of various trunk muscles to spine stability is currently unknown. Eight male subjects performed isometric exertions in trunk flexion, extension, lateral bending, and axial rotation, and isometric exertions under vertical trunk loading and in a lifting hold. Each isometric trial was repeated three times at 20%, 40%, and 60% of the maximum trunk flexion force or with a load of 0%, 20%, 40%, and 60% of body weight for the latter two exertions. Surface EMG data from 12 major trunk muscles were used in the biomechanical model to estimate stability of the lumbar spine. A simulation of each trial was performed repeatedly with one of the 10 major trunk muscle groups removed from the model. Relative contribution of each muscle to spine stability was significantly affected by the combination of loading magnitude and direction (3-way interaction). None of the removed muscles reduced spine stability by more than 30%. A single muscle cannot be identified as the most important for the stability of the lumbar spine. Rather, spine stability depends on the relative activation of all trunk muscles and other loading variables. This study will improve our understanding of individual trunk muscles' contribution to overall stability of the lumbar spine.

  9. Contracting out local services

    DEFF Research Database (Denmark)

    Petersen, Ole Helby; Houlberg, Kurt; Ring Christensen, Lasse

    2015-01-01

    Governments face a fundamental choice between in-house production and contracting out for the delivery of services to citizens. This article examines the importance of ideology, fiscal pressure, and size for contracting out in technical and social services. The analysis builds on a panel data set...... that the size effect is contingent on the transaction cost characteristics of the service....

  10. Gas contracts in transition

    Energy Technology Data Exchange (ETDEWEB)

    Wright, A.J. [Delhi Gas Pipeline Corp., Dallas, TX (United States)

    1992-12-31

    The transition of gas marketing by producers from a regulated and structured market to an open competitive and commodity market has created new challenges for attorneys drafting gas sales contracts. This article examines the following related topics: Interruptible contracts; pricing provisions; transport imbalances.

  11. BOT Outsourcing Contracts

    DEFF Research Database (Denmark)

    Ørberg Jensen, Peter D.; Petersen, Bent

    2012-01-01

    -firm linkages) and develop three scenarios for the implications for vendor firms. We find that BOT contracts, under certain circumstances, may imply benefits of process and knowledge upgrading for the emerging market vendor firm. However, given different sets of circumstances, engaging in a BOT contract carries...

  12. Partnering and contracting

    DEFF Research Database (Denmark)

    Bohnstedt, Kristian Ditlev

    2014-01-01

    Purpose - Partnering is often, by economists, and construction managerial literature related to more incomplete contracts. This can be explained by seeing partnering as something that neutralizes opportunism. The aim is to uncover whether partnering neutralizes opportunism when there is an incomp......Purpose - Partnering is often, by economists, and construction managerial literature related to more incomplete contracts. This can be explained by seeing partnering as something that neutralizes opportunism. The aim is to uncover whether partnering neutralizes opportunism when...... there is an incomplete contract or reduces transaction costs for renegotiation of complete contracts when new information arises. Design - The study is a cross-sectional design comprising document analysis and interviews. Findings - Firstly that partnering does not necessarily entail more incomplete contracts, which...... contradicts the incomplete contracting theory. Secondly, in complete contract setting partnering can be motivated when seen as a willingness to renegotiate complete contracts i.e. partnering lowers transaction costs for renegotiation. Partnering can make it rational for one party to accept disadvantageous...

  13. Contracting for Telecommunications Systems.

    Science.gov (United States)

    Brautigam, Arthur W.

    1984-01-01

    Reasons for changing telephone systems at colleges and universities and the preparation and evaluation of requests for proposals (RFP) are discussed. The negotiation and monitoring of the contract are also addressed. It is noted that contracting for a new telecommunications system is extremely complex. Reasons for changing systems include cost…

  14. Contracting Productivity Growth

    NARCIS (Netherlands)

    Francois, P.; Roberts, J.

    2001-01-01

    In this paper, we analyze the interactions between growth and the contracting environment in the production sector.Allowing incompleteness in contracting implies that viable production relationships for firms and workers, and therefore the profitability of industries, depend on the rates of

  15. Contract Teachers in India

    Science.gov (United States)

    Goyal, Sangeeta; Pandey, Priyanka

    2013-01-01

    In this paper, we use non-experimental data from government schools in Uttar Pradesh and Madhya Pradesh, two of the largest Indian states, to present average school outcomes by contract status of teachers. We find that contract teachers are associated with higher effort than civil service teachers with permanent tenures, before as well as after…

  16. Contract Training for Industry.

    Science.gov (United States)

    Averill, Donald F.

    1983-01-01

    Describes contract training whereby industries arrange with community colleges, technical institutes, and vocational schools to prepare employees for specific job assignments. Indicates that industrial training performed under contract with public institutions should be encouraged in favor of expansion of training that industry performs for…

  17. Glenohumeral range of motion (ROM) and isometric strength of professional team handball athletes, part III: changes over the playing season.

    Science.gov (United States)

    Fieseler, Georg; Jungermann, Philipp; Koke, Alexander; Irlenbusch, Lars; Delank, Karl-Stefan; Schwesig, René

    2015-12-01

    The aim of our study was to investigate the relation of workload on range of motion and isometric strength of team handball athletes' shoulders over a competitive season. 31 Professional male handball athletes underwent clinical shoulder examinations. Athletes were examined subsequently during the complete playing season (week 0, 6, 22 and 40) to determine bilateral isometric shoulder rotational strength and active range of motion (ROM). In addition, relative (intraclass correlation coefficients (ICC) and absolute (standard error of measurement) reliability were calculated. Intraobserver reliability was excellent (ICC 0.76-0.98) for isometric strength and flexibility measurements. Internal rotation (IR) and total arc ROM in the throwing shoulder (TS) decreased significantly (p handball players' shoulders changed significantly from the beginning to the end of a season. More specifically, the repetitive forces accumulated during the competitive season resulted in altered GIRD, ERG and isometric strength of the dominant glenohumeral joint.

  18. Isometric exercises with elements postisometric relaxation to eliminate the knee joint contracture after arthroscopic plastics of anterior cruciate ligament

    Directory of Open Access Journals (Sweden)

    Pylypenko O.V.

    2014-02-01

    Full Text Available Purpose : to determine the efficiency of isometric exercises and post isometric relaxation of character for removal and prevention of contractures and recovery of motor function after arthroscopic reconstruction of the anterior cruciate ligament in the late postoperative period. Material: The study involved 22 patients aged less than 40 years. Results: The results showed that the level of pain decreased equally in patients of main and control group from 3 to 0 points, the performance difference in the amplitude of the bending of the knee joint during the goniometry in the treatment group was 70 in the control group – 30 and the extension 10 – fixed, reaching 5 hyperextension and not changed in the control group. Conclusions: The use of isometric exercises and post isometric relaxation prevent postoperative contracture of the knee joint. Methods of their application are recommended for use in the comprehensive rehabilitation of patients after arthroscopic plastics anterior cruciate ligament.

  19. Changes in the tibialis anterior tendon moment arm from rest to maximum isometric dorsiflexion: in vivo observation in man

    NARCIS (Netherlands)

    Maganaris, C.N.; Baltzopoulos, V.; Sargeant, A.J.

    1999-01-01

    Objective. In the present study, we examined the hypothesis that the tibialis anterior tendon moment arm increases during maximum isometric dorsiflexion as compared with rest. Background. In musculoskeletal modelling applications, moment arms from passive muscles at rest are assumed representative

  20. Sustainable Food & Sustainable Economics

    OpenAIRE

    Alvarez, Mavis Dora

    2012-01-01

    Cuba today is immersed in a very intense process of perfecting its agricultural production structures with the goal of making them more efficient and sustainable in their economic administration and in their social and environmental management. Agricultural cooperatives in Cuba have the responsibility of producing on 73% of the country's farmland. Their contributions are decisive to developing agricultural production and to ensuring more and better food for the population, in addition to redu...

  1. Contribution to contract theory

    Directory of Open Access Journals (Sweden)

    Pantelić Svetlana

    2016-01-01

    Full Text Available Oliver Hart and Bengt Holmstrom share the Nobel Prize in Economic Sciences for 2016, awarded to them by Sveriges Riksbank. They have been rewarded for their work in enhancing the design of contracts, i.e. arrangements connecting employers with employees or companies with clients, in other words, for their contribution to contract theory in the 1970s and 1980s. Their analysis of optimal contractual arrangements lays an intellectual foundation for designing policies and institutions in many areas, from bankruptcy legislation to political constitutions. Hart is an expert in contract theory, theory of the firm, corporate finance, and law and economics. His contribution to contract theory is exquisite when it comes to designing contracts which cover eventualities that cannot be precisely specified in advance.

  2. Bunker purchasing with contracts

    DEFF Research Database (Denmark)

    Plum, Christian Edinger Munk; Neergaard Jensen, Peter; Pisinger, David

    2014-01-01

    constraints such as capacity limits, reserve requirements and sulphur content. Contracts are often used for bunker purchasing, ensuring supply and often giving a discounted price. A contract can supply any vessel in a period and port, and is thus a shared resource between vessels, which must be distributed...... optimally to reduce overall costs. The Bunker Purchasing with Contracts Problem has been formulated as a mixed integer programme, which has been Dantzig-Wolfe decomposed. To solve it, a novel column generation algorithm has been developed. The algorithm has been run on a series of real-world instances...... with up to 500+ vessels and 500+ contracts, and provide near optimal solutions. This makes it possible for a major liner shipping company to plan bunker purchasing on a global level, and provides an efficient tool for assessing new contracts....

  3. THE PSYCHOLOGICAL CONTRACT

    Directory of Open Access Journals (Sweden)

    Blanca Giorgiana GRAMA

    2015-04-01

    Full Text Available The psychological contract became known as a research paradigm within corporate research, providing a broad framework which explains the employee-company relations. Despite all this, there are still many debates on the concept and a series of criticism were expressed that led to the necessity of some more rigorous theoretical and empirical analysis. The psychological contract refers to the unwritten, implicit expectations that employees have from the company and vice versa; it is that which defines the things the employee expects from the employer. Consequently, each of the parties involved in the contract may have different perceptions on these commitments and obligations. Thus the psychological contract may be regarded as an exchange relation between the employer and the employee. Breaking the psychological contract affects the performance, the morale, and the motivation of the staff in a negative manner. The information presented in this paper is intended to contribute to the theoretical and methodological development of the concept.

  4. Central and peripheral fatigue development in the shoulder muscle with obesity during an isometric endurance task.

    Science.gov (United States)

    Pajoutan, Mojdeh; Ghesmaty Sangachin, Mahboobeh; Cavuoto, Lora A

    2017-07-21

    Fatigue increases the likelihood of developing work-related musculoskeletal disorders and injury. Due to the physiological and neuromuscular changes that accompany obesity, it may alter the fatigue development mechanism and exacerbate injury risk. The upper extremities have the highest incidence rates for work-related musculoskeletal disorders. Therefore, the goals of this study were to investigate the effect of obesity on central vs. peripheral fatigue as well as on the physical signs of fatigue on the middle deltoid muscle. A measure of central activation ratio was used to quantify central fatigue by considering the increment in the torque output by superimposed twitch relative to its corresponding maximum voluntary contraction. For this purpose, electrical stimulation was delivered at the middle deltoid muscles of 22 non-obese (18 fatiguing task at either 30 or 60% of the muscle capacity. Differences in endurance time, torque fluctuation, torque loss, and muscle activity measured by an electromyography sensor were also investigated. A greater reduction of voluntary activation of motor units (p = 0.001) with fatigue was observed for individuals who are obese. Contrary to the effect of obesity on central fatigue, a trend toward reduced peripheral fatigue (p = 0.06) was observed for the obese group compared to the non-obese group. On average, a 14% higher rate of torque loss per second was observed among individuals with obesity in comparison to non-obese participants. The observed greater contribution of central fatigue during the sustained endurance tasks suggests that among young healthy obese individuals, the faster fatigue development with obesity, commonly reported in the literature, is most likely due to the central elements rather than the peripheral factors. This finding has implications for fatigue prevention programs during sustained exertions and can help to develop training, work, and rest schedules considering obesity.

  5. Efficacy of post-isometric relaxation technique on muscle tissue and its viscoelastic properties after physical activity

    OpenAIRE

    Hloušková, Zuzana

    2012-01-01

    Title: Efficacy of post - isometric relaxation technique on muscle tissue and its viscoelastic properties after physical activity. Objective: This study is a pilot analytical and comparative study. The first aim of this thesis was evaluation of the effect of post-isometric relaxation technique on properties of muscle tissue after physical activity. The second aim of this thesis is to present a literature review regarding this topic using literature available. Methods: This study took place in...

  6. Capsule contraction syndrome

    Directory of Open Access Journals (Sweden)

    Mesut COŞKUN

    2009-06-01

    Full Text Available Capsule contraction syndrome occurs after fibrous metaplasia of lens proteins that leads to capsular bag contraction. Excessive front capsular wrinkling is seen in capsule contraction syndrome and there is an imbalance between powers supplying capsular integrity. This situation leads to zonular weakness. Capsule contraction syndrome is associated with pseudoexfoliation, older age, uveitis, pars planitis and myotonic muscular dystrophy. In order to decrease the risk of capsule contraction syndrome, front capsulerhexis area should be open as 5.5-6 mm diameter and a curysoft intraocular lens should be used. In order to prevent lens epithelial proliferation and metaplasia, lens epithelial cells at inferior surface of front capsule should be aspirated carefully. If postoperative capsular contraction detected, front capsulotomy should be performed by Nd-YAG laser at postoperative 2 to 3 weeks. In patients that Nd-YAG laser is unsuccessful, capsular tension should be decreased by surgical microincisions. In present study, we evaluated etiology, prevention and management of capsule contraction syndrome in the light of actual literature knowledge.

  7. ENFORCEMENT OF MORTGAGE CONTRACT

    Directory of Open Access Journals (Sweden)

    Alisa A. BELU

    2016-07-01

    Full Text Available A chattel mortgage contract is the expression of a real guarantee that gives the creditor precedence over other creditors, in addition to the general pledge upon the belongings of the debtor. It refers to the sale of mortgaged movable assets, exclusively or prioritized in favor of the mortgaging creditor, in case the debtor does not comply with his / her commitments, under the signed mortgage contract. Beginning from this purpose, shared by both sides (as the chattel mortgage contract is synallagmatic, in case the debtor is unable to fulfill his / her commitments, the sides reach a situation of enforcement of the signed chattel mortgage contract. Given the legal status of the chattel mortgage contract [Art. 2387-2477 Noul Cod Civil , Universul Juridic, Bucureşti, 2016, ISBN 978-606-673-792-0], the principle of binding force of the contract and the principle according to which signed legal conventions will entail legal effects, the Romanian law maker developed the proper legal framework for the enforcement of the chattel mortgage contract. [art. 622 si urm. Noul Cod de Procedură Civilă, ed. Hamangiu, Bucureşti, 2016, ISBN 978-606-27-0459-9].

  8. Retraining and assessing hand movement after stroke using the MusicGlove: comparison with conventional hand therapy and isometric grip training.

    Science.gov (United States)

    Friedman, Nizan; Chan, Vicky; Reinkensmeyer, Andrea N; Beroukhim, Ariel; Zambrano, Gregory J; Bachman, Mark; Reinkensmeyer, David J

    2014-04-30

    It is thought that therapy should be functional, be highly repetitive, and promote afferent input to best stimulate hand motor recovery after stroke, yet patients struggle to access such therapy. We developed the MusicGlove, an instrumented glove that requires the user to practice gripping-like movements and thumb-finger opposition to play a highly engaging, music-based, video game. The purpose of this study was to 1) compare the effect of training with MusicGlove to conventional hand therapy 2) determine if MusicGlove training was more effective than a matched form of isometric hand movement training; and 3) determine if MusicGlove game scores predict clinical outcomes. 12 chronic stroke survivors with moderate hemiparesis were randomly assigned to receive MusicGlove, isometric, and conventional hand therapy in a within-subjects design. Each subject participated in six one-hour treatment sessions three times per week for two weeks, for each training type, for a total of 18 treatment sessions. A blinded rater assessed hand impairment before and after each training type and at one-month follow-up including the Box and Blocks (B & B) test as the primary outcome measure. Subjects also completed the Intrinsic Motivation Inventory (IMI). Subjects improved hand function related to grasping small objects more after MusicGlove compared to conventional training, as measured by the B & B score (improvement of 3.21±3.82 vs. -0.29±2.27 blocks; P=0.010) and the 9 Hole Peg test (improvement of 2.14±2.98 vs. -0.85±1.29 pegs/minute; P=0.005). There was no significant difference between training types in the broader assessment batteries of hand function. Subjects benefited less from isometric therapy than MusicGlove training, but the difference was not significant (P>0.09). Subjects sustained improvements in hand function at a one month follow-up, and found the MusicGlove more motivating than the other two therapies, as measured by the IMI. MusicGlove games scores correlated

  9. Temporary labour contracts

    CERN Document Server

    1999-01-01

    The five contracts for Temporary Labour assignments on the CERN site (L020/PE, L021/PE, L022/PE, L023/PE and L024/PE) approved by the Finance Committee in March 1996 (CERN/FC/3857) will reach the end of their initial three-year contractual period at the end of December 1999. Following the satisfactory execution of these contracts during this period, CERN requests approval to extend them from January 2000 for the first of the two years foreseen in the original adjudication. The Finance Committee is invited: - to take note that the three-year expenditure for Temporary Labour contracts from 1997 to 1999 will not exceed 19 100 000 Swiss francs, compared to the 18 900 000 Swiss francs estimated at the time of the adjudication in March 1996; - to approve an extension of the present Temporary Labour contracts for the year 2000 for a total amount not exceeding 6 000 000 Swiss francs.

  10. Premature Ventricular Contractions (PVCs)

    Science.gov (United States)

    ... Premature ventricular contractions (PVCs) Symptoms & causes Diagnosis & treatment Advertisement Mayo Clinic does not endorse companies or products. ... a Job Site Map About This Site Twitter Facebook Google YouTube Pinterest Mayo Clinic is a not- ...

  11. Superfund Contract Laboratory Program

    Science.gov (United States)

    The Contract Laboratory Program (CLP) is a national network of EPA personnel, commercial laboratories, and support contractors whose primary mission is to provide data of known and documented quality to the Superfund program.

  12. Contracting the Facebook API

    Directory of Open Access Journals (Sweden)

    Ben Rubinger

    2010-09-01

    Full Text Available In recent years, there has been an explosive growth in the popularity of online social networks such as Facebook. In a new twist, third party developers are now able to create their own web applications which plug into Facebook and work with Facebook's "social" data, enabling the entire Facebook user base of more than 400 million active users to use such applications. These client applications can contain subtle errors that can be hard to debug if they misuse the Facebook API. In this paper we present an experience report on applying Microsoft's new code contract system for the .NET framework to the Facebook API.We wrote contracts for several classes in the Facebook API wrapper which allows Microsoft .NET developers to implement Facebook applications. We evaluated the usefulness of these contracts during implementation of a new Facebook application. Our experience indicates that having code contracts provides a better and quicker software development experience.

  13. Sweating responses to isometric hand-grip exercise and forearm muscle metaboreflex in prepubertal children and elderly.

    Science.gov (United States)

    Amano, Tatsuro; Kai, Seiko; Nakajima, Michi; Ichinose-Kuwahara, Tomoko; Gerrett, Nicola; Kondo, Narihiko; Inoue, Yoshimitsu

    2017-02-01

    What is the central question of this study? Non-thermal factors (e.g. muscle metaboreflex) contribute to the sweating response during exercise. Although it is well recognized that the sweating responses caused by core temperature elevation in prepubertal children and the elderly are attenuated compared with young adults, it is unknown whether non-thermal sweating is also attenuated in these populations. What is the main finding and its importance? The non-thermal sweating response during isometric hand-grip exercise and isolated muscle metaboreflex were attenuated in prepubertal children compared with young adults in a non-uniform manner over the body, but only during the muscle metaboreflex in the elderly. This may explain the maturation- and ageing-related decline of sweating during exercise. The purpose of the present study was to investigate sweating responses to isometric hand-grip (IH) exercise and muscle metaboreflex in prepubertal children and the elderly. In hot conditions (ambient temperature, 35°C; relative humidity, 45%), 13 healthy young adults, 10 prepubertal children and 10 elderly subjects (aged 20.4 ± 1.2, 11.4 ± 0.5 and 63.5 ± 3.1 years, respectively) repeated a three hand-grip exercise protocol that consisted of 1 min IH exercise at 15, 30 or 45% of maximal voluntary contraction (MVC) followed by 2 min postexercise forearm occlusion. Local sweat rates (SRs) on the forehead, chest, forearm, thigh and palm were continuously measured (ventilated capsule method). The forehead SR in prepubertal children during IH exercise at 45% MVC was significantly lower than that of young adults (0.26 ± 0.22 and 0.08 ± 0.15 mg cm-2  min-1 for young adults and children, respectively; P elderly at any exercise intensities. The SR on the chest (0.22 ± 0.22 and -0.01 ± 0.05 mg cm-2  min-1 for young adults and children, respectively), forearm (0.14 ± 0.12 and 0.03 ± 0.04 mg cm-2  min-1 ) and thigh (0.13 ± 0.10 and 0.02 ± 0

  14. Tetrodotoxin-insensitive electrical field stimulation-induced contractions on Crotalus durissus terrificus corpus cavernosum.

    Science.gov (United States)

    Campos, Rafael; Mónica, Fabíola Z; Rodrigues, Renata Lopes; Rojas-Moscoso, Julio Alejandro; Moreno, Ronilson Agnaldo; Cogo, José Carlos; de Oliveira, Marco Antonio; Antunes, Edson; De Nucci, Gilberto

    2017-01-01

    Reptiles are the first amniotes to develop an intromitent penis, however until now the mechanisms involved in the electrical field stimulation-induced contraction on corpora cavernosa isolated from Crotalus durissus terrificus were not investigated. Crotalus and rabbit corpora cavernosa were mounted in 10 mL organ baths for isometric tension recording. Electrical field stimulation (EFS)-induced contractions were performed in presence/absence of phentolamine (10 μM), guanethidine (30 μM), tetrodotoxin (1 μM and 1mM), A-803467 (10 μM), 3-iodo-L-Tyrosine (1 mM), salsolinol (3 μM) and a modified Krebs solution (equimolar substitution of NaCl by N-methyl-D-glucamine). Immuno-histochemistry for tyrosine hydroxylase was also performed. Electrical field stimulation (EFS; 8 Hz and 16 Hz) caused contractions in both Crotalus and rabbit corpora cavernosa. The contractions were abolished by previous incubation with either phentolamine or guanethidine. Tetrodotoxin (1 μM) also abolished the EFS-induced contractions of rabbit CC, but did not affect EFS-induced contractions of Crotalus CC. Addition of A-803467 (10 μM) did not change the EFS-induced contractions of Crotalus CC but abolished rabbit CC contractions. 3-iodo-L-Tyrosine and salsolinol had no effect on EFS-induced contractions of Crotalus CC and Rabbit CC. Replacement of NaCl by N- Methyl-D-glucamine (NMDG) abolished EFS-induced contractions of rabbit CC, but did not affect Crotalus CC. The presence of tyrosine hydroxylase was identified in endothelial cells only of Crotalus CC. Since the EFS-induced contractions of Crotalus CC is dependent on catecholamine release, insensitive to TTX, insensitive to A803467 and to NaCl replacement, it indicates that the source of cathecolamine is unlikely to be from adrenergic terminals. The finding that tyrosine hydroxylase is present in endothelial cells suggests that these cells can modulate Crotalus CC tone.

  15. Effects of involuntary eccentric contraction training by neuromuscular electrical stimulation on the enhancement of muscle strength.

    Science.gov (United States)

    Son, Jongsang; Lee, Dongyeop; Kim, Youngho

    2014-08-01

    Neuromuscular electrical stimulation is well-known as a modality to improve the performance of neuromuscular system, but its clinical value on muscle strengthening remains equivocal. In this study, we designed a system for an involuntary eccentric contraction of biceps brachii muscles using continuous passive movement and commercial neuromuscular electrical stimulation devices. To investigate the effects of involuntary eccentric contraction training by neuromuscular electrical stimulation on the enhancement of muscle strength, seven healthy men between the ages of 24 and 29 years participated in this study. Participants were trained two times per week for 12 weeks. Each exercise session was performed for 30 min with no rest intervals. Isometric elbow flexion torque and biceps brachii muscle thickness were chosen as evaluation indices, and were measured at pre-/post-training. After the 12-week training, the isometric elbow flexion torque of the trained side significantly increased by approximately 23% compared to the initial performance (P<0.01). Meanwhile, the torque of the untrained side showed no significant change (P=0.862). During the 12-week training period, the biceps brachii muscle thickness of the trained side significantly increased by around 8% at rest and 16% at maximum voluntary contraction (P<0.01). The developed system and the technique show promising results, suggesting that it has the potential to be used to increase the muscle strength in patients with neuromuscular disease and to be implemented in design rehabilitative protocols. Copyright © 2014 Elsevier Ltd. All rights reserved.

  16. Mechanomyography and Torque during FES-Evoked Muscle Contractions to Fatigue in Individuals with Spinal Cord Injury.

    Science.gov (United States)

    Mohamad, Nor Zainah; Hamzaid, Nur Azah; Davis, Glen M; Abdul Wahab, Ahmad Khairi; Hasnan, Nazirah

    2017-07-14

    A mechanomyography muscle contraction (MC) sensor, affixed to the skin surface, was used to quantify muscle tension during repetitive functional electrical stimulation (FES)-evoked isometric rectus femoris contractions to fatigue in individuals with spinal cord injury (SCI). Nine persons with motor complete SCI were seated on a commercial muscle dynamometer that quantified peak torque and average torque outputs, while measurements from the MC sensor were simultaneously recorded. MC-sensor-predicted measures of dynamometer torques, including the signal peak (SP) and signal average (SA), were highly associated with isometric knee extension peak torque (SP: r = 0.91, p < 0.0001), and average torque (SA: r = 0.89, p < 0.0001), respectively. Bland-Altman (BA) analyses with Lin's concordance (ρC) revealed good association between MC-sensor-predicted peak muscle torques (SP; ρC = 0.91) and average muscle torques (SA; ρC = 0.89) with the equivalent dynamometer measures, over a range of FES current amplitudes. The relationship of dynamometer torques and predicted MC torques during repetitive FES-evoked muscle contraction to fatigue were moderately associated (SP: r = 0.80, p < 0.0001; SA: r = 0.77; p < 0.0001), with BA associations between the two devices fair-moderate (SP; ρC = 0.70: SA; ρC = 0.30). These findings demonstrated that a skin-surface muscle mechanomyography sensor was an accurate proxy for electrically-evoked muscle contraction torques when directly measured during isometric dynamometry in individuals with SCI. The novel application of the MC sensor during FES-evoked muscle contractions suggested its possible application for real-world tasks (e.g., prolonged sit-to-stand, stepping,) where muscle forces during fatiguing activities cannot be directly measured.

  17. The identification of fall history using maximal and rapid isometric torque characteristics of the hip extensors in healthy, recreationally active elderly females: a preliminary investigation.

    Science.gov (United States)

    Palmer, Ty B; Thiele, Ryan M; Williams, Katherine B; Adams, Bailey M; Akehi, Kazuma; Smith, Douglas B; Thompson, Brennan J

    2015-08-01

    Maximal and rapid torque characteristics of the hip extensor muscles play an important role in fall prevention and other balance-related performances; however, few studies have investigated the ability of these variables at identifying fall-history status in healthy, recreationally active elderly adults. This study aimed to examine the effectiveness of maximal and rapid isometric torque characteristics of the hip extensor muscles to differentiate between healthy, recreationally active elderly females with (fallers) and without (non-fallers) a history a falls. Six elderly female fallers (mean ± SD: age = 73 ± 7 year; mass = 68 ± 16 kg; height = 160 ± 5 cm) and nine elderly female non-fallers (age = 71 ± 7 year; mass = 66 ± 16 kg; height = 157 ± 6 cm) performed two isometric maximal voluntary contractions (MVCs) of the hip extensor muscles. Peak torque (PT) and absolute and relative rate of torque development (RTD) at the early (0-50 ms) and late (100-200 ms) phases of muscle contraction were examined during each MVC. Absolute and relative RTD at 0-50 ms were greater (P = 0.039 and 0.011, respectively) in the non-fallers compared to the fallers. However, no group-related differences (P = 0.160-0.573) were observed for PT nor absolute and relative RTD at 100-200 ms. Early rapid strength production of the hip extensor muscles may be a sensitive and effective measure for discriminating between elderly females of different fall histories. These findings may provide important insight regarding implications for the assessment of fall risk and in the development of proper training programs aimed at minimizing the occurrence of falls and other balance-related injuries in the elderly.

  18. The influence of athletic status on maximal and rapid isometric torque characteristics and postural balance performance in Division I female soccer athletes and non-athlete controls.

    Science.gov (United States)

    Palmer, Ty B; Hawkey, Matt J; Thiele, Ryan M; Conchola, Eric C; Adams, Bailey M; Akehi, Kazuma; Smith, Doug B; Thompson, Brennan J

    2015-07-01

    The purpose of this study was to examine the effectiveness of maximal and rapid isometric torque characteristics of the hip extensor muscles and postural balance performance to discriminate between female collegiate soccer athletes and non-athlete controls. Ten athletes (mean ± SE: age = 19·20 ± 0·36 year; mass = 62·23 ± 3·12 kg; height = 162·43 ± 1·70 cm) and 10 non-athletes (age = 20·30 ± 0·40 year; mass = 69·64 ± 3·20 kg; height = 163·22 ± 2·10 cm) performed two isometric maximal voluntary contractions (MVCs) of the hip extensor muscles. Peak torque (PT) and absolute and relative rate of torque development (RTD) at early (0-50 ms) and late (100-200 ms) phases of muscle contraction were examined during each MVC. Postural balance was assessed using a commercially designed balance testing device, which provides a measurement of static stability based on sway index (SI). Results indicated that absolute and relative RTD at 0-50 ms (RTD50 and RTD50norm) were greater (P = 0·007 and 0·026), and postural SI was lower (P = 0·022) in the athletes compared with the non-athletes. However, no differences (P = 0·375-0·709) were observed for PT nor absolute and relative RTD at 100-200 ms (RTD100-200 and RTD100-200norm). Significant relationships were also observed between RTD50 and RTD50norm and SI (r = -0·559 and -0·521; P = 0·010 and 0·019). These findings suggest that early rapid torque characteristics of the hip extensor muscles and postural balance performance may be sensitive and effective measures for discriminating between college-aged athletes and non-athletes. Coaches and practitioners may use these findings as performance evaluation tools to help in identifying athletes with both superior early rapid torque and balance performance abilities, which may possibly be an indicator of overall athletic potential. © 2014 Scandinavian Society of Clinical Physiology and Nuclear Medicine. Published by John

  19. An unsatisfactory contract policy

    CERN Multimedia

    Association du personnel

    2012-01-01

    For the last 15 years contract policy has been one of the top priorities of CERN staff, as expressed in successive surveys initiated by the Staff Association. In one’s professional life, having some forward vision of one’s career prospects is the key to loyalty and motivation. On the contrary, instability about the future is always at the root of anxiety, conflicts, or even health problems. A good employer must therefore balance the needs of the Company and those of its employees. CERN’s current contract policy, as described in the Administrative Circular No 2, states that staff members should first obtain a limited duration (LD) contract of up to five years. Then, if they want to stay in the Organization, staff members must apply, usually once a year, and before the end of their LD contract, for an indefinite contract (IC) post. All candidates for an IC post are considered by the Review Board for the award of indefinite contracts (Review Board) which will choose the most suita...

  20. Influence of Whole Body Vibration and Specific Warm-ups on Force during an Isometric Mid-Thigh Pull

    Directory of Open Access Journals (Sweden)

    Vanessa L. Cazás-Moreno

    2015-10-01

    Full Text Available Purpose: The purpose of this study was to investigate the effects of general and specific warm-up protocols on rate of force development (RFD, relative RFD (rRFD, ground reaction force (GRF and relative ground reaction force (rGRF during an isometric mid-thigh pull (IMTP, after WBV exposure. Methods: Fifteen healthy recreationally trained males  (age: 24.1 ± 2.3 yrs, height: 72.9 ± 7.8 cm; mass: 86.9 ± 8.3 completed five protocols: baseline, isometric vibration (iVib, isometric no vibration (iNV, dynamic vibration (dVib and dynamic no vibration (dNV. The baseline was completed without any warm-up prior to the IMTP. The intervention protocols had the same prescription of 4 sets of 30-second bouts of quarter squats (dynamic [DQS] and isometric [IQS] on the WBV platform with or without vibration. Following a one-minute rest period after each protocol, participants completed three maximal IMTPs. Results: Repeated measures ANOVA with a Bonferroni post hoc demonstrated that RFD in dNV (7657.8 ± 2292.5 N/s was significantly greater than iVib (7156.4 ± 2170.0 N/s. However, the other experimental trials for RFD demonstrated no significant differences (p>0.05. There were also no significant differences for rRFD, GRF or rGRF between protocols. Conclusion: These results demonstrate that a dynamic warm-up without WBV elicits greater RFD than an isometric warm-up with WBV prior to a maximal isometric exercise. Further research needs to be investigated utilizing dynamic and isometric warm-ups in conjunction with WBV and power output. Keywords: males, recreationally trained, power

  1. 36 CFR 223.117 - Administration of cooperative or Federal sustained yield units.

    Science.gov (United States)

    2010-07-01

    ... or Federal sustained yield units. 223.117 Section 223.117 Parks, Forests, and Public Property FOREST... Contracts Contract Administration § 223.117 Administration of cooperative or Federal sustained yield units. With respect to sustained yield units established pursuant to the provisions of the Act of March 29...

  2. A Comparison of Exercise-Induced Muscle Damage Following Maximal Eccentric Contractions in Men and Boys.

    Science.gov (United States)

    Deli, Chariklia K; Fatouros, Ioannis G; Paschalis, Vassilis; Georgakouli, Kalliopi; Zalavras, Athanasios; Avloniti, Alexandra; Koutedakis, Yiannis; Jamurtas, Athanasios Z

    2017-08-01

    Research regarding exercise-induced muscle-damage mainly focuses on adults. The present study examined exercise-induced muscle-damage responses in adults compared with children. Eleven healthy boys (10-12 y) and 15 healthy men (18-45 y) performed 5 sets of 15 maximal eccentric contractions of the knee extensors. Range of motion (ROM), delayed onset muscle soreness (DOMS) during squat and walking, and peak isometric, concentric and eccentric torque were assessed before, post, 24, 48, 72, and 96 hr postexercise. Creatine kinase (CK) activity was assessed before and 72 hr postexercise. Eccentric exercise resulted in DOMS during squat that persisted for up to 96h in men, and 48 hr in boys (p < .05), and DOMS during walking that persisted for up to 72 hr in men, and 48 hr in boys (p < .01). The ROM was lower in both age groups 48 hr postexercise (p < .001). Isometric (p < .001), concentric (p < .01) and eccentric (p < .01) force decreased post, and up to 48 hr postexercise in men. Except for a reduction in isometric force immediately after exercise, no other changes occurred in boys' isokinetic force. CK activity increased in men at 72 hr postexercise compared with pre exercise levels (p = .05). Our data provide further confirmation that children are less susceptible to exercise-induced muscle damage compared with adults.

  3. Sustainable agriculture

    National Research Council Canada - National Science Library

    Lichtfouse, Eric

    2009-01-01

    ... : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 9 Part I CLIMATE CHANGE Soils and Sustainable Agriculture: A Review : : : : : : : : : : : : : : : : : : : : : : : : : : Rattan Lal 15 Soils and Food Sufficiency...

  4. Life-Cycle Based Climate Regulation Through Supply Chain Contracts

    DEFF Research Database (Denmark)

    Mitkidis, Katerina

    Environmental action is a necessary component of any corporate sustainability efforts. While companies address many environmental issues, climate change belongs to the most pressing ones for them. Companies report on their scope 1 and 2 emissions, set ambitious reduction goals and adopt policies...... to that end. The paper concludes with a discussion on that this big but dormant potential of commercial contracting could be triggered through policy, law and amended contract drafting style....

  5. Effects of a 16-week Pilates exercises training program for isometric trunk extension and flexion strength.

    Science.gov (United States)

    Kliziene, Irina; Sipaviciene, Saule; Vilkiene, Jovita; Astrauskiene, Audrone; Cibulskas, Gintautas; Klizas, Sarunas; Cizauskas, Ginas

    2017-01-01

    To evaluate the effects of Pilates exercises designed to improve isometric trunk extension and flexion strength of muscles in women with chronic low back pain (cLBP). Female volunteers with cLBP were divided into an experimental group (EG; n = 27) and a control group (CG; n = 27). Pilates exercises were performed twice per week by the EG; the duration of each session was 60 min. The program lasted for 16 weeks; thus patients underwent a total of 32 exercise sessions. The maximum isometric waist bending strength of the EG had improved significantly (p = 0.001) after 16 weeks of the Pilates program. The results of trunk flexion muscle endurance tests significantly depended on the trunk extension muscle endurance before the intervention, and at 1 month (r = 0.723, p Pilates exercise program. At the end of the 16-week exercise program, cLBP intensity decreased by 2.01 ± 0.8 (p Pilates exercise program the pain intensified and the functional state deteriorated much faster than the maximum trunk muscle strength. Therefore, it can be concluded that, to decrease pain and improve functional condition, regular exercise (and not only improved strength and endurance) is required. We established that, although the 16-week lumbar stabilization exercise program increased isometric trunk extension and flexion strength and this increase in strength persisted for 2 months, decreased LBP and improved functional condition endured for only 1 month. Copyright © 2016 Elsevier Ltd. All rights reserved.

  6. Molecular impact of clenbuterol and isometric strength training on rat EDL muscles.

    Science.gov (United States)

    Mounier, Rémi; Cavalié, Hélian; Lac, Gérard; Clottes, Eric

    2007-01-01

    Clenbuterol, a beta2-adrenergic-receptor agonist, is known to provoke muscle hypertrophy and a slow-to-fast phenotype change. A more glycolytic phenotype should be paralleled by changes in muscle glycolytic metabolism. Two groups (n=16 for each) of 3-month-old male Wistar rats (UCL: untrained clenbuterol, and ECL: exercised clenbuterol) received a chronic administration of clenbuterol (2 mg/kg body weight/day). Two other groups of animals (U: untrained and E: exercised), were given a 0.9% NaCl solution instead of clenbuterol. E and ECL animals followed an 8-week progressive isometric force strength-training program. Both clenbuterol administration and training resulted in an increase in extensor digitorum longus (EDL) mass despite the fact that this muscle was indirectly mobilised during isometric force strength training. Clenbuterol and training induced a consistent slow-to-fast phenotype change without drastically increasing specific activities of glycolytic enzymes. Except for GAPDH and hexokinase, modifications in glycolytic-enzyme-specific activities were not explained by transcriptional changes. Lactate dehydrogenase activity was not affected by clenbuterol but was strongly augmented by training. In EDL of ECL rats, both treatments presented an opposite effect compensating each other. GLUT1 mRNA expression was augmented in EDL of UCL and ECL animals, whereas monocarboxylate transporter 1 mRNA amounts were decreased in EDL of UCL rats. Citrate synthase activity was reduced by clenbuterol treatment but remained unchanged in EDL of E animals. Creatine kinase activity was enhanced only by clenbuterol alone. These data show that clenbuterol-induced muscle hypertrophy and slow-to-fast phenotype changes are not associated with a glycolytic-enzyme-activity increase. They also suggest that in EDL isometric force strength training can reverse clenbuterol-induced molecular adaptations.

  7. Comparison of regression models for estimation of isometric wrist joint torques using surface electromyography

    Directory of Open Access Journals (Sweden)

    Menon Carlo

    2011-09-01

    Full Text Available Abstract Background Several regression models have been proposed for estimation of isometric joint torque using surface electromyography (SEMG signals. Common issues related to torque estimation models are degradation of model accuracy with passage of time, electrode displacement, and alteration of limb posture. This work compares the performance of the most commonly used regression models under these circumstances, in order to assist researchers with identifying the most appropriate model for a specific biomedical application. Methods Eleven healthy volunteers participated in this study. A custom-built rig, equipped with a torque sensor, was used to measure isometric torque as each volunteer flexed and extended his wrist. SEMG signals from eight forearm muscles, in addition to wrist joint torque data were gathered during the experiment. Additional data were gathered one hour and twenty-four hours following the completion of the first data gathering session, for the purpose of evaluating the effects of passage of time and electrode displacement on accuracy of models. Acquired SEMG signals were filtered, rectified, normalized and then fed to models for training. Results It was shown that mean adjusted coefficient of determination (Ra2 values decrease between 20%-35% for different models after one hour while altering arm posture decreased mean Ra2 values between 64% to 74% for different models. Conclusions Model estimation accuracy drops significantly with passage of time, electrode displacement, and alteration of limb posture. Therefore model retraining is crucial for preserving estimation accuracy. Data resampling can significantly reduce model training time without losing estimation accuracy. Among the models compared, ordinary least squares linear regression model (OLS was shown to have high isometric torque estimation accuracy combined with very short training times.

  8. Reliability of isometric trunk moment measurements in healthy persons over 50 years of age.

    Science.gov (United States)

    Kienbacher, Thomas; Paul, Birgit; Habenicht, Richard; Starek, Christian; Wolf, Markus; Kollmitzer, Josef; Ebenbichler, Gerold

    2014-03-01

    To determine the short- and long-term test-retest reliability of maximum isometric trunk moment measurements in healthy volunteers over 50 years of age, to compare these results with those from volunteers younger than 50 years, and to test whether volunteers' anticipatory emotional state affects the precision of these measurements. Forty-two older persons (21 females; age range 50-90 years) and 44 younger persons (19 females; age range 18-49 years) performed maximum isometric trunk extensions, flexions, and rotations using dynamometers (DAVID, Fi, David Health Solutions Ltd, Helsinki, Finland). They repeated the tests after 1-2 days (short-term) and at 6 weeks (long-term). Retest-reliability was evaluated for age- and gender-specific subgroups, with assessment of intraclass correlation coefficient (ICC2,1) , standard error of measurement, smallest real difference, and smallest real difference, in percent. For the elderly group, smallest real difference, in percent values varied up to 33% and were similar to those obtained from young volunteers. Precision of the trunk rotation tests was lower than that of trunk flexion or extension. Retest agreement exceeded 0.75 (ICC2,1) for all tests, with no relevant differences observed between gender- and age-specific subgroups. Neither participants' motivation nor their anticipatory emotions correlated with the individual coefficients of variation of the trunk muscle moment measurements. Isometric maximum trunk extension and flexion moment measurements taken from healthy persons > 50 years old are as reliable as those from persons < 50 years old, and can be expected to enable an acceptable level of detection of expected changes in muscle strength parameters as a result of planned exercise interventions.

  9. Acute Effects of the Different Intensity of Static Stretching on Flexibility and Isometric Muscle Force.

    Science.gov (United States)

    Kataura, Satoshi; Suzuki, Shigeyuki; Matsuo, Shingo; Hatano, Genki; Iwata, Masahiro; Yokoi, Kazuaki; Tsuchida, Wakako; Banno, Yasuhiro; Asai, Yuji

    2017-12-01

    Kataura, S, Suzuki, S, Matsuo, S, Hatano, G, Iwata, M, Yokoi, K, Tsuchida, W, Banno, Y, and Asai, Y. Acute effects of the different intensity of static stretching on flexibility and isometric muscle force. J Strength Cond Res 31(12): 3403-3410, 2017-In various fields, static stretching is commonly performed to improve flexibility, whereas the acute effects of different stretch intensities are unclear. Therefore, we investigated the acute effects of different stretch intensities on flexibility and muscle force. Eighteen healthy participants (9 men and 9 women) performed 180-second static stretches of the right hamstrings at 80, 100, and 120% of maximum tolerable intensity without stretching pain, in random order. The following outcomes were assessed as markers of lower limb function and flexibility: static passive torque (SPT), range of motion (ROM), passive joint (muscle-tendon) stiffness, passive torque (PT) at onset of pain, and isometric muscle force. Static passive torque was significantly decreased after all stretching intensities (p ≤ 0.05). Compared with before stretching at 100 and 120% intensities, ROM and PT were significantly increased after stretching (p ≤ 0.05), and passive stiffness (p = 0.05) and isometric muscle force (p ≤ 0.05) were significantly decreased. In addition, ROM was significantly greater after stretching at 100 and 120% than at 80%, and passive stiffness was significantly lower after 120% than after 80% (p ≤ 0.05). However, all measurements except SPT were unchanged after 80% intensity. There was a weak positive correlation between the intensities of stretching and the relative change for SPT (p ≤ 0.05), a moderate positive correlation with ROM (p ≤ 0.05), and a moderate positive correlation with passive stiffness (p ≤ 0.05). These results indicate that static stretching at greater intensity is more effective for increasing ROM and decreasing passive muscle-tendon stiffness.

  10. Functional and muscular adaptations in an experimental model for isometric strength training in mice.

    Directory of Open Access Journals (Sweden)

    Karsten Krüger

    Full Text Available Exercise training induces muscular adaptations that are highly specific to the type of exercise. For a systematic study of the differentiated exercise adaptations on a molecular level mouse models have been used successfully. The aim of the current study was to develop a suitable mouse model of isometric strength exercise training characterized by specific adaptations known from strength training. C57BL/6 mice performed an isometric strength training (ST for 10 weeks 5 days/week. Additionally, either a sedentary control group (CT or a regular endurance training group (ET groups were used as controls. Performance capacity was determined by maximum holding time (MHT and treadmill spirometry, respectively. Furthermore, muscle fiber types and diameter, muscular concentration of phosphofructokinase 1 (PFK, succinate dehydrogenase (SDHa, and glucose transporter type 4 (GLUT4 were determined. In a further approach, the effect of ST on glucose intolerance was tested in diabetic mice. In mice of the ST group we observed an increase of MHT in isometric strength tests, a type II fiber hypertrophy, and an increased GLUT4 protein content in the membrane fraction. In contrast, in mice of the ET group an increase of VO(2max, a shift to oxidative muscle fiber type and an increase of oxidative enzyme content was measured. Furthermore strength training was effective in reducing glucose intolerance in mice fed a high fat diet. An effective murine strength training model was developed and evaluated, which revealed marked differences in adaptations known from endurance training. This approach seems also suitable to test for therapeutical effects of strength training.

  11. Evaluation of isometric strength and fatty infiltration of the subscapularis in latarjet surgery

    Science.gov (United States)

    dos Santos, Ricardo Barreto Monteiro; Kauffman, Fábio Neumann; de Lima, Gabriel Praxedes; Ferreira, Avraham Machado Costa; dos Santos, Saulo Monteiro; Aguiar, José Lamartine de Andrade

    2015-01-01

    OBJECTIVE: To evaluate the function of the subscapularis muscle by means of isometric strength, clinical examination and analysis of fatty infiltration in patients with recurrent anterior dislocation of the shoulder undergoing Latarjet-Patte surgery. METHODS: 38 patients operated from March 2011 to March 2012, with minimum follow-up of two years were evaluated, being 26 males and 12 females, with a mean age of 28.7 years old. Isometric strength was measured using a portable dynamometer and measuring the distance from the back of the hand during the lift-off test. We used the Rowe and Walch-Duplay scores for clinical evaluation. The degree of fatty infiltration of the subscapularis belly was assessed by computed tomography. RESULTS: The mean scores in the Walch-Duplay and Rowe were 84.7 and 89.4, respectively. The mean distance to the back of the hand was 7.34 cm on the operated side and 8.72 cm on the opposite side (p <0.0001). The mean strength measured in the lift-off test was 0.38 kg lower than on the contralateral side (p = 0.001). There was no fatty infiltration of the subscapularis in 16 patients (42.1%). Sixteen patients (42.1%) were classified as Goutallier grade 1 and six (15.8%) as grade 2. We found that the measured isometric strength decreases with increasing the degree of fatty infiltration (p <0.0001). CONCLUSIONS: The decrease in subscapularis strength, albeit of low magnitude (0.38 kg), was directly related to the degree of fatty infiltration and worse clinical outcomes. Level of Evidence III, Therapeutic Study - Investigating the Results of Treatment. PMID:26207088

  12. Isometric exercise training for blood pressure management: a systematic review and meta-analysis.

    Science.gov (United States)

    Carlson, Debra J; Dieberg, Gudrun; Hess, Nicole C; Millar, Philip J; Smart, Neil A

    2014-03-01

    To conduct a systematic review and meta-analysis quantifying the effects of isometric resistance training on the change in systolic blood pressure(SBP), diastolic blood pressure (DBP), and mean arterial pressure in subclinical populations and to examine whether the magnitude of change in SBP and DBP was different with respect to blood pressure classification. We conducted a systematic review and meta-analysis of randomized controlled trials lasting 4 or more weeks that investigated the effects of isometric exercise on blood pressure in healthy adults (aged ≥18 years) and were published in a peer-reviewed journal. PubMed, CINAHL, and the Cochrane Central Register of Controlled Trials were searched for trials reported between January 1, 1966, and July 31, 2013. We included 9 randomized trials, 6 of which studied normotensive participants and 3 that studied hypertensive patients, that included a total of 223 participants (127 who underwent exercise training and 96 controls). The following reductions were observed after isometric exercise training: SBP-mean difference (MD), -6.77 mm Hg (95% CI, -7.93 to -5.62 mm Hg; Ppressure-MD, -3.94 mm Hg (95% CI, -4.73 to -3.16 mm Hg; Ppressure. The magnitude of effect is larger than that previously reported in dynamic aerobic or resistance training. Our data suggest that this form of training has the potential to produce significant and clinically meaningful blood pressure reductions and could serve as an adjunctive exercise modality. Copyright © 2014 Mayo Foundation for Medical Education and Research. Published by Elsevier Inc. All rights reserved.

  13. Sustainable Marketing

    NARCIS (Netherlands)

    Dam, van Y.K.

    2017-01-01

    In this article, three different conceptions of sustainable marketing are discussed and compared. These different conceptions are referred to as social, green, and critical sustainable marketing. Social sustainable marketing follows the logic of demand-driven marketing management and places the

  14. Computerized analysis of isometric tension studies provides important additional information about vasomotor activity

    Directory of Open Access Journals (Sweden)

    Vincent M.B.

    1997-01-01

    Full Text Available Concentration-response curves of isometric tension studies on isolated blood vessels are obtained traditionally. Although parameters such as Imax, EC50 and pA2 may be readily calculated, this method does not provide information on the temporal profile of the responses or the actual nature of the reaction curves. Computerized data acquisition systems can be used to obtain average data that represent a new source of otherwise inaccessible information, since early and late responses may be observed separately in detail

  15. Complex myograph allows the examination of complex muscle contractions for the assessment of muscle force, shortening, velocity, and work in vivo

    Directory of Open Access Journals (Sweden)

    Ruhschulte Hainer

    2008-07-01

    Full Text Available Abstract Background The devices used for in vivo examination of muscle contractions assess only pure force contractions and the so-called isokinetic contractions. In isokinetic experiments, the extremity and its muscle are artificially moved with constant velocity by the measuring device, while a tetanic contraction is induced in the muscle, either by electrical stimulation or by maximal voluntary activation. With these systems, experiments cannot be performed at pre-defined, constant muscle length, single contractions cannot be evaluated individually and the separate examination of the isometric and the isotonic components of single contractions is not possible. Methods The myograph presented in our study has two newly developed technical units, i.e. a. a counterforce unit which can load the muscle with an adjustable, but constant force and b. a length-adjusting unit which allows for both the stretching and the contraction length to be infinitely adjustable independently of one another. The two units support the examination of complex types of contraction and store the counterforce and length-adjusting settings, so that these conditions may be accurately reapplied in later sessions. Results The measurement examples presented show that the muscle can be brought to every possible pre-stretching length and that single isotonic or complex isometric-isotonic contractions may be performed at every length. The applied forces act during different phases of contraction, resulting into different pre- and after-loads that can be kept constant – uninfluenced by the contraction. Maximal values for force, shortening, velocity and work may be obtained for individual muscles. This offers the possibility to obtain information on the muscle status and to monitor its changes under non-invasive measurement conditions. Conclusion With the Complex Myograph, the whole spectrum of a muscle's mechanical characteristics may be assessed.

  16. Isometric stress in cardiovascular magnetic resonance - a simple and easily replicable method of assessing cardiovascular differences not apparent at rest

    Energy Technology Data Exchange (ETDEWEB)

    Mortensen, Kristian H.; Jones, Alexander; Steeden, Jennifer A.; Taylor, Andrew M.; Muthurangu, Vivek [UCL Centre for Cardiovascular MR, UCL Institute of Cardiovascular Science, Level 6 Old Nurses Home, Cardiorespiratory Unit, Great Ormond Street Hospital for Children, London (United Kingdom)

    2016-04-15

    Isometric exercise may unmask cardiovascular disease not evident at rest, and cardiovascular magnetic resonance (CMR) imaging is proven for comprehensive resting assessment. This study devised a simple isometric exercise CMR methodology and assessed the hemodynamic response evoked by isometric exercise. A biceps isometric exercise technique was devised for CMR, and 75 healthy volunteers were assessed at rest, after 3-minute biceps exercise, and 5-minute of recovery using: (1) blood pressure (BP) and (2) CMR measured aortic flow and left ventricular function. Total peripheral resistance (SVR) and arterial compliance (TAC), cardiac output (CO), left ventricular volumes and function (ejection fraction, stroke volume, power output), blood pressure (BP), heart rate (HR), and rate pressure product were assessed at all time points. Image quality was preserved during stress. During exercise there were increases in CO (+14.9 %), HR (+17.0 %), SVR (+9.8 %), systolic BP (+22.4 %), diastolic BP (+25.4 %) and mean BP (+23.2 %). In addition, there were decreases in TAC (-22.0 %) and left ventricular ejection fraction (-6.3 %). Age and body mass index modified the evoked response, even when resting measures were similar. Isometric exercise technique evokes a significant cardiovascular response in CMR, unmasking physiological differences that are not apparent at rest. (orig.)

  17. Peripheral Vascular Resistance Impairment during Isometric Physical Exercise in Normotensive Offspring of Hypertensive Parents.

    Science.gov (United States)

    Portela, Natália; Amaral, Josária Ferraz; Mira, Pedro Augusto de Carvalho; Souza, Livia Victorino de; Martinez, Daniel Godoy; Laterza, Mateus Camaroti

    2017-07-10

    A family history of hypertension is associated with vascular and autonomic abnormalities, as well as an impaired neurohemodynamic response to exercise. To test the hypothesis that normotensive individuals with a family history of hypertension present an impaired peripheral vascular resistance response to exercise. The study included 37 normotensive volunteers of both sexes who were sedentary, eutrophic, and nonsmokers, comprising 23 with (FH+; 24 ± 3 years) and 14 without (FH-; 27 ± 5 years) a family history of hypertension. Blood pressure, heart rate (DIXTAL®), forearm blood flow (Hokanson®), and peripheral vascular resistance were simultaneously measured for 3 minutes during rest and, subsequently, for 3 minutes during an isometric exercise at 30% of maximal voluntary contraction (Jamar®). At rest, the FH+ and FH- groups present similar mean blood pressure (83 ± 7 versus 83 ± 5 mmHg, p = 0.96), heart rate (69 ± 8 bpm versus 66 ± 7 bpm, p = 0.18), forearm blood flow (3 ± 1 mL/min/100 mL versus 2.7 ± 1 mL/min/100 mL, p = 0.16), and peripheral vascular resistance (30 ± 9 units versus 34±9 units, p = 0.21), respectively. Both groups showed a significant and similar increase in mean blood pressure (∆ = 15 ± 7 mmHg versus 14 ± 7 mmHg, p = 0.86), heart rate (∆ = 12 ± 8 bpm versus 13 ± 7 bpm, p = 0.86), and forearm blood flow (∆ = 0.8 ± 1.2 mL/min/100 mL versus 1.4 ± 1.1 mL/min/100 mL, p = 0.25), respectively, during exercise. However, individuals in the FH+ group showed no reduction in peripheral vascular resistance during exercise, which was observed in the FH- group (∆ = -0.4 ± 8.6 units versus -7.2 ± 6.3 units, p = 0.03). Normotensive individuals with a family history of hypertension present an impaired peripheral vascular resistance response to exercise. O histórico familiar para hipertensão arterial está relacionado a anormalidades vasculares e autonômicas, bem como disfunções no comportamento neuro-hemodinâmico durante o exerc

  18. INDEFINITE CONTRACT REVIEW 2001

    CERN Multimedia

    Human Resources Division

    2001-01-01

    The Director-General has decided to review staff members in professional categories 2 to 5 satisfying the criteria for consideration for the award of an indefinite contract, in accordance with Article R II 1.20 of the Staff Regulations. Staff members holding a fixed-term contract which it has been decided not to renew will not be considered. The following stages are foreseen: 1. Candidates qualifying for review in accordance with Article R II 1.20 of the Staff Regulations and the Administrative Circular N° 9 will be contacted by Human Resources Division. 2. The criteria as to when staff members qualify for review are described in Administrative Circular N° 9. These include the following: staff members who are in their fourth year of service on a fixed-term contract; in addition, for staff members having three years or more of previous relevant service in the Organization on a contract of limited duration (or term-contract) and upon proposal by the division leader concerned, consideration fo...

  19. INDEFINITE CONTRACT REVIEW 2000

    CERN Multimedia

    Division des ressources humaines

    2000-01-01

    The Director-General has decided to review staff members in professional categories 2 to 5 satisfying the criteria for consideration for the award of an indefinite contract, in accordance with Article R II 1.20 of the Staff Regulations. Staff members holding a fixed-term contract which it has been decided not to renew will not be considered. The following stages are foreseen:1.\tCandidates qualifying for review in accordance with Article R II 1.20 of the Staff Regulations and the Administrative Circular N° 9 will be contacted by Human Resources Division. 2.\tThe criteria as to when staff members qualify for review are described in Administrative Circular N° 9. These include the following:staff members who are in their fourth year of service on a fixed-term contract;in addition, for staff members having three years or more of previous relevant service in the Organization on a contract of limited duration (or term-contract) and upon proposal by the division leader concerned, consid...

  20. Army Contract Writing System (ACWS)

    Science.gov (United States)

    2016-03-01

    2016 Major Automated Information System Annual Report Army Contract Writing System (ACWS) Defense Acquisition Management Information Retrieval...Program Information Program Name Army Contract Writing System (ACWS) DoD Component Army Responsible Office Program Manager References MAIS...UNCLASSIFIED 4 Program Description The Army Contract Writing System (ACWS) will be the Army’s single, next-generation, enterprise-wide contract writing

  1. Existing Sustainable Renovation Concepts

    DEFF Research Database (Denmark)

    Tommerup, Henrik M.; Vanhoutteghem, Lies; Gustavsson, Leif

    The Nordic single-family house renovation market is dominated by a craftsman based approach with individual solutions, traditional warehouses ”do-it-yourself-shops” and some actors marketing single products. To speed up the implementation of sustainable renovation of single-family houses...... there is a great need for full-service packages including consulting, contract work, follow-up, financing and operation and maintenance. There are few Nordic examples of such service models for renovation of single-family houses which entered the market recently. The success of these concepts is yet...

  2. Optimising contract design in modern food supply chains: The case of paprika sector in Central Malawi

    Directory of Open Access Journals (Sweden)

    Lana A. Repar

    2017-04-01

    Full Text Available Contract farming remains one of the most efficient tools for integrating small-scale farmers into modern food markets. However, the literature lacks evidence on best practices in designing contracts for food supply chains in developing countries. The purpose of this study is to analyse the design of an existing contract in the emerging Malawian paprika sector using a qualitative analytical approach. The study compared a contract design in Malawi’s paprika supply chain with four similar contracts from the horticultural sector in Malawi, India, Zambia and Cape Verde. This study employed a thematic qualitative analysis and developed 17 categories for analysing contracts. The findings showed that the Malawian contract contained in total eleven defined clauses. There were missing clauses that influenced the risk and power distribution between parties in the contract. The comparison of the Malawian contract with other contracts revealed that none of the analysed contracts included all clauses necessary for a sustainable and fair relationship. The study proposed improved contract design and future actions to contribute to decreasing inequalities between parties engaged in the Malawi’s paprika supply chain. The implications of the study include initiation of changes in public policies related to contract farming strategies as the findings suggest that vulnerable small-scale farmers might be left unprotected and generate low gains through supply contracts due to poorly formulated contract clauses.

  3. Amending Contracts for Choreographies

    Directory of Open Access Journals (Sweden)

    Laura Bocchi

    2011-07-01

    Full Text Available Distributed interactions can be suitably designed in terms of choreographies. Such abstractions can be thought of as global descriptions of the coordination of several distributed parties. Global assertions define contracts for choreographies by annotating multiparty session types with logical formulae to validate the content of the exchanged messages. The introduction of such constraints is a critical design issue as it may be hard to specify contracts that allow each party to be able to progress without violating the contract. In this paper, we propose three methods that automatically correct inconsistent global assertions. The methods are compared by discussing their applicability and the relationships between the amended global assertions and the original (inconsistent ones.

  4. PROCUREMENT AND CONTRACT MANAGEMENT

    CERN Multimedia

    Training & Development Group; Linda Orr-Easo; Tel. 72460; Nathalie Dumeaux; Tel. 78144

    2001-01-01

    We are pleased to announce the launch of a new training on: Procurement and Contract Management (This seminar will be run by CERN experts in French or in English) Level 1 The aim is to raise awareness of the key issues involved. Date : 8 June 2001 This level is open to everyone. Participants should register via our Web page as soon as possible. Level 2 To develop the skills needed to effectively manage contracts, from the Technical, Commercial and Legal aspects. Dates : Three days, Autumn 2001 This Level is open to those who are/will be more directly responsible for procurement and contract management. Participants should have followed Level 1. For a description of the seminar, please consult:   Level 1: http://training.web.cern.ch/Training/MANCO/P9798/9-cm_e.htm Level 2: http://training.web.cern.ch/Training/MANCO/P9798/9-cm2_e.htm

  5. Multiple causes of fatigue during shortening contractions in rat slow twitch skeletal muscle.

    Directory of Open Access Journals (Sweden)

    Kristin Halvorsen Hortemo

    Full Text Available Fatigue in muscles that shorten might have other causes than fatigue during isometric contractions, since both cross-bridge cycling and energy demand are different in the two exercise modes. While isometric contractions are extensively studied, the causes of fatigue in shortening contractions are poorly mapped. Here, we investigate fatigue mechanisms during shortening contractions in slow twitch skeletal muscle in near physiological conditions. Fatigue was induced in rat soleus muscles with maintained blood supply by in situ shortening contractions at 37°C. Muscles were stimulated repeatedly (1 s on/off at 30 Hz for 15 min against a constant load, allowing the muscle to shorten and perform work. Fatigue and subsequent recovery was examined at 20 s, 100 s and 15 min exercise. The effects of prior exercise were investigated in a second exercise bout. Fatigue developed in three distinct phases. During the first 20 s the regulatory protein Myosin Light Chain-2 (slow isoform, MLC-2s was rapidly dephosphorylated in parallel with reduced rate of force development and reduced shortening. In the second phase there was degradation of high-energy phosphates and accumulation of lactate, and these changes were related to slowing of muscle relengthening and relaxation, culminating at 100 s exercise. Slowing of relaxation was also associated with increased leak of calcium from the SR. During the third phase of exercise there was restoration of high-energy phosphates and elimination of lactate, and the slowing of relaxation disappeared, whereas dephosphorylation of MLC-2s and reduced shortening prevailed. Prior exercise improved relaxation parameters in a subsequent exercise bout, and we propose that this effect is a result of less accumulation of lactate due to more rapid onset of oxidative metabolism. The correlation between dephosphorylation of MLC-2s and reduced shortening was confirmed in various experimental settings, and we suggest MLC-2s as an

  6. The effect of short-term isometric training on core/torso stiffness.

    Science.gov (United States)

    Lee, Benjamin; McGill, Stuart

    2017-09-01

    "Core" exercise is a basic part of many physical training regimens with goals ranging from rehabilitation of spine and knee injuries to improving athletic performance. Core stiffness has been proposed to perform several functions including reducing pain by minimising joint micro-movements, and enhancing strength and speed performance. This study probes the links between a training approach and immediate but temporary changes in stiffness. Passive and active stiffness was measured on 24 participants; 12 having little to no experience in core training (inexperienced), and the other 12 being athletes experienced to core training methods; before and after a 15 min bout of isometric core exercises. Passive stiffness was assessed on a "frictionless" bending apparatus and active stiffness assessed via a quick release mechanism. Short-term isometric core training increased passive and active stiffness in most directions for both inexperienced and experienced participants, passive left lateral bend among experienced participants being the exception (P core stiffness, in this case following a single session. This may influence performance and injury resilience for a brief period.

  7. Transtibial technique versus two incisions in anterior cruciate ligament reconstruction: tunnel positioning, isometricity and functional evaluation

    Directory of Open Access Journals (Sweden)

    Ricardo Hideki Yanasse

    2016-06-01

    Full Text Available ABSTRACT OBJECTIVE: To compare the transtibial and two-incision techniques for anterior cruciate ligament (ACL reconstruction using a single band. METHODS: A prospective and randomized study was conducted in blocks. Patients underwent ACL reconstruction by means of two techniques: transtibial (group 1: 20 patients or two incisions (group 2: 20 patients. The radiographic positioning of the tunnel, inclination of the graft, graft isometricity and functional results (IKDC and Lysholm were evaluated. RESULTS: The positioning of the femoral tunnel on the anteroposterior radiograph, expressed as a mean percentage relative to the medial border of the tibial plateau, was 54.6% in group 1 and 60.8% in group 2 (p 0.05. Group 2 had better results from the pivot-shift maneuver (p < 0.05. CONCLUSION: The technique of two incisions allowed positioning of the femoral tunnel that was more lateralized and anteriorized, such that the graft was more inclined and there was a clinically better result from the pivot-shift maneuver. There was no difference in isometricity and no final functional result over the short follow-up time evaluated.

  8. New approach to isometric transformations in oblique local coordinate systems of reference

    Science.gov (United States)

    Stępień, Grzegorz; Zalas, Ewa; Ziębka, Tomasz

    2017-12-01

    The research article describes a method of isometric transformation and determining an exterior orientation of a measurement instrument. The method is based on a designation of a "virtual" translation of two relative oblique orthogonal systems to a common, known in the both systems, point. The relative angle orientation of the systems does not change as each of the systems is moved along its axis. The next step is the designation of the three rotation angles (e.g. Tait-Bryan or Euler angles), transformation of the system convoluted at the calculated angles and moving the system to the initial position where the primary coordinate system was. This way eliminates movements of the systems from the calculations and makes it possible to calculate angles of mutual rotation angles of two orthogonal systems primarily involved in the movement. The research article covers laboratory calculations for simulated data. The accuracy of the results is 10-6 m (10-3 regarding the accuracy of the input data). This confi rmed the correctness of the assumed calculation method. In the following step the method was verifi ed under fi eld conditions, where the accuracy of the method raised to 0.003 m. The proposed method enabled to make the measurements with the oblique and uncentered instrument, e.g. total station instrument set over an unknown point. This is the reason why the method was named by the authors as Total Free Station - TFS. The method may be also used for isometric transformations for photogrammetric purposes.

  9. Statutes and contracts

    DEFF Research Database (Denmark)

    Trosborg, Anna

    1995-01-01

    This paper is concerned with the language used in legal speech acts in legislative texts and contracts in the field of English Contract Law. The central objects of study are regulative functions with a particular view to establishing realization patterns of the rhetorical functions of directive...... and commissive acts. The findings show that the language of the law characteristically selects patterns of regulative distinct from, for example, the patterns typically selected in everyday conversational English. The characteristics of the language of the law can be interpreted within the adherence to legal...

  10. Do contracts help?

    DEFF Research Database (Denmark)

    Tumennasan, Norovsambuu

    Economists perceive moral hazard as an undesirable problem because it undermines efficiency. Carefully designed contracts can mitigate the moral hazard problem, but this assumes that a team is already formed. This paper demonstrates that these contracts are sometimes the reason why teams do...... transfers, then moral hazard affects stability positively in a large class of games. For example, a stable team structure exists if teams produce public goods or if the quota is two. However, these existence results no longer hold if efforts are verifiable....

  11. Analysis of maximal isometric force and EMG signal in lower limb exercise. 10.5007/1980-0037.2011v13n6p429

    Directory of Open Access Journals (Sweden)

    Cleiton Silva Correa

    2011-11-01

    Full Text Available The aim of this study was to compare maximal isometric force (MIF and the electrical activity of the vastus medialis, vastus lateralis, rectus femoris, gluteus maximus and biceps femoris long head muscles between maximal voluntary contractions (MVC performed at different joint angles, and to identify the most suitable positions to normalize the electromyography (EMG signals from each of these muscles when they are activated under dynamic conditions. Ten men ranging in age from 20 to 30 years, who were familiar with strength training exercise, were studied. MVC at different joint angles of the knee extensors and flexors (0°, 60°, 90° and hip extensors (-30°, 0°, 60° and flexors (90°, 120° were tested. The MIF values differed significantly between the 60° knee flexion and 60° and 90° knee extension positions (p0.05. Significantly higher EMG values were only observed for the rectus femoris muscle at 90° knee extension (p0.05. These results suggest that the 60° knee joint flexion position is the most suitable for assessment of knee extension and flexion MIF, and that all positions tested in this study are suitable for the assessment of hip flexion and extension.

  12. Experimental pain sensitivity in women with temporomandibular disorders and pain-free controls: the relationship to orofacial muscular contraction and cardiovascular responses.

    Science.gov (United States)

    Mohn, Christine; Vassend, Olav; Knardahl, Stein

    2008-05-01

    Chronic pain may result both from a generalized hypersensitivity to acute pain, suggestive of central sensitization processes, and dysfunction of the endogenous pain regulatory system. One purpose of this study was to compare experimental pain sensitivity at several anatomic sites in temporomandibular disorder (TMD) patients and pain-free controls during baseline and after standardized mechanical load of the orofacial region. A second purpose was to compare the pain-modulating effects of cardiovascular responses in TMD patients and pain-free controls. Experimental pain was induced by electrocutaneous stimulation of the dorsal left hand and pressure algometry at the right masseter muscle and the sternum. The pain sensitivity of the orofacial region was manipulated by isometric contraction of the masseter muscles. Elevations of mean arterial pressure and heart rate were induced by a simulated job interview. At baseline, the TMD patients exhibited a significantly higher electrocutaneous pain threshold. Relative to the healthy controls, the TMD patients reported increased electrocutaneous and pressure pain sensitivity after isometric contraction of the orofacial region. In addition, there were correlations between mean arterial pressure and pain sensitivity in the TMD group only. Significant increases in generalized pain sensitivity occurred in the TMD group, but not in the control group, after isometric contraction of the orofacial muscles, suggestive of a central sensitization process in TMD. Moreover, only in the TMD group there were significant associations between cardiovascular responsesand pain sensitivity, challenging previous assumptions of this relationship occurring mainly in pain-free individuals.

  13. CONCEPTUAL DELIMITATIONS ON SUSTAINABLE DEVELOPMENT

    Directory of Open Access Journals (Sweden)

    Ienciu Ionel-Alin

    2013-07-01

    Full Text Available Sustainable development is a model for resource use meant to satisfy human needs, without polluting the environment, so that these needs can be satisfied not only in the present, but in the future as well. It is a concept of nowadays with no generally accepted definition, placing environment first and foremost, aiming at implementing the environmental policies in all structures and at all economic levels. Within the present study we have aimed at creating a conceptual delimitation on sustainable development, sustainability and socialresponsibility, concepts of present interest, that tend to become a mystery for the academic community and practitioners by their variety and complexity of approaches. During our scientific endeavor we believe that social responsibility is the foundation of sustainable development. Sustainable development is a concept used especially at macro-economic level, while social responsibility is used at entity level and incorporates the economic, environmental and social dimension, which has a voluntary character and tries to respond to the information needs of the society and other stakeholders. Sustainability at the entity\\'s level is the goal or final objective of sustainable development – satisfaction of present needs without compromising the possibility for future generations to satisfy their own needs, while social responsibility is an intermediate phase of sustainability wherein entities try to balance the economic, social and environmental dimension. Thus, we can state we include ourselves within social corporatism, slightly close to social institutionalism, which is characteristic to developed countries, giving a particular importance to social contract and relations between entity and society. We believe that in Romania, a POSDRU funded project should be regarded as a legal person with social values, which must be based on sustainable development and to promote, besides legal liability of automatically deriving

  14. Relationships between Isometric Muscle Strength, Gait Parameters, and Gross Motor Function Measure in Patients with Cerebral Palsy.

    Science.gov (United States)

    Shin, Hyung Ik; Sung, Ki Hyuk; Chung, Chin Youb; Lee, Kyoung Min; Lee, Seung Yeol; Lee, In Hyeok; Park, Moon Seok

    2016-01-01

    This study investigated the correlation between isometric muscle strength, gross motor function, and gait parameters in patients with spastic cerebral palsy and to find which muscle groups play an important role for gait pattern in a flexed knee gait. Twenty-four ambulatory patients (mean age, 10.0 years) with spastic cerebral palsy who were scheduled for single event multilevel surgery, including distal hamstring lengthening, were included. Preoperatively, peak isometric muscle strength was measured for the hip flexor, hip extensor, knee flexor, and knee extensor muscle groups using a handheld dynamometer, and three-dimensional (3D) gait analysis and gross motor function measure (GMFM) scoring were also performed. Correlations between peak isometric strength and GMFM, gait kinematics, and gait kinetics were analyzed. Peak isometric muscle strength of all muscle groups was not related to the GMFM score and the gross motor function classification system level. Peak isometric strength of the hip extensor and knee extensor was significantly correlated with the mean pelvic tilt (r=-0.588, p=0.003 and r=-0.436, p=0.033) and maximum pelvic obliquity (r=-0.450, p=0.031 and r=-0.419, p=0.041). There were significant correlations between peak isometric strength of the knee extensor and peak knee extensor moment in early stance (r=0.467, p=0.021) and in terminal stance (r=0.416, p=0.043). There is no correlation between muscle strength and gross motor function. However, this study showed that muscle strength, especially of the extensor muscle group of the hip and knee joints, might play a critical role in gait by stabilizing pelvic motion and decreasing energy consumption in a flexed knee gait.

  15. Acute and Chronic Effects of Isometric Handgrip Exercise on Cardiovascular Variables in Hypertensive Patients: A Systematic Review

    Directory of Open Access Journals (Sweden)

    Breno Q. Farah

    2017-08-01

    Full Text Available The aim of this study was to describe, through a systematic review, the acute and chronic effects of isometric handgrip exercise on cardiovascular variables in hypertensive individuals. In this systematic review, we included studies that analyzed whether a single bout or a program with isometric exercises affect cardiovascular variables in hypertensive adults. The electronic database PubMed/Medline was searched for relevant studies published until May 2017. Of the 2927 studies initially identified, 2916 were excluded based on title and abstract and five on the basis of full-text assessment, leaving six studies remaining. In addition, one further study cited in the references of the included articles was included in this review, totaling seven studies included (five studies on the chronic effects of isometric handgrip exercise on cardiovascular parameters. None of the acute studies observed post-exercise hypotension. The majority of the chronic studies found decreases in office blood pressure after isometric handgrip training, with training ranging from 6 to 10 weeks, while heart rate variability parameters were improved in one study and did not change in another. Reduction in oxidative stress was observed; however, this variable was only analyzed in one study. In hypertensives, acute responses to isometric handgrip exercise are very limited due to the small number of studies, therefore more research is required. Furthermore, chronic isometric handgrip training reduces blood pressure; however, there is still a gap in the knowledge on the effects of this modality of exercise on other cardiovascular variables—such as endothelial function, oxidative stress, and cardiac autonomic modulation—which should be addressed in future studies.

  16. INFLUENCE OF TYPE OF MUSCLE CONTRACTION AND GENDER ON POSTACTIVATION POTENTIATION OF UPPER AND LOWER LIMB EXPLOSIVE PERFORMANCE IN ELITE FENCERS

    Directory of Open Access Journals (Sweden)

    Charilaos Tsolakis

    2011-09-01

    Full Text Available The purpose of this study was to evaluate the postactivation potentiation (PAP effect of isometric and plyometric contractions on explosive performance of the upper and the lower limbs in male and female elite athletes. Thirteen male and ten female international level fencers performed four protocols of either isometric (3 sets of 3 sec or plyometric (3 sets of 5 repetitions bench and leg press, in a within subject randomized design. Before and immediately after the PAP treatment and following 4, 8, 12 min, explosive performance was measured by performing a countermovement jump (CMJ or a bench press throw. Statistical analysis revealed significant time effect for peak leg power during the CMJ (p < 0.001 only for men, with values after the isometric PAP treatment being lower than baseline at the 8 and 12 min time points (by 7.5% (CI95% = 3.9-11.2% and 8.7% (CI95% = 6.0-11.5%, respectively, while after the plyometric PAP treatment peak leg power remained unchanged. A significant negative correlation was found between leg strength (as expressed by 1-RM leg press performance and the change in peak leg power between baseline and after 12 min of recovery only in male fencers (r = -0.55, p < 0.05, suggesting that stronger individuals may show a greater decrease in peak leg power. Based on the above results we conclude that lower body power performance in international level fencers may be negatively affected after isometric contractions and thus they should be advised against using isometric exercises to induce PAP with the protocol prescribed in the present study. Furthermore, gender and strength level must be considered in the practical application of PAP

  17. Sustainable Disruptions

    DEFF Research Database (Denmark)

    Friis, Silje Alberthe Kamille; Kjær, Lykke Bloch

    2016-01-01

    Since 2012 the Sustainable Disruptions (SD) project at the Laboratory for Sustainability at Design School Kolding (DK) has developed and tested a set of design thinking tools, specifically targeting the barriers to economically, socially, and environmentally sustainable business development....... The tools have been applied in practice in collaboration with 11 small and medium sized companies (SMEs). The study investigates these approaches to further understand how design thinking can contribute to sustainable transition in a business context. The study and the findings are relevant to organizations...... invested in the issue of sustainable business development, in particular the leaders and employees of SMEs, but also to design education seeking new ways to consciously handle and teach the complexity inherent in sustainable transformation. Findings indicate that the SD design thinking approach contributes...

  18. Acute effects of maximal isometric muscle action of the elbow extensors on contralateral dynamic task of the elbow flexors: a pilot study

    Directory of Open Access Journals (Sweden)

    Cauê V La Scala Teixeira

    2017-12-01

    Full Text Available ABSTRACT Aim the aim was to investigate the influence of a maximal isometric muscle action of the elbow extensors on the contralateral dynamic task of the elbow flexors. Methods Seventeen recreationally trained men (23.3 ± 4.9 yrs, BMI: 24.8 ± 2.2 Kg/m² underwent two randomized different testing sessions separated by one week. In the control session (CON all subjects performed a maximum number of repetitions test (RMs at 75%1RM using the right elbow flexors. The experimental session (EXP was similar to the CON; however, all subjects were instructed to perform RMs at 75%1RM by using the right elbow flexors and maintaining the maximal voluntary contraction of the left elbow extensors during the test. RMs, rating of perceived exertion (RPE, and training volume (TV were measured and compared between sessions. Results The EXP showed a significant 10.4% increase on the RMs (13.8 vs. 12.5, p < 0.001, d = 0.44 and 12.1% increase in TV (238.0 vs. 212.4 kg, p < 0.001, d = 0.43 than CON. No differences were observed for RPE between sessions. Conclusion The maximum voluntary contraction of the left elbow extensors increased the RMs of the contralateral elbow flexors, reflecting a higher TV, and no differences in the RPE. Our results suggest that the investigated method may be a viable and practical alternative to increase the acute strength performance of elbow flexors when using submaximal loads.

  19. Computational sustainability

    CERN Document Server

    Kersting, Kristian; Morik, Katharina

    2016-01-01

    The book at hand gives an overview of the state of the art research in Computational Sustainability as well as case studies of different application scenarios. This covers topics such as renewable energy supply, energy storage and e-mobility, efficiency in data centers and networks, sustainable food and water supply, sustainable health, industrial production and quality, etc. The book describes computational methods and possible application scenarios.

  20. 3 CFR - Government Contracting

    Science.gov (United States)

    2010-01-01

    ... contract oversight could reduce such sums significantly. Government outsourcing for services also raises... commercial services used by the Government, such as transportation, food, and maintenance. Office of... governmental functions. Agencies and departments must operate under clear rules prescribing when outsourcing is...

  1. Culture and Contract Laws

    DEFF Research Database (Denmark)

    Lando, Ole

    2007-01-01

    In the article it is argued that the wish to preserve the cultural values of national law should not prevent the EU from preparing a Code or an Optional Instrument. The no-code countries on the British Isles and in Scandinavia are the most ardent opponents to the idea of unifying European Contract...

  2. Muscle contraction and force

    DEFF Research Database (Denmark)

    Brüggemann, Dagmar Adeline; Risbo, Jens; Pierzynowski, Stefan G.

    2008-01-01

    Muscle contraction studies often focus solely on myofibres and the proteins known to be involved in the processes of sarcomere shortening and cross-bridge cycling, but skeletal muscle also comprises a very elaborate ancillary network of capillaries, which not only play a vital role in terms of nu...... contributor to force transfer within muscular tissue....

  3. Joint Contingency Contracting

    Science.gov (United States)

    2005-06-01

    parents, Ellsworth K. Johnson, Jr. and Helen E. Johnson, for their lifelong love and support. Mom, thanks for always being there when I needed you...Hurricanes Charley , Jeanne and Andrew are examples of domestic disaster emergency relief. 2. Phases of Contingency Contracting Contingency

  4. Construction Contract Provisions Analysis.

    Science.gov (United States)

    1982-09-01

    tractor, and localized variations characteristic of the subsurface materials of the region are anticipated and if encountered, such variations will...34Contract drawings, maps, and specification. On larger projects, provide one set of sepias , both large scale and reduced, in addition to the contact

  5. Cognition and Incomplete Contracts

    OpenAIRE

    Jean Tirole

    2009-01-01

    Thinking about contingencies, designing covenants, and seeing through their implications is costly. Parties to a contract accordingly use heuristics and leave it incomplete. The paper develops a model of limited cognition and examines its consequences for contractual design. (JEL D23, D82, D86, L22)

  6. Sustainable transformation

    DEFF Research Database (Denmark)

    Andersen, Nicolai Bo

    This paper is about sustainable transformation with a particular focus on listed buildings. It is based on the notion that sustainability is not just a question of energy conditions, but also about the building being robust. Robust architecture means that the building can be maintained and rebuilt...... theoretical lenses. It is proposed that three parameters concerning the ꞌtransformabilityꞌ of the building can contribute to a more nuanced understanding of sustainable transformation: technical aspects, programmatic requirements and narrative value. It is proposed that the concept of ꞌsustainable...

  7. Collaborative Contracting in Projects

    NARCIS (Netherlands)

    Suprapto, M.

    2016-01-01

    Project practitioners have increasingly recognized the importance of collaborative relationships to ensure successful executions of projects. However, the ability to sustain and consistenly drive real collaborative attitudes and behavior for achieving the desired outcomes remains of enduring

  8. Influence of type of muscle contraction, gender, and lifting experience on postactivation potentiation performance.

    Science.gov (United States)

    Rixon, Kendall P; Lamont, Hugh S; Bemben, Michael G

    2007-05-01

    Postactivation potentiation (PAP) or enhanced contractile capabilities may be influenced by a number of factors. This study examined the influence of type of muscle contraction (isometric vs. dynamic), gender, and previous weightlifting experience on PAP as demonstrated by changes in jump height and power output. Thirty young men (n = 15) and women (n = 15), classified as either having previous weightlifting experience (n = 20) or not (n = 10), performed 3 different sets of countermovement jumps, with the first set used to determine baseline measures of jump height and power. The second set was performed after a maximal isometric squat protocol (maximal voluntary contraction [MVC]-PAP) to induce PAP, and the third set of jumps was performed after a maximal dynamic squat (DS) protocol (DS-PAP). A 3-way repeated measures analysis of variance determined that jump height after the MVC-PAP protocol was significantly higher than both the pretest and DS-PAP values, that men performed significantly better than women, and that the experienced lifters responded more favorably than the inexperienced lifters. Jump power was also significantly greater for the MVC-PAP condition compared with the other 2 conditions, and DS-PAP power also improved when compared with the pretest values, with men performing significantly better than women. All results remained consistent after accounting for height and weight differences (body mass index) between the groups. In conclusion, the isometric condition (MVC-PAP) evoked a greater muscle postactivation potentiation than the dynamic condition (DS-PAP), and postactivation was enhanced by previous weightlifting experience. The practical manipulation of MVC by pushing, squatting, or both against fixed objects, such as walls and low ceilings, could be a very simple and cost-effective way to arouse a state of PAP before sports performance that requires high force and power outputs.

  9. Practical concepts in Contract Law

    OpenAIRE

    Ehsan, zarrokh

    2008-01-01

    A contract is a legally binding exchange of promises or agreement between parties that the law will enforce. Contract law is based on the Latin phrase pacta sunt servanda (literally, promises must be kept) [1]. Breach of a contract is recognised by the law and remedies can be provided. Almost everyone makes contracts everyday. Sometimes written contracts are required, e.g., when buying a house [2]. However the vast majority of contracts can be and are made orally, like buying a law text book,...

  10. Employee contract issues for dermatologists.

    Science.gov (United States)

    Brown, Christopher E; Indest, George F

    2013-12-01

    Employees and employers routinely face negotiating and preparing physician employment contracts. It is important for both sides to know and understand the basic information on what a comprehensive employment contract for a dermatologist should contain. There are various employment contract provisions from both the employee's perspective and the employer's perspective that must be considered when preparing physician employment contracts. This article provides basic advice and recommendations on requirements that should be included in such contracts. It suggests legal pitfalls that can be avoided through various contract clauses.

  11. Relations Between Lower Body Isometric Muscle Force Characteristics and Start Performance in Elite Male Sprint Swimmers

    Directory of Open Access Journals (Sweden)

    Igor Beretić

    2013-12-01

    Full Text Available The aim of the present study was twofold. The first aim was to examine the influence of absolute and relative lower body muscle force on kinematic component which determine the start performance. The second aim was to create multiregressional model which could use as a tool for swimming coaches with the purpose to start performance control and improvement. Twenty seven high-level trained male competitive swimmers all members of the Serbian National Youth and Senior Swimming Team (Age = 21.1 ± 4.3 yrs., Height = 1. 89 ± 0.10 m, Weight = 81.6 ± 8.4 kg, 50m freestyle - long course = 24.36 ± 0.86 s performed two trials of standing leg extensors isometric muscle force testing and three swimming start trials corresponding to 10m distance. The average start time significantly correlated with variables of leg extensors maximum voluntary force (Fmax, r = -0.559, p = 0.002, leg extensors relative muscle voluntary force (Frel, r = -0.727, p < 0.001, leg extensors specific rate of force development (RFD50%, r = -0.338, p = 0.047 and leg extensors relative value of specific rate of force development (RFD50%rel, r = -0.402, p = 0.040. Regression equation for t10m prediction was defined by following variables: maximum voluntary isometric force of leg extensors muscles at absolute and relative level (Fmax and Frel, as well as a specific rate of force development of the same muscle groups (RFD50% and RFD50%rel at absolute and relative level too with 74.4% of explained variance. Contractile abilities indicators of the leg extensors muscles included consideration: Fmax, RFD50%, Frel and RFD50%rel showed significant correlation with swimming start times on 10m. Additionally, the results suggest that swimmers, who possess greater isometric maximum force and specific rate of force development at absolute and relative levels, tend to be able to swim faster on initial 10m swim start perforamnce.

  12. Regulation of matrix contraction in chronic venous disease.

    Science.gov (United States)

    Pappas, P J; Lal, B K; Ohara, N; Saito, S; Zapiach, L; Durán, W N

    2009-10-01

    The role of TGF-beta(1) in venous ulcer healing and the signalling cascades regulating dermal fibroblast function are poorly understood. To elucidate these processes, we hypothesized that TGF-beta(1) facilitates wound healing by increasing chronic venous insufficiency (CVI) induced matrix contraction via intracellular cross-talk between TGF-beta(1) and the ERK-1/2 MAP kinase signalling cascades. Fibroblasts isolated from calf biopsies (LC) of patients with different severity of CVI (CEAP, Clinical Etiological Anatomical Pathological classes) were seeded into 200 microl collagen gels under isometric conditions. Fibroblasts from neonatal foreskins (HS68), non-CVI patients (NC), and the ipsilateral normal thigh of each CVI patient (LT) served as controls. Thirteen patients with CVI (class 2, n=5; class 4, n=5; class 6, n=3) and 2 non-CVI controls (NC, n=2) were included in the study. All experimental conditions were determined by dose-response and time-course experiments. Gels were cultured with/without 0.1 ng/ml TGF-beta(1) and with/without 50 microM PD98059 (MEK and downstream-MAPK inhibitor). Additional patient fibroblasts were transfected with constitutively active Ras (pCMV-Ras) or an empty vector (pCMV-beta) with/without 0.1 ng/ml TGF-beta(1) and with/without 50 microm PD98059. The collagen gels were released after 4 days and the percent contraction was determined by area measurements using image analysis. Differences in alpha-smooth muscle actin (alpha-SMA) and ERK-1/2 MAPK (phosphorylated and total) protein levels were analyzed with western blotting. Gels seeded with CVI fibroblasts contracted more than HS68, NC and LT fibroblasts. Inhibition of MAPK and/or stimulation with TGF-beta(1) increased the contraction of LC gels compared to unstimulated controls. Agonist induced gel contraction correlated with CVI disease severity. alpha-SMA protein expression in LC fibroblasts increased with MAPK inhibition with/without TGF-beta(1) stimulation, and correlated with

  13. Sustainable Transportation

    DEFF Research Database (Denmark)

    Hall, Ralph P.; Gudmundsson, Henrik; Marsden, Greg

    2014-01-01

    that relate to the construction and maintenance of transportation infrastructure and the operation or use of the different transportation modes. The concept of sustainable transportation emerged in response to these concerns as part of the broader notion of sustainable development. Given the transportation...

  14. Sustaining dairy

    NARCIS (Netherlands)

    Villarreal Herrera, Georgina

    2017-01-01

    Dairy in Europe has undergone many changes in the last few years—the abolition of milk production quotas being a fundamental one. This study explores these changes in relation to the sustained social and environmental viability of the sector and how dairy processors' sustainability

  15. Sustainable Universities

    DEFF Research Database (Denmark)

    Grindsted, Thomas Skou

    2011-01-01

    . Declarations tend to have impact on three trends. Firstly, there is emerging international consensus on the university’s role and function in relation to sustainable development; secondly, the emergence of national legislation, and thirdly, an emerging international competition to be leader in sustainable...... campus performance....

  16. Sustainable Transition

    DEFF Research Database (Denmark)

    Hansen, Ole Erik; Søndergård, Bent

    2014-01-01

    of agendas/vision, technologies, actors and institutions in the emergent design of an urban mobility system based on an electric car sharing system. Why. Designing for sustainability is a fundamental challenge for future design practices; designers have to obtain an ability to contribute to sustainable...

  17. Sustainable Learning

    Science.gov (United States)

    Cadwell, Louise; Dillon, Robert

    2011-01-01

    Green schools have moved into a new era that focuses on building a culture of sustainability in every aspect of learning in schools. In the early stages of sustainability education, the focus was on recycling and turning off the lights. Now, students and adults together are moving into the areas of advocacy and action that are based on a deep…

  18. Latent myofascial trigger points are associated with an increased antagonistic muscle activity during agonist muscle contraction.

    Science.gov (United States)

    Ibarra, José Miota; Ge, Hong-You; Wang, Chao; Martínez Vizcaíno, Vicente; Graven-Nielsen, Thomas; Arendt-Nielsen, Lars

    2011-12-01

    The aim of this study was to evaluate motor unit activity from a latent myofascial trigger point (MTP) in an antagonist muscle during isometric agonist muscle contraction. Intramuscular activity was recorded with an intramuscular electromyographic (EMG) needle inserted into a latent MTP or a non-MTP in the posterior deltoid muscle at rest and during isometric shoulder flexion performed at 25% of maximum voluntary contraction in 14 healthy subjects. Surface EMGs were recorded from the anterior and posterior deltoid muscles. Maximal pain intensity and referred pain induced by EMG needle insertion were recorded on a visual analogue scale. The results showed that higher local pain was observed following needle insertion into latent MTPs (4.64 ± .48 cm) than non-MTPs (2.35 ± .43 cm, P muscle was significantly higher at rest and during shoulder flexion at latent MTPs than non-MTPs (P muscle relaxation following exercise, disordered fine movement control, and unbalanced muscle activation. Elimination of latent MTPs and/or prevention of latent MTPs from becoming active may improve motor functions. Copyright © 2011 American Pain Society. Published by Elsevier Inc. All rights reserved.

  19. Navy construction contract regulations vs. the Board of Contract Appeals.

    OpenAIRE

    McMurray, Thomas David

    1987-01-01

    Approved for public release; distribution is unlimited This thesis addresses construction contracting in the United States Navy. It compares the Government construction contract regulations with decisions by the Boards of Contract Appeals. Nine topics are researched including submittal reviews, profit, change orders and changes, notices to proceed, acceleration, beneficial occupancy, weather delays, and extended overhead. The Boards' decisions are used to understand...

  20. Isometric abdominal wall muscle strength assessment in individuals with incisional hernia: a prospective reliability study

    DEFF Research Database (Denmark)

    Jensen, K. K.; Kjær, Michael; Jorgensen, L. N.

    2016-01-01

    Purpose To determine the reliability of measurements obtained by the Good Strength dynamometer, determining isometric abdominal wall and back muscle strength in patients with ventral incisional hernia (VIH) and healthy volunteers with an intact abdominal wall. Methods Ten patients with VIH and ten...... and extension showed excellent test–retest reliability for both patients with VIH (ICC 0.91 and 0.99) and healthy controls (ICC 0.97 and 0.96). Bland and Altman plots showed that no systematic bias was present for neither truncal flexion nor extension when assessing reliability. For patients with VIH...... and IPAQ was found. Conclusions The Good Strength dynamometer provided a reliable, low-cost measure of truncal flexion and extension in patients with VIH....

  1. Twenty weeks of isometric handgrip home training to lower blood pressure in hypertensive older adults

    DEFF Research Database (Denmark)

    Jørgensen, Martin Grønbech; Ryg, Jesper; Danielsen, Mathias Brix

    2018-01-01

    lower blood pressure levels beyond the 10-week mark. Recently, we developed a novel method for monitoring handgrip intensity using a standard Nintendo Wii Board (Wii). The primary aim of this study is to explore the effects of a 20-week IHG home training facilitated by a Wii in hypertensive older adults......BACKGROUND: Hypertension markedly increases the risk of cardiovascular diseases and overall mortality. Lifestyle modifications, such as increased levels of physical activity, are recommended as the first line of anti-hypertensive treatment. A recent systematic review showed that isometric handgrip...... (50 + years of age) on lowering SBP compared to usual care. Secondary aims are to explore if/when a leveling-off effect on SBP will occur during the 20-week intervention period in the training group and to explore adherence and potential harms related to the IHG home training. METHODS/DESIGN: Based...

  2. CGVIEW: A program to generate isometric and perspective views of combinatorial geometries

    Energy Technology Data Exchange (ETDEWEB)

    Burns, T.J.

    1992-07-01

    The prototype of a graphical debugger for combinatorial geometry (CG) is described. The prototype debugger consists of two parts: a FORTRAN-based ``view`` generator and a Microsoft Windows application for displaying the geometry. This document describes the code CGVIEW, which comprises the first part of the system. User-specified options permit the selection of an arbitrary viewpoint in space and the generation of either an isometric or perspective view. Additionally, any combination of zones, materials, or regions can be flagged as invisible to facilitate the inspection of internal details of the geometry. In the same manner, an arbitrary body can be cut away from the geometry to facilitate inspection and debugging. Examples illustrating the various options are described.

  3. CGVIEW: A program to generate isometric and perspective views of combinatorial geometries

    Energy Technology Data Exchange (ETDEWEB)

    Burns, T.J.

    1992-07-01

    The prototype of a graphical debugger for combinatorial geometry (CG) is described. The prototype debugger consists of two parts: a FORTRAN-based view'' generator and a Microsoft Windows application for displaying the geometry. This document describes the code CGVIEW, which comprises the first part of the system. User-specified options permit the selection of an arbitrary viewpoint in space and the generation of either an isometric or perspective view. Additionally, any combination of zones, materials, or regions can be flagged as invisible to facilitate the inspection of internal details of the geometry. In the same manner, an arbitrary body can be cut away from the geometry to facilitate inspection and debugging. Examples illustrating the various options are described.

  4. Error Propagation in Isometric Log-ratio Coordinates for Compositional Data: Theoretical and Practical Considerations.

    Science.gov (United States)

    Mert, Mehmet Can; Filzmoser, Peter; Hron, Karel

    2016-01-01

    Compositional data, as they typically appear in geochemistry in terms of concentrations of chemical elements in soil samples, need to be expressed in log-ratio coordinates before applying the traditional statistical tools if the relative structure of the data is of primary interest. There are different possibilities for this purpose, like centered log-ratio coefficients, or isometric log-ratio coordinates. In both the approaches, geometric means of the compositional parts are involved, and it is unclear how measurement errors or detection limit problems affect their presentation in coordinates. This problem is investigated theoretically by making use of the theory of error propagation. Due to certain limitations of this approach, the effect of error propagation is also studied by means of simulations. This allows to provide recommendations for practitioners on the amount of error and on the expected distortion of the results, depending on the purpose of the analysis.

  5. Contracts for dispatchable power

    Energy Technology Data Exchange (ETDEWEB)

    Kahn, E.P.; Stoft, S.; Marnay, C.; Berman, D.

    1990-10-01

    Competitive bidding for electric power is maturing. Increasing numbers of utilities are soliciting proposals from private suppliers. The amount of capacity being sought is increasing, and potential suppliers appear to be abundant. Analysis of these developments still remains limited. Evidence on the behavior of this market is scarce and sketchy. The underlying economic principles that are shaping the market have not clearly been articulated. In this report we examine the economics of competitive bidding both empirically and analytically. Previous study of this market has focused on the evaluation criteria specified in Requests for Proposals (RFPs), and highly aggregated summary statistics on participation and results. We continue the examination of RFPs, but also survey the details of long term contracts that have emerged from competitive bidding. Contracts provide a new level of specific detail that has not been previously available. 68 refs., 13 figs., 25 tabs.

  6. Russian Contract Procurement Document

    Energy Technology Data Exchange (ETDEWEB)

    Tobin, J G

    2010-03-29

    This contract supports the enhancement of physical protection or nuclear material control and accounting systems at institutes or enterprises of the newly independent states under the material protection control and accounting (MPC&A) program. The contract is entered into pursuant to the MPC&A Program, a gratuitous technical assistance program, in accordance with the bilateral Agreements between the Russian Federation and the United States of America concerning the Safe and Secure Transportation, Storage and Destruction of Weapons and the Prevention of Weapons Proliferation of June 1992, as extended and amended by Protocol signed of June 1999, Agreement between the Government of the Russian Federation regarding Cooperation in the Area of Nuclear Materials Physical Protection, Control and Accounting of October 1999 and the Russian Federation law of May 1999 on the taxation exemption of gratuitous technical assistance with Russian Federation under registration No.DOE001000.

  7. An examination of lower limb asymmetry in ankle isometric force control.

    Science.gov (United States)

    Yen, Sheng-Che; Olsavsky, Laura C; Cloonan, Caitlin M; Llanos, Amelia R; Dwyer, Kara J; Nabian, Mohsen; Farjadian, Amir Bahador

    2017-11-11

    While asymmetries have been observed between the dominant and non-dominant legs, it is unclear whether they have different abilities in isometric force control (IFC). The purpose of this study was to compare ankle IFC between the legs. IFC is important for stabilization rather than object manipulation, and people typically use their non-dominant leg for stabilization tasks. Additionally, studies suggested that a limb can better acquire a motor task when the control mechanism of the task is related to what the limb is specialized for. We hypothesized that the non-dominant leg would better (1) control ankle IFC with speed and accuracy, and (2) acquire an ankle IFC skill through direct learning and transfer of learning. Two participant groups practiced an IFC task using either their dominant or non-dominant ankle. In a virtual environment, subjects moved a cursor to hit 24 targets in a maze by adjusting the direction and magnitude of ankle isometric force with speed (measured by the time required to hit all targets or movement time) and accuracy (number of collisions to a maze wall). Both groups demonstrated similar movement time and accuracy between the dominant and non-dominant limbs before practicing the task. After practice, both groups showed improvement in both variables on both the practiced and non-practiced sides (p < .01), but no between-group difference was detected in the degree of improvement on each side. The ability to control and acquire the IFC skill was similar between the legs, which did not support the brain is lateralized for ankle IFC. Copyright © 2017 Elsevier B.V. All rights reserved.

  8. Preliminary Results Towards Contract Monitorability

    Directory of Open Access Journals (Sweden)

    Annalizz Vella

    2016-05-01

    Full Text Available This paper discusses preliminary investigations on the monitorability of contracts for web service descriptions. There are settings where servers do not guarantee statically whether they satisfy some specified contract, which forces the client (i.e., the entity interacting with the server to perform dynamic checks. This scenario may be viewed as an instance of Runtime Verification, where a pertinent question is whether contracts can be monitored for adequately at runtime, otherwise stated as the monitorability of contracts. We consider a simple language of finitary contracts describing both clients and servers, and develop a formal framework that describes server contract monitoring. We define monitor properties that potentially contribute towards a comprehensive notion of contract monitorability and show that our simple contract language satisfies these properties.

  9. Utility Energy Services Contracts Guide

    Energy Technology Data Exchange (ETDEWEB)

    None

    2013-09-01

    The UESC Guide is a compilation of samples and templates developed as a resource to help contracting officers implement task orders for UESCs under existing U.S. General Services Administration areawide contracts.

  10. Reliability of Isometric Lower-Extremity Muscle Strength Measurements in Children With Cerebral Palsy: Implications for Measurement Design

    NARCIS (Netherlands)

    Willemse, A.A.M.; Brehm, M.A.; Scholtes, V.A.B.; Jansen, L.; Woudenberg-Vos, H.; Dallmeijer, A.J.

    2013-01-01

    Background. Children with cerebral palsy (CP) typically show muscle weakness of the lower extremities, which can be measured with the use of handheld dynamometry (HHD). Objective. The purposes of this study were: (1) to determine test-retest reliability and measurement error of isometric

  11. Reliability of isometric lower-extremity muscle strength measurements in children with cerebral palsy: implications for measurement design

    NARCIS (Netherlands)

    Willemse, Lydia; Brehm, Merel A.; Scholtes, Vanessa A.; Jansen, Laura; Woudenberg-Vos, Hester; Dallmeijer, Annet J.

    2013-01-01

    Children with cerebral palsy (CP) typically show muscle weakness of the lower extremities, which can be measured with the use of handheld dynamometry (HHD). The purposes of this study were: (1) to determine test-retest reliability and measurement error of isometric lower-extremity strength

  12. Validity and reliability of a low-cost digital dynamometer for measuring isometric strength of lower limb.

    Science.gov (United States)

    Romero-Franco, Natalia; Jiménez-Reyes, Pedro; Montaño-Munuera, Juan A

    2017-11-01

    Lower limb isometric strength is a key parameter to monitor the training process or recognise muscle weakness and injury risk. However, valid and reliable methods to evaluate it often require high-cost tools. The aim of this study was to analyse the concurrent validity and reliability of a low-cost digital dynamometer for measuring isometric strength in lower limb. Eleven physically active and healthy participants performed maximal isometric strength for: flexion and extension of ankle, flexion and extension of knee, flexion, extension, adduction, abduction, internal and external rotation of hip. Data obtained by the digital dynamometer were compared with the isokinetic dynamometer to examine its concurrent validity. Data obtained by the digital dynamometer from 2 different evaluators and 2 different sessions were compared to examine its inter-rater and intra-rater reliability. Intra-class correlation (ICC) for validity was excellent in every movement (ICC > 0.9). Intra and inter-tester reliability was excellent for all the movements assessed (ICC > 0.75). The low-cost digital dynamometer demonstrated strong concurrent validity and excellent intra and inter-tester reliability for assessing isometric strength in the main lower limb movements.

  13. Muscle Activation Differs between Three Different Knee Joint-Angle Positions during a Maximal Isometric Back Squat Exercise

    Directory of Open Access Journals (Sweden)

    Paulo Henrique Marchetti

    2016-01-01

    Full Text Available The purpose of this study was to compare muscle activation of the lower limb muscles when performing a maximal isometric back squat exercise over three different positions. Fifteen young, healthy, resistance-trained men performed an isometric back squat at three knee joint angles (20°, 90°, and 140° in a randomized, counterbalanced fashion. Surface electromyography was used to measure muscle activation of the vastus lateralis (VL, vastus medialis (VM, rectus femoris (RF, biceps femoris (BF, semitendinosus (ST, and gluteus maximus (GM. In general, muscle activity was the highest at 90° for the three quadriceps muscles, yet differences in muscle activation between knee angles were muscle specific. Activity of the GM was significantly greater at 20° and 90° compared to 140°. The BF and ST displayed similar activation at all joint angles. In conclusion, knee position alters muscles activation of the quadriceps and gluteus maximus muscles. An isometric back squat at 90° generates the highest overall muscle activation, yet an isometric back squat at 140° generates the lowest overall muscle activation of the VL and GM only.

  14. Comparison of the Effect of Massage Therapy and Isometric Exercises on Primary Dysmenorrhea: A Randomized Controlled Clinical Trial.

    Science.gov (United States)

    Azima, Sara; Bakhshayesh, Hajar Rajaei; Kaviani, Maasumeh; Abbasnia, Keramatallah; Sayadi, Mehrab

    2015-12-01

    Dysmenorrhea is the most common cyclic pelvic pain, and it affects the quality of life of many women. We sought to compare the effects of massage and isometric exercises on primary dysmenorrhea. We conducted a randomized controlled trial at the dormitories of Shiraz University among 102 students with primary dysmenorrheal. The student groups were randomly divided into massage, isometric exercises, and control groups. The first group received 2 consecutive cycles of effleurage massage with lavender oil. The second group had 8 weeks of isometric exercises. No intervention was performed for the control group. Pain intensity was measured and recorded by using a visual analog scale. In addition, the duration of pain was measured in hours, and Spielberger's questionnaire was used to measure the anxiety level. Pain intensity had significantly reduced in the massage and exercises groups; the reduction was more significant in the massage group (P massage group after the third cycle (P = .017). Based on the present findings, it seems that massage therapy and isometric exercises were effective in reducing some symptoms of dysmenorrhea. Copyright © 2015 North American Society for Pediatric and Adolescent Gynecology. Published by Elsevier Inc. All rights reserved.

  15. Muscle force generation and force control of finger movements in children with spastic hemiplegia during isometric tasks.

    NARCIS (Netherlands)

    Smits-Engelsman, B.C.M.; Rameckers, E.A.A.; Duysens, J.E.J.

    2005-01-01

    Force control ability was investigated in 10 males and 10 females, between 5 and 15 years old with spastic hemiplegia (mild and moderate hand dysfunction), and an aged-matched control group (eight males, 12 females). An isometric force production task at five different levels of maximum voluntary

  16. Muscle force generation and force control of finger movements in children with spastic hemiplegia during isometric tasks

    NARCIS (Netherlands)

    Smits-Engelsman, B.C.M.; Rameckers, E.A.A.; Duysens, J.E.J.

    2005-01-01

    Force control ability was investigated in 10 males and 10 females, between 5 and 15 years old with spastic hemiplegia (mild and moderate hand dysfunction), and an aged-matched control group (eight males, 12 females). An isometric force production task at five different levels of maximum voluntary

  17. Effects of Isometric Brain-Body Size Scaling on the Complexity of Monoaminergic Neurons in a Minute Parasitic Wasp

    NARCIS (Netherlands)

    Woude, van der Emma; Smid, Hans M.

    2017-01-01

    Trichogramma evanescens parasitic wasps show large phenotypic plasticity in brain and body size, resulting in a 5-fold difference in brain volume among genetically identical sister wasps. Brain volume scales linearly with body volume in these wasps. This isometric brain scaling forms an exception to

  18. Isometric and isokinetic muscle strength in patients with fibrositis syndrome. New characteristics for a difficult definable category of patients

    DEFF Research Database (Denmark)

    Jacobsen, Søren; Danneskiold-Samsøe, B

    1987-01-01

    A common complaint among patients with fibrositis syndrome is exhaustion and fatique. It was therefore felt desirable to evaluate the muscle strength of these patients compared with normal subjects. Maximum isometric and isokinetic strength of knee extension was measured in 15 patients and 15...... in patients with fibrositis syndrome than in healthy subjects....

  19. Do isometric and isotonic exercise programs reduce pain in athletes with patellar tendinopathy in-season? : A randomised clinical trial

    NARCIS (Netherlands)

    van Ark, Mathijs; Cook, Jill L; Docking, Sean I; Zwerver, Hans; Gaida, James E; van den Akker-Scheek, Inge; Rio, Ebonie

    Objectives: Many athletes with patellar tendinopathy participate in sports with symptoms during or after activities. Current treatments do not decrease pain in-season; eccentric exercises in-season result in an increase in pain. This study examined if isometric and isotonic exercises relieved pain

  20. Arterial blood pressure is inversely associated with vascular sympathetic reactivity (isometric handgrip exercise) in Gujarati Indian adolescents.

    Science.gov (United States)

    Shaikh, Wasim A; Patel, Minal; Shah, Hasmukh D; Nimbalkar, Archana S; Patel, Nilesh; Singh, S K

    2014-01-01

    Studies conducted earlier have found that vascular sympathetic reactivity to isometric handgrip exercise is either low or high in adolescents with higher blood pressure (Hypertensives) as compared to adolescents with relatively lower blood pressure (Normotensive). The current study was conducted to determine the correlation of vascular sympathetic reactivity to isometric handgrip exercise with blood pressure in Gujarati Indian adolescents so as to understand the pathogenesis and/consequences of Hypertension in this population. A cross-sectional study was conducted on 651 Gujarati Indian adolescents (285 girls, 366 boys) of age group 13-19 years. Blood pressure was measured by oscillometry and vascular sympathetic reactivity (Percentage rise in Diastolic Blood Pressure, %RDBP) was assessed using isometric handgrip test. Pearson's correlation coefficient was determined to study the correlation between %RDBP and blood pressure. In both girls and boys, %RDBP showed significant negative correlation with resting SBP, DBP and MAP. The study thus indicates that an inverse association exist between arterial blood pressure and vascular sympathetic reactivity to isometric handgrip exercise in Gujarati Indian adolescents.

  1. A multiple degree of freedom lower extremity isometric device to simultaneously quantify hip, knee, and ankle torques

    NARCIS (Netherlands)

    Sánchez, N.; Acosta, A.M.; Stienen, Arno; Dewald, Julius Paulus Antonius

    2015-01-01

    Characterization of the joint torque coupling strategies used in the lower extremity to generate maximal and submaximal levels of torque at either the hip, knee, or ankle is lacking. Currently, there are no available isometric devices that quantify all concurrent joint torques in the hip, knee, and

  2. CONTRACT FOLLOW UP TRAINING

    CERN Multimedia

    Technical Training; Tel. 74460

    2001-01-01

    SPL is organizing Training Sessions on the Contract Follow Up application. CFU is a Web based tool, developped and supported by the Administrative Information Services. It allows the creation of Divisional Requests and the follow up of their processing, from the Market Survey to the Invitation to Tender or Price Enquiry, approval by the Finance Committee, up to the actual signature of a Contract, acccording to the CERN Purchasing procedures. It includes a document management component. It also provides link with other AIS applications such as BHT and EDH. The course is primarily intended for DPOs, Contract Technical responsibles in the division and their assistants, but is beneficial to anybody involved in the follow up of such Purchasing Procedures. This course is free of charge, but application is necessary. The details of the course may be found at http://training.web.cern.ch/Training/ENSTEC/P2001/Bureautique/cfu4_f.htm General information of CFU may be found at http://ais.cern.ch/apps/cfu/ The dates of t...

  3. The interpretation of administrative contracts

    Directory of Open Access Journals (Sweden)

    Cătălin-Silviu SĂRARU

    2014-06-01

    Full Text Available The article analyzes the principles of interpretation for administrative contracts, in French law and in Romanian law. In the article are highlighted derogations from the rules of contract interpretation in common law. Are examined the exceptions to the principle of good faith, the principle of common intention (willingness of the parties, the principle of good administration, the principle of extensive interpretation of the administrative contract. The article highlights the importance and role of the interpretation in administrative contracts.

  4. Why radiologists lose their hospital contracts: is your contract secure?

    Science.gov (United States)

    Muroff, Lawrence R

    2010-03-01

    Previously, a hospital contract meant tenure for the incumbent group of radiologists; however, those days are long gone. Exclusive contracts have morphed into exclusive contracts with carve-outs. Turf erosion has become a fact of life for radiology practices. Now radiologists are losing their hospital contracts in record numbers. Group size, though helpful for a variety of reasons, does not ensure that a practice will be secure in its hospital setting. The reasons that groups lose their hospital contracts are varied, and in this paper, the author discusses the most common ones. Suggestions to help practices avoid this unfortunate fate are presented.

  5. Allometric scaling relationship between frequency of intestinal contraction and body size in rodents and rabbits.

    Science.gov (United States)

    Arab, Hossein-Ali; Muhammadnejad, Samad; Naeimi, Saeideh; Arab, Attieh

    2013-06-01

    This study aimed to establish an allometric scaling relationship between the frequency of intestinal contractions and body mass of different mammalian species. The frequency of intestinal contractions of rabbit, guinea pig, rat and mouse were measured using an isolated organ system. The isolated rings were prepared from proximal segments of jejunums and the frequency of contractions was recorded by an isometric force procedure. The coefficients of the obtained allometric equation were ascertained by computation of least squares after logarithmic transformation of both body mass and frequency. Significant differences (p less than 0.001) were shown in the frequency of contractions between different species. The highest frequency that corresponded to the mice was 57.7 min-1 and the 95 percent confidence interval (CI) ranged from 45.4 to 70, while rabbits showed the lowest frequency (12.71 min-1, CI: 8.6-16.8). Logarithms of frequency were statistically proportional to logarithms of body mass (r00.99; p less than 0.001). The data fitted an equation F 1/4 18:51B 0:31 and the 95 percent confidence interval of the exponent ranged from -0.30 to -0.32. The results of this study suggest that it is probably possible to extrapolate the intestinal contraction frequency of other mammalian species by the means of allometry scaling.

  6. Dietary apple polyphenols have preventive effects against lengthening contraction-induced muscle injuries.

    Science.gov (United States)

    Nakazato, Koichi; Ochi, Eisuke; Waga, Toshiaki

    2010-03-01

    We examined whether polyphenols from dietary apple have protective effects against exercise-induced muscle strain injury. Sixteen male Wistar rats were randomly assigned into the apple polyphenol (APP; N=8) and control (CON; N=8) groups. The APP and the CON groups were fed diets with and without 5% APP, respectively. After a 3-wk feeding period, the gastrocnemii of the animals were subject to lengthening contractions with electrical stimulation and forced ankle dorsiflexion. Isometric torques were measured before and after the lengthening contractions and on days 1, 2, 3, 5, and 7 after the contractions. On day 7, the animals were sacrificed and the gastrocnemii harvested. Thiobarbituric-acid-reactive substances, protein carbonyl, and mRNA of antioxidative proteins in the muscles were quantified. The APP group had significantly lower torque deficits than the CON group on days 3, 5, and 7 after the eccentric contractions. The thiobarbituric-acid-reactive substances and protein carbonyl levels in the case of the APP group were significantly lower than those in the case of the CON group. The APP group had significantly higher glutathione-S-transferase alpha1 mRNA levels than the CON group. Therefore, we conclude that dietary APPs have protective effects against lengthening contraction-induced muscle injury.

  7. Cross-education of muscle strength is greater with stimulated than voluntary contractions.

    Science.gov (United States)

    Hortobágyi, T; Scott, K; Lambert, J; Hamilton, G; Tracy, J

    1999-04-01

    Cross-education enhances the performance of muscles not directly involved in the chronic conditioning of the muscles in a remote limb. Substantial cross-education occurs after training with eccentric contractions or with contractions evoked by electromyostimulation (EMS). Since during EMS and eccentric contractions, skin and muscle afferents are activated that have excitatory effects on contralateral homologous muscles, it was hypothesized that exercise training with stimulated vs. voluntary eccentric contractions would lead to greater cross-education. Thirty-two women were randomly assigned to a voluntary (Vol), an EMS, or remote EMS (rEMS) exercise group and performed 840 voluntary or stimulated eccentric contractions over 6 weeks. All subjects, including nonexercising controls (Con), were tested pre- and posttraining for maximal voluntary and stimulated isometric and eccentric quadriceps strength. Ipsilateral voluntary and stimulated forces increased in all groups. Changes in EMG activity paralleled those in voluntary force in each limb. No changes occurred in grip strength. The great contra- and ipsilateral strength gains after EMS training were most likely related to an additive effect of EMS and muscle lengthening.

  8. Relaxing and contracting activities of heartworm extract on isolated canine abdominal aorta.

    Science.gov (United States)

    Kitoh, K; Oka, A; Kitagawa, H; Unno, T; Komori, S; Sasaki, Y

    2001-06-01

    Effect of adult heartworm (HW) crude extract on isolated canine abdominal aortic strips precontracted with noradrenaline was examined by recording isometric changes in tension. HW extract caused contraction of the aortic strip at a low concentration (LC) and its relaxation at a high concentration (HC). In aortic strips without endothelium, LC extract elicited a contraction similar to that in the strips with endothelium, whereas HC extract failed to produce any relaxation but instead produced a contraction. The relaxing effect of HC extract was blocked after treatment with 300 microM NG-nitro-L-arginine methyl ester hydrochloride, with reversal by additional treatment with 3 mM L-arginine. It was also markedly reduced or abolished after treatment with 3 microM oxyhemoglobin or 1 microM methylene blue. Fractionation of HW extract by high-performance liquid chromatography revealed that the relaxing and contracting activities are due to different substances in the extract. The results indicate that HW extract contains 2 different vasoactive substances, 1 causing contraction of canine abdominal aorta via a direct action on the smooth muscle, and the other its relaxation indirectly by releasing nitric oxide from endothelial cells. These vasoactive substances might play a role in HW extract-induced shock in dogs, and in the pathogenesis of HW infection.

  9. Effect of sodium deprivation on contraction and charge movement in frog skeletal muscle fibres.

    Science.gov (United States)

    Garcia, M C; Diaz, A F; Godinez, R; Sanchez, J A

    1992-06-01

    Measurements of isometric tension were performed in single twitch skeletal muscle fibres and the effect of extracellular Na+ removal on contraction was investigated. Na+ withdrawal brought about an increase in the amplitude of K+ contractures and their time course became faster. The potentiation of K+ contractures depended strongly on extracellular Ca2+ and developed slowly following an exponential time course with a time constant of approximately 8 min. Removal of extracellular Na+ greatly increased the amplitude of caffeine contractures and lowered its threshold: caffeine (0.5 mM) had no effect on resting tension in Ringer's but produced contractures in Na(+)-free solutions. Intramembrane charge movement (charge 1) was monitored in contracting voltage-clamped segments of frog skeletal muscle fibres using the triple-Vaseline-gap technique. Movement of charge 1 did not depend on the presence of extracellular Na+. However, the mechanical threshold decreased by approximately 10 mV at several pulse durations and the charge which produced just detectable contractions decreased by approximately 5 nC microF-1 in the absence of extracellular Na+. Intracellular heparin (40 mg ml-1) increased the mechanical threshold by approximately 20 mV without affecting the movement of charge 1. The effect of Na(+)-free solutions on the mechanical threshold was additive to that of heparin. It is concluded that the effects of Na(+)-withdrawal on contraction take place at a location beyond the voltage sensor of excitation-contraction coupling.

  10. Pressure drop in contraction flow

    DEFF Research Database (Denmark)

    Rasmussen, Henrik Koblitz

    This note is a supplement to Dynamic of Polymeric Liquids (DPL) page 178. DPL gives an equation for the pressure drop in a tapered (and circular) contraction, valid only at low angles. Here the general definition of contraction flow (the Bagley correction) and a more general method to find...... the pressure drop in a contraction are given....

  11. Service quality in contracted facilities.

    Science.gov (United States)

    Rabbani, Fauziah; Pradhan, Nousheen Akber; Zaidi, Shehla; Azam, Syed Iqbal; Yousuf, Farheen

    2015-01-01

    The purpose of this paper is to explore the readiness of contracted and non-contracted first-level healthcare facilities in Pakistan to deliver quality maternal and neonatal health (MNH) care. A balanced scorecard (BSC) was used as the assessment framework. Using a cross-sectional study design, two rural health centers (RHCs) contracted out to Aga Khan Health Service, Pakistan were compared with four government managed RHCs. A BSC was designed to assess RHC readiness to deliver good quality MNH care. In total 20 indicators were developed, representing five BSC domains: health facility functionality, service provision, staff capacity, staff and patient satisfaction. Validated data collection tools were used to collect information. Pearson χ2, Fisher's Exact and the Mann-Whitney tests were applied as appropriate to detect significant service quality differences among the two facilities. Contracted facilities were generally found to be better than non-contracted facilities in all five BSC domains. Patients' inclination for facility-based delivery at contracted facilities was, however, significantly higher than non-contracted facilities (80 percent contracted vs 43 percent non-contracted, p=0.006). The study shows that contracting out initiatives have the potential to improve MNH care. This is the first study to compare MNH service delivery quality across contracted and non-contracted facilities using BSC as the assessment framework.

  12. Transnational Law of Public Contracts

    NARCIS (Netherlands)

    Audit, M.; Schill, S.W.

    2016-01-01

    Public contracts were traditionally conceived as instruments of domestic public law and used within markets confined to the territory of the state party to the contract. Globalization, however, subjects public contracting to an increasing number of processes that take place at a transnational level

  13. Influence of Isometric Exercise Training on Quadriceps Muscle Architecture and Strength in Obese Subjects with Knee Osteoarthritis

    Directory of Open Access Journals (Sweden)

    Waleed S Mahmoud

    2017-03-01

    Full Text Available Obese individuals have reduced quadriceps muscle strength relative to body mass that may increase the rate of progression of knee osteoarthritis (OA. The purpose of this study was to evaluate the effects of isometric exercise training on quadriceps muscle architecture and strength in obese subjects with knee osteoarthritis. Methods: Fortyfour obese male subjects aged 40–65 years diagnosed with knee osteoarthritis were randomly assigned into group A (n=32 and group B (n=12. Group A subjects performed a 12-week isometric exercise program. Group B subjects did not participate in any exercise program and maintained their ordinary activities for the same period. Both groups received the same conventional physical therapy program including hot packs and therapeutic ultrasonic. Muscle thickness, pennation angles and fascicle length of the vastus lateralis (VL muscle of the affected knee were measured at rest by B-mode ultrasonography. Maximal voluntary isometric knee extension torque (MVIC of the affected knee was measured using an isokinetic dynamometer. Knee pain and function were evaluated using visual analogue pain scale (VAS and Western Ontario and McMaster Universities Arthritis Index (WOMAC. All variables were evaluated before and the end of the intervention period for both groups. Results: at the end of the program, group A subjects showed significant improvements compared with group B subjects regarding MVIC and muscle architecture parameters (p<0.05. Also, there was significant improvement in post-test VAS and WOMAC scores in group A subjects compared to group B subjects (p<0.05. Conclusion: A 12-week quadriceps isometric training program improves knee pain and quadriceps muscle strength and architecture in obese subjects with knee OA. These results indicate that isometric training should be regarded as a proper exercise intervention for obese patients with knee OA.

  14. The influence of isometric exercises of the quadriceps muscle on young female patients with anterior knee pain

    Directory of Open Access Journals (Sweden)

    Jacek Wilczyński

    2015-10-01

    Full Text Available Introduction: Anterior knee pain is a disease associated with abnormalities in the patellofemoral joint. It is a common reason for seeking advice from an orthopaedist. This problem is characterised by chronic pain in the anterior part of one or both knees. This issue often affects women, especially at a young age. The effect of this ailment is deterioration of the quality of life. This dysfunction significantly reduces abilities, and often prevents the performance of daily activities. Pain usually occurs during physical activity, but may also be accompanied by prolonged immobilisation of the knee joint. In defining the type of patellofemoral instability, orthopaedists use magnetic resonance imaging, arthroscopy, ultrasonography, and X-ray examination. A relatively effective method of treatment of pain in the patellofemoral joint is through isometric exercises of the quadriceps. They increase the strength of the quadriceps femoris muscle and reduce instability in the patellofemoral joint. Aim of the research: To evaluate the effectiveness of isometric exercises of the quadriceps muscle on young female patients with anterior knee pain. Material and methods : The study involved 30 women aged 13–44 years (mean age: 26.8 years, who had been diagnosed with pain in the front of the knee. Results and conclusions: Isometric exercises of the quadriceps muscle are an effective method of reducing anterior knee pain. Isometric exercises have a beneficial influence on improving physical activity, including performing basic activities of daily living. Student’s t distribution showed, that isometric exercises of the quadriceps muscle reduce pain at the front of the knee. Kruskal-Wallis test confirmed a significant reduction of anterior knee pain.

  15. Is it Actually a Contract the Civil Union Agreement?

    Directory of Open Access Journals (Sweden)

    Mario Alejandro Opazo González

    2017-12-01

    Full Text Available The present work aims to determine whether the civil union agreement, introduced into the Chilean legislation through the Act number 20.830, is a patrimonial contract, as it is established by its first article, or a Family Law contract. Assuming one option or the other will lead us into whether it is possible or not to apply the Private Autonomy Principle to this contract. The thesis that it is sustained is that it is a Family Law contract and, therefore, the Private Autonomy Principle appears to be restricted in this agreement, so the people who celebrate the civil union agreement in Chile will not be able to alter the legal rules established for it.

  16. Leader Fairness, Social Contract and Corporate Sustainability Performance

    NARCIS (Netherlands)

    Hadders, Henk; Miedema, Joost; Politis, J

    2009-01-01

    The world badly needs organizations who harness private interest to serve the public interest and who accrue fair returns to shareholders, but not at the expense of the legitimate interest of other stakeholders. We need new principles for future corporate design and new strategic leadership for

  17. Sustainable consumption

    DEFF Research Database (Denmark)

    Prothero, Andrea; Dobscha, Susan; Freund, Jim

    2011-01-01

    This essay explores sustainable consumption and considers possible roles for marketing and consumer researchers and public policy makers in addressing the many sustainability challenges that pervade our planet. Future research approaches to this interdisciplinary topic need to be comprehensive...... and systematic and will benefit from a variety of different perspectives. There are a number of opportunities for future research, and three areas are explored in detail. First, the essay considers the inconsistency between the attitudes and behaviors of consumers with respect to sustainability; next, the agenda...... is broadened to explore the role of individual citizens in society; and finally, a macro institutional approach to fostering sustainability is explored. Each of these areas is examined in detail and possible research avenues and public policy initiatives are considered within each of these separate...

  18. Stabilizing Sustainability

    DEFF Research Database (Denmark)

    Reitan Andersen, Kirsti

    The publication of the Brundtland Report in 1987 put the topic of sustainable development on the political and corporate agenda. Defining sustainable development as “a development that meets the needs of the future without compromising the ability of future generations to meet their own needs......” (WCED, 1987, p. 43), the Report also put a positive spin on the issue of sustainability by upholding capitalist beliefs in the possibility of infinite growth in a world of finite resources. While growth has delivered benefits, however, it has done so unequally and unsustainably. This thesis focuses...... on the textile and fashion industry, one of the world’s most polluting industries and an industry to some degree notorious for leading the ‘race to the bottom’ in global labour standards. Despite being faced with increasing demands to practise sustainability, most textile and fashion companies continue to fail...

  19. Sustainability reporting

    NARCIS (Netherlands)

    Kolk, A.

    2005-01-01

    This article gives an overview of developments in sustainability (also sometimes labelled corporate social responsibility) reporting. The article will first briefly indicate how accountability on social and environmental issues started, already in the 1970s when social reports were published.

  20. Sustainable Cities

    DEFF Research Database (Denmark)

    Georg, Susse; Garza de Linde, Gabriela Lucía

    Judging from the number of communities and cities striving or claiming to be sustainable and how often eco-development is invoked as the means for urban regeneration, it appears that sustainable and eco-development have become “the leading paradigm within urban development” (Whitehead 2003......), urban design competitions are understudied mechanisms for bringing about field level changes. Drawing on actor network theory, this paper examines how urban design competitions may bring about changes within the professional field through the use of intermediaries such as a sustainable planning....../assessment tool. The context for our study is urban regeneration in one Danish city, which had been suffering from industrial decline and which is currently investing in establishing a “sustainable city”. Based on this case study we explore how the insights and inspiration evoked in working with the tool...

  1. Sustainable responsibilities?

    DEFF Research Database (Denmark)

    Lystbæk, Christian Tang

    2015-01-01

    This working paper analyzes the conceptions of corporate responsibility for sustainable development in EU policies on CSR. The notion of corporate responsibility has until recently been limited to economical and legal responsibilities. Based on this narrow conception of corporate responsibility.......e. a combination of destruction and construction, this chapter will deconstruct conceptions of responsibility for sustainable development in these EU documents on CSR. A deconstructive conceptual analysis involves destructing dominant interpretations of a text and allowing for constructions of alternative...... such as sustainability actually means, but on what the concept says and does not say. A deconstructive analysis of EU policies on CSR, then, pinpoints that such policies are sites of conceptual struggles. This kind of analysis is suitable for studying conceptions of corporate responsibility for sustainable development...

  2. Agriculture: Sustainability

    Science.gov (United States)

    Sustainability creates and maintains the conditions under which humans and nature can exist in productive harmony, that permit fulfilling the food, feed, and fiber needs of our country and the social, economic and other requirements.

  3. Sustainable finance

    OpenAIRE

    Boersma-de Jong, Margreet F.

    2012-01-01

    Presentation for Springschool of Strategy, University of Groningen, 10 October 2012. The role of CSR is to stimulate ethical behaviour, and as a result, mutual trust in society. Advantage of CSR for the company and the evolution of CSR. From CSR to Sustainable Finance: how does CSR influence Sustainable Business Administration & Management Accounting, Financial Leadership and what is the importance of CSR in the financial sector

  4. SUSTAINABLE TRANSPORTATION

    Directory of Open Access Journals (Sweden)

    Linda STEG

    2007-01-01

    Full Text Available This paper discusses possible contributions of psychologists to sustainable transportation. It is argued that in order to reach sustainable transportation, among others, behaviour changes of individual car users are needed. As transport policies will be more effective if they target important antecedents of travel behaviour, first, factors influencing such behaviour are discussed. It is argued that car use is very attractive and sometimes even necessary for many different reasons. This implies that a combination of policies is called for, each targeting different factors that support car use and hinder the use of more sustainable modes of transport. Next, the paper elaborates on policy strategies that may be employed to achieve sustainable transportation by changing car use. Increasing the attractiveness of sustainable transport modes by means of pull measures seems not sufficient to reduce the level of car use. Besides, car use should be made less attractive by means of push measures to force drivers to reconsider their travel behaviour. The acceptability of such policies may be increased by clearly communicating the aim of these policies, and the expected positive consequences (e.g., less congestion, improved environmental quality. Moreover, possible negative effects for individual freedom may be compensated by implementing additional policies aimed at facilitating the use of sustainable transport modes.

  5. Sustainable markets for sustainable energy

    Energy Technology Data Exchange (ETDEWEB)

    Millan, J.; Smyser, C.

    1997-12-01

    The author discusses how the Inter-American Development Bank (IDB) is involved in sustainable energy development. It presently has 50 loans and grants for non conventional renewable energy projects and ten grants for efficiency programs for $600 and $17 million respectively, representing 100 MW of power. The IDB is concerned with how to create a sustainable market for sustainable energy projects. The IDB is trying to work with government, private sector, NGOs, trading allies, credit sources, and regulators to find proper roles for such projects. He discusses how the IDB is working to expand its vision and objectives in renewable energy projects in Central and South America.

  6. The Lanthanide Contraction Revisited

    Science.gov (United States)

    Seitz, Michael; Oliver, Allen G.; Raymond, Kenneth N.

    2011-01-01

    A complete, isostructural series of complexes with La-Lu (except Pm) with the ligand TREN-1,2-HOIQO has been synthesized and structurally characterized by means of single-crystal X-ray analysis. All complexes are 1D-polymeric species in the solid state, with the lanthanide being in an eight-coordinate, distorted trigonal-dodecahedral environment with a donor set of eight unique oxygen atoms. This series constitutes the first complete set of isostructural complexes from La-Lu (without Pm) with a ligand of denticity greater than two. The geometric arrangement of the chelating moieties slightly deviates across the lanthanide series, as analyzed by a shape parameter metric based on the comparison of the dihedral angles along all edges of the coordination polyhedron. The apparent lanthanide contraction in the individual Ln-O bond lengths deviates considerably from the expected quadratic decrease that was found previously in a number of complexes with ligands of low denticity. The sum of all bond lengths around the trivalent metal cation, however, is more regular, showing an almost ideal quadratic behavior across the entire series. The quadratic nature of the lanthanide contraction is derived theoretically from Slater’s model for the calculation of ionic radii. In addition, the sum of all distances along the edges of the coordination polyhedron show exactly the same quadratic dependence as the Ln-X bond lengths. The universal validity of this coordination sphere contraction, concomitant with the quadratic decrease in Ln-X bond lengths, was confirmed by reexamination of four other, previously published series of lanthanide complexes. Due to the importance of multidentate ligands for the chelation of rare-earth metals, this result provides a significant advance for the prediction and rationalization of the geometric features of the corresponding lanthanide complexes, with great potential impact for all aspects of lanthanide coordination. PMID:17705483

  7. The Lanthanide Contraction Revisited

    Energy Technology Data Exchange (ETDEWEB)

    Seitz, Michael; Oliver, Allen G.; Raymond, Kenneth N.

    2007-04-19

    A complete, isostructural series of lanthanide complexes (except Pm) with the ligand TREN-1,2-HOIQO has been synthesized and structurally characterized by means of single-crystal X-ray analysis. All complexes are 1D-polymeric species in the solid state, with the lanthanide being in an eight-coordinate, distorted trigonal-dodecahedral environment with a donor set of eight unique oxygen atoms. This series constitutes the first complete set of isostructural lanthanide complexes with a ligand of denticity greater than two. The geometric arrangement of the chelating moieties slightly deviates across the lanthanide series, as analyzed by a shape parameter metric based on the comparison of the dihedral angles along all edges of the coordination polyhedron. The apparent lanthanide contraction in the individual Ln-O bond lengths deviates considerably from the expected quadratic decrease that was found previously in a number of complexes with ligands of low denticity. The sum of all bond lengths around the trivalent metal cation, however, is more regular, showing an almost ideal quadratic behavior across the entire series. The quadratic nature of the lanthanide contraction is derived theoretically from Slater's model for the calculation of ionic radii. In addition, the sum of all distances along the edges of the coordination polyhedron show exactly the same quadratic dependency as the Ln-X bond lengths. The universal validity of this coordination sphere contraction, concomitant with the quadratic decrease in Ln-X bond lengths, was confirmed by reexamination of four other, previously published, almost complete series of lanthanide complexes. Due to the importance of multidentate ligands for the chelation of rare-earth metals, this result provides a significant advance for the prediction and rationalization of the geometric features of the corresponding lanthanide complexes, with great potential impact for all aspects of lanthanide coordination.

  8. Contracting singular horseshoe

    Science.gov (United States)

    Morales, C. A.; San Martín, B.

    2017-11-01

    We suggest a notion of hyperbolicity adapted to the geometric Rovella attractor (Robinson 2012 An Introduction to Dynamical Systems—Continuous and Discrete (Pure and Applied Undergraduate Texts vol 19) 2nd edn (Providence, RI: American Mathematical Society)) . More precisely, we call a partially hyperbolic set asymptotically sectional-hyperbolic if its singularities are hyperbolic and if its central subbundle is asymptotically sectional expanding outside the stable manifolds of the singularities. We prove that there are highly chaotic flows with Rovella-like singularities exhibiting this kind of hyperbolicity. We shall call them contracting singular horseshoes.

  9. Negotiating Efficient PPP Contracts

    DEFF Research Database (Denmark)

    Tvarnø, Christina D.

    should consider tendering out PPP projects in the spirit of joint utility because joint utility can increase the concept of more value for money; the cornerstone of the PPP concept. This paper discusses the positive gains from negotiation and compares it with the upcoming possibilities in the EU public....... Joint utility can increase the concept of more value for money; the cornerstone of the PPP concept. The paper draws upon existing legal content regarding collaboration and common goals and game theory to explain the benefits from implementing similar clauses in PPP contracts....

  10. Defining Acquisition and Contracting Terms Associated with Contract Administration

    Science.gov (United States)

    1990-09-01

    Riemer Handbook of Government Contract Administration, the Armed Services Pricing Manual ( ASPM ), and AFIT’s Govern- ment Contract Law course and case book...these duties into general categories, as outlined in the ASPM and Government Contract Cost (16:B-3) (36:25-7,GL-3). NCMA’s Desktop Guide to Basic...processes by listing exactly how an audit is carried out and what it determines. For example, Arnavas, Rishe, and the ASPM conclude that an au- dit is

  11. Using Maximal Isometric Force to Determine the Optimal Load for Measuring Dynamic Muscle Power

    Science.gov (United States)

    Spiering, Barry A.; Lee, Stuart M. C.; Mulavara, Ajitkumar P.; Bentley, Jason R.; Nash, Roxanne E.; Sinka, Joseph; Bloomberg, Jacob J.

    2009-01-01

    Maximal power output occurs when subjects perform ballistic exercises using loads of 30-50% of one-repetition maximum (1-RM). However, performing 1-RM testing prior to power measurement requires considerable time, especially when testing involves multiple exercises. Maximal isometric force (MIF), which requires substantially less time to measure than 1-RM, might be an acceptable alternative for determining the optimal load for power testing. PURPOSE: To determine the optimal load based on MIF for maximizing dynamic power output during leg press and bench press exercises. METHODS: Twenty healthy volunteers (12 men and 8 women; mean +/- SD age: 31+/-6 y; body mass: 72 +/- 15 kg) performed isometric leg press and bench press movements, during which MIF was measured using force plates. Subsequently, subjects performed ballistic leg press and bench press exercises using loads corresponding to 20%, 30%, 40%, 50%, and 60% of MIF presented in randomized order. Maximal instantaneous power was calculated during the ballistic exercise tests using force plates and position transducers. Repeated-measures ANOVA and Fisher LSD post hoc tests were used to determine the load(s) that elicited maximal power output. RESULTS: For the leg press power test, six subjects were unable to be tested at 20% and 30% MIF because these loads were less than the lightest possible load (i.e., the weight of the unloaded leg press sled assembly [31.4 kg]). For the bench press power test, five subjects were unable to be tested at 20% MIF because these loads were less than the weight of the unloaded aluminum bar (i.e., 11.4 kg). Therefore, these loads were excluded from analysis. A trend (p = 0.07) for a main effect of load existed for the leg press exercise, indicating that the 40% MIF load tended to elicit greater power output than the 60% MIF load (effect size = 0.38). A significant (p . 0.05) main effect of load existed for the bench press exercise; post hoc analysis indicated that the effect of

  12. Project management plan for Contract Management Information System (CONTRACT)

    Energy Technology Data Exchange (ETDEWEB)

    Severud, K.J.

    1995-01-27

    The office of the Vice President of A/E Construction for ICF Kaiser has requested that OSHA compliance statistics be made available to management for companies subcontracting to the ICF Kaiser Company. In addition, a need to better manage contract administrative data for the Contracts Administration and the Construction Management Projects organizations has been identified. The Contract Management Information System is being developed to achieve these objectives. This document provides a Project Management Plan for development of the Contract Management Administration System (CONTRACT) by Design Services DAD/CAE Support. The Project Management Plan describes the project work breakdown structure, safety and quality considerations, with associated cost, schedule and project management information. The CONTRACT System is intended to aid the ICF Kaiser divisions with tracking of A/E subcontractor information to include general contract administration information used by the Contracts Administration organization, contract and safety performance data used by the Construction Management Projects and office of the organization and Vice President of A/E Construction.

  13. 48 CFR 716.406 - Contract clauses.

    Science.gov (United States)

    2010-10-01

    ... 48 Federal Acquisition Regulations System 5 2010-10-01 2010-10-01 false Contract clauses. 716.406 Section 716.406 Federal Acquisition Regulations System AGENCY FOR INTERNATIONAL DEVELOPMENT CONTRACTING METHODS AND CONTRACT TYPES TYPES OF CONTRACTS Cost Reimbursement Contracts 716.406 Contract clauses. The...

  14. 48 CFR 1416.405 - Contract clauses.

    Science.gov (United States)

    2010-10-01

    ... 48 Federal Acquisition Regulations System 5 2010-10-01 2010-10-01 false Contract clauses. 1416.405 Section 1416.405 Federal Acquisition Regulations System DEPARTMENT OF THE INTERIOR CONTRACTING METHODS AND CONTRACT TYPES TYPES OF CONTRACTS Incentive Contracts 1416.405 Contract clauses. The BPC, without the power...

  15. 48 CFR 732.111 - Contract clauses.

    Science.gov (United States)

    2010-10-01

    ... 48 Federal Acquisition Regulations System 5 2010-10-01 2010-10-01 false Contract clauses. 732.111... CONTRACTING REQUIREMENTS CONTRACT FINANCING General 732.111 Contract clauses. (a) (b) USAID may obtain short... indefinite quantity contracts that are a combination of contract types. Rather than using the fixed-price...

  16. 48 CFR 916.307 - Contract clauses.

    Science.gov (United States)

    2010-10-01

    ... 48 Federal Acquisition Regulations System 5 2010-10-01 2010-10-01 false Contract clauses. 916.307 Section 916.307 Federal Acquisition Regulations System DEPARTMENT OF ENERGY CONTRACTING METHODS AND CONTRACT TYPES TYPES OF CONTRACTS Cost-Reimbursement Contracts 916.307 Contract clauses. (g) Insert the...

  17. Roundtabling Sustainability

    DEFF Research Database (Denmark)

    Ponte, Stefano

    2014-01-01

    The willingness of public authority to delegate social and environmental regulation to the private sector has varied from sector to sector, but has often led to the establishment of ‘voluntary’ standards and certifications on sustainability. Many of these have taken the form of ‘stewardship...... councils’ and ‘sustainability roundtables’ and have been designed around a set of institutional features seeking to establish legitimacy, fend off possible criticism, and ‘sell’ certifications to potential users. The concept of ‘roundtabling’ emphasizes the fitting a variety of commodity......-specific sustainability situations into a form that not only ‘hears more voices’ (as in ‘multi-stakeholder’), but also portrays to give them equal standing at the table of negotiations (roundtable), thus raising higher expectations on accountability, transparency and inclusiveness. In this article, I examine to what...

  18. Sustainability Evaluation.

    Science.gov (United States)

    Stichnothe, Heinz

    2017-03-17

    The long-term substitution of fossil resources can only be achieved through a bio-based economy, with biorefineries and bio-based products playing a major role. However, it is important to assess the implications of the transition to a bio-based economy. Life cycle-based sustainability assessment is probably the most suitable approach to quantify impacts and to identify trade-offs at multiple levels. The extended utilisation of biomass can cause land use change and affect food security of the most vulnerable people throughout the world. Although this is mainly a political issue and governments should be responsible, the responsibility is shifted to companies producing biofuels and other bio-based products. Organic wastes and lignocellulosic biomass are considered to be the preferred feedstock for the production of bio-based products. However, it is unlikely that a bio-based economy can rely only on organic wastes and lignocellulosic biomass.It is crucial to identify potential problems related to socio-economic and environmental issues. Currently there are many approaches to the sustainability of bio-based products, both quantitative and qualitative. However, results of different calculation methods are not necessarily comparable and can cause confusion among decision-makers, stakeholders and the public.Hence, a harmonised, globally agreed approach would be the best solution to secure sustainable biomass/biofuels/bio-based chemicals production and trade, and to avoid indirect effects (e.g. indirect land use change). However, there is still a long way to go.Generally, the selection of suitable indicators that serve the purpose of sustainability assessment is very context-specific. Therefore, it is recommended to use a flexible and modular approach that can be adapted to various purposes. A conceptual model for the selection of sustainability indicators is provided that facilitates identifying suitable sustainability indicators based on relevance and significance in a

  19. Prediction of isometric motor tasks and effort levels based on high-density EMG in patients with incomplete spinal cord injury

    Science.gov (United States)

    Jordanić, Mislav; Rojas-Martínez, Mónica; Mañanas, Miguel Angel; Francesc Alonso, Joan

    2016-08-01

    Objective. The development of modern assistive and rehabilitation devices requires reliable and easy-to-use methods to extract neural information for control of devices. Group-specific pattern recognition identifiers are influenced by inter-subject variability. Based on high-density EMG (HD-EMG) maps, our research group has already shown that inter-subject muscle activation patterns exist in a population of healthy subjects. The aim of this paper is to analyze muscle activation patterns associated with four tasks (flexion/extension of the elbow, and supination/pronation of the forearm) at three different effort levels in a group of patients with incomplete Spinal Cord Injury (iSCI). Approach. Muscle activation patterns were evaluated by the automatic identification of these four isometric tasks along with the identification of levels of voluntary contractions. Two types of classifiers were considered in the identification: linear discriminant analysis and support vector machine. Main results. Results show that performance of classification increases when combining features extracted from intensity and spatial information of HD-EMG maps (accuracy = 97.5%). Moreover, when compared to a population with injuries at different levels, a lower variability between activation maps was obtained within a group of patients with similar injury suggesting stronger task-specific and effort-level-specific co-activation patterns, which enable better prediction results. Significance. Despite the challenge of identifying both the four tasks and the three effort levels in patients with iSCI, promising results were obtained which support the use of HD-EMG features for providing useful information regarding motion and force intention.

  20. Some ancestors of contraction analysis

    DEFF Research Database (Denmark)

    Jouffroy, Jerome

    2005-01-01

    Contraction analysis is a recent tool for analyzing the convergence behavior of nonlinear systems in state-space form (see Lohmiller and Slotine [16] for the main reference). However, it seems that earlier results derived by mathematicians in the 1950s closely match some of the results...... of contraction analysis. In this paper, we review and place into perspective some references of this era, and relate them with contraction....