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Sample records for sustained muscle contractions

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

    Directory of Open Access Journals (Sweden)

    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. 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.

  4. 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

  5. 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.

  6. 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

  7. 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...

  8. 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.

  9. 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....

  10. Adaptations of upper trapezius muscle activity during sustained contractions in women with fibromyalgia

    DEFF Research Database (Denmark)

    Falla, Deborah Lorraine; Andersen, Helle; Danneskiold-Samsøe, Bente

    2010-01-01

    The study compared the distribution of electromyographic (EMG) signal amplitude in the upper trapezius muscle in 10 women with fibromyalgia and in 10 healthy women before and after experimentally-induced muscle pain. Surface EMG signals were recorded over the right upper trapezius muscle with a 10...

  11. Adaptations of upper trapezius muscle activity during sustained contractions in women with fibromyalgia

    DEFF Research Database (Denmark)

    Falla, Deborah Lorraine; Andersen, Helle; Danneskiold-Samsøe, Bente

    2010-01-01

    The study compared the distribution of electromyographic (EMG) signal amplitude in the upper trapezius muscle in 10 women with fibromyalgia and in 10 healthy women before and after experimentally-induced muscle pain. Surface EMG signals were recorded over the right upper trapezius muscle with a 1...

  12. 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.

  13. Calcium regulation of muscle contraction.

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    Szent-Györgyi, A G

    1975-07-01

    Calcium triggers contraction by reaction with regulatory proteins that in the absence of calcium prevent interaction of actin and myosin. Two different regulatory systems are found in different muscles. In actin-linked regulation troponin and tropomyosin regulate actin by blocking sites on actin required for complex formation with myosin; in myosin-linked regulation sites on myosin are blocked in the absence of calcium. The major features of actin control are as follows: there is a requirement for tropomyosin and for a troponin complex having three different subunits with different functions; the actin displays a cooperative behavior; and a movement of tropomyosin occurs controlled by the calcium binding on troponin. Myosin regulation is controlled by a regulatory subunit that can be dissociated in scallop myosin reversibly by removing divalent cations with EDTA. Myosin control can function with pure actin in the absence of tropomyosin. Calcium binding and regulation of molluscan myosins depend on the presence of regulatory light chains. It is proposed that the light chains function by sterically blocking myosin sites in the absence of calcium, and that the "off" state of myosin requires cooperation between the two myosin heads. Both myosin control and actin control are widely distributed in different organisms. Many invertebrates have muscles with both types of regulation. Actin control is absent in the muscles of molluscs and in several minor phyla that lack troponin. Myosin control is not found in striated vertebrate muscles and in the fast muscles of crustacean decapods, although regulatory light chains are present. While in vivo myosin control may not be excluded from vertebrate striated muscles, myosin control may be absent as a result of mutations of the myosin heavy chain.

  14. Increased muscle glucose uptake during contractions

    DEFF Research Database (Denmark)

    Ploug, Thorkil; Galbo, Henrik; Richter, Erik

    1984-01-01

    We reinvestigated the prevailing concept that muscle contractions only elicit increased muscle glucose uptake in the presence of a so-called "permissive" concentration of insulin (Berger et al., Biochem. J. 146: 231-238, 1975; Vranic and Berger, Diabetes 28: 147-163, 1979). Hindquarters from rats...... in severe ketoacidosis were perfused with a perfusate containing insulin antiserum. After 60 min perfusion, electrical stimulation increased glucose uptake of the contracting muscles fivefold. Also, subsequent contractions increased glucose uptake in hindquarters from nondiabetic rats perfused for 1.5 h......-methylglucose uptake increased during contractions and glucose uptake was negative at rest and zero during contractions. An increase in muscle transport and uptake of glucose during contractions does not require the presence of insulin. Furthermore, glucose transport in contracting muscle may only increase if glycogen...

  15. Diaphragmatic lymphatic vessel behavior during local skeletal muscle contraction.

    Science.gov (United States)

    Moriondo, Andrea; Solari, Eleonora; Marcozzi, Cristiana; Negrini, Daniela

    2015-02-01

    The mechanism through which the stresses developed in the diaphragmatic tissue during skeletal muscle contraction sustain local lymphatic function was studied in 10 deeply anesthetized, tracheotomized adult Wistar rats whose diaphragm was exposed after thoracotomy. To evaluate the direct effect of skeletal muscle contraction on the hydraulic intraluminal lymphatic pressures (Plymph) and lymphatic vessel geometry, the maximal contraction of diaphragmatic fibers adjacent to a lymphatic vessel was elicited by injection of 9.2 nl of 1 M KCl solution among diaphragmatic fibers while Plymph was recorded through micropuncture and vessel geometry via stereomicroscopy video recording. In lymphatics oriented perpendicularly to the longitudinal axis of muscle fibers and located at 900 μm from the vessel, Dmc enlarged to 131.1 ± 2.3% of Drest. In vessels parallel to muscle fibers, Dmc increased to 122.8 ± 2.9% of Drest. During contraction, Plymph decreased as much as 22.5 ± 2.6 cmH2O in all submesothelial superficial vessels, whereas it increased by 10.7 ± 5.1 cmH2O in deeper vessels running perpendicular to contracting muscle fibers. Hence, the three-dimensional arrangement of the diaphragmatic lymphatic network seems to be finalized to efficiently exploit the stresses exerted by muscle fibers during the contracting inspiratory phase to promote lymph formation in superficial submesothelial lymphatics and its further propulsion in deeper intramuscular vessels. Copyright © 2015 the American Physiological Society.

  16. Vasodilatory mechanisms in contracting skeletal muscle

    DEFF Research Database (Denmark)

    Clifford, Philip S.; Hellsten, Ylva

    2004-01-01

    Skeletal muscle blood flow is closely coupled to metabolic demand, and its regulation is believed to be mainly the result of the interplay of neural vasoconstrictor activity and locally derived vasoactive substances. Muscle blood flow is increased within the first second after a single contraction...... and stabilizes within 30 s during dynamic exercise under normal conditions. Vasodilator substances may be released from contracting skeletal muscle, vascular endothelium, or red blood cells. The importance of specific vasodilators is likely to vary over the time course of flow, from the initial rapid rise...

  17. Dynamics of smooth muscle contraction

    NARCIS (Netherlands)

    G.A. van Kloeveringe (Gommert)

    1997-01-01

    textabstractSmooth muscle can economically maintain tonus for a long time and in many organs, its purpose is to maintain organ dimensions. It is however relatively slow and also inefficient as far as mechanical work is concerned. Smooth muscle is found in the majority of organs in the human body. It

  18. Energy consumption in static muscle contraction

    NARCIS (Netherlands)

    Koerhuis, CL; Hof, AL; van der Heide, F.M.

    Energy consumption during static contraction of the human triceps surae muscles was studied in 11 healthy subjects. The subjects had to stand intermittently on the left and then right foot at different frequencies (for periods of 15 s, 10 s or 5 s), first on the whole foot and then on the forefoot.

  19. On the thermodynamics of smooth muscle contraction

    Science.gov (United States)

    Stålhand, Jonas; McMeeking, Robert M.; Holzapfel, Gerhard A.

    2016-09-01

    Cell function is based on many dynamically complex networks of interacting biochemical reactions. Enzymes may increase the rate of only those reactions that are thermodynamically consistent. In this paper we specifically treat the contraction of smooth muscle cells from the continuum thermodynamics point of view by considering them as an open system where matter passes through the cell membrane. We systematically set up a well-known four-state kinetic model for the cross-bridge interaction of actin and myosin in smooth muscle, where the transition between each state is driven by forward and reverse reactions. Chemical, mechanical and energy balance laws are provided in local forms, while energy balance is also formulated in the more convenient temperature form. We derive the local (non-negative) production of entropy from which we deduce the reduced entropy inequality and the constitutive equations for the first Piola-Kirchhoff stress tensor, the heat flux, the ion and molecular flux and the entropy. One example for smooth muscle contraction is analyzed in more detail in order to provide orientation within the established general thermodynamic framework. In particular the stress evolution, heat generation, muscle shorting rate and a condition for muscle cooling are derived.

  20. Muscle pain induced by static contraction in rats is modulated by peripheral inflammatory mechanisms.

    Science.gov (United States)

    Santos, Diogo Francisco da Silva Dos; Melo Aquino, Bruna de; Jorge, Carolina Ocanha; Azambuja, Graciana de; Schiavuzzo, Jalile Garcia; Krimon, Suzy; Neves, Juliana Dos Santos; Parada, Carlos Amilcar; Oliveira-Fusaro, Maria Claudia Gonçalves

    2017-09-01

    Muscle pain is an important health issue and frequently related to static force exertion. The aim of this study is to evaluate whether peripheral inflammatory mechanisms are involved with static contraction-induced muscle pain in rats. To this end, we developed a model of muscle pain induced by static contraction performed by applying electrical pulses through electrodes inserted into muscle. We also evaluated the involvement of neutrophil migration, bradykinin, sympathetic amines and prostanoids. A single session of sustained static contraction of gastrocnemius muscle induced acute mechanical muscle hyperalgesia without affecting locomotor activity and with no evidence of structural damage in muscle tissue. Static contraction increased levels of creatine kinase but not lactate dehydrogenase, and induced neutrophil migration. Dexamethasone (glucocorticoid anti-inflammatory agent), DALBK (bradykinin B1 antagonist), Atenolol (β1 adrenoceptor antagonist), ICI 118,551 (β2 adrenoceptor antagonist), indomethacin (cyclooxygenase inhibitor), and fucoidan (non-specific selectin inhibitor) all reduced static contraction-induced muscle hyperalgesia; however, the bradykinin B2 antagonist, bradyzide, did not have an effect on static contraction-induced muscle hyperalgesia. Furthermore, an increased hyperalgesic response was observed when the selective bradykinin B1 agonist des-Arg9-bradykinin was injected into the previously stimulated muscle. Together, these findings demonstrate that static contraction induced mechanical muscle hyperalgesia in gastrocnemius muscle of rats is modulated through peripheral inflammatory mechanisms that are dependent on neutrophil migration, bradykinin, sympathetic amines and prostanoids. Considering the clinical relevance of muscle pain, we propose the present model of static contraction-induced mechanical muscle hyperalgesia as a useful tool for the study of mechanisms underlying static contraction-induced muscle pain. Copyright © 2017 IBRO

  1. Poorly Understood Aspects of Striated Muscle Contraction

    Directory of Open Access Journals (Sweden)

    Alf Månsson

    2015-01-01

    Full Text Available Muscle contraction results from cyclic interactions between the contractile proteins myosin and actin, driven by the turnover of adenosine triphosphate (ATP. Despite intense studies, several molecular events in the contraction process are poorly understood, including the relationship between force-generation and phosphate-release in the ATP-turnover. Different aspects of the force-generating transition are reflected in the changes in tension development by muscle cells, myofibrils and single molecules upon changes in temperature, altered phosphate concentration, or length perturbations. It has been notoriously difficult to explain all these events within a given theoretical framework and to unequivocally correlate observed events with the atomic structures of the myosin motor. Other incompletely understood issues include the role of the two heads of myosin II and structural changes in the actin filaments as well as the importance of the three-dimensional order. We here review these issues in relation to controversies regarding basic physiological properties of striated muscle. We also briefly consider actomyosin mutation effects in cardiac and skeletal muscle function and the possibility to treat these defects by drugs.

  2. Dynamic contraction behaviour of pneumatic artificial muscle

    Science.gov (United States)

    Doumit, Marc D.; Pardoel, Scott

    2017-07-01

    The development of a dynamic model for the Pneumatic Artificial Muscle (PAM) is an imperative undertaking for understanding and analyzing the behaviour of the PAM as a function of time. This paper proposes a Newtonian based dynamic PAM model that includes the modeling of the muscle geometry, force, inertia, fluid dynamic, static and dynamic friction, heat transfer and valve flow while ignoring the effect of bladder elasticity. This modeling contribution allows the designer to predict, analyze and optimize PAM performance prior to its development. Thus advancing successful implementations of PAM based powered exoskeletons and medical systems. To date, most muscle dynamic properties are determined experimentally, furthermore, no analytical models that can accurately predict the muscle's dynamic behaviour are found in the literature. Most developed analytical models adequately predict the muscle force in static cases but neglect the behaviour of the system in the transient response. This could be attributed to the highly challenging task of deriving such a dynamic model given the number of system elements that need to be identified and the system's highly non-linear properties. The proposed dynamic model in this paper is successfully simulated through MATLAB programing and validated the pressure, contraction distance and muscle temperature with experimental testing that is conducted with in-house built prototype PAM's.

  3. Reduced blood flow to contracting skeletal muscle in ageing humans

    DEFF Research Database (Denmark)

    Nyberg, Michael Permin; Hellsten, Ylva

    2016-01-01

    consequences of ageing and physical inactivity can be challenging; yet, observations from cross-sectional and longitudinal studies on the effects of physical activity have provided some insight. Physical activity has the potential to offset the age-related decline in blood flow to contracting skeletal muscle...... the O2 demand of the active skeletal muscle of aged individuals during conditions where systemic blood flow is not limited by cardiac output seems to a large extent to be related to the level of physical activity. This article is protected by copyright. All rights reserved.......The ability to sustain a given absolute submaximal workload declines with advancing age likely due to a lower level of blood flow and O2 delivery to the exercising muscles. Given that physical inactivity mimics many of the physiological changes associated with ageing, separating the physiological...

  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. Eccentric Contraction-Induced Muscle Fibre Adaptation

    Directory of Open Access Journals (Sweden)

    Arabadzhiev T. I.

    2009-12-01

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

  6. Glucose uptake and transport in contracting, perfused rat muscle with different pre-contraction glycogen concentrations

    DEFF Research Database (Denmark)

    Hespel, P; Richter, Erik

    1990-01-01

    1. Glucose uptake and transport, muscle glycogen, free glucose and glucose-6-phosphate concentrations were studied in perfused resting and contracting rat skeletal muscle with different pre-contraction glycogen concentrations. Rats were pre-conditioned by a combination of swimming exercise and diet...... on the preceding day. 4. Muscle membrane glucose transport, as measured by the rate of accumulation of 14C-3-O-methylglucose in the contracting muscles, was 25% lower in supercompensated than in glycogen-depleted muscles at the onset as well as at the end of the 15 min contraction period. 5. Intracellular...... as with glucose-6-phosphate (r = -0.49; P less than 0.01) concentrations. 6. It is concluded that: (a) The rate of glucose uptake in contracting skeletal muscle is dependent on the pre-contraction muscle glycogen concentration. Regulating mechanisms include limitations of membrane glucose transport as well...

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

    DEFF Research Database (Denmark)

    Kristiansen, S; Asp, Svend; Richter, Erik

    1996-01-01

    Eccentric exercise causes muscle damage and decreased muscle glycogen and glucose transporter isoform (GLUT-4) protein content. We investigated whether the contraction-induced increase in skeletal muscle glucose transport and muscle performance is affected by prior eccentric contractions. The calf...... contractions. EC rats had a significantly lower total GLUT-4 protein content in the white gastrocnemius (GW) muscle (55%) and red gastrocnemius (GR) muscle (34%) compared with muscle from the CT, ST, and CC rats. In contrast, GLUT-1 protein content was approximately twofold higher in the GW muscle in EC rats...... than in CT rats. In the GW and GR muscle, prior eccentric exercise decreased contraction-induced stimulation of glucose transport compared with CT, ST, and CC rats despite no difference in tension development and oxygen uptake among the groups. There was no change in total GLUT-4 content and glucose...

  8. Glucose uptake and transport in contracting, perfused rat muscle with different pre-contraction glycogen concentrations

    DEFF Research Database (Denmark)

    Hespel, P; Richter, Erik

    1990-01-01

    1. Glucose uptake and transport, muscle glycogen, free glucose and glucose-6-phosphate concentrations were studied in perfused resting and contracting rat skeletal muscle with different pre-contraction glycogen concentrations. Rats were pre-conditioned by a combination of swimming exercise and diet......, resulting in either low (glycogen-depleted rats), normal (control rats) or high (supercompensated rats) muscle glycogen concentrations at the time their hindlimbs were perfused. 2. Compared with control rats, pre-contraction muscle glycogen concentration was approximately 40% lower in glycogen-depleted rats......, whereas it was 40% higher in supercompensated rats. Muscle glycogen break-down correlated positively (r = 0.76; P less than 0.001) with pre-contraction muscle glycogen concentration. 3. Glucose uptake during contractions was approximately 50% higher in glycogen-depleted hindquarters than in control...

  9. Generation of Electrical Power from Stimulated Muscle Contractions Evaluated

    Science.gov (United States)

    Lewandowski, Beth; Kilgore, Kevin; Ercegovic, David B.

    2004-01-01

    This project is a collaborative effort between NASA Glenn Research Center's Revolutionary Aeropropulsion Concepts (RAC) Project, part of the NASA Aerospace Propulsion and Power Program of the Aerospace Technology Enterprise, and Case Western Reserve University's Cleveland Functional Electrical Stimulation (FES) Center. The RAC Project foresees implantable power requirements for future applications such as organically based sensor platforms and robotics that can interface with the human senses. One of the goals of the FES Center is to develop a totally implantable neural prosthesis. This goal is based on feedback from patients who would prefer a system with an internal power source over the currently used system with an external power source. The conversion system under investigation would transform the energy produced from a stimulated muscle contraction into electrical energy. We hypothesize that the output power of the system will be greater than the input power necessary to initiate, sustain, and control the electrical conversion system because of the stored potential energy of the muscle. If the system can be made biocompatible, durable, and with the potential for sustained use, then the biological power source will be a viable solution.

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

    DEFF Research Database (Denmark)

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

    2001-01-01

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

  11. Calcium-sensitivity of smooth muscle contraction in the isolated ...

    African Journals Online (AJOL)

    sensitivity of smooth muscle contraction were studied in the isolated perfused rat tail artery, employing the activators noradrenaline (NA) (3ìM) sand potassium chloride (KC1) (100mM). Experiments were conduced in Ca2+ - buffered saline.

  12. Intramuscular fatty acid metabolism in contracting and non-contracting human skeletal muscle

    DEFF Research Database (Denmark)

    Sacchetti, M; Saltin, B; Osada, T

    2002-01-01

    The present study was undertaken to investigate the fate of blood-borne non-esterified fatty acids (NEFA) entering contracting and non-contracting knee extensor muscles of healthy young individuals. [U-(13)C]-palmitate was infused into a forearm vein during 5 h of one-legged knee extensor exercis...... and degraded and that the metabolic fate of plasma NEFA entering the muscle is influenced by muscle contraction, so that a higher proportion is directed towards oxidation at the expense of storage in mTAG....

  13. Imaging two-dimensional mechanical waves of skeletal muscle contraction.

    Science.gov (United States)

    Grönlund, Christer; Claesson, Kenji; Holtermann, Andreas

    2013-02-01

    Skeletal muscle contraction is related to rapid mechanical shortening and thickening. Recently, specialized ultrasound systems have been applied to demonstrate and quantify transient tissue velocities and one-dimensional (1-D) propagation of mechanical waves during muscle contraction. Such waves could potentially provide novel information on musculoskeletal characteristics, function and disorders. In this work, we demonstrate two-dimensional (2-D) mechanical wave imaging following the skeletal muscle contraction. B-mode image acquisition during multiple consecutive electrostimulations, speckle-tracking and a time-stamp sorting protocol were used to obtain 1.4 kHz frame rate 2-D tissue velocity imaging of the biceps brachii muscle contraction. The results present novel information on tissue velocity profiles and mechanical wave propagation. In particular, counter-propagating compressional and shear waves in the longitudinal direction were observed in the contracting tissue (speed 2.8-4.4 m/s) and a compressional wave in the transverse direction of the non-contracting muscle tissue (1.2-1.9 m/s). In conclusion, analysing transient 2-D tissue velocity allows simultaneous assessment of both active and passive muscle tissue properties. Copyright © 2013 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

  14. The architecture and contraction time of intrinsic foot muscles.

    Science.gov (United States)

    Tosovic, Danijel; Ghebremedhin, Estifanos; Glen, Christopher; Gorelick, Mark; Mark Brown, J

    2012-12-01

    Although critical for effective human locomotion and posture, little data exists regarding the segmentation, architecture and contraction time of the human intrinsic foot muscles. To address this issue, the Abductor Hallucis (AH), Abductor Digiti Minimi (ADM), Flexor Digitorum Brevis (FDB) and Extensor Digitorum Brevis (EDB) were investigated utilizing a cadaveric dissection and a non-invasive whole muscle mechanomyographic (wMMG) technique. The segmental structure and architecture of formaldehyde-fixed foot specimens were determined in nine cadavers aged 60-80 years. The wMMG technique was used to determine the contraction time (Tc) of individual muscle segments, within each intrinsic foot muscle, in 12 volunteers of both genders aged between 19 and 24 years. While the pattern of segmentation and segmental -architecture (e.g. fibre length) and -Tc of individual muscle segments within the same muscle were similar, they varied between muscles. Also, the average whole muscle Tc of FDB was significantly (p muscles investigated (ADM Tc = 72 ms, EDB Tc = 72 ms and ABH Tc = 69 ms). The results suggest that the architecture and contraction time of the FDB reflect its unique direct contribution, through toe flexion, to postural stability and the rapid development of ground reaction forces during forceful activities such as running and jumping. Copyright © 2012 Elsevier Ltd. All rights reserved.

  15. Electromyography Exposes Heterogeneity in Muscle Co-Contraction following Stroke

    Directory of Open Access Journals (Sweden)

    Caitlin L. Banks

    2017-12-01

    Full Text Available Walking after stroke is often described as requiring excessive muscle co-contraction, yet, evidence that co-contraction is a ubiquitous motor control strategy for this population remains inconclusive. Co-contraction, the simultaneous activation of agonist and antagonist muscles, can be assessed with electromyography (EMG but is often described qualitatively. Here, our goal is to determine if co-contraction is associated with gait impairments following stroke. Fifteen individuals with chronic stroke and nine healthy controls walked on an instrumented treadmill at self-selected speed. Surface EMGs were collected from the medial gastrocnemius (MG, soleus (SOL, and tibialis anterior (TA of each leg. EMG envelope amplitudes were assessed in three ways: (1 no normalization, (2 normalization to the maximum value across the gait cycle, or (3 normalization to maximal M-wave. Three co-contraction indices were calculated across each agonist/antagonist muscle pair (MG/TA and SOL/TA to assess the effect of using various metrics to quantify co-contraction. Two factor ANOVAs were used to compare effects of group and normalization for each metric. Co-contraction during the terminal stance (TSt phase of gait is not different between healthy controls and the paretic leg of individuals post-stroke, regardless of the metric used to quantify co-contraction. Interestingly, co-contraction was similar between M-max and non-normalized EMG; however, normalization does not impact the ability to resolve group differences. While a modest correlation is revealed between the amount of TSt co-contraction and walking speed, the relationship is not sufficiently strong to motivate further exploration of a causal link between co-contraction and walking function after stroke. Co-contraction does not appear to be a common strategy employed by individuals after stroke. We recommend exploration of alternative EMG analysis approaches in an effort to learn more about the causal

  16. Unilateral muscle contractions enhance creative thinking.

    Science.gov (United States)

    Goldstein, Abraham; Revivo, Ketty; Kreitler, Michal; Metuki, Nili

    2010-12-01

    Following the notion of relative importance of the right hemisphere (RH) in creative thinking, we explored the possibility of enhancing creative problem solving by artificially activating the RH ahead of time using unilateral hand contractions. Participants attempted to complete the Remote Associates Test after squeezing a ball with either their left or right hand. As predicted, participants who contracted their left hand (thus activating the RH) achieved higher scores than those who used their right hand and those who did not contract either hand. Our findings indicate that tilting the hemispheric balance toward the processing mode of one hemisphere by motor activation can greatly influence the outcome of thought processes. Regardless of the specific mechanism involved, this technique has the potential for acting as a therapeutic or remedial manipulation and could have wide applications in aiding individuals with language impairments or other disorders that are believed to be related to hemispheric imbalances.

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

    Science.gov (United States)

    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.

  18. 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

  19. Airway smooth muscle excitation-contraction coupling and airway hyperresponsiveness.

    Science.gov (United States)

    Hirota, Simon; Helli, Peter B; Catalli, Adriana; Chew, Allyson; Janssen, Luke J

    2005-01-01

    The primary complaints from patients with asthma pertain to function of airway smooth muscle (ASM) function including shortness of breath, wheezing, and coughing. Thus, it is imperative to better understand the mechanisms underlying excitation-contraction coupling in ASM. Here, we review the various signaling pathways underlying contraction in ASM, and then examine how these are altered in asthma and airway hyperresponsiveness (a hallmark feature of asthma). Throughout, we highlight how studies of vascular smooth muscle have helped or hindered progress in understanding ASM physiology and pathophysiology.

  20. A 3D skeletal muscle model coupled with active contraction of muscle fibres and hyperelastic behaviour.

    Science.gov (United States)

    Tang, C Y; Zhang, G; Tsui, C P

    2009-05-11

    This paper presents a three-dimensional finite element model of skeletal muscle which was developed to simulate active and passive non-linear mechanical behaviours of the muscle during lengthening or shortening under either quasi-static or dynamic condition. Constitutive relation of the muscle was determined by using a strain energy approach, while active contraction behaviour of the muscle fibre was simulated by establishing a numerical algorithm based on the concept of the Hill's three-element muscle model. The proposed numerical algorithm could be used to predict concentric, eccentric, isometric and isotonic contraction behaviours of the muscle. The proposed numerical algorithm and constitutive model for the muscle were derived and implemented into a non-linear large deformation finite element programme ABAQUS by using user-defined material subroutines. A number of scenarios have been used to demonstrate capability of the model for simulating both quasi-static and dynamic response of the muscle. Validation of the proposed model has been performed by comparing the simulated results with the experimental ones of frog gastrocenemius muscle deformation. The effects of the fusiform muscle geometry and fibre orientation on the stress and fibre stretch distributions of frog muscle during isotonic contraction have also been investigated by using the proposed model. The predictability of the present model for dynamic response of the muscle has been demonstrated by simulating the extension of a squid tentacle during a strike to catch prey.

  1. Dynamic epigenetic responses to muscle contraction

    DEFF Research Database (Denmark)

    Rasmussen, Morten; Zierath, Juleen R; Barrès, Romain

    2014-01-01

    Skeletal muscle is a malleable organ that responds to a single acute exercise bout by inducing the expression of genes involved in structural, metabolic and functional adaptations. Several epigenetic mechanisms including histone H4 deacetylation and loss of promoter methylation have been implicated...... in modifying exercise-responsive gene expression. These transient changes suggest that epigenetic mechanisms are not restricted to early stages of human development but are broad dynamic controllers of genomic plasticity in response to environmental factors....

  2. Prior history of FDI muscle contraction: different effect on MEP amplitude and muscle activity.

    Science.gov (United States)

    Talis, V L; Kazennikov, O V; Castellote, J M; Grishin, A A; Ioffe, M E

    2014-03-01

    Motor evoked potentials (MEPs) in the right first dorsal interosseous (FDI) muscle elicited by transcranial magnetic stimulation of left motor cortex were assessed in ten healthy subjects during maintenance of a fixed FDI contraction level. Subjects maintained an integrated EMG (IEMG) level with visual feedback and reproduced this level by memory afterwards in the following tasks: stationary FDI muscle contraction at the level of 40 ± 5 % of its maximum voluntary contraction (MVC; 40 % task), at the level of 20 ± 5 % MVC (20 % task), and also when 20 % MVC was preceded by either no contraction (0-20 task), by stronger muscle contraction (40-20 task) or by no contraction with a previous strong contraction (40-0-20 task). The results show that the IEMG level was within the prescribed limits when 20 and 40 % stationary tasks were executed with and without visual feedback. In 0-20, 40-20, and 40-0-20 tasks, 20 % IEMG level was precisely controlled in the presence of visual feedback, but without visual feedback the IEMG and force during 20 % IEMG maintenance were significantly higher in the 40-0-20 task than those in 0-20 and 40-20 tasks. That is, without visual feedback, there were significant variations in muscle activity due to different prehistory of contraction. In stationary tasks, MEP amplitudes in 40 % task were higher than in 20 % task. MEPs did not differ significantly during maintenance of the 20 % level in tasks with different prehistory of muscle contraction with and without visual feedback. Thus, in spite of variations in muscle background activity due to different prehistory of contraction MEPs did not vary significantly. This dissociation suggests that the voluntary maintenance of IEMG level is determined not only by cortical mechanisms, as reflected by corticospinal excitability, but also by lower levels of CNS, where afferent signals and influences from other brain structures and spinal cord are convergent.

  3. beta-Catenin regulates airway smooth muscle contraction

    NARCIS (Netherlands)

    Jansen, Sepp R.; Van Ziel, Anna M.; Baarsma, Hoeke A.; Gosens, Reinoud

    Jansen SR, Van Ziel AM, Baarsma HA, Gosens R. beta-Catenin regulates airway smooth muscle contraction. Am J Physiol Lung Cell Mol Physiol 299: L204-L214, 2010. First published May 14, 2010; doi:10.1152/ajplung.00020.2010.-beta-Catenin is an 88-kDa member of the armadillo family of proteins that is

  4. Measurement of Periodical Contraction of Cultured Muscle Tube with Laser

    Directory of Open Access Journals (Sweden)

    Jun Takase

    2009-06-01

    Full Text Available Periodical contraction of a cultured muscle tube has been measured with laser in vitro. C2C12 (mouse myoblast cell line was cultured with High-glucose Dulbecco's Modified Eagle's Medium on a dish to make muscle tubes. Differentiation from myoblasts to myotubes was induced with an additional horse serum. Repetitive contraction of the tube was generated by electric pulses lower than sixty volts of amplitude with one milli-second of width through the electrodes of platinum, and observed with a phase-contrast microscope. A laser beam of 632.8 nm wavelength was restricted to 0.096 mm diameter, and applied to the muscle tubes on the bottom of the culture dish. Fluctuating intensity of the transmitted laser beam through the periodically contracting muscle tubes was measured, and its spectrum was analyzed. The analyzed data show that the repetitive contraction is synchronized with stimulation of the periodical electric pulses between 0.2 s and 2 s.

  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. 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...

  7. Improved Cell Culture Method for Growing Contracting Skeletal Muscle Models

    Science.gov (United States)

    Marquette, Michele L.; Sognier, Marguerite A.

    2013-01-01

    An improved method for culturing immature muscle cells (myoblasts) into a mature skeletal muscle overcomes some of the notable limitations of prior culture methods. The development of the method is a major advance in tissue engineering in that, for the first time, a cell-based model spontaneously fuses and differentiates into masses of highly aligned, contracting myotubes. This method enables (1) the construction of improved two-dimensional (monolayer) skeletal muscle test beds; (2) development of contracting three-dimensional tissue models; and (3) improved transplantable tissues for biomedical and regenerative medicine applications. With adaptation, this method also offers potential application for production of other tissue types (i.e., bone and cardiac) from corresponding precursor cells.

  8. 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

  9. 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.

  10. Nanosecond electric pulses modulate skeletal muscle calcium dynamics and contraction

    Science.gov (United States)

    Valdez, Chris; Jirjis, Michael B.; Roth, Caleb C.; Barnes, Ronald A.; Ibey, Bennett L.

    2017-02-01

    Irreversible electroporation therapy is utilized to remove cancerous tissues thru the delivery of rapid (250Hz) and high voltage (V) (1,500V/cm) electric pulses across microsecond durations. Clinical research demonstrated that bipolar (BP) high voltage microsecond pulses opposed to monophasic waveforms relieve muscle contraction during electroporation treatment. Our group along with others discovered that nanosecond electric pulses (nsEP) can activate second messenger cascades, induce cytoskeletal rearrangement, and depending on the nsEP duration and frequency, initiate apoptotic pathways. Of high interest across in vivo and in vitro applications, is how nsEP affects muscle physiology, and if nuances exist in comparison to longer duration electroporation applications. To this end, we exposed mature skeletal muscle cells to monopolar (MP) and BP nsEP stimulation across a wide range of electric field amplitudes (1-20 kV/cm). From live confocal microscopy, we simultaneously monitored intracellular calcium dynamics along with nsEP-induced muscle movement on a single cell level. In addition, we also evaluated membrane permeability with Yo-PRO-1 and Propidium Iodide (PI) across various nsEP parameters. The results from our findings suggest that skeletal muscle calcium dynamics, and nsEP-induced contraction exhibit exclusive responses to both MP and BP nsEP exposure. Overall the results suggest in vivo nsEP application may elicit unique physiology and field applications compared to longer pulse duration electroporation.

  11. Differences in muscle activation patterns during pelvic floor muscle contraction and Valsalva maneuver.

    Science.gov (United States)

    Thompson, Judith A; O'Sullivan, Peter B; Briffa, N Kathryn; Neumann, Patricia

    2006-01-01

    To investigate the different muscle activation patterns around the abdomino-pelvic cavity in continent women and their effect on pressure generation during a correct pelvic floor muscle (PFM) contraction and a Valsalva maneuver. Thirteen continent women were assessed. Abdominal, chest wall, and PFM activity and vaginal and intra-abdominal pressure (IAP), were recorded during two tasks: PFM contraction and Valsalva whilst bladder base position was monitored on trans-abdominal ultrasound. A correct PFM contraction was defined as one that resulted in bladder base elevation and a Valsalva resulted in bladder base depression. Comparison of the mean of the normalized EMG activity of all the individual muscle groups was significantly different between PFM contraction and Valsalva (P = 0.04). During a correct PFM contraction, the PFM were more active than during Valsalva (P = 0.001). During Valsalva, all the abdominal muscles (IO (P = 0.006), EO (P < 0.001), RA (P = 0.011)), and the chest wall (P < 0.001) were more active than during PFM contraction. The change in IAP was greater during Valsalva (P = 0.001) but there was no difference in the change in vaginal pressure between PFM contraction and Valsalva (P = 0.971). This study demonstrates a difference in muscle activation patterns between a correct PFM contraction and Valsalva maneuver. It is important to include assessment of the abdominal wall, chest wall, and respiration in the clinical evaluation of women performing PFM exercises as abdominal wall bracing combined with an increase in chest wall activity may cause rises in IAP and PFM descent. (c) 2005 Wiley-Liss, Inc.

  12. Importance of contraction history on muscle force of porcine urinary bladder smooth muscle.

    Science.gov (United States)

    Menzel, Robin; Böl, Markus; Siebert, Tobias

    2017-02-01

    The purpose of this study was to provide a comprehensive dataset of porcine urinary bladder smooth muscle properties. Particularly, the history dependence of force production, namely force depression (FD) following shortening and force enhancement (FE) following stretch, was analysed. During active micturition, the circumference of the urinary bladder changes enormously. Thus, FD might be an important phenomenon during smooth muscle contraction. Electrically stimulated, intact urinary bladder strips from pigs (n = 10) were suspended in an aerated-filled organ bath, and different isometric, isotonic, and isokinetic contraction protocols were performed to determine the force-length and the force-velocity relation. FD and FE were assessed in concentric and eccentric contractions with different ramp lengths and ramp velocities. Bladder smooth muscles exhibit considerable amounts of FD and FE. The amount of FD increased significantly with ramp length, while FE did not change. However, FE and FD were independent of ramp velocity. The results imply that smooth muscle bladder strips exhibit similar muscle properties and history-dependent behaviour compared to striated muscles. The provided dataset of muscle properties is important for bladder modelling as well as for the analyses and interpretation of dynamic bladder filling and voiding.

  13. Computation of fractal features based on the fractal analysis of surface electromyogram to estimate force of contraction of different muscles.

    Science.gov (United States)

    Poosapadi Arjunan, Sridhar; Kumar, Dinesh Kant

    2014-01-01

    This research study investigates the fractal properties of surface Electromyogram (sEMG) to estimate the force levels of contraction of three muscles with different cross-sectional areas (CSA): m. quadriceps--vastus lateralis, m. biceps brachii, andm. flexor digitorum superficialis. The fractal features were computed based on the fractal analysis of sEMG, signal recorded while performing sustained muscle contraction at different force levels. A comparison was performed between the fractal features and five other features reported in the literature. Linear regression analysis was carried out to determine the relationship between the force of contraction (20-100%) and features of sEMG. The results from the coefficients of regression r² show that the new fractal feature, maximum fractal length of the signal has highest correlation (range 0.88-0.90) when compared with other features which ranges from 0.34 to 0.74 for the three different muscles. This study suggests that the estimation of various levels of sustained contraction of muscles with varied CSA will provide a better insight into the biomechanics model that involves muscle properties and muscle activation.

  14. Modulation effects of cordycepin on the skeletal muscle contraction of toad gastrocnemius muscle.

    Science.gov (United States)

    Yao, Li-Hua; Meng, Wei; Song, Rong-Feng; Xiong, Qiu-Ping; Sun, Wei; Luo, Zhi-Qiang; Yan, Wen-Wen; Li, Yu-Ping; Li, Xin-Ping; Li, Hai-Hang; Xiao, Peng

    2014-03-05

    Isolated toad gastrocnemius muscle is a typical skeletal muscle tissue that is frequently used to study the motor system because it is an important component of the motor system. This study investigates the effects of cordycepin on the skeletal muscle contractile function of isolated toad gastrocnemius muscles by electrical field stimulation. Results showed that cordycepin (20 mg/l to 100 mg/l) significantly decreased the contractile responses in a concentration-dependent manner. Cordycepin (50 mg/l) also produced a rightward shift of the contractile amplitude-stimulation intensity relationship, as indicated by the increases in the threshold stimulation intensity and the saturation stimulation intensity. However, the most notable result was that the maximum amplitude of the muscle contractile force was significantly increased under cordycepin application (122±3.4% of control). This result suggests that the skeletal muscle contractile function and muscle physical fitness to the external stimulation were improved by the decreased response sensitivity in the presence of cordycepin. Moreover, cordycepin also prevented the repetitive stimulation-induced decrease in muscle contractile force and increased the recovery amplitude and recovery ratio of muscle contraction. However, these anti-fatigue effects of cordycepin on muscle contraction during long-lasting muscle activity were absent in Ca2+-free medium or in the presence of all Ca2+ channels blocker (0.4 mM CdCl2). These results suggest that cordycepin can positively affect muscle performance and provide ergogenic and prophylactic benefits in decreasing skeletal muscle fatigue. The mechanisms involving excitation-coupled Ca2+ influxes are strongly recommended.

  15. Deloading tape reduces muscle stress at rest and during contraction.

    Science.gov (United States)

    Hug, François; Ouellette, Adam; Vicenzino, Bill; Hodges, Paul W; Tucker, Kylie

    2014-12-01

    Taping techniques that aim to protect and reduce stress on an injured tissue during rehabilitation are common in sport. Called deloading tape, the mechanism of action is hypothesized to involve effects ranging from direct mechanical deloading of the underlying soft tissues to psychological effects on confidence. There is no evidence that deloading tape has direct mechanical effects. This study used an elastographic technique (supersonic shear imaging) to test the hypothesis that deloading tape applied to the skin over the rectus femoris would reduce stress within the taped area of this muscle. Thirteen healthy volunteers participated in this experiment. Muscle shear elastic modulus was compared between three treatments (no tape, deloading tape, and sham tape) in four conditions: three conditions without muscle contraction at different rectus femoris muscle-tendon unit lengths (moderately stretched, highly stretched, and shortened) and during submaximal isometric leg extension. Although there was no effect of treatment when the muscle was shortened (P = 0.99), the shear elastic modulus was significantly affected by treatment for the three other conditions (all P elastic modulus was significantly less during application of deloading tape than that during both the no tape and sham tape conditions (all P ≤ 0.001; e.g., vs no tape: moderately stretched, 8.4 ± 2.7 vs 6.7 ± 1.7 kPa; highly stretched, 25.2 ± 8.2 vs 14.4 ± 4.3 kPa; submaximal contraction, 21.3 ± 4.8 vs 14.2 ± 4.3 kPa). Through the use of elastography, this is the first study to support the hypothesis that deloading tape reduces stress in the underlying muscle region, thereby providing a biomechanical explanation for the effect observed during rehabilitation in clinical practice (reduce pain, restore function, and aid recovery). Further investigations are necessary to confirm these results in injured tissues.

  16. Characterization of muscle contraction with second harmonic generation microscopy

    Science.gov (United States)

    Prent, Nicole

    Muscle cells have the ability to change length and generate force due to orchestrated action of myosin nanomotors that cause sliding of actin filaments along myosin filaments in the sarcomeres, the fundamental contractile units, of myocytes. The correlated action of hundreds of sarcomeres is needed to produce the myocyte contractions. This study probes the molecular structure of the myofilaments and investigates the movement correlations between sarcomeres during contraction. In this study, second harmonic generation (SHG) microscopy is employed for imaging striated myocytes. Myosin filaments in striated myocytes inherently have a nonzero second-order susceptibility, [special characters omitted] and therefore generate efficient SHG. Employing polarization-in polarization-out (PIPO) SHG microscopy allows for the accurate determination of the characteristic ratio, [special characters omitted] in birefringent myocytes, which describes the structure of the myosin filament. Analysis shows that the b value at the centre of the myosin filament, where the nonlinear dipoles are better aligned, is slightly lower than the value at the edges of the filament, where there is more disorder in orientation of the nonlinear dipoles from the myosin heads. Forced stretching of myocytes resulted in an SHG intensity increase with the elongation of the sarcomere. SHG microscopy captured individual sarcomeres during contraction, allowing for the measurement of sarcomere length (SL) and SHG intensity (SI) fluctuations. The fluctuations also revealed higher SHG intensity in elongated sarcomeres. The sarcomere synchronization model (SSM) for contracting and quiescent myocytes was developed, and experimentally verified for three cases (isolated cardiomyocyte, embryonic chicken cardiomyocyte, and larva myocyte). During contraction, the action of SLs and SIs between neighbouring sarcomeres partially correlated, whereas in quiescent myocytes the SLs show an anti-correlation and the SIs have no

  17. Kinesthetic imagery training of forceful muscle contractions increases brain signal and muscle strength.

    Science.gov (United States)

    Yao, Wan X; Ranganathan, Vinoth K; Allexandre, Didier; Siemionow, Vlodek; Yue, Guang H

    2013-01-01

    The purpose of this study was to compare the effect of training using internal imagery (IMI; also known as kinesthetic imagery or first person imagery) with that of external imagery (EMI; also known as third-person visual imagery) of strong muscle contractions on voluntary muscle strengthening. Eighteen young, healthy subjects were randomly assigned to one of three groups (6 in each group): internal motor imagery (IMI), external motor imagery (EMI), or a no-practice control (CTRL) group. Training lasted for 6 weeks (~15 min/day, 5 days/week). The participants' right arm elbow-flexion strength, muscle electrical activity, and movement-related cortical potential (MRCP) were evaluated before and after training. Only the IMI group showed significant strength gained (10.8%) while the EMI (4.8%) and CTRL (-3.3%) groups did not. Only the IMI group showed a significant elevation in MRCP on scalp locations over both the primary motor (M1) and supplementary motor cortices (EMI group over M1 only) and this increase was significantly greater than that of EMI and CTRL groups. These results suggest that training by IMI of forceful muscle contractions was effective in improving voluntary muscle strength without physical exercise. We suggest that the IMI training likely strengthened brain-to-muscle (BTM) command that may have improved motor unit recruitment and activation, and led to greater muscle output. Training by IMI of forceful muscle contractions may change the activity level of cortical motor control network, which may translate into greater descending command to the target muscle and increase its strength.

  18. KINESTHETIC IMAGERY TRAINING OF FORCEFUL MUSCLE CONTRACTIONS INCREASES BRAIN SIGNAL AND MUSCLE STRENGTH

    Directory of Open Access Journals (Sweden)

    Wan X Yao

    2013-09-01

    Full Text Available The purpose of this study was to compare the effect of training using internal imagery (IMI; also known as kinesthetic imagery or first person imagery with that of external imagery (EMI; also known as third-person visual imagery of strong muscle contractions on voluntary muscle strengthening. Eighteen young, healthy subjects were randomly assigned to one of three groups (6 in each group: internal motor imagery (IMI, external motor imagery (EMI, or a no-practice control (CTRL group. Training lasted for 6 weeks (~15 min/day, 5 days/week. The participants’ right arm elbow-flexion strength, muscle electrical activity and movement-related cortical potential (MRCP were evaluated before and after training. Only the IMI group showed significant strength gained (10.8% while the EMI (4.8% and CTRL (-3.3% groups did not. Only the IMI group showed a significant elevation in MRCP on scalp locations over both the primary motor (M1 and supplementary motor cortices (EMI group over M1 only and this increase was significantly greater than that of EMI and CTRL groups. These results suggest that training by IMI of forceful muscle contractions was effective in improving voluntary muscle strength without physical exercise. We suggest that the IMI training likely strengthened brain-to-muscle (BTM command that may have improved motor unit recruitment and activation, and led to greater muscle output. Training by internal motor imagery of forceful muscle contractions may change the activity level of cortical motor control network, which may translate into greater descending command to the target muscle and increase its strength.

  19. Mechanism of soman-induced contractions in canine tracheal smooth muscle. (Reannouncement with new availability information)

    Energy Technology Data Exchange (ETDEWEB)

    Adler, M.; Moore, D.H.; Filbert, M.G.

    1992-12-31

    The actions of the irreversible organophosphorus cholinesterase (ChE) inhibitor soman were investigated on canine trachea smooth muscle in vitro. Concentrations of soman > or - 1 nM increased the amplitude and decay of contractions elicited by electric field stimulation. The effect on decay showed a marked dependence on stimulation frequency, undergoing a 2.4-fold increase between 3 and 60 Hz. Soman also potentiated tensions due to bath applied acetylcholine (ACh). Little or no potentiation was observed for contractions elicited by carbamylcholine, an agonist that is not hydrolyzed by ChE. Concentration of soman > or - 3 nM led to the appearance of sustained contractures. These contractures developed with a delayed onset and were well correlated with ChE activity. Alkylation of muscarinic receptors by propylbenzilylcholine mustard antagonized the actions of soman on both spontaneous and electrically-evoked muscle contractions. The results are consistent with a mechanism in which the toxic actions of soman are mediated by accumulation of neurally-released ACh secondary to inhibition of ChE activity. An important factor in this accumulation is suggested to be the buffering effect of the muscarinic receptors on the efflux of ACh from the neuroeffector junction. Tracheal smooth muscle, Cholinesterase inhibitors, Muscarinic receptor, Soman, Organophosphate.

  20. 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.

  1. Repetitive muscle compression reduces vascular mechano-sensitivity and the hyperemic response to muscle contraction.

    Science.gov (United States)

    Messere, A; Turturici, M; Millo, G; Roatta, S

    2017-06-01

    Animal studies have shown that the rapid hyperemic response to external muscle compression undergoes inactivation upon repetitive stimulation, but this phenomenon has never been observed in humans. The aim of the present study was to determine whether 1) the vascular mechano-sensitivity underlying muscle compression-induced hyperemia is inactivated in an inter-stimulus interval (ISI)-dependent fashion upon repetitive stimulation, as suggested by animal studies, and 2) whether such inactivation also attenuates contraction-induced hyperemia. Brachial artery blood flow was measured by echo Doppler sonography in 13 healthy adults in response to 1) single and repetitive cuff muscle compression (CMC) of the forearm (20 CMCs, 1 s ISI); 2) a sequence of CMC delivered at decreasing ISI from 120 to 2 s; and 3) electrically-stimulated contraction of the forearm muscles before and after repetitive CMC. The peak amplitude of hyperemia in response to CMC normalized to baseline decreased from 2.2 ± 0.6 to 1.4 ± 0.4 after repetitive CMC and, in general, was decreased at ISI < 240 s. The peak amplitude of contraction-induced hyperemia was attenuated after as compared to before repeated CMC (1.7 ± 0.4 and 2.6 ± 0.6, respectively). Mechano-sensitivity of the vascular network can be conditioned by previous mechanical stimulation, and such preconditioning may substantially decrease contraction-induced hyperemia.

  2. 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.

  3. Grounding after moderate eccentric contractions reduces muscle damage.

    Science.gov (United States)

    Brown, Richard; Chevalier, Gaétan; Hill, Michael

    2015-01-01

    Grounding a human to the earth has resulted in changes in the physiology of the body. A pilot study on grounding and eccentric contractions demonstrated shortened duration of pain, reduced creatine kinase (CK), and differences in blood parameters. This follow-up study was conducted to investigate the effects of grounding after moderate eccentric contractions on pain, CK, and complete blood counts. Thirty-two healthy young men were randomly divided into grounded (n=16) and sham-grounded (n=16) groups. On days 1 through 4, visual analog scale for pain evaluations and blood draws were accomplished. On day 1, the participants performed eccentric contractions of 200 half-knee bends. They were then grounded or sham-grounded to the earth for 4 hours on days 1 and 2. Both groups experienced pain on all posttest days. On day 2, the sham-grounded group experienced significant CK increase (Pgrounded group did not increase significantly; the between-group difference was significant (P=0.04). There was also an increase in the neutrophils of the grounded group on day 3 (P=0.05) compared to the sham-grounded group. There was a significant increase in platelets in the grounded group on days 2 through 4. Grounding produced changes in CK and complete blood counts that were not shared by the sham-grounded group. Grounding significantly reduced the loss of CK from the injured muscles indicating reduced muscle damage. These results warrant further study on the effects of earthing on delayed onset muscle damage.

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

    Science.gov (United States)

    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.

  5. 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.

  6. Muscle-contraction properties in overarm throwing movements.

    Science.gov (United States)

    Grezios, Apostolos K; Gissis, Ioannis Th; Sotiropoulos, Aristomenis A; Nikolaidis, Dimitrios V; Souglis, Athanasios G

    2006-02-01

    On the basis of dynamic and kinematic data, this study identifies the type of muscle contraction in unloaded overarm throwing movements. An unloaded throw or nearly unloaded throw is defined as the throw in which the external resistance is too small (e.g., the team handball, baseball, and water polo throws as well as the tennis and badminton smashes). A special arm-force-measuring apparatus was constructed to imitate an overarm throw. Forty-two subjects were placed into 3 groups: untrained subjects, weight-trained athletes, and team handball players. The measured parameters included the velocity of the initial movement, the release velocity, the velocity of the first 50 milliseconds of the concentric phase, the force value at the moment of deceleration of the initial movement, and the impulse values during the eccentric and concentric phases of the test movement. Statistically significant higher values of the above parameters (p thesis that the stretch-shortening cycle is the type of muscle contraction in unloaded overarm throws. Furthermore, it is possible to increase the throw velocity by increasing the velocity of the initial movement (i.e., by provoking higher inertia forces).

  7. Interleukin-6 production in contracting human skeletal muscle is influenced by pre-exercise muscle glycogen content

    DEFF Research Database (Denmark)

    Steensberg, A; Febbraio, M A; Osada, T

    2001-01-01

    1. Prolonged exercise results in a progressive decline in glycogen content and a concomitant increase in the release of the cytokine interleukin-6 (IL-6) from contracting muscle. This study tests the hypothesis that the exercise-induced IL-6 release from contracting muscle is linked...

  8. Noninvasive Cu-64-ATSM and PET/CT Assessment of Hypoxia in Rat Skeletal Muscles and Tendons During Muscle Contractions

    DEFF Research Database (Denmark)

    Skovgaard, D.; Kjaer, M.; Madsen, J.

    2009-01-01

    expression of 2 hypoxia-related genes, hypoxia-inducible factor 1 alpha (HIF1 alpha) and carbonic anhydrase III (CAIII). Methods: Two groups of Wistar rats performed 1-leg contractions of the calf muscle by electrostimulation of the sciatic nerve. After 10 min of muscle contractions, Cu-64-ATSM was injected...

  9. Muscle tissue oxygenation, pressure, electrical, and mechanical responses during dynamic and static voluntary contractions

    DEFF Research Database (Denmark)

    Vedsted, Pernille; Blangsted, Anne Katrine; Søgaard, Karen

    2006-01-01

    Dynamic muscle contractions have been shown to cause greater energy turnover and fatigue than static contractions performed at a corresponding force level. Therefore, we hypothesized that: (1) electro- (EMG) and mechanomyography (MMG), intramuscular pressure (IMP), and reduction in muscle oxygen...... similar in spite of major differences in the MMG and EMG responses of the muscle during contraction periods. This may relate to the surprisingly lower IMP in DYN than IST....

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

    Directory of Open Access Journals (Sweden)

    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

  11. 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.

  12. 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...

  13. Dynamics of Muscle Microcirculatory and Blood-myocyte O2 Flux During Contractions

    Science.gov (United States)

    Poole, David C.; Copp, Steven W.; Hirai, Daniel M.; Musch, Timothy I.

    2011-01-01

    The O2 requirements of contracting skeletal muscle may increase 100-fold above rest. In 1919 August Krogh’s brilliant insights recognized the capillary as the principal site for this increased blood-myocyte O2 flux. Based on the premise that most capillaries did not sustain RBC flux at rest Krogh proposed that capillary recruitment (i.e., initiation of red blood cell (RBC) flux in previously non-flowing capillaries) increased the capillary surface area available for O2 flux and reduced mean capillary-to-mitochondrial diffusion distances. More modern experimental approaches reveal that most muscle capillaries may support RBC flux at rest. Thus, rather than contraction-induced capillary recruitment per se, increased RBC flux and hematocrit within already-flowing capillaries likely elevate perfusive and diffusive O2 conductances and hence blood-myocyte O2 flux. Additional surface area for O2 exchange is recruited but, crucially, this may occur along the length of already-flowing capillaries (i.e. longitudinal recruitment). Today, the capillary is still considered the principal site for O2 and substrate delivery to contracting skeletal muscle. Indeed, the presence of very low intramyocyte O2 partial pressures (PO2’s) and the absence of PO2 gradients, whilst refuting the relevance of diffusion distances, place an even greater importance on capillary hemodynamics. This emergent picture calls for a paradigm-shift in our understanding of the function of capillaries by de-emphasizing de novo ‘capillary recruitment.’ Diseases such as heart failure impair blood-myocyte O2 flux, in part, by decreasing the proportion of RBC-flowing capillaries. Knowledge of capillary function in healthy muscle is requisite for identification of pathology and efficient design of therapeutic treatments. PMID:21199399

  14. 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

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

    Science.gov (United States)

    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.

  16. NO-sGC Pathway Modulates Ca2+ Release and Muscle Contraction in Zebrafish Skeletal Muscle

    Directory of Open Access Journals (Sweden)

    Zhou Xiyuan

    2017-08-01

    Full Text Available Vertebrate skeletal muscle contraction and relaxation is a complex process that depends on Ca2+ ions to promote the interaction of actin and myosin. This process can be modulated by nitric oxide (NO, a gas molecule synthesized endogenously by (nitric oxide synthase NOS isoforms. At nanomolar concentrations NO activates soluble guanylate cyclase (sGC, which in turn activates protein kinase G via conversion of GTP into cyclic GMP. Alternatively, NO post-translationally modifies proteins via S-nitrosylation of the thiol group of cysteine. However, the mechanisms of action of NO on Ca2+ homeostasis during muscle contraction are not fully understood and we hypothesize that NO exerts its effects on Ca2+ homeostasis in skeletal muscles mainly through negative modulation of Ca2+ release and Ca2+ uptake via the NO-sGC-PKG pathway. To address this, we used 5–7 days-post fecundation-larvae of zebrafish, a well-established animal model for physiological and pathophysiological muscle activity. We evaluated the response of muscle contraction and Ca2+ transients in presence of SNAP, a NO-donor, or L-NAME, an unspecific NOS blocker in combination with specific blockers of key proteins of Ca2+ homeostasis. We also evaluate the expression of NOS in combination with dihydropteridine receptor, ryanodine receptor and sarco/endoplasmic reticulum Ca2+ ATPase. We concluded that endogenous NO reduced force production through negative modulation of Ca2+ transients via the NO-sGC pathway. This effect could be reversed using an unspecific NOS blocker or sGC blocker.

  17. Rac1 is a novel regulator of contraction-stimulated glucose uptake in skeletal muscle

    DEFF Research Database (Denmark)

    Sylow, Lykke; Jensen, Thomas Elbenhardt; Kleinert, Maximilian

    2013-01-01

    In skeletal muscle, the actin cytoskeleton-regulating GTPase, Rac1, is necessary for insulin-dependent GLUT4 translocation. Muscle contraction increases glucose transport and represents an alternative signaling pathway to insulin. Whether Rac1 is activated by muscle contraction and regulates...... contraction-induced glucose uptake is unknown. Therefore, we studied the effects of in vivo exercise and ex vivo muscle contractions on Rac1 signaling and its regulatory role in glucose uptake in mice and humans. Muscle Rac1-GTP binding was increased after exercise in mice (~60-100%) and humans (~40......%), and this activation was AMP-activated protein kinase independent. Rac1 inhibition reduced contraction-stimulated glucose uptake in mouse muscle by 55% in soleus and by 20-58% in extensor digitorum longus (EDL; P glucose uptake was decreased by 27% (P = 0...

  18. Contractions induced by sodium withdrawal in crab (Callinectes danae) muscle fibres.

    Science.gov (United States)

    Madeira, A C; Suarez-Kurtz, G

    1983-05-01

    A study was made of the effects of Na removal on the resting tension of single muscle fibres of the crab Callinectes danae. Reduction of [Na]o (replacement with Li, Tris or choline) below a threshold value, typical for each fibre, induced spontaneous, local contractions randomly dispersed along the fibres; this was followed by propagated contractile waves and tension oscillations. Sustained contractures were occasionally seen at threshold [Na]o and were consistently observed when [Na]o was further reduced. The Na withdrawal contractions depended on [Ca]o and were abolished in Ca-free media; they were restored within seconds after the addition of Ca (3-12 mM) or Sr (15-25 mM), but not Ba (10-100 mM), to the media. Caffeine (0.2-1.0 mM) facilitated, whereas La (2-5 mM), procaine (1 mM) or lidocaine (10 mM) inhibited the Na-withdrawal contractions. It is concluded that increased Ca influx across the sarcolemma and release of stored Ca from the sarcoplasmic reticulum are involved in the contractions induced by Na-deficient solutions in crab fibres.

  19. Mechanistic role of movement and strain sensitivity in muscle contraction.

    Science.gov (United States)

    Davis, Julien S; Epstein, Neal D

    2009-04-14

    Tension generation can be studied by applying step perturbations to contracting muscle fibers and subdividing the mechanical response into exponential phases. The de novo tension-generating isomerization is associated with one of these phases. Earlier work has shown that a temperature jump perturbs the equilibrium constant directly to increase tension. Here, we show that a length jump functions quite differently. A step release (relative movement of thick and thin filaments) appears to release a steric constraint on an ensemble of noncompetent postphosphate release actomyosin cross-bridges, enabling them to generate tension, a concentration jump in effect. Structural studies [Taylor KA, et al. (1999) Tomographic 3D reconstruction of quick-frozen, Ca(2+)-activated contracting insect flight muscle. Cell 99:421-431] that map to these kinetics indicate that both catalytic and lever arm domains of noncompetent myosin heads change angle on actin, whereas lever arm movement alone mediates the power stroke. Together, these kinetic and structural observations show a 13-nm overall interaction distance of myosin with actin, including a final 4- to 6-nm power stroke when the catalytic domain is fixed on actin. Raising fiber temperature with both perturbation techniques accelerates the forward, but slows the reverse rate constant of tension generation, kinetics akin to the unfolding/folding of small proteins. Decreasing strain, however, causes both forward and reverse rate constants to increase. Despite these changes in rate, the equilibrium constant is strain-insensitive. Activation enthalpy and entropy data show this invariance to be the result of enthalpy-entropy compensation. Reaction amplitudes confirm a strain-invariant equilibrium constant and thus a strain-insensitive ratio of pretension- to tension-generating states as work is done.

  20. Aging interferes central control mechanism for eccentric muscle contraction.

    Science.gov (United States)

    Yao, Wan X; Li, Jinqi; Jiang, Zhiguo; Gao, Jia-Hong; Franklin, Crystal G; Huang, Yufei; Lancaster, Jack L; Yue, Guang H

    2014-01-01

    Previous studies report greater activation in the cortical motor network in controlling eccentric contraction (EC) than concentric contraction (CC) despite lower muscle activation level associated with EC vs. CC in healthy, young individuals. It is unknown, however, whether elderly people exhibiting increased difficulties in performing EC than CC possess this unique cortical control mechanism for EC movements. To address this question, we examined functional magnetic resonance imaging (fMRI) data acquired during EC and CC of the first dorsal interosseous (FDI) muscle in 11 young (20-32 years) and 9 old (67-73 years) individuals. During the fMRI experiment, all subjects performed 20 CC and 20 EC of the right FDI with the same angular distance and velocity. The major findings from the behavioral and fMRI data analysis were that (1) movement stability was poorer in EC than CC in the old but not the young group; (2) similar to previous electrophysiological and fMRI reports, the EC resulted in significantly stronger activation in the motor control network consisting of primary, secondary and association motor cortices than CC in the young and old groups; (3) the biased stronger activation towards EC was significantly greater in the old than the young group especially in the secondary and association cortices such as supplementary and premotor motor areas and anterior cingulate cortex; and (4) in the primary motor and sensory cortices, the biased activation towards EC was significantly greater in the young than the old group. Greater activation in higher-order cortical fields for controlling EC movement by elderly adults may reflect activities in these regions to compensate for aging-related impairments in the ability to control complex EC movements. Our finding is useful for potentially guiding the development of targeted therapies to counteract age-related movement deficits and to prevent injury.

  1. Muscle co-contraction patterns in robot-mediated force field learning to guide specific muscle group training.

    Science.gov (United States)

    Pizzamiglio, Sara; Desowska, Adela; Shojaii, Pegah; Taga, Myriam; Turner, Duncan L

    2017-01-01

    Muscle co-contraction is a strategy of increasing movement accuracy and stability employed in dealing with force perturbation of movement. It is often seen in neuropathological populations. The direction of movement influences the pattern of co-contraction, but not all movements are easily achievable for populations with motor deficits. Manipulating the direction of the force instead, may be a promising rehabilitation protocol to train movement with use of a co-contraction reduction strategy. Force field learning paradigms provide a well described procedure to evoke and test muscle co-contraction. The aim of this study was to test the muscle co-contraction pattern in a wide range of arm muscles in different force-field directions utilising a robot-mediated force field learning paradigm of motor adaptation. Forty-two participants volunteered to participate in a study utilising robot-mediated force field motor adaptation paradigm with a clockwise or counter-clockwise force field. Kinematics and surface electromyography (EMG) of eight arm muscles were measured. Both muscle activation and co-contraction was earlier and stronger in flexors in the clockwise condition and in extensors in the counter-clockwise condition. Manipulating the force field direction leads to changes in the pattern of muscle co-contraction.

  2. Adenosine formation in contracting primary rat skeletal muscle cells and endothelial cells in culture

    DEFF Research Database (Denmark)

    Hellsten, Ylva; Frandsen, Ulrik

    1997-01-01

    1. The present study examined the capacity for adenosine formation, uptake and metabolism in contracting primary rat muscle cells and in microvascular endothelial cells in culture. 2. Strong and moderate electrical simulation of skeletal muscle cells led to a significantly greater increase...... in the extracellular adenosine concentration (421 +/- 91 and 235 +/- 30 nmol (g protein)-1, respectively; P muscle cells (161 +/- 20 nmol (g protein)-1). The ATP concentration was lower (18%; P muscle cells....... 3. Addition of microvascular endothelial cells to the cultured skeletal muscle cells enhanced the contraction-induced accumulation of extracellular adenosine (P cells in culture alone did not cause extracellular accumulation of adenosine. 4. Skeletal muscle cells were...

  3. Regulation of GPCR-mediated smooth muscle contraction : implications for asthma and pulmonary hypertension

    NARCIS (Netherlands)

    Wright, D B; Tripathi, S; Sikarwar, A; Santosh, K T; Perez-Zoghbi, J; Ojo, O O; Irechukwu, N; Ward, J P T; Schaafsma, D

    Contractile G-protein-coupled receptors (GPCRs) have emerged as key regulators of smooth muscle contraction, both under healthy and diseased conditions. This brief review will discuss some key topics and novel insights regarding GPCR-mediated airway and vascular smooth muscle contraction as

  4. 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.

  5. Rac1- a novel regulator of contraction-stimulated glucose uptake in skeletal muscle

    DEFF Research Database (Denmark)

    Sylow, Lykke; Møller, Lisbeth L V; Kleinert, Maximilian

    2014-01-01

    Muscle contraction stimulates muscle glucose uptake by facilitating translocation of the glucose transporter 4 from intracellular locations to the cell surface, which allows for diffusion of glucose into the myofibers. However, the intracellular mechanisms regulating this process are not well...... understood. The GTPase, Rac1 has, until recently, only been investigated with regards to its involvement in insulin-stimulated glucose uptake. However, we recently found that Rac1 is activated during muscle contraction and exercise in mice and humans. Remarkably, Rac1 seems to be necessary for exercise....../contraction-stimulated glucose uptake in skeletal muscle, since muscle-specific Rac1 knockout mice display reduced ex vivo contraction- and in vivo exercise-stimulated glucose uptake in skeletal muscle. The molecular mechanisms by which Rac1 regulate glucose uptake is presently unknown. However, recent studies link Rac1...

  6. Calibration of EMG to force for knee muscles is applicable with submaximal voluntary contractions

    NARCIS (Netherlands)

    Doorenbosch, C.A.M.; Joosten, A.; Harlaar, J.

    2005-01-01

    Purpose: In this study, the influence of using submaximal isokinetic contractions about the knee compared to maximal voluntary contractions as input to obtain the calibration of an EMG-force model for knee muscles is investigated. Methods: Isokinetic knee flexion and extension contractions were

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

    Directory of Open Access Journals (Sweden)

    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.

  8. Changes in Quadriceps Muscle Activity During Sustained Recreational Alpine Skiing

    OpenAIRE

    Josef Kröll; Erich Müller; Seifert, John G.; Wakeling, James M.

    2011-01-01

    During a day of skiing thousands of repeated contractions take place. Previous research on prolonged recreational alpine skiing show that physiological changes occur and hence some level of fatigue is inevitable. In the present paper the effect of prolonged skiing on the recruitment and coordination of the muscle activity was investigated. Six subjects performed 24 standardized runs. Muscle activity during the first two (PREskiing) and the last two (POSTskiing) runs was measured from the vast...

  9. Membrane charge moved at contraction thresholds in skeletal muscle fibres.

    Science.gov (United States)

    Horowicz, P; Schneider, M F

    1981-05-01

    1. The current I(Q) due to membrane charge movement and the threshold pulse duration t(th) required to produce microscopically just-detectable contraction were determined for pulses to a variety of membrane potentials in tendon-terminated short segments of cut frog skeletal muscle fibres voltage-clamped using a single gap technique.2. The time course Q(t) of membrane charge movement was calculated as the running integral of I(Q). The threshold charge Q(th) moved by pulses which produced just-detectable contraction was estimated as Q(t(th)).3. Q(th) was constant for pulses to potentials ranging from about -45 mV, the rheobase potential for contraction, to about -15 mV, where t(th) was about 9 msec. The mean Q(th) from fourteen fibres was 11.5 nC/muF, when the holding potential was about -100 mV.4. Prepulses of 50 msec which were themselves sub-rheobase for producing contraction decreased the t(th) for an immediately following test pulse. The total threshold charge moved during the prepulse and during t(th) of the test pulse was equal to Q(th) for the test pulse without prepulse.5. Items 3 and 4 above indicate that t(th) is determined by the time required to move a set amount of intramembrane charge, independent of the kinetics of the charge movement.6. Steady partial fibre depolarization to between -70 and -55 mV increased t(th) at all membrane potentials and elevated the rheobase potential for contraction. Slight further steady depolarization totally eliminated contraction.7. Steady partial depolarization decreased the total ON charge movement Q(ON) by about the same factor for pulses to all potentials tested.8. Q(th) for partially depolarized but still-contracting fibres remained approximately independent of membrane potential from rheobase to about 0 mV but was slightly less than Q(th) for the same fibres when fully polarized.9. Steady partial depolarizations which reduced the mean (+/-s.d.) ON charge movement Q(ON) to 60 +/- 8% of its value under full

  10. Charge movement and depolarization-contraction coupling in arthropod vs. vertebrate skeletal muscle.

    OpenAIRE

    Scheuer, T; Gilly, W F

    1986-01-01

    Voltage-dependent charge movement has been characterized in arthropod skeletal muscle. Charge movement in scorpion (Centuroides sculpturatus) muscle is distinguishable from that in vertebrate skeletal muscle by criteria of kinetics, voltage dependence, and pharmacology. The function of scorpion charge movement is gating of calcium channels in the sarcolemma, and depolarization-contraction coupling relies on calcium influx through these channels.

  11. Charge movement and depolarization-contraction coupling in arthropod vs. vertebrate skeletal muscle.

    Science.gov (United States)

    Scheuer, T; Gilly, W F

    1986-11-01

    Voltage-dependent charge movement has been characterized in arthropod skeletal muscle. Charge movement in scorpion (Centuroides sculpturatus) muscle is distinguishable from that in vertebrate skeletal muscle by criteria of kinetics, voltage dependence, and pharmacology. The function of scorpion charge movement is gating of calcium channels in the sarcolemma, and depolarization-contraction coupling relies on calcium influx through these channels.

  12. Contractions but not AICAR increase FABPpm content in rat muscle sarcolemma

    DEFF Research Database (Denmark)

    Jeppesen, Jacob; Albers, Peter; Luiken, Joost J.

    2009-01-01

    In the present study, it was investigated whether acute muscle contractions in rat skeletal muscle increased the protein content of FABPpm in the plasma membrane. Furthermore, the effect of AICAR stimulation on FAT/CD36 and FABPpm protein content in sarcolemma of rat skeletal muscle was evaluated...

  13. Toward Optimizing Vestibular Evoked Myogenic Potentials: Normalization Reduces the Need for Strong Neck Muscle Contraction.

    Science.gov (United States)

    Noij, Kimberley S; Herrmann, Barbara S; Rauch, Steven D; Guinan, John J

    2018-01-12

    The cervical vestibular evoked myogenic potential (cVEMP) represents an inhibitory reflex of the saccule measured in the ipsilateral sternocleidomastoid muscle (SCM) in response to acoustic or vibrational stimulation. Since the cVEMP is a modulation of SCM electromyographic (EMG) activity, cVEMP amplitude is proportional to muscle EMG amplitude. We sought to evaluate muscle contraction influences on cVEMP peak-to-peak amplitudes (VEMPpp), normalized cVEMP amplitudes (VEMPn), and inhibition depth (VEMPid). cVEMPs at 500 Hz were measured in 25 healthy subjects for 3 SCM EMG contraction ranges: 45-65, 65-105, and 105-500 μV root mean square (r.m.s.). For each range, we measured cVEMP sound level functions (93-123 dB peSPL) and sound off, meaning that muscle contraction was measured without acoustic stimulation. The effect of muscle contraction amplitude on VEMPpp, VEMPn, and VEMPid and the ability to distinguish cVEMP presence/absence were evaluated. VEMPpp amplitudes were significantly greater at higher muscle contractions. In contrast, VEMPn and VEMPid showed no significant effect of muscle contraction. Cohen's d indicated that for all 3 cVEMP metrics contraction amplitude variations produced little change in the ability to distinguish cVEMP presence/absence. VEMPid more clearly indicated saccular output because when no acoustic stimulus was presented the saccular inhibition estimated by VEMPid was zero, unlike those by VEMPpp and VEMPn. Muscle contraction amplitude strongly affects VEMPpp amplitude, but contractions 45-300 μV r.m.s. produce stable VEMPn and VEMPid values. Clinically, there may be no need for subjects to exert high contraction effort. This is especially beneficial in patients for whom maintaining high SCM contraction amplitudes is challenging. © 2018 S. Karger AG, Basel.

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

    Science.gov (United States)

    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.

  15. Reduced exercise hyperaemia in claf muscles working at high contraction frequencies.

    Science.gov (United States)

    Kagaya, A

    1992-01-01

    The effects of muscle contraction frequency on blood flow to the calf muscle (Qcalf) were studied in six female subjects, who performed dynamic plantar flexions at frequencies of 20, 40, 60, 80 and 100 contractions.min-1, in a supine position. The Qcalf measured by a mercury-in-rubber strain gauge plethysmograph, increased as contraction frequency increased and reached a peak at 60-80 contractions.min-1. After 100 plantar flexions at 60 contractions.min-1, the mean Qcalf was 30.95 (SEM 4.52) ml.100 ml-1.min-1. At 100 contractions.min-1, however, it decreased significantly compared with that at 60 contractions.min-1 at a specified time (2 min or exhaustion) or after a fixed amount of work (100 contractions). The contraction frequency at which Qcalf reached a peak depended on the duration of exercise. The heart rate showed its highest mean value at 60 contractions.min-1 and decreased significantly at 100 contractions.min-1. The mean blood pressure was lower at 100 contractions.min-1 than at 60 contractions.min-1. The relaxation period between contractions, measured by recording the electromyogram from the gastrocnemius muscles, shortened markedly as the frequency increased; the mean value at 100 contractions.min-1 was 0.14 (SEM 0.02) s, which corresponded to 35.7% of the contraction time. This shortened relaxation period between contractions should have led to the inhibition of exercise hyperaemia at the higher contraction frequencies.

  16. Agonist muscle adaptation accompanied by antagonist muscle atrophy in the hindlimb of mice following stretch-shortening contraction training.

    Science.gov (United States)

    Rader, Erik P; Naimo, Marshall A; Ensey, James; Baker, Brent A

    2017-02-02

    The vast majority of dynamometer-based animal models for investigation of the response to chronic muscle contraction exposure has been limited to analysis of isometric, lengthening, or shortening contractions in isolation. An exception to this has been the utilization of a rat model to study stretch-shortening contractions (SSCs), a sequence of consecutive isometric, lengthening, and shortening contractions common during daily activity and resistance-type exercise. However, the availability of diverse genetic strains of rats is limited. Therefore, the purpose of the present study was to develop a dynamometer-based SSC training protocol to induce increased muscle mass and performance in plantarflexor muscles of mice. Young (3 months old) C57BL/6 mice were subjected to 1 month of plantarflexion SSC training. Hindlimb muscles were analyzed for muscle mass, quantitative morphology, myogenesis/myopathy relevant gene expression, and fiber type distribution. The main aim of the research was achieved when training induced a 2-fold increase in plantarflexion peak torque output and a 19% increase in muscle mass for the agonist plantaris (PLT) muscle. In establishing this model, several outcomes emerged which raised the value of the model past that of being a mere recapitulation of the rat model. An increase in the number of muscle fibers per transverse muscle section accounted for the PLT muscle mass gain while the antagonist tibialis anterior (TA) muscle atrophied by 30% with preferential atrophy of type IIb and IIx fibers. These alterations were accompanied by distinct gene expression profiles. The findings confirm the development of a stretch-shortening contraction training model for the PLT muscle of mice and demonstrate that increased cross-sectional fiber number can occur following high-intensity SSC training. Furthermore, the TA muscle atrophy provides direct evidence for the concept of muscle imbalance in phasic non-weight bearing muscles, a concept largely

  17. 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.

  18. 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

  19. Enhanced muscle insulin sensitivity after contraction/exercise is mediated by AMPK

    DEFF Research Database (Denmark)

    Kjøbsted, Rasmus; Munk-Hansen, Nanna; Birk, Jesper Bratz

    2017-01-01

    Earlier studies have demonstrated that muscle insulin sensitivity to stimulate glucose uptake is enhanced several hours after an acute bout of exercise. Using 5-aminoimidazole-4-carboxamide-ribonucleotide (AICAR), we recently demonstrated that prior activation of AMPK is sufficient to increase...... insulin sensitivity in mouse skeletal muscle. Here we aimed to determine whether activation of AMPK is also a prerequisite for the ability of muscle contraction to increase insulin sensitivity. We found that prior in situ contraction of m. extensor digitorum longus (EDL) and treadmill exercise increased...... muscle and whole body insulin sensitivity in wild type (WT) mice, respectively. These effects were not found in AMPKα1α2 muscle-specific knockout mice. Prior in situ contraction did not increase insulin sensitivity in m. soleus from either genotype. Improvement in muscle insulin sensitivity...

  20. Cell bodies of the trigeminal proprioceptive neurons that transmit reflex contraction of the levator muscle are located in the mesencephalic trigeminal nucleus in rats.

    Science.gov (United States)

    Fujita, Kenya; Matsuo, Kiyoshi; Yuzuriha, Shunsuke; Kawagishi, Kyutaro; Moriizumi, Tetsuji

    2012-12-01

    Since the levator and frontalis muscles lack interior muscle spindles despite being antigravity mixed muscles to involuntarily sustain eyelid opening and eyebrow lifting, this study has proposed a hypothetical mechanism to compensate for this anatomical defect. The voluntary contraction of fast-twitch fibres of the levator muscle stretches the mechanoreceptors in Müller's muscle to evoke proprioception, which continuously induces reflex contraction of slow-twitch fibres of the levator and frontalis muscles. This study confirmed the presence of cell bodies of the trigeminal proprioceptive neurons that transmit reflex contraction of the levator and frontalis muscles. After confirming that severing the trigeminal proprioceptive fibres that innervate the mechanoreceptors in Müller's muscle induced ipsilateral eyelid ptosis, Fluorogold was applied as a tracer to the proximal stump of the trigeminal proprioceptive nerve in rats. Fluorogold labelled the cell bodies of the trigeminal proprioceptive neurons, not in any regions of the rat brain including the trigeminal ganglion, but in the ipsilateral mesencephalic trigeminal nucleus neighbouring the locus ceruleus. Some Fluorogold particles accumulated in the area of the locus ceruleus. The trigeminal proprioceptive neurons could be considered centrally displaced ganglion cells to transmit afferent signal from the mechanoreceptors in Müller's muscle to the mesencephalon, where they may be able to make excitatory synaptic connections with both the oculomotor neurons and the frontalis muscle motoneurons for the involuntary coordination of the eyelid and eyebrow activities, and potentially to the locus ceruleus.

  1. Analysis of Muscle Contraction on Pottery Manufacturing Process Using Electromyography (EMG)

    Science.gov (United States)

    Soewardi, Hartomo; Azka Rahmayani, Amalia

    2016-01-01

    One of the most common problems in pottery manufacturing process is musculoskeletal disorders on workers. This disorder was caused by uncomfortable posture where the workers sit on the floor with one leg was folded and another was twisted for long duration. Back, waist, buttock, and right knee frequently experience the disorders. The objective of this research is to investigate the muscle contraction at such body part of workers in manufacturing process of pottery. Electromyography is used to investigate the muscle contraction based on the median frequency signal. Focus measurements is conducted on four muscles types. They are lower interscapular muscle on the right and left side, dorsal lumbar muscle, and lateral hamstring muscle. Statistical analysis is conducted to test differences of muscle contraction between female and male. The result of this research showed that the muscle which reached the highest contraction is dorsal lumbar muscle with the average of median frequency is 51,84 Hz. Then followed by lower interscapular muscle on the left side with the average of median frequency is 31,30 hz, lower interscapular muscle on the right side average of median frequency is 31,24 Hz, and lateral hamstring muscle average of median frequency is 21,77 Hz. Based on the statistic analysis result, there were no differences between male and female on left and right lower interscapular muscle and dorsal lumbar muscle but there were differences on lateral hamstring muscle with the significance level is 5%. Besides that, there were differences for all combination muscle types with the level of significance is 5%.

  2. Comparative Biomechanics of Thick Filaments and Thin Filaments with Functional Consequences for Muscle Contraction

    Directory of Open Access Journals (Sweden)

    Mark S. Miller

    2010-01-01

    Full Text Available The scaffold of striated muscle is predominantly comprised of myosin and actin polymers known as thick filaments and thin filaments, respectively. The roles these filaments play in muscle contraction are well known, but the extent to which variations in filament mechanical properties influence muscle function is not fully understood. Here we review information on the material properties of thick filaments, thin filaments, and their primary constituents; we also discuss ways in which mechanical properties of filaments impact muscle performance.

  3. Soleus muscle in glycosylation-deficient muscular dystrophy is protected from contraction-induced injury.

    Science.gov (United States)

    Gumerson, Jessica D; Kabaeva, Zhyldyz T; Davis, Carol S; Faulkner, John A; Michele, Daniel E

    2010-12-01

    The glycosylation of dystroglycan is required for its function as a high-affinity laminin receptor, and loss of dystroglycan glycosylation results in congenital muscular dystrophy. The purpose of this study was to investigate the functional defects in slow- and fast-twitch muscles of glycosylation-deficient Large(myd) mice. While a partial alteration in glycosylation of dystroglycan in heterozygous Large(myd/+) mice was not sufficient to alter muscle function, homozygous Large(myd/myd) mice demonstrated a marked reduction in specific force in both soleus and extensor digitorum longus (EDL) muscles. Although EDL muscles from Large(myd/myd) mice were highly susceptible to lengthening contraction-induced injury, Large(myd/myd) soleus muscles surprisingly showed no greater force deficit compared with wild-type soleus muscles even after five lengthening contractions. Despite no increased susceptibility to injury, Large(myd/myd) soleus muscles showed loss of dystroglycan glycosylation and laminin binding activity and dystrophic pathology. Interestingly, we show that soleus muscles have a markedly higher sarcolemma expression of β(1)-containing integrins compared with EDL and gastrocnemius muscles. Therefore, we conclude that β(1)-containing integrins play an important role as matrix receptors in protecting muscles containing slow-twitch fibers from contraction-induced injury in the absence of dystroglycan function, and that contraction-induced injury appears to be a separable phenotype from the dystrophic pathology of muscular dystrophy.

  4. 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.

  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.

    Science.gov (United States)

    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. Tendon palpation during agonist contraction and antagonist co-contraction to assess wrist flexor and extensor muscle function.

    Science.gov (United States)

    Bertelli, J A

    2015-04-01

    The aim of this study was to validate direct tendon palpation during agonist contraction and antagonist co-contraction as a method to assess wrist flexor and extensor muscle function in cases of upper limb paralysis. On one occasion, five doctors examined 17 patients with partial paralysis of the upper limb resulting from brachial plexus or cervical spinal cord injury. We asked examiners to determine if the extensor carpi radialis longus (ECRL), extensor carpi radialis brevis (ECRB), extensor carpi ulnaris (ECU), flexor carpi radialis (FCR), flexor carpi ulnaris (FCU) and palmaris longus (PL) were paralyzed, weak or strong in each patient. Examiners tested flexion - extension and radial - ulnar deviation against resistance and palpated wrist motor tendons. While palpating tendons, co-contractions were encouraged by soliciting finger extension to evaluate the FCU, thumb extension to evaluate the ECU, and finger flexion to evaluate the ECRB. Kappa values were 0.8 for the ECRL, 0.7 for the ECRB, 0.5 for the ECU, 0.8 for the FCR, 0.6 for the PL, and 0.8 for the FCU, indicating moderate to almost perfect agreement between examiners. Tendon palpation during muscle examination was adequate to identify complete paralysis, as well as weak and strong muscle contractions. This assessment helps to identify muscles that could be used during nerve or tendon transfer for reconstruction of extensive upper limb paralysis. Copyright © 2015 Elsevier Masson SAS. All rights reserved.

  8. Shakuyaku-kanzo-to inhibits smooth muscle contractions of human pregnant uterine tissue in vitro.

    Science.gov (United States)

    Tsuji, Shoko; Yasuda, Katsuhiko; Sumi, Genichiro; Cho, Hisayuu; Tsuzuki, Tomoko; Okada, Hidetaka; Kanzaki, Hideharu

    2012-07-01

    Shakuyaku-kanzo-to (SK) is a herbal medicine and is known to possess an antispasmodic effect on skeletal muscle and intestinal smooth muscle. However, it is unclear whether SK is effective in antagonizing uterine smooth muscle contractions. Herein, we investigated the effects of SK on smooth muscle contractions of human pregnant uterine samples. We prepared myometrial strips from uterine tissues of pregnant women who underwent cesarean section for obstetrical indications, and examined the inhibitory effects of SK and its components, shakuyaku (S) and kanzo (K), on agonist-induced and spontaneous contractions in vitro. Oxytocin, prostaglandinF(2α) , and high KCl were utilized as agonists in this study. SK inhibited agonist-induced and spontaneous contractions in a dose-dependent manner. Inhibition of SK on oxytocin-induced contractions occurred at a concentration of 100 µg/mL and reached maximum effect at a concentration of more than 1000 µg/mL. The half max inhibitory concentration of SK was approximately 440 µg/mL in oxytocin-induced contractions. SK at 1000 µg/mL completely inhibited the oxytocin- and prostaglandinF(2α)-induced contractions but not the high KCl-induced contractions. The inhibitory effects on agonist-induced contractions of K, but not S, matched those of SK. These results suggest that the inhibitory effect of SK on smooth muscle contractions is due to K. The mechanism of the inhibitory effects of SK on oxytocin- and prostaglandinF(2α) -induced contractions may differ from that on KCl-induced contractions. © 2012 The Authors. Journal of Obstetrics and Gynaecology Research © 2012 Japan Society of Obstetrics and Gynecology.

  9. Significance of insulin for glucose metabolism in skeletal muscle during contractions

    DEFF Research Database (Denmark)

    Hespel, P; Vergauwen, Lieven; Vandenberghe, K

    1996-01-01

    is effected primarily via mechanisms exerted within the muscle cell related to the contractile activity per se. Yet contractions become a more potent stimulus of muscle glucose uptake as the plasma insulin level is increased. In addition, enhanced glucose delivery to muscle, which during exercise...... is essentially effected via increased blood flow, significantly contributes to stimulate glucose uptake. Again, however, increased glucose delivery appears to be a more potent stimulus of muscle glucose uptake as the circulating insulin level is increased. Furthermore, contractions and elevated flow prove...... to be additive stimuli of muscle glucose uptake at any plasma insulin level. In conclusion, the extent to which muscle glucose uptake is stimulated during exercise depends on various factors, including 1) the intensity of the contractile activity, 2) the magnitude of the exercise-associated increase in muscle...

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

    Directory of Open Access Journals (Sweden)

    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.

  11. Evidence of long term muscle fatigue following prolonged intermittent contractions based on mechano- and electromyograms

    DEFF Research Database (Denmark)

    Søgaard, K; Blangsted, A K; Jørgensen, L V

    2003-01-01

    The focus of the present study is the long term element of muscle fatigue provoked by prolonged intermittent contractions at submaximal force levels and analysed by force, surface electromyography (EMG) and mechanomyogram (MMG). It was hypothesized that fatigue related changes in mechanical...... performance of the biceps muscle are more strongly reflected in low than in high force test contractions, more prominent in the MMG than in the EMG signal and less pronounced following contractions controlled by visual compared to proprioceptive feedback. Further, it was investigated if fatigue induced by 30...... min intermittent contractions at 30% as well as 10% of maximal voluntary contraction (MVC) lasted more than 30 min recovery. In six male subjects the EMG and MMG were recorded from the biceps brachii muscle during three sessions with fatiguing exercise at 10% with visual feedback and at 30% MVC...

  12. Skeletal muscle contraction in protecting joints and bones by absorbing mechanical impacts

    Science.gov (United States)

    Rudenko, O. V.; Tsyuryupa, S.; Sarvazyan, A.

    2016-09-01

    We have previously hypothesized that the dissipation of mechanical energy of external impact is a fundamental function of skeletal muscle in addition to its primary function to convert chemical energy into mechanical energy. In this paper, a mathematical justification of this hypothesis is presented. First, a simple mechanical model, in which the muscle is considered as a simple Hookean spring, is considered. This analysis serves as an introduction to the consideration of a biomechanical model taking into account the molecular mechanism of muscle contraction, kinetics of myosin bridges, sarcomere dynamics, and tension of muscle fibers. It is shown that a muscle behaves like a nonlinear and adaptive spring tempering the force of impact and increasing the duration of the collision. The temporal profiles of muscle reaction to the impact as functions of the levels of muscle contraction, durations of the impact front, and the time constants of myosin bridges closing, are obtained. The absorption of mechanical shock energy is achieved due to the increased viscoelasticity of the contracting skeletal muscle. Controlling the contraction level allows for the optimization of the stiffness and viscosity of the muscle necessary for the protection of the joints and bones.

  13. Whey protein hydrolysate augments tendon and muscle hypertrophy independent of resistance exercise contraction mode

    DEFF Research Database (Denmark)

    Farup, Jean; Rahbek, S K; Vendelbo, M H

    2014-01-01

    In a comparative study, we investigated the effects of maximal eccentric or concentric resistance training combined with whey protein or placebo on muscle and tendon hypertrophy. 22 subjects were allocated into either a high-leucine whey protein hydrolysate + carbohydrate group (WHD...... or contraction mode effects. In conclusion, high-leucine whey protein hydrolysate augments muscle and tendon hypertrophy following 12 weeks of resistance training – irrespective of contraction mode....

  14. High glycogen levels enhance glycogen breakdown in isolated contracting skeletal muscle

    DEFF Research Database (Denmark)

    Richter, Erik; Galbo, H

    1986-01-01

    and after 15 min of intermittent electrical muscle stimulation. Before stimulation, glycogen was higher in rats that swam on the preceding day (supercompensated rats) compared with controls. During muscle contractions, glycogen breakdown in fast-twitch red and white fibers was larger in supercompensated...

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

    Science.gov (United States)

    Helge, J W; Therkildsen, K J; Jørgensen, T B; Wu, B J; Storlien, L H; Asp, S

    2001-09-01

    This study investigated if prior eccentric contractions, and thus mechanical strain and muscle damage, exert an effect on the muscle membrane phospholipid fatty acid composition in rats, and whether a possible effect could be attenuated by dietary supplements. Twenty-three rats were randomised to three groups who received chow with added fish oil (n = 8), vitamin C (n = 8) or no supplement (n = 7). After 3 weeks of feeding, calf muscles on one side were stimulated electrically during anaesthesia causing eccentric contractions. Two days later the white gastrocnemius, a part of the stimulated calf muscle, was excised from both legs. In the muscles stimulated to contract eccentrically, compared to the control muscles, the proportion of arachidonic acid, C20:4,n-6 (17.7 +/- 0.6; 16.4 +/- 0.4% of total fatty acids, respectively) and docosapentanoeic acid, C22:5,n-3 (2.9 +/- 0.1 and 2.7 +/- 0.1% of total fatty acids, respectively) was uniformly higher across groups (P muscle. Thus one severe bout of eccentric contractions modulates the fatty acid composition of the muscle membrane phospholipids when compared to a control leg, and supplemental intake of fish oil or vitamin C did not attenuate this effect.

  16. 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

  17. Interleukin-6 receptor expression in contracting human skeletal muscle: regulating role of IL-6

    DEFF Research Database (Denmark)

    Keller, Pernille; Penkowa, Milena; Keller, Charlotte

    2005-01-01

    Contracting muscle fibers produce and release IL-6, and plasma levels of this cytokine are markedly elevated in response to physical exercise. We recently showed autocrine regulation of IL-6 in human skeletal muscle in vivo and hypothesized that this may involve up-regulation of the IL-6 receptor...

  18. Co-contraction training, muscle explosive force and associated electromyography activity.

    Science.gov (United States)

    Zbidi, Sana; Zinoubi, Badrane; Hammouda, Omar; Vandewalle, Henry; Serrau, Virgile; Driss, Tarak

    2017-06-01

    The effects of a six-week Maximal isometric voluntary co-contraction (MIVCC) training program of the elbow flexor and extensor muscles on maximal and explosive muscle strength have been studied. Ten active men underwent 6-week MIVCC. Maximal rate of force development (MRFD) of the elbow flexor (MRFDflex) and extensor (MRFDext) were measured in addition to maximal voluntary contraction (MVC) of these muscles (MVCflex and MVCext) before (T0), after 4-week (T1) and 6-week (T2) MIVCC training program. During each test session, integrated electromyographic activity (iEMG) of agonistic and antagonistic muscles during MVC, MRFD, submaximal contractions (30% and 60% MVC) and MIVCC of the elbow flexor and extensor muscles were measured. At T2, MVCflex (13.3±11.7%) and MVCext (22.5±6.1%) increased significantly (Pmuscles during MVC increased significantly for flexor (+29.9%) and extensor (+29.6%) muscles (Pmuscles without inducing an alteration of MRFD or an increase in muscles co-activation during contractions of the agonist muscles. Interestingly, the improvement of estimated forces during MIVCC after 6-week-training suggested that the higher level of MIVCC previously observed in bodybuilders could be the result of specific training exercises (posing). The fact that MIVCC training did not alter "explosive" force production, which is important in optimal design of sports-specific resistance training as well as in rehabilitation programs.

  19. Growth factor-induced contraction of human bronchial smooth muscle is Rho-kinase-dependent

    NARCIS (Netherlands)

    Gosens, Reinout; Schaafsma, D.; Grootte Bromhaar, M.M; Vrugt, B.; Zaagsma, Hans; Meurs, Herman; Nelemans, Herman

    2004-01-01

    Growth factors have been implicated in the pathophysiology of asthma. However, the putative effects of these growth factors on human airway smooth muscle tone are still largely unknown. We performed contraction experiments using human bronchial smooth muscle ring preparations. The growth factor

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

    DEFF Research Database (Denmark)

    Asp, S; Richter, Erik

    1996-01-01

    We have recently shown that eccentric contractions (Ecc) of rat calf muscles cause muscle damage and decreased glycogen and glucose transporter GLUT-4 protein content in the white (WG) and red gastrocnemius (RG) but not in the soleus (S) (S. Asp, S. Kristiansen, and E. A. Richter. J. Appl. Physio...

  1. Wortmannin inhibits both insulin- and contraction-stimulated glucose uptake and transport in rat skeletal muscle

    DEFF Research Database (Denmark)

    Wojtaszewski, Jørgen; Hansen, B F; Ursø, Birgitte

    1996-01-01

    stimulation but was unaffected by contractions. In addition, the insulin-stimulated PI 3-kinase activity and muscle glucose uptake and transport in individual muscles were dose-dependently inhibited by wortmannin with one-half maximal inhibition values of approximately 10 nM and total inhibition at 1 micro......The role of phosphatidylinositol (PI) 3-kinase for insulin- and contraction-stimulated muscle glucose transport was investigated in rat skeletal muscle perfused with a cell-free perfusate. The insulin receptor substrate-1-associated PI 3-kinase activity was increased sixfold upon insulin......-stimulated glucose uptake but also decreased the contractility. In conclusion, inhibition of PI 3-kinase with wortmannin in skeletal muscle coincides with inhibition of insulin-stimulated glucose uptake and transport. Furthermore, in contrast to recent findings in incubated muscle, wortmannin also inhibited...

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

    Science.gov (United States)

    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.

  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. Measurement of lumbar multifidus muscle contraction with rehabilitative ultrasound imaging.

    Science.gov (United States)

    Kiesel, Kyle B; Uhl, Tim L; Underwood, Frank B; Rodd, Donald W; Nitz, Arthur J

    2007-05-01

    Rehabilitative Ultrasound Imaging (RUSI) has been validated as a noninvasive method to measure activation of selected muscles. The purpose of this study was to determine the relationship between muscle thickness change, as measured by ultrasonography, and electromyography (EMG) activity of the lumbar multifidus (LM) muscle in normal subjects. Bipolar fine wire electrodes were inserted into the LM at the L4 level of five subjects. Simultaneous EMG and RUSI data (muscle thickness) were collected while subjects performed increasingly demanding postural response tasks thought to activate the LM muscle. To determine the relationship between muscle thickness change and EMG activity, the normalized EMG data were correlated to normalized RUSI data. To determine if the tasks increased the demand on the LM, the mean EMG data were compared over each of the four tasks. Muscle thickness change as measured by RUSI was highly correlated with EMG activity of LM in asymptomatic subjects (r=.79,PRUSI is a valid and potentially useful method to measure activation of the LM muscle in a narrow range (19-34% of MVIC) in an asymptomatic population.

  5. 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

  6. The influence of tendon compliance on muscle power output and efficiency during cyclic contractions.

    Science.gov (United States)

    Lichtwark, G A; Barclay, C J

    2010-03-01

    Muscle power output and efficiency during cyclical contractions are influenced by the timing and duration of stimulation of the muscle and the interaction of the muscle with its mechanical environment. It has been suggested that tendon compliance may reduce the energy required for power production from the muscle by reducing the required shortening of the muscle fibres. Theoretically this may allow the muscle to maintain both high power output and efficiency during cyclical contraction; however, this has yet to be demonstrated experimentally. To investigate how tendon compliance might act to increase muscle power output and/or efficiency, we attached artificial tendons of varying compliance to muscle fibre bundles in vitro and measured power output and mechanical efficiency during stretch-shorten cycles (2 Hz) with a range of stretch amplitudes and stimulation patterns. The results showed that peak power, average power output and efficiency (none of which can have direct contributions from the compliant tendon) all increased with increasing tendon compliance, presumably due to the tendon acting to minimise muscle energy use by allowing the muscle fibres to shorten at optimal speeds. Matching highly compliant tendons with a sufficiently large amplitude length change and appropriate stimulation pattern significantly increased the net muscle efficiency compared with stiff tendons acting at the same frequency. The maximum efficiency for compliant tendons was also similar to the highest value measured under constant velocity and force conditions, which suggests that tendon compliance can maximise muscle efficiency in the conditions tested here. These results provide experimental evidence that during constrained cyclical contractions, muscle power and efficiency can be enhanced with compliant tendons.

  7. Validation of new ultrasound parameters for quantifying pelvic floor muscle contraction.

    Science.gov (United States)

    Yang, S-H; Huang, W-C; Yang, S-Y; Yang, E; Yang, J-M

    2009-04-01

    To determine the reliability and validity of new ultrasound parameters, measured in the polar coordinate system, for quantifying pelvic floor muscle action. This was a prospective study, from January 2005 to December 2007, in 209 women with urodynamic stress incontinence, to validate new ultrasound parameters for quantifying pelvic floor muscle contraction. The examination of each patient included intravaginal digital palpation of voluntary pelvic floor muscle contractility and an ultrasound assessment of the positions of the bladder neck and anorectal junction at rest and during pelvic floor muscle contraction. The position of the bladder neck was expressed by bladder neck angle and bladder neck distance from the lower border of the pubic symphysis, and the position of the anorectal junction was expressed by the levator hiatal angle and sagittal hiatal diameter. The vector lengths of the motion of the bladder neck and anorectal junction during pelvic floor muscle contraction were calculated from the positions at rest and during pelvic floor muscle contraction by mathematical formulae. There was good inter- and intraobserver reliability of measurement of ultrasound parameters on stored volumes. During pelvic floor muscle contraction, elevated bladder neck distance and shortened sagittal hiatal diameter were valid parameters representing stronger pelvic floor muscle contractility, with shortened sagittal hiatal diameter having the best correlation (r = - 0.348, P < 0.001). The methods used in this study appear to be reliable for quantifying pelvic floor muscle action. The bladder neck distance with respect to the lower border of the pubic symphysis and the sagittal hiatal diameter were both valid parameters reflecting PFM contractility. (c) 2009 ISUOG. Published by John Wiley & Sons, Ltd.

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

    DEFF Research Database (Denmark)

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

    2001-01-01

    This study investigated if prior eccentric contractions, and thus mechanical strain and muscle damage, exert an effect on the muscle membrane phospholipid fatty acid composition in rats, and whether a possible effect could be attenuated by dietary supplements. Twenty-three rats were randomised...... muscle, was excised from both legs. In the muscles stimulated to contract eccentrically, compared to the control muscles, the proportion of arachidonic acid, C20:4,n-6 (17.7 +/- 0.6; 16.4 +/- 0.4% of total fatty acids, respectively) and docosapentanoeic acid, C22:5,n-3 (2.9 +/- 0.1 and 2.7 +/- 0.......1% of total fatty acids, respectively) was uniformly higher across groups (P acids) compared to the control leg (38.2 +/- 0...

  9. Prostaglandins induce vasodilatation of the microvasculature during muscle contraction and induce vasodilatation independent of adenosine.

    Science.gov (United States)

    Murrant, Coral L; Dodd, Jason D; Foster, Andrew J; Inch, Kristin A; Muckle, Fiona R; Ruiz, Della A; Simpson, Jeremy A; Scholl, Jordan H P

    2014-03-15

    Blood flow data from contracting muscle in humans indicates that adenosine (ADO) stimulates the production of nitric oxide (NO) and vasodilating prostaglandins (PG) to produce arteriolar vasodilatation in a redundant fashion such that when one is inhibited the other can compensate. We sought to determine whether these redundant mechanisms are employed at the microvascular level. First, we determined whether PGs were involved in active hyperaemia at the microvascular level. We stimulated four to five skeletal muscle fibres in the anaesthetized hamster cremaster preparation in situ and measured the change in diameter of 2A arterioles (maximum diameter 40 μm, third arteriolar level up from the capillaries) at a site of overlap with the stimulated muscle fibres before and after 2 min of contraction [stimulus frequencies: 4, 20 and 60 Hz at 15 contractions per minute (CPM) or contraction frequencies of 6, 15 or 60 CPM at 20 Hz; 250 ms train duration]. Muscle fibres were stimulated in the absence and presence of the phospholipase A2 inhibitor quinacrine. Further, we applied a range of concentrations of ADO (10(-7)-10(-5) M) extraluminally, (to mimic muscle contraction) in the absence and presence of L-NAME (NO synthase inhibitor), indomethacin (INDO, cyclooxygenase inhibitor) and L-NAME + INDO and observed the response of 2A arterioles. We repeated the latter experiment on a different level of the cremaster microvasculature (1A arterioles) and on the microvasculature of a different skeletal muscle (gluteus maximus, 2A arterioles). We observed that quinacrine inhibited vasodilatation during muscle contraction at intermediate and high contraction frequencies (15 and 60 CPM). L-NAME, INDO and L-NAME + INDO were not effective at inhibiting vasodilatation induced by any concentration of ADO tested in 2A and 1A arterioles in the cremaster muscle or 2A arterioles in the gluteus maximus muscle. Our data show that PGs are involved in the vasodilatation of the microvasculature in

  10. Contractions activate hormone-sensitive lipase in rat muscle by protein kinase C and mitogen-activated protein kinase

    DEFF Research Database (Denmark)

    Donsmark, Morten; Langfort, Jozef; Holm, Cecilia

    2003-01-01

    and contractions. Adrenaline acts via cAMP-dependent protein kinase (PKA). The signalling mediating the effect of contractions is unknown and was explored in this study. Incubated soleus muscles from 70 g male rats were electrically stimulated to perform repeated tetanic contractions for 5 min. The contraction...... of the inhibitors reduced adrenaline-induced HSL activation in soleus muscle. Both phorbol-12-myristate-13-acetate (PMA), which activates PKC and, in turn, ERK, and caffeine, which increases intracellular Ca2+ without eliciting contraction, increased HSL activity. Activated ERK increased HSL activity in supernatant...... from basal but not from electrically stimulated muscle. In conclusion, in muscle, PKC can stimulate HSL through ERK. Contractions and adrenaline enhance muscle HSL activity by different signalling mechanisms. The effect of contractions is mediated by PKC, at least partly via the ERK pathway....

  11. EMG-force relationship during static contraction: effects on sensor placement locations on biceps brachii muscle.

    Science.gov (United States)

    Ahamed, Nizam Uddin; Sundaraj, Kenneth; Alqahtani, Mahdi; Altwijri, Omar; Ali, Md Asraf; Islam, Md Anamul

    2014-01-01

    The relationship between surface electromyography (EMG) and force have been the subject of ongoing investigations and remain a subject of controversy. Even under static conditions, the relationships at different sensor placement locations in the biceps brachii (BB) muscle are complex. The aim of this study was to compare the activity and relationship between surface EMG and static force from the BB muscle in terms of three sensor placement locations. Twenty-one right hand dominant male subjects (age 25.3±1.2 years) participated in the study. Surface EMG signals were detected from the subject's right BB muscle. The muscle activation during force was determined as the root mean square (RMS) electromyographic signal normalized to the peak RMS EMG signal of isometric contraction for 10 s. The statistical analysis included linear regression to examine the relationship between EMG amplitude and force of contraction [40-100% of maximal voluntary contraction (MVC)], repeated measures ANOVA to assess differences among the sensor placement locations, and coefficient of variation (CoV) for muscle activity variation. The results demonstrated that when the sensor was placed on the muscle belly, the linear slope coefficient was significantly greater for EMG versus force testing (r2=0.62, P0.05) and upper part of the muscle belly (r2=0.29, PEMG signal activity on the muscle belly had less variability than the upper and lower parts (8.55% vs. 15.12% and 12.86%, respectively). These findings indicate the importance of applying the surface EMG sensor at the appropriate locations that follow muscle fiber orientation of the BB muscle during static contraction. As a result, EMG signals of three different placements may help to understand the difference in the amplitude of the signals due to placement.

  12. 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.

  13. Association of interleukin-6 signalling with the muscle stem cell response following muscle-lengthening contractions in humans.

    Directory of Open Access Journals (Sweden)

    Bryon R McKay

    Full Text Available BACKGROUND: The regulation of muscle stem cells in humans in response to muscle injury remains largely undefined. Recently, interleukin-6 (IL-6 has been implicated in muscle stem cell (satellite cell-mediated muscle hypertrophy in animals; however, the role of IL-6 in the satellite cell (SC response following muscle-lengthening contractions in humans has not been studied. METHODOLOGY/PRINCIPAL FINDINGS: Eight subjects (age 22+/-1 y; 79+/-8 kg performed 300 maximal unilateral lengthening contractions (3.14 rad.s(-1 of the knee extensors. Blood and muscle samples were collected before and at 4, 24, 72, and 120 hours post intervention. IL-6, IL-6 receptor, IL-6R(alpha, cyclin D1, suppressor of cytokine signling-3 (SOCS3 mRNA were measured using quantitative RT-PCR and serum IL-6 protein was measured using an ELISA kit. JAK2 and STAT3 phosphorylated and total protein was measured using western blotting techniques. Immunohistochemical analysis of muscle cross-sections was performed for the quantification of SCs (Pax7(+ cells as well as the expression of phosphorylated STAT3, IL-6, IL-6R(alpha, and PCNA across all time-points. The SC response, as defined by an amplification of Pax7(+ cells, was rapid, increasing by 24 h and peaking 72 h following the intervention. Muscle IL-6 mRNA increased following the intervention, which correlated strongly (R(2 = 0.89, p<0.002 with an increase in serum IL-6 concentration. SC IL-6R(alpha protein was expressed on the fiber, but was also localized to the SC, and IL-6(+ SC increased rapidly following muscle-lengthening contractions and returned to basal levels by 72 h post-intervention, demonstrating an acute temporal expression of IL-6 with SC. Phosphorylated STAT3 was evident in SCs 4 h after lengthening contraction, and the downstream genes, cyclin D1 and SOCS3 were significantly elevated 24 hours after the intervention. CONCLUSIONS/SIGNIFICANCE: The increased expression of STAT3 responsive genes and expression of

  14. 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.

  15. Muscle Fatigue Affects the Interpolated Twitch Technique When Assessed Using Electrically-Induced Contractions in Human and Rat Muscles.

    Science.gov (United States)

    Neyroud, Daria; Cheng, Arthur J; Bourdillon, Nicolas; Kayser, Bengt; Place, Nicolas; Westerblad, Håkan

    2016-01-01

    The interpolated twitch technique (ITT) is the gold standard to assess voluntary activation and central fatigue. Yet, its validity has been questioned. Here we studied how peripheral fatigue can affect the ITT. Repeated contractions at submaximal frequencies were produced by supramaximal electrical stimulations of the human adductor pollicis muscle in vivo and of isolated rat soleus fiber bundles; an extra stimulation pulse was given during contractions to induce a superimposed twitch. Human muscles fatigued by repeated 30-Hz stimulation trains (3 s on-1 s off) showed an ~80% reduction in the superimposed twitch force accompanied by a severely reduced EMG response (M-wave amplitude), which implies action potential failure. Subsequent experiments combined a less intense stimulation protocol (1.5 s on-3 s off) with ischemia to cause muscle fatigue, but which preserved M-wave amplitude. However, the superimposed twitch force still decreased markedly more than the potentiated twitch force; with ITT this would reflect increased "voluntary activation." In contrast, the superimposed twitch force was relatively spared when a similar protocol was performed in rat soleus bundles. Force relaxation was slowed by >150% in fatigued human muscles, whereas it was unchanged in rat soleus bundles. Accordingly, results similar to those in the human muscle were obtained when relaxation was slowed by cooling the rat soleus muscles. In conclusion, our data demonstrate that muscle fatigue can confound the quantification of central fatigue using the ITT.

  16. Contraction induced secretion of VEGF from skeletal muscle cells is mediated by adenosine

    DEFF Research Database (Denmark)

    Høier, Birgitte; Olsen, Karina; Nyberg, Michael Permin

    2010-01-01

    The role of adenosine and contraction for secretion of VEGF in skeletal muscle was investigated in human subjects and rat primary skeletal muscle cells. Microdialysis probes were inserted into the thigh muscle of seven male subjects and dialysate was collected at rest, during infusion of adenosine...... and during knee extensor exercise. The dialysate was analyzed for content of VEGF protein and adenosine. The mechanism of VEGF secretion from muscle cells in culture was examined in resting and electro stimulated cells, and in response to the adenosine analogue NECA, and the adenosine A(2A) receptor specific...... infusion enhanced (Pmuscle cells, NECA...

  17. CHANGES IN QUADRICEPS MUSCLE ACTIVITY DURING SUSTAINED RECREATIONAL ALPINE SKIING

    Directory of Open Access Journals (Sweden)

    Josef Kröll

    2011-03-01

    Full Text Available During a day of skiing thousands of repeated contractions take place. Previous research on prolonged recreational alpine skiing show that physiological changes occur and hence some level of fatigue is inevitable. In the present paper the effect of prolonged skiing on the recruitment and coordination of the muscle activity was investigated. Six subjects performed 24 standardized runs. Muscle activity during the first two (PREskiing and the last two (POSTskiing runs was measured from the vastus lateralis (VL and rectus femoris (RF using EMG and quantified using wavelet and principal component analysis. The frequency content of the EMG signal shifted in seven out of eight cases significantly towards lower frequencies with highest effects observed for RF on outside leg. A significant pronounced outside leg loading occurred during POSTskiing and the timing of muscle activity peaks occurred more towards turn completion. Specific EMG frequency changes were observed at certain time points throughout the time windows and not over the whole double turn. It is suggested that general muscular fatigue, where additional specific muscle fibers have to be recruited due to the reduced power output of other fibers did not occur. The EMG frequency decrease and intensity changes for RF and VL are caused by altered timing (coordination within the turn towards a most likely more uncontrolled skiing technique. Hence, these data provide evidence to suggest recreational skiers alter their skiing technique before a potential change in muscle fiber recruitment occurs

  18. Concentric muscle contractions before static stretching minimize, but do not remove, stretch-induced force deficits.

    Science.gov (United States)

    Kay, Anthony D; Blazevich, Anthony J

    2010-03-01

    The effects of concentric contractions and passive stretching on musculotendinous stiffness and muscle activity were studied in 18 healthy human volunteers. Passive and concentric plantar flexor joint moment data were recorded on an isokinetic dynamometer with simultaneous electromyogram (EMG) monitoring of the triceps surae, real-time motion analysis of the lower leg, and ultrasound imaging of the Achilles-medial gastrocnemius muscle-tendon junction. The subjects then performed six 8-s ramped maximal voluntary concentric contractions before repeating both the passive and concentric trials. Concentric moment was significantly reduced (6.6%; P static plantar flexor stretches before being retested 2 and 30 min poststretch. A further reduction in concentric joint moment (5.8%; P activity or Achilles tendon stiffness, but a significant increase in muscle operating length and decrease in tendon length was apparent at this range of motion (P stretching, muscle activity significantly recovered to pre-maximal voluntary concentric contractions levels, whereas concentric moment and Achilles tendon stiffness remained depressed. These data show that the performance of maximal concentric contractions can substantially reduce neuromuscular activity and muscle force, but this does not prevent a further stretch-induced loss in active plantar flexor joint moment. Importantly, the different temporal changes in EMG and concentric joint moment indicate that a muscle-based mechanism was likely responsible for the force losses poststretch.

  19. Comparison of contraction rates of abdominal muscles of chronic low back pain patients in different postures.

    Science.gov (United States)

    Cho, Sung-Hak; Kim, Kang Hoon; Baek, Il-Hun; Goo, Bong-Oh

    2013-08-01

    [Purpose] This study examined the contraction rates of abdominal muscles in relation to the posture of chronic lumbar pain patients and normal subjects. [Subjects] The subjects were 17 chronic low back pain (CLBP) patients and 17 normal people between the ages of 20 and 59. [Methods] Experimental postures included a supine position, a sitting position, and a standing position. Measurements were taken at rest and during abdominal contraction. The measurement at rest was taken during expiration with comfortable breathing, and the measurement during contraction was taken at maximum expiration of forced expiration. Muscle contraction rates (on contraction and at relaxation) were calculated. [Results] There were significant differences between CLBP patients and normal subjects in the transversus abdominis (TrA) in the standing position. [Conclusion] Changes in contraction rates of the abdominal muscles of normal subjects and CLBP patients were examined in different postures at maximum expiration. It was found that the contraction rate of TrA in CLBP patients in a standing position, is significantly lower than that of normal subjects.

  20. Alternating activation is related to fatigue in lumbar muscles during sustained sitting.

    Science.gov (United States)

    Ringheim, Inge; Indahl, Aage; Roeleveld, Karin

    2014-06-01

    The aim of this study was to investigate the relation between variability in muscle activity and fatigue during a sustained low level contraction in the lumbar muscles. Twenty-five healthy participants (13 men 12 women) performed a 30min sitting task with 5 degrees inclination of the trunk. Surface electromyographic (EMG) signals were recorded bilaterally from the lumbar muscles with 2 high density surface EMG grids of 9×14 electrodes. Median frequency (MDF) decrease, amplitude (RMS) increase and the rating of perceived exertion (RPE) were used as fatigue indices. Alternating activation and spatial and temporal variability were computed and relations with the fatigue indices were explored. During sitting, the mono- and bipolar RMS slightly increased while the MDF remained unchanged indicating no systematic muscle fatigue, although the average RPE increased from 6 to 13 on a scale ranging between 6 and 20. Higher frequency of alternating activation between the left and right side was associated with increased RPE (p=0.03) and decreased MDF (p=0.05). A tendency in the same direction was seen between increased spatial and temporal variation within the grids and increased RPE and decreased MDF. Present findings provide evidence for a relationship between variability in muscle activity and fatigue. Copyright © 2014 Elsevier Ltd. All rights reserved.

  1. 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.

  2. Classical and adaptive control of ex vivo skeletal muscle contractions using Functional Electrical Stimulation (FES.

    Directory of Open Access Journals (Sweden)

    Paola Jaramillo Cienfuegos

    Full Text Available Functional Electrical Stimulation is a promising approach to treat patients by stimulating the peripheral nerves and their corresponding motor neurons using electrical current. This technique helps maintain muscle mass and promote blood flow in the absence of a functioning nervous system. The goal of this work is to control muscle contractions from FES via three different algorithms and assess the most appropriate controller providing effective stimulation of the muscle. An open-loop system and a closed-loop system with three types of model-free feedback controllers were assessed for tracking control of skeletal muscle contractions: a Proportional-Integral (PI controller, a Model Reference Adaptive Control algorithm, and an Adaptive Augmented PI system. Furthermore, a mathematical model of a muscle-mass-spring system was implemented in simulation to test the open-loop case and closed-loop controllers. These simulations were carried out and then validated through experiments ex vivo. The experiments included muscle contractions following four distinct trajectories: a step, sine, ramp, and square wave. Overall, the closed-loop controllers followed the stimulation trajectories set for all the simulated and tested muscles. When comparing the experimental outcomes of each controller, we concluded that the Adaptive Augmented PI algorithm provided the best closed-loop performance for speed of convergence and disturbance rejection.

  3. The interrelation between aPKC and glucose uptake in the skeletal muscle during contraction and insulin stimulation.

    Science.gov (United States)

    Santos, J M; Benite-Ribeiro, S A; Queiroz, G; Duarte, J A

    2014-12-01

    Contraction and insulin increase glucose uptake in skeletal muscle. While the insulin pathway, better characterized, requires activation of phosphoinositide 3-kinase (PI3K) and atypical protein kinase (aPKC), muscle contraction seems to share insulin-activated components to increase glucose uptake. This study aimed to investigate the interrelation between the pathway involved in glucose uptake evoked by insulin and muscle contraction. Isolated muscle of rats was treated with solvent (control), insulin, wortmannin (PI3K inhibitor) and the combination of insulin plus wortmannin. After treatment, muscles were electrically stimulated (contracted) or remained at rest. Glucose transporter 4 (GLUT4) localization, glucose uptake and phospho-aPKC (aPKC activated form) were assessed. Muscle contraction and insulin increased glucose uptake in all conditions when compared with controls not stimulating an effect that was accompanied by an increase in GLUT4 and of phospho-aPKC at the muscle membrane. Contracted muscles treated with insulin did not show additive effects on glucose uptake or aPKC activity compared with the response when these stimuli were applied alone. Inhibition of PI3K blocked insulin effect on glucose uptake and aPKC but not in the contractile response. Thus, muscle contraction seems to stimulate aPKC and glucose uptake independently of PI3K. Therefore, aPKC may be a convergence point and a rate limit step in the pathway by which, insulin and contraction, increase glucose uptake in skeletal muscle. Copyright © 2014 John Wiley & Sons, Ltd.

  4. 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

  5. Insulin and Contraction-induced GLUT4 Traffic in Muscle: Insights from a Novel Imaging Approach

    OpenAIRE

    Lauritzen, Hans P.M.M.

    2013-01-01

    Insulin and contraction-mediated glucose transporter 4 (GLUT4) trafficking have different kinetics in mature skeletal muscle. Intravital imaging indicates that insulin-stimulated GLUT4 trafficking differs between t-tubules and sarcolemma. In contrast, contraction-induced GLUT4 trafficking does not differ between membrane surfaces. This distinction is likely due to differences in the underlying signaling pathways regulating GLUT4 vesicle depletion, GLUT4 membrane fusion and GLUT4 re-internaliz...

  6. Comparison of Contraction Rates of Abdominal Muscles of Chronic Low Back Pain Patients in Different Postures

    OpenAIRE

    Cho, Sung-Hak; Kim, Kang Hoon; Baek, Il-Hun; Goo, Bong-Oh

    2013-01-01

    [Purpose] This study examined the contraction rates of abdominal muscles in relation to the posture of chronic lumbar pain patients and normal subjects. [Subjects] The subjects were 17 chronic low back pain (CLBP) patients and 17 normal people between the ages of 20 and 59. [Methods] Experimental postures included a supine position, a sitting position, and a standing position. Measurements were taken at rest and during abdominal contraction. The measurement at rest was taken during expiration...

  7. 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, ...

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

    DEFF Research Database (Denmark)

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

    2006-01-01

    +) kinetics in human muscle. Ten male subjects performed five bouts of static knee extension with 10-min rest in between. Each bout of RSC (target torque 66% of maximal voluntary contraction torque) was maintained to fatigue. Muscle biopsies were taken preexercise and 0.3 and 24 h postexercise from vastus......Repeated static contractions (RSC) induce large fluctuations in tissue oxygen tension and increase the generation of reactive oxygen species (ROS). This study investigated the effect of RSC on muscle contractility, mitochondrial respiratory function, and in vitro sarcoplasmic reticulum (SR) Ca(2......, decreased mitochondrial efficiency (phosphorylated ADP-to-oxygen consumed ratio), and increased noncoupled respiration (HPX/Con post- vs. preexercise). SR Ca(2+) uptake rate was lower 0.3 vs. 24 h postexercise, whereas SR Ca(2+) release rate was unchanged. RSC resulted in long-lasting changes in muscle...

  9. 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.

  10. 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.

  11. Muscle contraction phenotypic analysis enabled by optogenetics reveals functional relationships of sarcomere components in Caenorhabditis elegans

    Science.gov (United States)

    Hwang, Hyundoo; Barnes, Dawn E.; Matsunaga, Yohei; Benian, Guy M.; Ono, Shoichiro; Lu, Hang

    2016-01-01

    The sarcomere, the fundamental unit of muscle contraction, is a highly-ordered complex of hundreds of proteins. Despite decades of genetics work, the functional relationships and the roles of those sarcomeric proteins in animal behaviors remain unclear. In this paper, we demonstrate that optogenetic activation of the motor neurons that induce muscle contraction can facilitate quantitative studies of muscle kinetics in C. elegans. To increase the throughput of the study, we trapped multiple worms in parallel in a microfluidic device and illuminated for photoactivation of channelrhodopsin-2 to induce contractions in body wall muscles. Using image processing, the change in body size was quantified over time. A total of five parameters including rate constants for contraction and relaxation were extracted from the optogenetic assay as descriptors of sarcomere functions. To potentially relate the genes encoding the sarcomeric proteins functionally, a hierarchical clustering analysis was conducted on the basis of those parameters. Because it assesses physiological output different from conventional assays, this method provides a complement to the phenotypic analysis of C. elegans muscle mutants currently performed in many labs; the clusters may provide new insights and drive new hypotheses for functional relationships among the many sarcomere components.

  12. 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

  13. Modeling force-velocity relation in skeletal muscle isotonic contraction using an artificial neural network.

    Science.gov (United States)

    Dariani, Sharareh; Keshavarz, Mansoor; Parviz, Mohsen; Raoufy, Mohammad Reza; Gharibzadeh, Shahriar

    2007-01-01

    The aim of this study is to design an artificial neural network (ANN) to model force-velocity relation in skeletal muscle isotonic contraction. We obtained the data set, including physiological and morphometric parameters, by myography and morphometric measurements on frog gastrocnemius muscle. Then, we designed a multilayer perceptron ANN, the inputs of which are muscle volume, muscle optimum length, tendon length, preload, and afterload. The output of the ANN is contraction velocity. The experimental data were divided randomly into two parts. The first part was used to train the ANN. In order to validate the model, the second part of experimental data, which was not used in training, was employed to the ANN and then, its output was compared with Hill model and the experimental data. The behavior of ANN in high forces was more similar to experimental data, but in low forces the Hill model had better results. Furthermore, extrapolation of ANN performance showed that our model is more or less able to simulate eccentric contraction. Our results indicate that ANNs represent a powerful tool to capture some essential features of muscle isotonic contraction.

  14. Changes in quadriceps muscle activity during sustained recreational alpine skiing.

    Science.gov (United States)

    Kröll, Josef; Müller, Erich; Seifert, John G; Wakeling, James M

    2011-01-01

    During a day of skiing thousands of repeated contractions take place. Previous research on prolonged recreational alpine skiing show that physiological changes occur and hence some level of fatigue is inevitable. In the present paper the effect of prolonged skiing on the recruitment and coordination of the muscle activity was investigated. Six subjects performed 24 standardized runs. Muscle activity during the first two (PREskiing) and the last two (POSTskiing) runs was measured from the vastus lateralis (VL) and rectus femoris (RF) using EMG and quantified using wavelet and principal component analysis. The frequency content of the EMG signal shifted in seven out of eight cases significantly towards lower frequencies with highest effects observed for RF on outside leg. A significant pronounced outside leg loading occurred during POSTskiing and the timing of muscle activity peaks occurred more towards turn completion. Specific EMG frequency changes were observed at certain time points throughout the time windows and not over the whole double turn. It is suggested that general muscular fatigue, where additional specific muscle fibers have to be recruited due to the reduced power output of other fibers did not occur. The EMG frequency decrease and intensity changes for RF and VL are caused by altered timing (coordination) within the turn towards a most likely more uncontrolled skiing technique. Hence, these data provide evidence to suggest recreational skiers alter their skiing technique before a potential change in muscle fiber recruitment occurs. Key pointsThe frequency content of the EMG signal shifted in seven out of eight cases significantly towards lower frequencies with highest effects observed for RF.General muscular fatigue, where additional specific fibers have to be recruited due to the reduced power output of other fibers, did not occur.A modified skiing style towards a less functional and hence more uncontrolled skiing technique seems to be a key issue

  15. A DIC Based Technique to Measure the Contraction of a Skeletal Muscle Engineered Tissue

    Directory of Open Access Journals (Sweden)

    Emanuele Rizzuto

    2016-01-01

    Full Text Available Tissue engineering is a multidisciplinary science based on the application of engineering approaches to biologic tissue formation. Engineered tissue internal organization represents a key aspect to increase biofunctionality before transplant and, as regarding skeletal muscles, the potential of generating contractile forces is dependent on the internal fiber organization and is reflected by some macroscopic parameters, such as the spontaneous contraction. Here we propose the application of digital image correlation (DIC as an independent tool for an accurate and noninvasive measurement of engineered muscle tissue spontaneous contraction. To validate the proposed technique we referred to the X-MET, a promising 3-dimensional model of skeletal muscle. The images acquired through a high speed camera were correlated with a custom-made algorithm and the longitudinal strain predictions were employed for measuring the spontaneous contraction. The spontaneous contraction reference values were obtained by studying the force response. The relative error between the spontaneous contraction frequencies computed in both ways was always lower than 0.15%. In conclusion, the use of a DIC based system allows for an accurate and noninvasive measurement of biological tissues’ spontaneous contraction, in addition to the measurement of tissue strain field on any desired region of interest during electrical stimulation.

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

    OpenAIRE

    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 ...

  17. Fructose 2,6-bisphosphate in rat skeletal muscle during contraction.

    OpenAIRE

    Minatogawa, Y; Hue, Louis

    1984-01-01

    Fructose 2,6-bisphosphate and several glycolytic intermediates were measured in two rat muscles, extensor digitorum longus and gastrocnemius, which were electrically stimulated in situ. Both the duration and the frequency of stimulation were varied to obtain different rates of glycolysis. There was no relationship between fructose 2,6-bisphosphate content and the increase in tissue lactate in contracting muscle. However, in gastrocnemius stimulated at low frequencies (less than or equal to 5 ...

  18. Changes in glucose 1,6-bisphosphate content in rat skeletal muscle during contraction.

    OpenAIRE

    Bassols, A M; Carreras, J; Cussó, R

    1986-01-01

    Glucose 1,6-bisphosphate, fructose 2,6-bisphosphate, glycogen, lactate and other glycolytic metabolites were measured in rat gastrocnemius muscle, which was electrically stimulated in situ via the sciatic nerve. Both the frequency and the duration of stimulation were varied to obtain different rates of glycolysis. There was no apparent relationship between fructose 2,6-bisphosphate content and lactate accumulation in contracting muscle. In contrast, glucose 1,6-bisphosphate content increased ...

  19. Excitation-contraction coupling and mechano-sensitivity in denervated skeletal muscles

    Directory of Open Access Journals (Sweden)

    Fabio Francini

    2010-09-01

    Full Text Available Skeletal muscle atrophy can be defined as a wasting or decrease in muscle mass and muscle force generation owing lack of use, ageing, injury or disease. Thus, the etiology of atrophy can be different. Atrophy in denervated muscle is a consequence of two factors: 1 the complete lack of motoneuron activity inducing the deficiency of neurotransmitter release and 2 the muscles disuse. The balance of the muscular functions depends on extra- and intra-muscular signals. In the balance are involved the excitation-contraction coupling (ECC, local growth factors, Ca2+-dependent and independent intracellular signals, mechano-sensitivity and mechano-transduction that activate Ca2+-dependent signaling proteins and cytoskeleton- nucleus pathways to the nucleus, that regulate the gene expression. Moreover, retrograde signal from intracellular compartments and cytoskeleton to the sarcolemma are additional factors that regulate the muscle function. Proteolytic systems that operate in atrophic muscles progressively reduce the muscle protein content and so the sarcolemma, ECC and the force generation. In this review we will focus on the more relevant changes of the sarcolemma, excitation-contraction coupling, ECC and mechano-transduction evaluated by electrophysiological methods and observed from early- to long-term denervated skeletal muscles. This review put in particular evidence that long-term denervated muscle maintain a sub-population of fibers with ECC and contractile machinery able to be activated, albeit in lesser amounts, by electrical and mechanical stimulation. Accordingly, this provides a potential molecular explanation of the muscle recovery that occurs in response to rehabilitation strategy as transcutaneous electrical stimulation and passive stretching of denervated muscles, which wre developed as a result of empirical clinical observations.

  20. 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.

  1. Muscle involvement during intermittent contraction patterns with different target force feedback modes

    DEFF Research Database (Denmark)

    Sjøgaard, G; Jørgensen, L V; Ekner, D

    2000-01-01

    feedback) or a weight to be held in position (proprioceptive feedback) both corresponding to 30% maximal voluntary contraction. Contraction and relaxation timing of 6 and 4 s, respectively, was shown on a VDU screen as colour code identical in both conditions. RESULTS: Test contractions performed before......OBJECTIVE: Assess the effect of different feedback modes during intermittent contractions on primary and assessory muscle activity. BACKGROUND: Intermittent contractions and physiological responses have been studied in laboratory settings. However, the feedback given to the subjects regarding...... timing and force level is generally not specified. DESIGN: Repeated measure design in which six subjects in randomized order performed two experimental conditions only differing in feedback mode. METHODS: Intermittent static elbow flexion was performed against either a fixed-force transducer (visual...

  2. 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

  3. 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

  4. Kinetics of contraction-induced GLUT4 translocation in skeletal muscle fibers from living mice

    DEFF Research Database (Denmark)

    Lauritzen, Hans Peter M. Mortensen; Galbo, Henrik; Toyoda, Taro

    2010-01-01

    Exercise is an important strategy for the treatment of type 2 diabetes. This is due in part to an increase in glucose transport that occurs in the working skeletal muscles. Glucose transport is regulated by GLUT4 translocation in muscle, but the molecular machinery mediating this process is poorly...... understood. The purpose of this study was to 1) use a novel imaging system to elucidate the kinetics of contraction-induced GLUT4 translocation in skeletal muscle and 2) determine the function of AMP-activated protein kinase alpha2 (AMPKalpha2) in this process....

  5. 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.

  6. Augmentation of Skeletal Muscle Contraction by NaF

    OpenAIRE

    服部, 敏己

    1980-01-01

    For the purpose of elucidation of the mechanism of convulsion induced as the acute intoxication of sodium fluoride (NaF), the actions of NaF on the frog sciatic nerve-sar-torius muscle preparation were investigated electrophysiologically. The results obtained were summarised as follows: 1) Both twitch and tetanus tension were augmented by NaF dose-dependently. 2) NaF had little effect on the compound action potential of nerves, resting membrane potential, action potential and membrane resista...

  7. 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

  8. Effects of real and sham whole-body mechanical vibration on spinal excitability at rest and during muscle contraction

    NARCIS (Netherlands)

    Hortobagyi, T.; Rider, P.; DeVita, P.

    2014-01-01

    We examined the effects of whole-body mechanical vibration (WBV) on indices of motoneuronal excitability at rest and during muscle contraction in healthy humans. Real and sham WBV at 30Hz had no effect on reflexes measured during muscle contraction. Real WBV at 30 and 50Hz depressed the H-reflex

  9. RELATIONSHIP BETWEEN ELECTRICAL AND VIBRATORY OUTPUT OF MUSCLE DURING VOLUNTARY CONTRACTION AND FATIGUE

    NARCIS (Netherlands)

    ZWARTS, MJ; KEIDEL, M

    Measurements were done on the biceps muscles of 6 healthy volunteers to record simultaneously the surface electromyogram (EMG) and vibromyogram (VMG) by means of a piezoelectric device (accelerometer). The VMG is generated by mechanical waves due to the contraction mechanism and often measured as

  10. Contraction and AICAR Stimulate IL-6 Vesicle Depletion From Skeletal Muscle Fibers In Vivo

    DEFF Research Database (Denmark)

    Lauritzen, Hans P M M; Brandauer, Josef; Schjerling, Peter

    2013-01-01

    Recent studies suggest that interleukin 6 (IL-6) is released from contracting skeletal muscles; however, the cellular origin, secretion kinetics, and signaling mechanisms regulating IL-6 secretion are unknown. To address these questions, we developed imaging methodology to study IL-6 in fixed mouse...

  11. Blood flow response to electrically induced twitch and tetanic lower-limb muscle contractions.

    NARCIS (Netherlands)

    Janssen, T.W.; Hopman, M.T.E.

    2003-01-01

    OBJECTIVES: To compare the effect of electric stimulation (ES)-induced twitch with tetanic leg muscle contractions on blood flow responses and to assess blood flow responses in the contralateral inactive leg. DESIGN: Intervention with within-subject comparisons. SETTING: University research

  12. Blood flow response to electrically induced twitch and tetanic lower-limb muscle contractions

    NARCIS (Netherlands)

    Janssen, T.W.J.; Hopman, M.T.E.

    2003-01-01

    Objectives: To compare the effect of electric stimulation (ES)-induced twitch with tetanic leg muscle contractions on blood flow responses and to assess blood flow responses in the contralateral inactive leg. Design: Intervention with within-subject comparisons. Setting: University research

  13. Formation of hydrogen peroxide and nitric oxide in rat skeletal muscle cells during contractions

    DEFF Research Database (Denmark)

    Silveira, Leonardo R.; Pereira-Da-Silva, Lucia; Juel, Carsten

    2003-01-01

    We examined intra- and extracellular H(2)O(2) and NO formation during contractions in primary rat skeletal muscle cell culture. The fluorescent probes DCFH-DA/DCFH (2,7-dichlorofluorescein-diacetate/2,7-dichlorofluorescein) and DAF-2-DA/DAF-2 (4,5-diaminofluorescein-diacetate/4,5-diaminofluoresce...

  14. Muscle-Type Specific Autophosphorylation of CaMKII Isoforms after Paced Contractions

    NARCIS (Netherlands)

    Eilers, W.; Gevers, W.; van Overbeek, D.; de Haan, A.; Jaspers, R.T.; Hilbers, P.A.; van Riel, A.C.R.; Flueck, M.

    2014-01-01

    We explored to what extent isoforms of the regulator of excitation-contraction and excitation-transcription coupling, calcium/calmodulin protein kinase II (CaMKII) contribute to the specificity of myocellular calcium sensing between muscle types and whether concentration transients in its

  15. Evaluation of a Hill based muscle model for the energy cost and efficiency of muscular contraction

    NARCIS (Netherlands)

    Houdijk, J.H.P.; Bobbert, M.F.; de Haan, A.

    2006-01-01

    The purpose of this study was to evaluate a Hill-based mathematical model of muscle energetics and to disclose inconsistencies in existing experimental data. For this purpose, we simulated iso-velocity contractions of mouse fast twitch EDL and slow twitch SOL fibers, and we compared the outcome to

  16. Prototype Multifunctional Device for Contraction Exercises of Joints and Muscles of the Lower Limb

    Directory of Open Access Journals (Sweden)

    Pawel JURECZKO

    2013-12-01

    Full Text Available In the article Authors are showing the endurance test of the prototype multifunctional device for contraction exercises of joints and strengthening muscles. The endurance test was conducted with finite element method in the Ansys Workbench program and permitted the durability of material checking, whether the structural figure of the device is safe from the side for patients.

  17. Messenger molecules of the phospholipase signaling system have dual effects on vascular smooth muscle contraction.

    Science.gov (United States)

    Vidulescu, Cristina; Mironneau, J.; Mironneau, Chantal; Popescu, L. M.

    2000-01-01

    Background and methods. In order to investigate the role of phospholipases and their immediately derived messengers in agonist-induced contraction of portal vein smooth muscle, we used the addition in the organ bath of exogenous molecules such as: phospholipases C, A(2), and D, diacylglycerol, arachidonic acid, phosphatidic acid, choline. We also used substances modulating activity of downstream molecules like protein kinase C, phosphatidic acid phosphohydrolase, or cyclooxygenase. Results. a) Exogenous phospholipases C or A(2), respectively, induced small agonist-like contractions, while exogenous phospholipase D did not. Moreover, phospholipase D inhibited spontaneous contractions. However, when added during noradrenaline-induced plateau, phospholipase D shortly potentiated it. b) The protein kinase C activator, phorbol dibutyrate potentiated both the exogenous phospholipase C-induced contraction and the noradrenaline-induced plateau, while the protein kinase C inhibitor 1-(-5-isoquinolinesulfonyl)-2-methyl-piperazine relaxed the plateau. c) When added before noradrenaline, indomethacin inhibited both phasic and tonic contractions, but when added during the tonic contraction shortly potentiated it. Arachidonic acid strongly potentiated both spontaneous and noradrenaline-induced contractions, irrespective of the moment of its addition. d) In contrast, phosphatidic acid inhibited spontaneous contractile activity, nevertheless it was occasionally capable of inducing small contractions, and when repetitively added during the agonist-induced tonic contraction, produced short potentiations of the plateau. Pretreatment with propranolol inhibited noradrenaline-induced contractions and further addition of phosphatidic acid augmented this inhibition. Choline augmented the duration and amplitude of noradrenaline-induced tonic contraction and final contractile oscillations. Conclusions. These data suggest that messengers produced by phospholipase C and phospholipase A(2

  18. 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.

  19. Connective tissue regeneration in skeletal muscle after eccentric contraction-induced injury

    DEFF Research Database (Denmark)

    Mackey, Abigail Louise; Kjaer, Michael

    2017-01-01

    Human skeletal muscle has the potential to regenerate completely after injury induced under controlled experimental conditions. The events inside the myofibres as they undergo necrosis, followed closely by satellite cell mediated myogenesis, have been mapped in detail. Much less is known about...... against this however is the association between muscle matrix protein remodelling and protection against re-injury, which suggests that a (so far undefined) period of vulnerability to re-injury may exist during the remodelling phases. The role of individual muscle matrix components and their spatial...... interaction during adaptation to eccentric contractions is an unexplored field in human skeletal muscle and may provide insight into the optimal timing of rest vs. return to activity after muscle injury....

  20. Uncoupling of in vivo torque production from EMG in mouse muscles injured by eccentric contractions

    Science.gov (United States)

    Warren, Gordon L; Ingalls, Christopher P; Shah, Shree J; Armstrong, R B

    1999-01-01

    The main objective of this study was to determine whether eccentric contraction-induced muscle injury causes impaired plasmalemmal action potential conduction, which could explain the injury-induced excitation-contraction coupling failure. Mice were chronically implanted with stimulating electrodes on the left common peroneal nerve and with electromyographic (EMG) electrodes on the left tibialis anterior (TA) muscle. The left anterior crural muscles of anaesthetized mice were stimulated to perform 150 eccentric (ECC) (n = 12 mice) or 150 concentric (CON) (n = 11 mice) contractions. Isometric torque, EMG root mean square (RMS) and M-wave mean and median frequencies were measured before, immediately after, and at 1, 3, 5 and 14 days after the protocols. In parallel experiments, nicotinic acetylcholine receptor (AChR) concentration was measured in TA muscles to determine whether the excitation failure elicited a denervation-like response.Immediately after the ECC protocol, torque was reduced by 47–89%, while RMS was reduced by 9–21%; the RMS decrement was not different from that observed for the CON protocol, which did not elicit large torque deficits. One day later, both ECC and CON RMS had returned to baseline values and did not change over the next 2 weeks. However, torque production by the ECC group showed a slow recovery over that time and was still depressed by 12–30% after 2 weeks. M-wave mean and median frequencies were not affected by performance of either protocol.AChR concentration was elevated by 79 and 368% at 3 and 5 days, respectively, after the ECC protocol; AChR concentration had returned to control levels 2 weeks after the protocol. At the time of peak AChR concentration in the ECC protocol muscles (i.e. 5 days), AChR concentration in CON protocol muscles was not different from the control level.In conclusion, these data demonstrate no major role for impaired plasmalemmal action potential conduction in the excitation-contraction coupling

  1. Lower working heights decrease contraction intensity of shoulder muscles in a herringbone 30° milking parlor.

    Science.gov (United States)

    Cockburn, Marianne; Schick, Matthias; Maffiuletti, Nicola A; Gygax, Lorenz; Savary, Pascal; Umstätter, Christina

    2017-06-01

    Musculoskeletal disorders have been a main concern in milkers for many years. To improve posture, a formula was developed in a previous study to calculate ergonomically optimal working heights for various milking parlor types. However, the working height recommendations based on the formula for the herringbone 30° parlor were broad. To clarify the recommendations for the optimal working height, we investigated the effect of working height on upper limb and shoulder muscle contraction intensities. We evaluated 60 milking cluster attachment procedures in a herringbone 30° milking parlor in 7 men and 9 women. Specifically, we examined the effect of working height on muscle contraction intensity of 4 arm and shoulder muscles bilaterally (flexor carpi ulnaris, biceps brachii, deltoideus anterior, and upper trapezius) by using surface electromyography. The working heights (low, medium, and high), which reflect the ratio of the subject's height to the height of the udder base, were used in the milking health formula to determine and fit individual depth of pits. Data were evaluated for each muscle and arm side in the functions holding and attaching. Statistical analysis was performed using linear mixed effects models, where muscle contraction intensity served as a target variable, whereas working height coefficient, sex, subject height, and repetition were treated as fixed effects, and repetition group nested in working height nested in subject was considered a random effect. Contraction intensities decreased with decreasing working height for the deltoideus anterior and upper trapezius, but not for the flexor carpi ulnaris or the biceps brachii muscles in both holding and attaching arm functions. We found that milking at a lower working height reduced muscle contraction intensities of the shoulder muscles. Women showed higher contraction intensities than men, whereas subject height had no effect. The study demonstrated that a lower working height decreased muscular

  2. Controlled intermittent shortening contractions of a muscle-tendon complex: muscle fibre damage and effects on force transmission from a single head of rat EDL

    NARCIS (Netherlands)

    Maas, H.; Lehti, T.M.; Tiihonen, V.; Komulainen, J.; Huijing, P.A.J.B.M.

    2005-01-01

    This study was performed to examine effects of prolonged (3 h) intermittent shortening (amplitude 2 mm) contractions (muscles were excited maximally) of head III of rat extensor digitorum longus muscle (EDL III) on indices of muscle damage and on force transmission within the intact anterior crural

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

    Directory of Open Access Journals (Sweden)

    Seung-Jun Choi

    2016-09-01

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

  4. Torque decrease during submaximal evoked contractions of the quadriceps muscle is linked not only to muscle fatigue.

    Science.gov (United States)

    Matkowski, Boris; Lepers, Romuald; Martin, Alain

    2015-05-01

    The aim of this study was to analyze the neuromuscular mechanisms involved in the torque decrease induced by submaximal electromyostimulation (EMS) of the quadriceps muscle. It was hypothesized that torque decrease after EMS would reflect the fatigability of the activated motor units (MUs), but also a reduction in the number of MUs recruited as a result of changes in axonal excitability threshold. Two experiments were performed on 20 men to analyze 1) the supramaximal twitch superimposed and evoked at rest during EMS (Experiment 1, n = 9) and 2) the twitch response and torque-frequency relation of the MUs activated by EMS (Experiment 2, n = 11). Torque loss was assessed by 15 EMS-evoked contractions (50 Hz; 6 s on/6 s off), elicited at a constant intensity that evoked 20% of the maximal voluntary contraction (MVC) torque. The same stimulation intensity delivered over the muscles was used to induce the torque-frequency relation and the single electrical pulse evoked after each EMS contraction (Experiment 2). In Experiment 1, supramaximal twitch was induced by femoral nerve stimulation. Torque decreased by ~60% during EMS-evoked contractions and by only ~18% during MVCs. This was accompanied by a rightward shift of the torque-frequency relation of MUs activated and an increase of the ratio between the superimposed and posttetanic maximal twitch evoked during EMS contraction. These findings suggest that the torque decrease observed during submaximal EMS-evoked contractions involved muscular mechanisms but also a reduction in the number of MUs recruited due to changes in axonal excitability. Copyright © 2015 the American Physiological Society.

  5. Correlation of digital palpation and transabdominal ultrasound for assessment of pelvic floor muscle contraction.

    Science.gov (United States)

    Arab, Amir Massoud; Behbahani, Roxana Bazaz; Lorestani, Leila; Azari, Afsaneh

    2009-01-01

    Pelvic floor muscle (PFM) dysfunction has been commonly associated with urinary disorders and lumbo-pelvic pain. Transabdominal (TA) ultrasound is currently used by physical therapists to assess PFM function. Controversy exists regarding the correlation between TA ultrasound measurement and vaginal palpation for assessment of PFM contraction, and this relationship has not yet been examined concurrently during the same contraction. The purpose of this study was to determine the correlation of digital palpation and TA ultrasound to assess PFM contraction when recorded 1) simultaneous to digital palpation during one contraction and 2) following digital palpation testing in another contraction. A descriptive correlational design was used to describe the relationship between variables. A total of 19 women (both asymptomatic women and those with incontinence or lumbo-pelvic pain) participated in the study. The modified Oxford scale was used to grade PFM contraction in digital palpation testing. The amount of bladder base movement on ultrasound was measured and considered as an indicator of PFM activity. Two trials were performed for TA ultrasound measurement: 1) simultaneous to digital palpation during one contraction, and 2) following digital palpation testing in another contraction. Spearman's correlation coefficient was used for analysis. There was a significant correlation between digital palpation and TA ultrasound for PFM assessment when measured simultaneously in one contraction (rho=0.62, p=0.01) and separately in a different contraction (rho=0.52, p=0.02), with a stronger correlation found in simultaneous testing. In conclusion, digital palpation and TA ultrasound measurement are significantly correlated and measure comparable parameters in evaluation of PFM contraction.

  6. Genomic profiling reveals Pitx2 controls expression of mature extraocular muscle contraction-related genes.

    Science.gov (United States)

    Zhou, Yuefang; Gong, Bendi; Kaminski, Henry J

    2012-04-18

    To assess the influence of the Pitx2 transcription factor on the global gene expression profile of extraocular muscle (EOM) of mice. Mice with a conditional knockout of Pitx2, designated Pitx2(Δflox/Δflox) and their control littermates Pitx2(flox/flox), were used. RNA was isolated from EOM obtained at 3, 6, and 12 weeks of age and processed for microarray-based profiling. Pairwise comparisons were performed between mice of the same age and differentially expressed gene lists were generated. Select genes from the profile were validated using real-time quantitative polymerase chain reaction and protein immunoblot. Ultrastructural analysis was performed to evaluate EOM sarcomeric structure. The number of differentially expressed genes was relatively small. Eleven upregulated and 23 downregulated transcripts were identified common to all three age groups in the Pitx2-deficient extraocular muscle compared with littermate controls. These fell into a range of categories including muscle-specific structural genes, transcription factors, and ion channels. The differentially expressed genes were primarily related to muscle contraction. We verified by protein and ultrastructural analysis that myomesin 2 was expressed in the Pitx2-deficient mice, and this was associated with development of M lines evident in their orbital region. The global transcript expression analysis uncovered that Pitx2 primarily regulates a relatively select number of genes associated with muscle contraction. Pitx2 loss led to the development of M line structures, a feature more typical of other skeletal muscle.

  7. [Phallotoxins as an instrument for studying the intramyofibrillar regulation of muscle contraction].

    Science.gov (United States)

    Bukatina, A E; Sik, G S

    2003-01-01

    The contraction of myofibrils is regulated by the coordinated action of Ca2+ and myosin cross-bridges. Phallotoxins induce a variety of specific changes in myofibrillar functioning and are therefore a potentially valuable tool for muscle research. There are two greatly differing classes of drugs among phallotoxins: (1) recently discovered secophalloidin and its derivatives. The unique property of secophalloidin is muscle activation without Ca2+, possibly by direct influence on actomyosin interaction. These drugs seem to be especially useful for studying the role of cross-bridges in muscle regulation; (2) the phalloidin group, which includes the majority of phallotoxins. When binding to the phalloidin site on F-actin, they cause muscle-specific changes. In cardiac muscle they work as Ca2+ sensitizers, increasing both the maximal force and Ca2+ sensitivity. An advantage of these drugs is that the target site is known, which allows one to unravel the sequence of molecular events leading to increased contractile function. Presumably, the complex effect of phalloidin in skeletal muscle is related to the disturbance of the actin-nebulin interaction, which may help to clarify the role of nebulin in the regulation contraction.

  8. The cellular stress response of rat skeletal muscle following lengthening contractions.

    Science.gov (United States)

    Pollock-Tahiri, Evan; Locke, Marius

    2017-07-01

    The cellular stress response of the rat tibialis anterior (TA) muscle was investigated following 20, 40, or 60 lengthening contractions (LCs) using an in vivo model of electrical stimulation. Muscles were removed at 0, 1, 3, or 24 h after LCs and assessed for heat shock transcription factor (HSF) activation, heat shock protein (HSP) content, and/or morphological evidence of muscle fibre damage. When compared with the first muscle contraction, peak muscle torque was reduced by 26% (p < 0.05) after 20 LCs and further reduced to 56% and 60% (p < 0.001) after 40 and 60 LCs, respectively. Following 60 LCs, HSF activation was detected at 0, 1, and 3 h but was undetectable at 24 h. Hsp72 content was elevated at 24 h after 20 LCs (2.34 ± 0.37 fold, p < 0.05), 40 LCs (3.02 ± 0.31 fold, p < 0.01), and 60 LCs (3.37 ± 0.21 fold, p < 0.001). Hsp25 content increased after 40 (2.36 ± 0.24 fold, p < 0.01) and 60 LCs (2.80 ± 0.37 fold, p < 0.01). Morphological assessment of TA morphology revealed that very few fibres were damaged following 20 LCs while multiple sets of LCs (40 and 60) caused greater amounts of fibre damage. Electron microscopy showed disrupted Z-lines and sarcomeres were detectable in some muscles fibres following 20 LCs but were more prevalent and severe in muscles subjected to 40 or 60 LCs. These results suggest LCs elevate HSP content by an HSF-mediated mechanism (60 LC) and a single set of 20 LCs is capable of increasing muscle HSP content without causing significant muscle fibre damage.

  9. Upregulation of heart PFK-2/FBPase-2 isozyme in skeletal muscle after persistent contraction.

    Science.gov (United States)

    Rovira, Jordi; Irimia, Jose Maria; Guerrero, Mario; Cadefau, Joan Aureli; Cussó, Roser

    2012-04-01

    Fructose-2,6-bisphosphate (Fru-2,6-P(2)) is the most potent allosteric activator of liver 6-phosphofructo-1-kinase enzyme, which is crucial for glycolysis. It is present in skeletal muscle but its importance is controversial as a regulator of muscle glycolysis. This study aims to determine the role of Fru-2,6-P(2) in the control of muscle glycolysis during contraction. Muscle contraction was produced by chronic low-frequency stimulation of rabbit tibialis anterior for 24 h, followed by a rest period of 48 h. To determine muscle glycolysis adaptation, we applied a short functional electrostimulation test using the same system of low-frequency stimulation for 1, 3, and 10 s. The variation in concentration of lactate and pyruvate was used to calculate the flux along the glycolysis pathway and the Fru-1,6-P(2)/Fru-6-P ratio permitted to analyze the 6-phosphofructo-1-kinase activation. Fru-2,6-P(2) levels increased over the 24 h of stimulation and remained elevated after the rest period, this being the only metabolite that kept the changes produced by chronic low-frequency stimulation during the rest. During the short functional electrostimulation test, the glycolytic pathway in stimulated and rested muscle was more active than in control muscle, which coincided with higher kinase activity of the 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase (PFK-2/FBPase-2) enzyme. Furthermore, we found a decrease in muscle, liver, and ubiquitous PFK-2/FBPase-2 isoform expression and an increase in heart isoform expression. For the first time, we demonstrate that a persistent increase in Fru-2,6-P(2) produced by a change in PFK-2/FBPase-2 isoform expression may play an important role in the regulation of muscle glycolysis during the first moments of exercise.

  10. 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.

  11. Towards a unified theory of muscle contraction. I: foundations.

    Science.gov (United States)

    Smith, D A; Geeves, M A; Sleep, J; Mijailovich, S M

    2008-10-01

    Molecular models of contractility in striated muscle require an integrated description of the action of myosin motors, firstly in the filament lattice of the half-sarcomere. Existing models do not adequately reflect the biochemistry of the myosin motor and its sarcomeric environment. The biochemical actin-myosin-ATP cycle is reviewed, and we propose a model cycle with two 4- to 5-nm working strokes, where phosphate is released slowly after the first stroke. A smaller third stroke is associated with ATP-induced detachment from actin. A comprehensive model is defined by applying such a cycle to all myosin-S1 heads in the half-sarcomere, subject to generic constraints as follows: (a) all strain-dependent kinetics required for actin-myosin interactions are derived from reaction-energy landscapes and applied to dimeric myosin, (b) actin-myosin interactions in the half-sarcomere are controlled by matching rules derived from the structure of the filaments, so that each dimer may be associated with a target zone of three actin sites, and (c) the myosin and actin filaments are treated as elastically extensible. Numerical predictions for such a model are presented in the following paper.

  12. Ca2+-induced contraction of cat esophageal circular smooth muscle cells.

    Science.gov (United States)

    Cao, W; Chen, Q; Sohn, U D; Kim, N; Kirber, M T; Harnett, K M; Behar, J; Biancani, P

    2001-04-01

    ACh-induced contraction of esophageal circular muscle (ESO) depends on Ca2+ influx and activation of protein kinase Cepsilon (PKCepsilon). PKCepsilon, however, is known to be Ca2+ independent. To determine where Ca2+ is needed in this PKCepsilon-mediated contractile pathway, we examined successive steps in Ca2+-induced contraction of ESO muscle cells permeabilized by saponin. Ca2+ (0.2-1.0 microM) produced a concentration-dependent contraction that was antagonized by antibodies against PKCepsilon (but not by PKCbetaII or PKCgamma antibodies), by a calmodulin inhibitor, by MLCK inhibitors, or by GDPbetas. Addition of 1 microM Ca2+ to permeable cells caused myosin light chain (MLC) phosphorylation, which was inhibited by the PKC inhibitor chelerythrine, by D609 [phosphatidylcholine-specific phospholipase C inhibitor], and by propranolol (phosphatidic acid phosphohydrolase inhibitor). Ca2+-induced contraction and diacylglycerol (DAG) production were reduced by D609 and by propranolol, alone or in combination. In addition, contraction was reduced by AACOCF(3) (cytosolic phospholipase A(2) inhibitor). These data suggest that Ca2+ may directly activate phospholipases, producing DAG and arachidonic acid (AA), and PKCepsilon, which may indirectly cause phosphorylation of MLC. In addition, direct G protein activation by GTPgammaS augmented Ca2+-induced contraction and caused dose-dependent production of DAG, which was antagonized by D609 and propranolol. We conclude that agonist (ACh)-induced contraction may be mediated by activation of phospholipase through two distinct mechanisms (increased intracellular Ca2+ and G protein activation), producing DAG and AA, and activating PKCepsilon-dependent mechanisms to cause contraction.

  13. Implantable power generation system utilizing muscle contractions excited by electrical stimulation.

    Science.gov (United States)

    Sahara, Genta; Hijikata, Wataru; Tomioka, Kota; Shinshi, Tadahiko

    2016-06-01

    An implantable power generation system driven by muscle contractions for supplying power to active implantable medical devices, such as pacemakers and neurostimulators, is proposed. In this system, a muscle is intentionally contracted by an electrical stimulation in accordance with the demands of the active implantable medical device for electrical power. The proposed system, which comprises a small electromagnetic induction generator, electrodes with an electrical circuit for stimulation and a transmission device to convert the linear motion of the muscle contractions into rotational motion for the magneto rotor, generates electrical energy. In an ex vivo demonstration using the gastrocnemius muscle of a toad, which was 28 mm in length and weighed 1.3 g, the electrical energy generated by the prototype exceeded the energy consumed for electrical stimulation, with the net power being 111 µW. It was demonstrated that the proposed implantable power generation system has the potential to replace implantable batteries for active implantable medical devices. © IMechE 2016.

  14. 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

  15. Changes in presumed motor cortical activity during fatiguing muscle contraction in humans

    DEFF Research Database (Denmark)

    Seifert, Thomas; Petersen, Nicolas Caesar

    2010-01-01

    failure the suppression had reached 16 +/- 2.1%. In control experiments without fatigue we did not find a similar increase in suppression with increasing levels of ongoing EMG activity. CONCLUSION: Using a form of TMS which reduces cortical output to motor neurones (and disfacilitates them), this study......AIM: Changes in sensory information from active muscles accompany fatiguing exercise and the force-generating capacity deteriorates. The central motor commands therefore must adjust depending on the task performed. Muscle potentials evoked by transcranial magnetic stimulation (TMS) change during...... voluntary contraction) of the elbow flexor muscles we applied TMS over the motor cortex. At an intensity below motor threshold, TMS reduced the ongoing muscle activity in biceps brachii. This reduction appears as a suppression at short latency of the stimulus-triggered average of rectified electromyographic...

  16. Inefficient functional sympatholysis is an overlooked cause of malperfusion in contracting skeletal muscle

    DEFF Research Database (Denmark)

    Saltin, Bengt; Mortensen, Stefan P

    2012-01-01

    sympatholysis and muscle blood flow are impaired compared to young men, but regular physical activity can prevent these age related impairments. In young subjects, two weeks of leg immobilization causes a reduced ability for functional sympatholysis, whereas the trained leg maintained this function. Patients......Contracting skeletal muscle can overcome sympathetic vasoconstrictor activity (functional sympatholysis), which allows for a blood supply that matches the metabolic demand. This ability is thought to be mediated by locally released substances that modulate the effect of noradrenaline (NA) on the α......-receptor. Tyramine induces local NA release and can be used in humans to investigate the underlying mechanisms and physiological importance of functional sympatholysis in the muscles of healthy and diseased individuals as well as the impact of the active muscles' training status. In sedentary elderly men, functional...

  17. 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.

  18. Seven skeletal muscles rich in slow muscle fibers may function to sustain neutral position in the rodent hindlimb.

    Science.gov (United States)

    Hitomi, Yoshiaki; Kizaki, Takako; Watanabe, Sumiko; Matsumura, George; Fujioka, Yasunori; Haga, Shukoh; Izawa, Tetsuya; Taniguchi, Naoyuki; Ohno, Hideki

    2005-01-01

    Skeletal muscles consist of slow-twitch and fast-twitch muscle fibers, which have distinct physiological and biochemical properties. The muscle fiber composition determines the contractile velocity and fatigability of a particular skeletal muscle. We analyzed the systemic distribution of slow muscle fibers in all rodent skeletal muscles by myosin ATPase staining and found that only seven hindlimb skeletal muscles were extremely rich in slow muscle fibers. These included the mouse piriformis (56.5%), gluteus minimus (35.7%), vastus intermedius (24.7%), quadratus femoris (69.9%), adductor brevis (44.3%), gracilis (24.6%), and soleus muscles (35.1%). In mice, the relative proportion of slow muscle fibers did not exceed 15% in skeletal muscles in other regions. The distribution of slow muscle fibers was well conserved in rats and rabbits. The soleus muscle is an important antigravity muscle in both rodents and humans; therefore, these skeletal muscles rich in slow muscle fibers might play an important role in sustaining neutral alignment of the lower extremity.

  19. Effects of adenosine triphosphate concentration on motor force regulation during skeletal muscle contraction

    Science.gov (United States)

    Wei, J.; Dong, C.; Chen, B.

    2017-04-01

    We employ a mechanical model of sarcomere to quantitatively investigate how adenosine triphosphate (ATP) concentration affects motor force regulation during skeletal muscle contraction. Our simulation indicates that there can be negative cross-bridges resisting contraction within the sarcomere and higher ATP concentration would decrease the resistance force from negative cross-bridges by promoting their timely detachment. It is revealed that the motor force is well regulated only when ATP concentration is above a certain level. These predictions may provide insights into the role of ATP in regulating coordination among multiple motors.

  20. 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.

  1. Evaluation of an in vitro muscle contraction model in mouse primary cultured myotubes.

    Science.gov (United States)

    Manabe, Yasuko; Ogino, Shinya; Ito, Miyuki; Furuichi, Yasuro; Takagi, Mayumi; Yamada, Mio; Goto-Inoue, Naoko; Ono, Yusuke; Fujii, Nobuharu L

    2016-03-15

    To construct an in vitro contraction model with the primary cultured myotubes, we isolated satellite cells from the mouse extensor digitorum longus. Differentiated myotubes possessed a greater number of sarcomere assemblies and higher expression levels of myosin heavy chain, cytochrome c oxidase IV, and myoglobin than in C2C12 myotubes. In agreement with these results regarding the sarcomere assemblies and protein expressions, the primary myotubes showed higher contractile activity stimulated by the electric pulses than that in the C2C12 myotubes. These data suggest that mouse primary myotubes will be a valuable research tool as an in vitro muscle contraction model. Copyright © 2015 Elsevier Inc. All rights reserved.

  2. Leucine-Enriched Essential Amino Acids Augment Muscle Glycogen Content in Rats Seven Days after Eccentric Contraction

    Directory of Open Access Journals (Sweden)

    Hiroyuki Kato

    2017-10-01

    Full Text Available Eccentric contractions induce muscle damage, which impairs recovery of glycogen and adenosine tri-phosphate (ATP content over several days. Leucine-enriched essential amino acids (LEAAs enhance the recovery in muscles that are damaged after eccentric contractions. However, the role of LEAAs in this process remains unclear. We evaluated the content in glycogen and high energy phosphates molecules (phosphocreatine (PCr, adenosine di-phosphate (ADP and ATP in rats that were following electrically stimulated eccentric contractions. Muscle glycogen content decreased immediately after the contraction and remained low for the first three days after the stimulation, but increased seven days after the eccentric contraction. LEAAs administration did not change muscle glycogen content during the first three days after the contraction. Interestingly, however, it induced a further increase in muscle glycogen seven days after the stimulation. Contrarily, ATP content decreased immediately after the eccentric contraction, and remained lower for up to seven days after. Additionally, LEAAs administration did not affect the ATP content over the experimental period. Finally, ADP and PCr levels did not significantly change after the contractions or LEAA administration. LEAAs modulate the recovery of glycogen content in muscle after damage-inducing exercise.

  3. Effect of fiber type and nutritional state on AICAR- and contraction-stimulated glucose transport in rat muscle

    DEFF Research Database (Denmark)

    Ai, Hua; Ihlemann, Jacob; Hellsten, Ylva

    2002-01-01

    AMP-activated protein kinase (AMPK) may mediate the stimulatory effect of contraction and 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR) on glucose transport in skeletal muscle. In muscles with different fiber type composition from fasted rats, AICAR increased 2-deoxyglucose transport......)- and alpha(2)-isoforms of AMPK. Expression of both isoforms varied with fiber types, and alpha(2) was highly expressed in nuclei. In conclusion, AICAR-stimulated glucose transport varies with muscle fiber type and nutritional state. AMPK is unlikely to be the sole mediator of contraction-stimulated glucose...... and total AMPK activity approximately twofold in epitrochlearis (EPI), less in flexor digitorum brevis, and not at all in soleus muscles. Contraction increased both transport and AMPK activity more than AICAR did. In EPI muscles, the effects of AICAR and contractions on glucose transport were partially...

  4. Disturbance of smooth muscle regulatory function by Eisenia foetida toxin lysenin: insight into the mechanism of smooth muscle contraction.

    Science.gov (United States)

    Czuryło, Edward A; Kulikova, Natalia; Sobota, Andrzej

    2008-05-01

    Lysenin, a toxin present in the coelomic fluid of the earthworm Eisenia foetida, is known to cause a long-lasting contraction of rat aorta smooth muscle strips. We addressed the mechanisms underlying its action on smooth muscle cells and present the first report demonstrating a completely new property of lysenin unrelated to its basic sphingomyelin-binding ability. Here we report lysenin enhancement effect on smooth muscle actomyosin ATPase activity and the ability of networking the actin filaments. The maximum enhancement of the ATPase activity of actomyosin at 120 mM KCl was observed at a molar ratio of lysenin to actin of about 1:10(5), while at 70 mM KCl at the ratio of about 1:10(6). The effect of lysenin became most pronounced only when both smooth muscle regulatory proteins, tropomyosin and caldesmon, were present. Co-sedimentation experiments indicated that lysenin did not displace neither tropomyosin nor caldesmon from the thin filament. Thus, the lysenin-dependent abolishment of the inhibitory effect of caldesmon on the ATPase activity was related rather to the modification of the filament structure. The ability of the toxin to exert its stimulatory effect at extremely low concentrations (as low as one molecule of lysenin per 10(6) actin molecules) may result from the long-range cooperative transitions in the entire thin filament with an involvement of smooth muscle tropomyosin, while the role of caldesmon may be limited exclusively to the inhibition of ATPase activity.

  5. Female striated urogenital sphincter contraction measured by shear wave elastography during pelvic floor muscle activation: Proof of concept and validation.

    Science.gov (United States)

    Aljuraifani, Rafeef; Stafford, Ryan E; Hug, François; Hodges, Paul W

    2017-04-13

    Investigation of the function of the striated urogenital sphincter (SUS) is challenging because it is difficult to access and requires invasive measures. Ultrasound shear wave elastography (SWE) is a non-invasive real-time technique used to estimate tissue stiffness. As muscle stiffness can be used as an estimate of muscle force, SWE provides an opportunity to study contraction of the peri-urethral musculature. Validation of SWE to study SUS during functional tasks, such as pelvic floor muscle contractions, is required prior to application in clinical populations. Ten healthy females (34[5] years) participated. Stiffness in a region expected to contain the SUS was quantified using SWE at rest and during a pelvic floor muscle contractions performed at 10%, 25%, and 50% of maximal voluntary contraction (MVC). Two repetitions were performed for 10 s. During contraction, stiffness increased in the region of the SUS in all participants and at all contraction intensities. Multiple regions of increased stiffness were detected, with 95.8% of regions situated ventral to the mid-urethra within the anatomical area of the SUS. The increase in stiffness was greater for 50% MVC than both 10% and 25% MVC contraction intensities (P < 0.01). Stiffness increased within the anatomical region of the SUS during voluntary pelvic floor muscle contractions with predictable response to changes in contraction intensity. These observations support the potential for ultrasound SWE to study SUS function non-invasively. © 2017 Wiley Periodicals, Inc.

  6. Ultrasound evaluation of muscle thickness changes in the external oblique, internal oblique, and transversus abdominis muscles considering the influence of posture and muscle contraction.

    Science.gov (United States)

    Sugaya, Tomoaki; Abe, Yota; Sakamoto, Masaaki

    2014-09-01

    [Purpose] The aim of this study was to investigate muscle thickness changes in the external oblique (EO), internal oblique (IO), and transversus abdominis (TrA) muscles between the neutral position and trunk rotation, under a state of rest without voluntary contractions, and isometric contractions to both sides with resistance of 50% of the maximum trunk rotation strength. [Subjects] The subjects of this study were 21 healthy young men. [Methods] Muscle thickness changes in the EO, IO, and TrA in each position and state were evaluated by ultrasound. The range of motion at maximum trunk rotation and the maximum strength of trunk rotation were measured using a hand-held dynamometer. [Results] In the neutral position and at 50% trunk rotation to the right side, the thicknesses of the IO and TrA significantly increased with resistance. In both states, the thicknesses of the IO and TrA significantly increased at 50% trunk rotation to the right side. [Conclusion] The muscular contractions of the IO and TrA were stronger during ipsilateral rotation than in the neutral position and with resistance than at rest. Moreover, the muscular contraction was strongest in the resistive state during ipsilateral rotation.

  7. Depression of corticomotor excitability after muscle fatigue induced by electrical stimulation and voluntary contraction

    Directory of Open Access Journals (Sweden)

    Shinichi eKotan

    2015-06-01

    Full Text Available In this study, we examined the effect of muscle fatigue induced by tetanic electrical stimulation (ES and submaximal isometric contraction on corticomotor excitability. Experiments were performed in a cross-over design. Motor-evoked potentials (MEPs were elicited by transcranial magnetic stimulation. Corticomotor excitability was recorded before and after thumb opposition muscle fatigue tasks, in which 10% of the maximal tension intensity was induced by tetanic ES or voluntary contraction (VC. The participants were 10 healthy individuals who performed each task for 10 min. Surface electrodes placed over the abductor pollicis brevis (APB muscle recorded MEPs. F- and M-waves were elicited from APB by supramaximal ES of the median nerve. After the ES1-and VC tasks, MEP amplitudes were significantly lower than before the task. However, F-and M-wave amplitudes remained unchanged. These findings suggest that corticospinal excitability is reduced by muscle fatigue as a result of intracortical inhibitory mechanisms. Our results also suggest that corticomotor excitability is reduced by muscle fatigue caused by both VC and tetanic ES.

  8. Use-dependence of ryanodine effects on postrest contraction in ferret cardiac muscle.

    Science.gov (United States)

    Malecot, C O; Katzung, B G

    1987-04-01

    During an investigation of the effect of ryanodine on contractions in cardiac muscle, it was found that long rest periods removed all or most of the drug's effect. Therefore, we studied the kinetics of block development and recovery from block produced by low concentrations of ryanodine (1-100 pM) on the postrest contractions of ferret papillary muscle. At 100 pM, ryanodine depressed steady-state contraction amplitude slightly (4.2 +/- 1.1% mean +/- SEM, n = 10) but strongly inhibited (40-80%) the first contraction (postrest contraction) elicited on restimulation of the preparation after rest periods of 1 second to 5 minutes. Under control conditions, the nearly maximal potentiation of the twitch occurring after a standard test rest period (30 seconds of rest) was not affected by a preceding conditioning rest of up to 20 minutes. In the presence of 100 pM ryanodine, a conditioning rest increased the amplitude of the twitch elicited after a test rest, and the test rest contraction recovered toward control (drug-free) amplitude monoexponentially (time constant, 582 +/- 105 seconds). Block of postrest contraction could be reinduced by stimulation and occurred faster when higher rates were used (time constants, 758 seconds at 1 Hz and 107 +/- 26 seconds at 3 Hz). Since rest potentiation of twitch tension is believed to be mostly dependent on extra calcium released from the sarcoplasmic reticulum, the results suggest that the ryanodine-induced blockade of calcium release from the sarcoplasmic reticulum is use-dependent and recovers during diastole.(ABSTRACT TRUNCATED AT 250 WORDS)

  9. Intra-subject variability in muscle activity and co-contraction during jumps and landings in children and adults

    DEFF Research Database (Denmark)

    Raffalt, P C; Alkjaer, T; Simonsen, E B

    2017-01-01

    and 60 cm for the children and 60 and 90 cm for the adults. The adults also performed ten DJ from 60 cm. EMG was recorded from nine lower limb muscles in the right leg and normalized to isometric MVC. Statistical parametric mapping was used to reveal differences in the muscle activity and intra......We investigated muscle activity, intra-subject variability in muscle activity and co-contraction during vertical jumps and landings in children and adults. Ten male children and 10 male adults completed 10 countermovement jumps (CMJ), 10 drop jumps (DJ) from 30 cm, 10 low and high landings from 30......-subject variability in the muscle activity. Co-contraction was quantified for two thigh muscle pairs and one plantar flexor/dorsiflexor muscle pair and group differences were assessed (two-way ANOVA). No significant differences were observed in the less eccentric demanding CMJ while significantly higher muscle...

  10. Dynamic measurement of pennation angle of gastrocnemius muscles during contractions based on ultrasound imaging

    Directory of Open Access Journals (Sweden)

    Zhou Yongjin

    2012-09-01

    Full Text Available Abstract Background Muscle fascicle pennation angle (PA is an important parameter related to musculoskeletal functions, and ultrasound imaging has been widely used for measuring PA, but manually and frame by frame in most cases. We have earlier reported an automatic method to estimate aponeurosis orientation based on Gabor transform and Revoting Hough Transform (RVHT. Methods In this paper, we proposed a method to estimate the overall orientation of muscle fascicles in a region of interest, in order to complete computing the orientation of the other side of the pennation angle, but the side found by RVHT. The measurements for orientations of both fascicles and aponeurosis were conducted in each frame of ultrasound images, and then the dynamic change of pennation angle during muscle contraction was obtained automatically. The method for fascicle orientation estimation was evaluated using synthetic images with different noise levels and later on 500 ultrasound images of human gastrocnemius muscles during isometric plantarflexion. Results The muscle fascicle orientations were also estimated manually by two operators. From the results it’s found that the proposed automatic method demonstrated a comparable performance to the manual method. Conclusions With the proposed methods, ultrasound measurement for muscle pennation angles can be more widely used for functional assessment of muscles.

  11. Functional implications of muscle co-contraction during gait in advanced age.

    Science.gov (United States)

    Lo, Justine; Lo, On-Yee; Olson, Erin A; Habtemariam, Daniel; Iloputaife, Ikechukwu; Gagnon, Margaret M; Manor, Brad; Lipsitz, Lewis A

    2017-03-01

    Older adults often exhibit high levels of lower extremity muscle co-contraction, which may be the cause or effect of age-related impairments in gait and associated falls. Normal gait requires intact executive function and thus can be slowed by challenging executive resources available to the neuromuscular system through the performance of a dual task. We therefore investigated associations between lower limb co-contraction and gait characteristics under normal and dual task conditions in healthy older adults (85.4±5.9years). We hypothesized that greater co-contraction is associated with slower gait speed during dual task conditions that stress executive and attentional abilities. Co-contraction was quantified during different phases of the gait cycle using surface electromyography (EMG) signals obtained from the anterior tibialis and lateral gastrocnemius while walking at preferred speed during normal and dual task conditions. Variables included the time difference to complete the Trail Making Test A and B (ΔTMT) and gait measures during normal or dual task walking. Higher co-contraction levels during the swing phase of both normal and dual task walking were associated with longer ΔTMT (normal: R2=0.25, p=0.02; dual task: R2=0.27, p=0.01). Co-contraction was associated with gait measures during dual task walking only; greater co-contraction levels during stride and stance were associated with slower gait speed (stride: R2=0.38, p=0.04; stance: R2=0.38, p=0.04), and greater co-contraction during stride was associated with longer stride time (R2=0.16, p=0.03). Our results suggest that relatively high lower limb co-contraction may explain some of the mobility impairments associated with the conduct of executive tasks in older adults. Copyright © 2017 Elsevier B.V. All rights reserved.

  12. Change in muscle thickness under contracting conditions following return to sports after a hamstring muscle strain injury—A pilot study

    Directory of Open Access Journals (Sweden)

    Yasuharu Nagano

    2015-04-01

    Full Text Available The purpose of this study was to measure the change in hamstring muscle thickness between contracting and relaxing conditions following a return to sports after a hamstring muscle strain and thereby evaluate muscle function. Six male track and field sprinters participated in this study. All had experienced a prior hamstring strain injury that required a minimum of 2 weeks away from sport participation. Transverse plane scans were performed at the following four points on the affected and unaffected sides under contracting and relaxing conditions: proximal biceps femoris long head, proximal semitendinosus, middle biceps femoris long head, and middle semitendinosus. The results demonstrated an increase in the thickness of the middle biceps femoris long head and middle semitendinosus regions on the unaffected side with contraction, whereas the affected side did not show a significant increase. The proximal semitendinosus muscle thickness was increased with contraction on both the unaffected and the affected sides. By contrast, the proximal biceps femoris muscle thickness did not show a significant increase on both sides. The results of this study show that evaluation of muscle thickness during contraction may be useful for assessing the change in muscle function after a hamstring muscle strain injury.

  13. Pennation angle dependency in skeletal muscle tissue doppler strain in dynamic contractions.

    Science.gov (United States)

    Lindberg, Frida; Öhberg, Fredrik; Granåsen, Gabriel; Brodin, Lars-Åke; Grönlund, Christer

    2011-07-01

    Tissue velocity imaging (TVI) is a Doppler based ultrasound technique that can be used to study regional deformation in skeletal muscle tissue. The aim of this study was to develop a biomechanical model to describe the TVI strain's dependency on the pennation angle. We demonstrate its impact as the subsequent strain measurement error using dynamic elbow contractions from the medial and the lateral part of biceps brachii at two different loadings; 5% and 25% of maximum voluntary contraction (MVC). The estimated pennation angles were on average about 4° in extended position and increased to a maximal of 13° in flexed elbow position. The corresponding relative angular error spread from around 7% up to around 40%. To accurately apply TVI on skeletal muscles, the error due to angle changes should be compensated for. As a suggestion, this could be done according to the presented model. Copyright © 2011 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

  14. Membrane Cholesterol in Skeletal Muscle: A Novel Player in Excitation-Contraction Coupling and Insulin Resistance.

    Science.gov (United States)

    Barrientos, G; Sánchez-Aguilera, P; Jaimovich, E; Hidalgo, C; Llanos, P

    2017-01-01

    Membrane cholesterol is critical for signaling processes in a variety of tissues. We will address here current evidence supporting an emerging role of cholesterol on excitation-contraction coupling and glucose transport in skeletal muscle. We have centered our review on the transverse tubule system, a complex network of narrow plasma membrane invaginations that propagate membrane depolarization into the fiber interior and allow nutrient delivery into the fibers. We will discuss current evidence showing that transverse tubule membranes have remarkably high cholesterol levels and we will address how modifications of cholesterol content influence excitation-contraction coupling. In addition, we will discuss how membrane cholesterol levels affect glucose transport by modulating the insertion into the membrane of the main insulin-sensitive glucose transporter GLUT4. Finally, we will address how the increased membrane cholesterol levels displayed by obese animals, which also present insulin resistance, affect these two particular skeletal muscle functions.

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

    Directory of Open Access Journals (Sweden)

    Wan X Yao

    2016-11-01

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

  16. Capsiate supplementation reduces oxidative cost of contraction in exercising mouse skeletal muscle in vivo.

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    Kazuya Yashiro

    Full Text Available Chronic administration of capsiate is known to accelerate whole-body basal energy metabolism, but the consequences in exercising skeletal muscle remain very poorly documented. In order to clarify this issue, the effect of 2-week daily administration of either vehicle (control or purified capsiate (at 10- or 100-mg/kg body weight on skeletal muscle function and energetics were investigated throughout a multidisciplinary approach combining in vivo and in vitro measurements in mice. Mechanical performance and energy metabolism were assessed strictly non-invasively in contracting gastrocnemius muscle using magnetic resonance (MR imaging and 31-phosphorus MR spectroscopy (31P-MRS. Regardless of the dose, capsiate treatments markedly disturbed basal bioenergetics in vivo including intracellular pH alkalosis and decreased phosphocreatine content. Besides, capsiate administration did affect neither mitochondrial uncoupling protein-3 gene expression nor both basal and maximal oxygen consumption in isolated saponin-permeabilized fibers, but decreased by about twofold the Km of mitochondrial respiration for ADP. During a standardized in vivo fatiguing protocol (6-min of repeated maximal isometric contractions electrically induced at a frequency of 1.7 Hz, both capsiate treatments reduced oxidative cost of contraction by 30-40%, whereas force-generating capacity and fatigability were not changed. Moreover, the rate of phosphocreatine resynthesis during the post-electrostimulation recovery period remained unaffected by capsiate. Both capsiate treatments further promoted muscle mass gain, and the higher dose also reduced body weight gain and abdominal fat content. These findings demonstrate that, in addition to its anti-obesity effect, capsiate supplementation improves oxidative metabolism in exercising muscle, which strengthen this compound as a natural compound for improving health.

  17. 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

  18. In Graves' disease, increased muscle tension and reduced elasticity of affected muscles is primarily caused by active muscle contraction

    NARCIS (Netherlands)

    H.J. Simonsz (Huib); G. Kommerell (Guntram)

    1989-01-01

    textabstractIn three patients with Graves' disease of recent onset, length-tension diagrams were made during surgery for squint under eyedrop anesthesia, while the other eye looked ahead, into the field of action, or out of the field of action of the muscle that was measured. The affected muscles

  19. Assessment of pelvic floor muscle contraction with palpation, perineometry and transperineal ultrasound: a cross-sectional study.

    Science.gov (United States)

    Volløyhaug, I; Mørkved, S; Salvesen, Ø; Salvesen, K Å

    2016-06-01

    To study the correlation between palpation, perineometry and transperineal ultrasound for assessment of pelvic floor muscle contraction and to define a contraction scale for ultrasound measurements. This was a cross-sectional study of 608 women examined with palpation of pelvic floor muscle contraction, using the Modified Oxford Scale, and measurement of the vaginal squeeze pressure with a vaginal balloon connected to a fiber-optic microtip transducer (perineometry). Transperineal ultrasound was used for measurements of levator hiatal area and anteroposterior (AP) diameter in the plane of minimal hiatal dimensions, at rest and on contraction. The pelvic floor muscle contraction was expressed as the percentage difference between values at rest and on contraction. Spearman's rank was used to test for correlation between the different methods of assessment. Significant correlations were found between all assessment methods (P 35% corresponded to strong contractions. We found moderate to strong correlation between ultrasound measurements, palpation and perineometry for assessing pelvic floor muscle contraction. The proportional change in levator hiatal AP diameter was the ultrasound measurement with strongest correlation to palpation and perineometry and formed the basis for the contraction scale for ultrasound measurements. Copyright © 2015 ISUOG. Published by John Wiley & Sons Ltd. Copyright © 2015 ISUOG. Published by John Wiley & Sons Ltd.

  20. 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.

  1. Influence of clove oil and eugenol on muscle contraction of silkworm (Bombyx mori).

    Science.gov (United States)

    Kheawfu, Kantaporn; Pikulkaew, Surachai; Hamamoto, Hiroshi; Sekimizu, Kazuhisa; Okonogi, Siriporn

    2017-05-30

    Clove oil is used in fish anesthesia and expected to have a mechanism via glutamic receptor. The present study explores the activities of clove oil and its major compound, eugenol, in comparison with L-glutamic acid on glutamic receptor of silkworm muscle and fish anesthesia. It was found that clove oil and eugenol had similar effects to L-glutamic acid on inhibition of silkworm muscle contraction after treated with D-glutamic acid and kainic acid. Anesthetic activity of the test samples was investigated in goldfish. The results demonstrated that L-glutamic acid at 20 and 40 mM could induce the fish to stage 3 of anesthesia that the fish exhibited total loss of equilibrium and muscle tone, whereas clove oil and eugenol at 60 ppm could induce the fish to stage 4 of anesthesia that the reflex activity of the fish was lost. These results suggest that clove oil and eugenol have similar functional activities and mechanism to L-glutamic acid on muscle contraction and fish anesthesia.

  2. Aging impairs contraction-induced human skeletal muscle mTORC1 signaling and protein synthesis

    Directory of Open Access Journals (Sweden)

    Fry Christopher S

    2011-03-01

    Full Text Available Abstract Background Sarcopenia, the loss of skeletal muscle mass during aging, increases the risk for falls and dependency. Resistance exercise (RE training is an effective treatment to improve muscle mass and strength in older adults, but aging is associated with a smaller amount of training-induced hypertrophy. This may be due in part to an inability to stimulate muscle-protein synthesis (MPS after an acute bout of RE. We hypothesized that older adults would have impaired mammalian target of rapamycin complex (mTORC1 signaling and MPS response compared with young adults after acute RE. Methods We measured intracellular signaling and MPS in 16 older (mean 70 ± 2 years and 16 younger (27 ± 2 years subjects. Muscle biopsies were sampled at baseline and at 3, 6 and 24 hr after exercise. Phosphorylation of regulatory signaling proteins and MPS were determined on successive muscle biopsies by immunoblotting and stable isotopic tracer techniques, respectively. Results Increased phosphorylation was seen only in the younger group (PP >0.05. After exercise, MPS increased from baseline only in the younger group (PP 0.05. Conclusions We conclude that aging impairs contraction-induced human skeletal muscle mTORC1 signaling and protein synthesis. These age-related differences may contribute to the blunted hypertrophic response seen after resistance-exercise training in older adults, and highlight the mTORC1 pathway as a key therapeutic target to prevent sarcopenia.

  3. Glycolysis in contracting rat skeletal muscle is controlled by factors related to energy state

    DEFF Research Database (Denmark)

    Ørtenblad, Niels; Macdonald, Will A; Sahlin, Kent

    2009-01-01

    The control of glycolysis in contracting muscle is not fully understood. The aim of the present study was to examine whether activation of glycolysis is mediated by factors related to the energy state or by a direct effect of Ca2+ on the regulating enzymes. Extensor digitorum longus muscles from...... and 58% of those in Con respectively. Glycolytic rate in BTS was only 51% of that in Con but the relative contribution of ATP derived from PCr (phosphocreatine) and glycolysis and the relation between muscle contents of PCr and Lac (lactate) were not different. Prolonged cyanide incubation of quiescent...... contribution of energy delivered from PCr and glycolysis during both conditions suggests that the glycolytic rate is controlled by factors related to energy state....

  4. Influence on muscle oxygenation to EMG parameters at different skeletal muscle contraction

    Science.gov (United States)

    Zhang, Li; Song, Gaoqing

    2010-02-01

    The purpose of this study is to investigate the influence of muscle oxygenation on EMG parameters during isometric and incremental exercises and to observe the relationship between EMG parameters and muscle oxygenation. Twelve rowers took part in the tests. Near infrared spectrometer was utilized for measurements of muscle oxygenation on lateral quadriceps. sEMG measurement is performed for EMG parameters during isometric and incremental exercises. Results indicated that Oxy-Hb decrease significantly correlated with IEMG, E/T ratio and frequency of impulse signal during 1/3 MVC and 2/3 MVC isometric exercise, and it is also correlated with IEMG, E/T ratio and frequency of impulse signal. Increase of IEMG occurred at the time after Oxy-Hb decrease during incremental exercise and highly correlated with BLa. It is concluded that no matter how heavy the intensity is, Oxy-Hb dissociation may play an important role in affecting EMG parameters of muscle fatigue during isometric exercise. 2) EMG parameters may be influenced by Oxy-Hb dissociation and blood lactate concentration during dynamic exercise.

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

    Directory of Open Access Journals (Sweden)

    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

  6. Effects of contraction on localization of GLUT4 and v-SNARE isoforms in rat skeletal muscle

    DEFF Research Database (Denmark)

    Rose, Adam John; Jeppesen, Jacob; Kiens, Bente

    2009-01-01

    In skeletal muscle, contractions increase glucose uptake due to a translocation of GLUT4 glucose transporters from intracellular storage sites to the surface membrane. Vesicle associated membrane proteins (VAMPs) are believed to play an important role in docking and fusion of the GLUT4 transporters...... at the surface membrane. However, knowledge about which VAMP isoforms in fact co-localize with GLUT4 vesicles in mature skeletal muscle and whether they translocate during muscle contractions is incomplete. The aim of the present study was to further identify VAMP isoforms which are associated with GLUT4...... vesicles and examine which VAMP isoforms translocate to surface membranes in skeletal muscles undergoing contractions. VAMP2, VAMP3, VAMP5 and VAMP7 were enriched in immuno-precipitated GLUT4 vesicles. In response to 20 min of in situ contractions, there was a redistribution of GLUT4 (+64 +/- 13...

  7. Elastic, Viscous, and Mass Load Effects on Poststroke Muscle Recruitment and Co-contraction During Reaching: A Pilot Study

    OpenAIRE

    Stoeckmann, Tina M.; Sullivan, Katherine J.; Scheidt, Robert A.

    2009-01-01

    Background: Resistive exercise after stroke can improve strength (force-generating capacity) without increasing spasticity (velocity-dependent hypertonicity). However, the effect of resistive load type on muscle activation and co-contraction after stroke is not clear.

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

    DEFF Research Database (Denmark)

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

    2017-01-01

    Purpose: Delayed onset muscle soreness (DOMS) occur within 1-2 days after eccentric exercise but the mechanism mediating hypersensitivity is unclear. This study hypothesized that eccentric exercise reduces the blood flow response following muscle contractions and cuff occlusion, which may result ...... that eccentric contractions decreased vessel diameter, impaired the blood flow response and promoted hyperalgesia. Thus, the results suggest that the blood flow reduction may be involved in the increased pain response after eccentric exercise....

  9. Does the prevalence of levator ani muscle avulsion differ when assessed using tomographic ultrasound imaging at rest vs on maximum pelvic floor muscle contraction?

    NARCIS (Netherlands)

    Delft, K. van; Thakar, R.; Sultan, A.H.; Kluivers, K.B.

    2015-01-01

    OBJECTIVE: It has been suggested that transperineal ultrasound images obtained during maximum pelvic floor muscle contraction improve the diagnosis of levator ani muscle (LAM) avulsion by comparison with those obtained at rest. The objective of this study was to establish, using transperineal

  10. Disruption of microtubules in rat skeletal muscle does not inhibit insulin- or contraction-stimulated glucose transport

    DEFF Research Database (Denmark)

    Ai, Hua; Ralston, Evelyn; Lauritzen, Hans P M M

    2003-01-01

    found in all muscle fibers. Here, we test whether microtubules are required mediators of the effect of insulin and contractions. In three different incubated rat muscles with distinct fiber type composition, depolymerization of microtubules with colchicine for ...- or contraction-stimulated 2-deoxyglucose transport or force production. On the contrary, colchicine at least partially prevented the approximately 30% decrease in insulin-stimulated transport that specifically developed during 8 h of incubation in soleus muscle but not in flexor digitorum brevis...... or epitrochlearis muscles. In contrast, nocodazole, another microtubule-disrupting drug, rapidly and dose dependently blocked insulin- and contraction-stimulated glucose transport. A similar discrepancy between colchicine and nocodazole was also found in their ability to block glucose transport in muscle giant...

  11. Memories of early work on muscle contraction and regulation in the 1950's and 1960's.

    Science.gov (United States)

    Huxley, Hugh E

    2008-04-25

    Professor Ebashi's epic work on the biochemistry of the regulation of muscle contraction began in the early 1950's, during the same period that work on the molecular basis of force production in muscle was also beginning. The latter work started in two MRC Research Units in the UK, and was continued jointly by the two workers from those Units who had, independently, gone to MIT to learn the new techniques of electron microscopy and to apply them to muscle. In a somewhat similar fashion, Professor Ebashi also spent one or two years in the USA, continuing his work on the role of calcium in muscle regulation in Lippman's laboratory, before returning to Japan to achieve the great breakthroughs in this work during the 1960's. Hanson and Huxley, after putting forward the overlapping actin and myosin filament arrays model for the striated muscle sarcomere, and subsequently the sliding filament model of muscle contraction (simultaneously with A.F Huxley and R. Niedergerke), returned to the UK to pursue detailed structural studies in separate Research Units, in a mixture of consultation, collaboration, and competition, during the later 1950's and throughout the 1960's. However, the path to enlightenment described here in some detail was somewhat more tortuous than the standard literature perhaps reveals. Nevertheless, by the time of the Cold Spring Harbor Symposium on Muscle Contraction in 1972, the two lines of enquiry on regulation itself, and on the tilting cross-bridge model of force production, had arrived at a good deal of common ground, and indeed the identification of troponin and its periodic distribution along the actin filaments had helped resolve a long-standing puzzle in the interpretation of the low angle X-ray diagram. Since then, an enormous amount of remarkable new work has been necessary to establish troponin regulation and the tilting cross-bridge mechanism in molecular detail, but the work in the 1950's and 1960's has provided a firm and accurate basis

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

    DEFF Research Database (Denmark)

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

    2015-01-01

    content during post-exercise recovery from eccentric contractions. Analysis was completed on five male subjects performing an exercise bout consisting of 15 x 10 maximal eccentric contractions. Carbohydrate-rich drinks were subsequently ingested throughout a 48 h recovery period and muscle biopsies...

  13. Contraction of the transverse abdominal muscle in pelvic girdle pain is enhanced by pain provocation during the task

    NARCIS (Netherlands)

    Mens, Jan M A; Pool-Goudzwaard, A.L.

    2017-01-01

    BACKGROUND: Understanding of the pathogenesis of pain in the lumbopelvic region remains a challenge. It is suggested that lumbopelvic pain is related to decreased contraction of the transverse abdominal muscles (TrA). OBJECTIVE: To investigate how pain provoked by a task influences TrA contraction

  14. Identification of the main generator source of longitudinal muscle contraction in the earthworm ventral nerve cord

    Directory of Open Access Journals (Sweden)

    Y.C. Chang

    1998-10-01

    Full Text Available The main generator source of a longitudinal muscle contraction was identified as an M (mechanical-stimulus-sensitive circuit composed of a presynaptic M-1 neuron and a postsynaptic M-2 neuron in the ventral nerve cord of the earthworm, Amynthas hawayanus, by simultaneous intracellular response recording and Lucifer Yellow-CH injection with two microelectrodes. Five-peaked responses were evoked in both neurons by a mechanical, but not by an electrical, stimulus to the mechanoreceptor in the shaft of a seta at the opposite side of an epidermis-muscle-nerve-cord preparation. This response was correlated to 84% of the amplitude, 73% of the rising rate and 81% of the duration of a longitudinal muscle contraction recorded by a mechano-electrical transducer after eliminating the other possible generator sources by partitioning the epidermis-muscle piece of this preparation. The pre- and postsynaptic relationship between these two neurons was determined by alternately stimulating and recording with two microelectrodes. Images of the Lucifer Yellow-CH-filled M-1 and M-2 neurons showed that both of them are composed of bundles of longitudinal processes situated on the side of the nerve cord opposite to stimulation. The M-1 neuron has an afferent process (A1 in the first nerve at the stimulated side of this preparation and the M-2 neuron has two efferent processes (E1 and E3 in the first and third nerves at the recording side where their effector muscle cell was identified by a third microelectrode.

  15. Muscle-Type Specific Autophosphorylation of CaMKII Isoforms after Paced Contractions

    Directory of Open Access Journals (Sweden)

    Wouter Eilers

    2014-01-01

    Full Text Available We explored to what extent isoforms of the regulator of excitation-contraction and excitation-transcription coupling, calcium/calmodulin protein kinase II (CaMKII contribute to the specificity of myocellular calcium sensing between muscle types and whether concentration transients in its autophosphorylation can be simulated. CaMKII autophosphorylation at Thr287 was assessed in three muscle compartments of the rat after slow or fast motor unit-type stimulation and was compared against a computational model (CaMuZclE coupling myocellular calcium dynamics with CaMKII Thr287 phosphorylation. Qualitative differences existed between fast- (gastrocnemius medialis and slow-type muscle (soleus for the expression pattern of CaMKII isoforms. Phospho-Thr287 content of δA CaMKII, associated with nuclear functions, demonstrated a transient and compartment-specific increase after excitation, which contrasted to the delayed autophosphorylation of the sarcoplasmic reticulum-associated βM CaMKII. In soleus muscle, excitation-induced δA CaMKII autophosphorylation demonstrated frequency dependence (P = 0.02. In the glycolytic compartment of gastrocnemius medialis, CaMKII autophosphorylation after excitation was blunted. In silico assessment emphasized the importance of mitochondrial calcium buffer capacity for excitation-induced CaMKII autophosphorylation but did not predict its isoform specificity. The findings expose that CaMKII autophosphorylation with paced contractions is regulated in an isoform and muscle type-specific fashion and highlight properties emerging for phenotype-specific regulation of CaMKII.

  16. Myofibrillar proteolysis in response to voluntary or electrically stimulated muscle contractions in humans

    DEFF Research Database (Denmark)

    Hansen, M; Trappe, T; Crameri, R M

    2008-01-01

    Knowledge about the effects of exercise on myofibrillar protein breakdown in human subjects is limited. Our purpose was to measure the changes in the degradation of myofibrillar proteins in response to different ways of eliciting muscle contractions using the local interstitial 3-methyl-histidine......Knowledge about the effects of exercise on myofibrillar protein breakdown in human subjects is limited. Our purpose was to measure the changes in the degradation of myofibrillar proteins in response to different ways of eliciting muscle contractions using the local interstitial 3-methyl...... contractions (ES). Microdialysis probes were placed in m. vastus lateralis in both the legs immediately after, and 1 and 3 days post-exercise. Interstitial 3-MH was higher in ES vs VOL immediately after exercise (Pexercise no difference between the two exercise types was observed...... enhanced after ES compared with VOL immediately after exercise, while the level of 3-MH did not change in the post-exercise period after VOL. These results indicate that the local myofibrillar breakdown is accelerated after ES associated with severe myofiber damage....

  17. Knockout of the predominant conventional PKC isoform, PKCalpha, in mouse skeletal muscle does not affect contraction-stimulated glucose uptake

    DEFF Research Database (Denmark)

    Jensen, Thomas E; Maarbjerg, Stine J; Rose, Adam J

    2009-01-01

    -induced glucose uptake were similar in muscles lacking PKCalpha and in the wild type. It can be concluded that PKCalpha, representing approximately 97% of cPKC in skeletal muscle, is not required for contraction-stimulated glucose uptake. Thus the effect of the PKC blockers on glucose uptake is either nonspecific...

  18. Presynaptic and postsynaptic regulation of muscle contractions in the ascarid nematode Ascaris suum: a target for drug action.

    Science.gov (United States)

    Trailović, S M; Zurovac, Z; Gruborović, S; Marjanović, D S; Nedeljković-Trailović, J

    2016-11-01

    The aim of this study was to determine the role in contractions of postsynaptic nicotinic acetylcholine (nACh) and γ-aminobutyric acid (GABA) receptors, in the bag region of Ascaris suum muscle cells, as well as the role of synaptic receptors between interneurons and motor neurons in the dorsal and ventral nerve cord. We have measured the isometric contractions of isolated segments of A. suum, with or without the nerve cord (dorsal or ventral). Contractions were caused by increasing concentrations of ACh or by electrical field stimulation (EFS). Based on our results, the presence of the nerve cord is essential for the contractile effects of ACh. The EC50 value of ACh for innervated muscle strips was 10.88 μm. Unlike intact (innervated) preparations, there was no contraction of the muscle flaps when the nerve cord was mechanically removed. Furthermore, continuous EFS produced stable contractions of innervated muscle strips, but they are not sensitive to mecamylamine (100 μm). However, GABA (30 μm) significantly inhibited the EFS-induced contractions. EFS with the same characteristics did not cause muscle contractions of denervated muscle strips, but EFS with a wider pulse induced the increasing of tone and irregular contractions. These contractions were completely insensitive to the effect of GABA. The EC50 for ACh did not differ between the dorsal and ventral segments (9.83 μm and 9.45 μm), while GABA exhibited features of competitive and non-competitive antagonists, regardless of whether it acted on the dorsal or ventral segments of A. suum. It is obvious that drugs will be more effective if they act on both the synaptic and extrasynaptic nACh and GABA receptors.

  19. Skeletal muscle inflammation following repeated bouts of lengthening contractions in humans

    Directory of Open Access Journals (Sweden)

    Michael Roger Deyhle

    2016-01-01

    Full Text Available Skeletal muscle responds to exercise-induced damage by orchestrating an adaptive process that protects the muscle from damage by subsequent bouts of exercise, a phenomenon called the repeated bout effect (RBE. The mechanisms underlying the RBE are not understood. We hypothesized that an attenuated inflammation response following a repeated bout of lengthening contractions (LC would be coincidental with a RBE, suggesting a potential relationship. Fourteen men (n=7 and women (n=7 completed 2 bouts of lengthening contractions (LC separated by 28 days. Muscle biopsies were taken before the first bout (B1 from the non-exercised leg, and from the exercised leg 2- and 27-d post-B1 and 2-d following the second bout (B2. A 29-plex cytokine array identified alterations in inflammatory cytokines. Immunohistochemistry quantified inflammatory cell infiltration and major histocompatibility complex class 1 (MHC-1. Muscle soreness was attenuated in the days following B2 relative to B1, indicating a RBE. Intramuscular monocyte chemoattractant protein (MCP1 and interferon gamma-induced protein 10 (IP10 increased following B2 relative to the pre-exercise sample (7 pg/ml to 52 pg/ml, and 11 pg/ml to 36 pg/ml, respectively p<0.05. Interleukin 4 (IL4 decreased (26 pg/ml to 13 pg/ml, p<0.05 following B2 relative to the pre-exercise sample. Infiltration of CD68+ macrophages and CD8+ T-cells were evident following B2, but not B1. Moreover, CD8+ T-cells were observed infiltrating apparently necrotic muscle fibers. No changes in MHC-1 were found. We conclude that inflammation is not attenuated following a repeated bout of LC and that CD8+ T-cells may play a role in muscle adaptation following LC. Moreover, it appears that the muscle or the immune system becomes sensitized to an initial bout of damaging exercise such that inflammatory cell infiltration into the muscle is enhanced upon a repeated bout of damaging exercise.

  20. Clonal derivation of a rat muscle cell strain that forms contraction-competent myotubes.

    Science.gov (United States)

    Merrill, G F

    1989-05-01

    A muscle cell strain capable of forming contracting myotubes was isolated from an established rat embryo cell line. The myogenic cells, termed rat myoblast omega or RMo cells, have a diploid complement of chromosomes (n = 42). In the presence of mitogen-containing growth medium, RMo cells proliferated with a cell generation time of about 12 hours. In mitogen-depleted medium, RMo cells withdrew from the cell cycle and formed myotubes that spontaneously contracted. Differentiated RMo cells produced creatine kinase isozymes in a ratio characteristic of skeletal muscle cells. RMo cells were easy to cultivate. Cells proliferated and differentiated equally well on gelatin-coated or noncoated culture dishes, at clonal or mass culture densities, and in all basal media tested. In most experiments, growth medium consisted of horse serum-containing medium supplemented with either chicken embryo extract or FGF activity; cells proliferated equally well in medium containing unsupplemented calf serum. RMo cells differentiated if growth medium was not replenished regularly. Alternatively, differentiation was induceable by incubation in mitogen-depleted medium consisting of basal medium supplemented either with 10(-6) M insulin, 0.5% serum, or 50% conditioned growth medium. RMo cells were competently transformed with cloned exogenous genes. Because it forms functional myofibrils, the RMo cell line constitutes a useful model system for studying the cell biology and biochemistry of proteins involved in contractile apparatus assembly and muscle disease.

  1. Behaviour of human motor units in different muscles during linearly varying contractions

    Science.gov (United States)

    de Luca, C. J.; LeFever, R. S.; McCue, M. P.; Xenakis, A. P.

    1982-01-01

    1. The electrical activity of up to eight concurrently active motor units has been recorded from the human deltoid and first dorsal interosseous (f.d.i.) muscles. The detected myoelectric signals have been decomposed into their constituent motor-unit action potential trains using a recently developed technique. 2. Concurrently active motor unit behaviour has been examined during triangular force-varying isometric contractions reaching 40 and 80% of maximal voluntary contraction (m.v.c.). Experiments were performed on four normal subjects and three groups of highly trained performers (long-distance swimmers, powerlifters and pianists). 3. Results revealed a highly ordered recruitment and decruitment scheme, based on motoneurone excitability, in both muscles and in all subject groups. 4. Differences were observed between the initial (recruitment) and final (decruitment) firing rates in each muscle. These parameters were invariant with respect to the force rates studied, although some differences were observed among subject groups. 5. In general, firing rates of f.d.i. motor units increased steadily with increasing force (up to 80% m.v.c.). The firing rates of deltoid motor units rose sharply just after recruitment and then increased only slightly thereafter. 6. Recruitment was found to be the major mechanism for generating extra force between 40 and 80% m.v.c. in the deltoid, while rate coding played the major role in the f.d.i. 7. The potential of rate coding for increasing force levels up to m.v.c. is discussed. PMID:7143246

  2. 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.

  3. Comparison of changes in the mobility of the pelvic floor muscle on during the abdominal drawing-in maneuver, maximal expiration, and pelvic floor muscle maximal contraction

    Science.gov (United States)

    Jung, Halim; Jung, Sangwoo; Joo, Sunghee; Song, Changho

    2016-01-01

    [Purpose] The purpose of this study was to compare changes in the mobility of the pelvic floor muscle during the abdominal drawing-in maneuver, maximal expiration, and pelvic floor muscle maximal contraction. [Subjects] Thirty healthy adults participated in this study (15 men and 15 women). [Methods] All participants performed a bridge exercise and abdominal curl-up during the abdominal drawing-in maneuver, maximal expiration, and pelvic floor muscle maximal contraction. Pelvic floor mobility was evaluated as the distance from the bladder base using ultrasound. [Results] According to exercise method, bridge exercise and abdominal curl-ups led to significantly different pelvic floor mobility. The pelvic floor muscle was elevated during the abdominal drawing-in maneuver and descended during maximal expiration. Finally, pelvic floor muscle mobility was greater during abdominal curl-up than during the bridge exercise. [Conclusion] According to these results, the abdominal drawing-in maneuver induced pelvic floor muscle contraction, and pelvic floor muscle contraction was greater during the abdominal curl-up than during the bridge exercise. PMID:27065532

  4. 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.

  5. Contraction-induced muscle fiber damage is increased in soleus muscle of streptozotocin-diabetic rats and is associated with elevated expression of brain-derived neurotrophic factor mRNA in muscle fibers and activated satellite cells

    NARCIS (Netherlands)

    Copray, S; Liem, R; Brouwer, N; Greenhaff, P; Habens, F; Fernyhough, P

    The expression of brain-derived neurotrophic factor (BDNF) is elevated in the soleus muscle of streptozotocin-diabetic rats. To determine whether this diabetes-induced elevation was associated with or enhanced by muscle activity we have induced high-intensity muscle contraction by electrically

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

    Science.gov (United States)

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

    2017-03-01

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

  7. Strength training to contraction failure increases voluntary activation of the quadriceps muscle shortly after total knee arthroplasty

    DEFF Research Database (Denmark)

    Mikkelsen, Elin Karin; Jakobsen, Thomas Linding; Holsgaard-Larsen, Anders

    2016-01-01

    arthroplasty. One set of knee extensions was performed until contraction failure, using a predetermined 10 repetition maximum loading. In the operated leg, electromyographic (EMG) activity of the lateral and medial vastus, semitendinosus, and biceps femoris muscles was recorded during the set. Muscle activity...... failure (P = 0.0006 and 0.0187). CONCLUSION: In patients shortly after total knee arthroplasty, 10 repetition maximum-loaded knee extensions performed in one set until contraction failure increases voluntary activation of the quadriceps muscle during the set. CLINICAL TRIALS: Gov-identifier: NCT01713140...

  8. Potassium Channels in Regulation of Vascular Smooth Muscle Contraction and Growth.

    Science.gov (United States)

    Jackson, W F

    2017-01-01

    Potassium channels importantly contribute to the regulation of vascular smooth muscle (VSM) contraction and growth. They are the dominant ion conductance of the VSM cell membrane and importantly determine and regulate membrane potential. Membrane potential, in turn, regulates the open-state probability of voltage-gated Ca2+ channels (VGCC), Ca2+ influx through VGCC, intracellular Ca2+, and VSM contraction. Membrane potential also affects release of Ca2+ from internal stores and the Ca2+ sensitivity of the contractile machinery such that K+ channels participate in all aspects of regulation of VSM contraction. Potassium channels also regulate proliferation of VSM cells through membrane potential-dependent and membrane potential-independent mechanisms. VSM cells express multiple isoforms of at least five classes of K+ channels that contribute to the regulation of contraction and cell proliferation (growth). This review will examine the structure, expression, and function of large conductance, Ca2+-activated K+ (BKCa) channels, intermediate-conductance Ca2+-activated K+ (KCa3.1) channels, multiple isoforms of voltage-gated K+ (KV) channels, ATP-sensitive K+ (KATP) channels, and inward-rectifier K+ (KIR) channels in both contractile and proliferating VSM cells. © 2017 Elsevier Inc. All rights reserved.

  9. 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.

  10. A study on contraction of pneumatic artificial muscle (PAM) for load-lifting

    Science.gov (United States)

    Najmuddin, W. S. W. A.; Mustaffa, M. T.

    2017-10-01

    Pneumatic Artificial Muscles (PAMs) have been known for its wide application in various aspects of industrial automation and robotic equipments. Many advantages in terms of high power-to-volume ratio, high power-to-weight ratio, stick-slip-free operation and high degree of safety offer by PAM compare to traditional actuators. However, behind this benefits lie a limitation of significant compatibility of PAM mechanism which have to be considered so as to fully understand how the PAM works during load-lifting. In this study, the mesh suitability experiment and the effect of force load on PAM contraction experiment have been carried out. PAM is constructed and compatibility of bladder and the braided mesh to produce uniform expansion is investigated. Moreover, the first experimental result of finding compatibility is used to verify the contraction value under various loads.

  11. A neuroprosthesis for tremor management through the control of muscle co-contraction.

    Science.gov (United States)

    Gallego, Juan Álvaro; Rocon, Eduardo; Belda-Lois, Juan Manuel; Pons, José Luis

    2013-04-15

    Pathological tremor is the most prevalent movement disorder. Current treatments do not attain a significant tremor reduction in a large proportion of patients, which makes tremor a major cause of loss of quality of life. For instance, according to some estimates, 65% of those suffering from upper limb tremor report serious difficulties during daily living. Therefore, novel forms for tremor management are required. Since muscles intrinsically behave as a low pass filter, and tremor frequency is above that of volitional movements, the authors envisioned the exploitation of these properties as a means of developing a novel treatment alternative. This treatment would rely on muscle co-contraction for tremor management, similarly to the strategy employed by the intact central nervous system to stabilize a limb during certain tasks. We implemented a neuroprosthesis that regulated the level of muscle co-contraction by injecting current at a pair of antagonists through transcutaneous neurostimulation. Co-contraction was adapted to the instantaneous parameters of tremor, which were estimated from the raw recordings of a pair of solid state gyroscopes with a purposely designed adaptive algorithm. For the experimental validation, we enrolled six patients suffering from parkinsonian or essential tremor of different severity, and evaluated the effect of the neuroprosthesis during standard tasks employed for neurological examination. The neuroprosthesis attained significant attenuation of tremor (pneuroprosthesis, although there was a subtle trend towards larger attenuation of more severe tremors. Tremor frequency was not altered during neurostimulation, as expected from the central origin of Parkinson's disease and essential tremor. All patients showed a good tolerance to neurostimulation in terms of comfort and absence of pain, and some spontaneously reported that they felt that tremor was reduced when the neuroprosthesis was activated. The results presented herein demonstrate

  12. Functional Echomyography: thickness, ecogenicity, contraction and perfusion of the LMN denervated human muscle before and during h-bFES

    Directory of Open Access Journals (Sweden)

    Riccardo Zanato

    2010-03-01

    Full Text Available Permanent denervated muscles were evaluated by ultrasound to monitor changes in morphology, thickness, contraction-relaxation kinetics and perfusion due to the electrical stimulation program of the Rise2-Italy project. In a case of monolateral lesion, morphology and ultrasonographic structure of the denervated muscles changed during the period of stimulation from a pattern typical of complete denervation-induced muscle atrophy to a pattern which might be considered “normal” when detected in an old patient. Thickness improved significantly more in the middle third of the denervated muscle, reaching the same value as the contralateral innervated muscle. Contraction-relaxation kinetics, measured by recording the muscle movements during electrical stimulation, showed an abnormal behavior of the chronically denervated muscle during the relaxation phase, which resulted to be significantly longer than in normal muscle. The long-term denervated muscles analyzed with Echo Doppler showed at rest a low resistance arterial flow that became pulsed during and after electrical stimulation. As expected, the ultra sound measured electrical stimulation-induced hyperemia lasted longer than the stimulation period. The higher than normal energy of the delivered electrical stimuli of the Vienna home-based Functional Electrical Stimulation strategy (h-b FES demonstrate that the explored muscles were still almost completely denervated during the one-year of training. In conclusion, this pilot study confirms the usefulness of Functional Echomyography in the follow-up and the positive effects of h-b FES of denervated muscles.

  13. Involvement of Rac1 and the actin cytoskeleton in insulin- and contraction-stimulated intracellular signaling and glucose uptake in mature skeletal muscle

    DEFF Research Database (Denmark)

    Sylow, Lykke

    to hyperinsulinemia and hyperglycemia. Blood glucose is taken up into skeletal muscle when glucose transporters move to the muscle cell surface. In muscle cells this process depends on the protein Rac1. Glucose uptake into skeletal muscle can also occur via insulin-independent mechanisms, such as during muscle...... contractions. Contraction-stimulated glucose uptake is not affected by insulin resistance, likely because the intracellular events that regulate GLUT4 translocation by insulin and muscle contraction are distinct. In addition, muscle contraction has insulin sensitizing effects. Activation of glucose uptake...... understood. The aim of the current PhD was therefore to investigate the involvement of Rac1 and the actin cytoskeleton in the regulation of insulin- and contraction-stimulated glucose uptake in mature skeletal muscle. The central findings of this PhD thesis was that Rac1 was activated by both insulin...

  14. The effects of wild-type and mutant SOD1 on smooth muscle contraction

    Directory of Open Access Journals (Sweden)

    Nikolić-Kokić Aleksandra

    2015-01-01

    Full Text Available In this work we compared the mutated liver copper zinc-containing superoxide dismutase (SOD1 protein G93A of the transgenic rat model of familial amyotrophic lateral sclerosis (FALS, to wild-type (WT rat SOD1. We examined their enzymatic activities and effects on isometric contractions of uteri of healthy virgin rats. G93A SOD1 showed a slightly higher activity than WT SOD1 and, in contrast to WT SOD1, G93A SOD1 did not induce smooth muscle relaxation. This result indicates that effects on smooth muscles are not related to SOD1 enzyme activity and suggest that heterodimers of G93A SOD1 form an ion-conducting pore that diminishes the relaxatory effects of SOD1. We propose that this type of pathogenic feedback affects neurons in FALS. [Projekat Ministarstva nauke Republike Srbije, br. 173014 i br. 175083

  15. 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.

  16. Does pelvic floor muscle contraction early after delivery cause perineal pain in postpartum women?

    Science.gov (United States)

    Neels, Hedwig; De Wachter, Stefan; Wyndaele, Jean-Jacques; Wyndaele, Michel; Vermandel, Alexandra

    2017-01-01

    Pelvic floor muscle training is effective and necessary in the prevention and treatment of pelvic floor dysfunction during pregnancy and after childbirth. But because of the high prevalence of perineal pain observed in women after childbirth, many women and caregivers fear to start pelvic floor muscle training immediately after childbirth. However, it is unknown whether pelvic floor muscle contractions (PFMC) provoke perineal pain in women shortly after childbirth. Therefore, the main objective is to study whether PFMC performed immediately after childbirth is painful or not. Observational longitudinal study. Perineal pain was assessed (1-6 days and 9 weeks postpartum) using a visual analogue scale (VAS 0-10) during PFMC and during several activities of daily living (ADL), during micturition and defecation. Descriptive statistics, Wilcoxon and McNemar tests were used. A total of 233 women participated (148 primiparous and 85 multiparous). Immediately postpartum the prevalence and intensity of pain during ADL (73%; VAS 4.9 (±2.3)), micturition (47%; VAS 3.4 (±1.7)) and defecation (19%; VAS 3.6 (±2.2)) were significantly higher (all ppelvic floor muscle training shortly after childbirth. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

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

    Directory of Open Access Journals (Sweden)

    Leonardo Coelho Rabello Lima

    2015-10-01

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

  18. Evoked EMG versus muscle torque during fatiguing functional electrical stimulation-evoked muscle contractions and short-term recovery in individuals with spinal cord injury.

    Science.gov (United States)

    Estigoni, Eduardo H; Fornusek, Che; Hamzaid, Nur Azah; Hasnan, Nazirah; Smith, Richard M; Davis, Glen M

    2014-12-03

    This study investigated whether the relationship between muscle torque and m-waves remained constant after short recovery periods, between repeated intervals of isometric muscle contractions induced by functional electrical stimulation (FES). Eight subjects with spinal cord injury (SCI) were recruited for the study. All subjects had their quadriceps muscles group stimulated during three sessions of isometric contractions separated by 5 min of recovery. The evoked-electromyographic (eEMG) signals, as well as the produced torque, were synchronously acquired during the contractions and during short FES bursts applied during the recovery intervals. All analysed m-wave variables changed progressively throughout the three contractions, even though the same muscle torque was generated. The peak to peak amplitude (PtpA), and the m-wave area (Area) were significantly increased, while the time between the stimulus artefact and the positive peak (PosT) were substantially reduced when the muscles became fatigued. In addition, all m-wave variables recovered faster and to a greater extent than did torque after the recovery intervals. We concluded that rapid recovery intervals between FES-evoked exercise sessions can radically interfere in the use of m-waves as a proxy for torque estimation in individuals with SCI. This needs to be further investigated, in addition to seeking a better understanding of the mechanisms of muscle fatigue and recovery.

  19. Evoked EMG versus Muscle Torque during Fatiguing Functional Electrical Stimulation-Evoked Muscle Contractions and Short-Term Recovery in Individuals with Spinal Cord Injury

    Directory of Open Access Journals (Sweden)

    Eduardo H. Estigoni

    2014-12-01

    Full Text Available This study investigated whether the relationship between muscle torque and m-waves remained constant after short recovery periods, between repeated intervals of isometric muscle contractions induced by functional electrical stimulation (FES. Eight subjects with spinal cord injury (SCI were recruited for the study. All subjects had their quadriceps muscles group stimulated during three sessions of isometric contractions separated by 5 min of recovery. The evoked-electromyographic (eEMG signals, as well as the produced torque, were synchronously acquired during the contractions and during short FES bursts applied during the recovery intervals. All analysed m-wave variables changed progressively throughout the three contractions, even though the same muscle torque was generated. The peak to peak amplitude (PtpA, and the m-wave area (Area were significantly increased, while the time between the stimulus artefact and the positive peak (PosT were substantially reduced when the muscles became fatigued. In addition, all m-wave variables recovered faster and to a greater extent than did torque after the recovery intervals. We concluded that rapid recovery intervals between FES-evoked exercise sessions can radically interfere in the use of m-waves as a proxy for torque estimation in individuals with SCI. This needs to be further investigated, in addition to seeking a better understanding of the mechanisms of muscle fatigue and recovery.

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

    Directory of Open Access Journals (Sweden)

    Darryn S. Willoughby

    2006-12-01

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

  1. Fiber type effects on contraction-stimulated glucose uptake and GLUT4 abundance in single fibers from rat skeletal muscle.

    Science.gov (United States)

    Castorena, Carlos M; Arias, Edward B; Sharma, Naveen; Bogan, Jonathan S; Cartee, Gregory D

    2015-02-01

    To fully understand skeletal muscle at the cellular level, it is essential to evaluate single muscle fibers. Accordingly, the major goals of this study were to determine if there are fiber type-related differences in single fibers from rat skeletal muscle for: 1) contraction-stimulated glucose uptake and/or 2) the abundance of GLUT4 and other metabolically relevant proteins. Paired epitrochlearis muscles isolated from Wistar rats were either electrically stimulated to contract (E-Stim) or remained resting (No E-Stim). Single fibers isolated from muscles incubated with 2-deoxy-d-[(3)H]glucose (2-DG) were used to determine fiber type [myosin heavy chain (MHC) isoform protein expression], 2-DG uptake, and abundance of metabolically relevant proteins, including the GLUT4 glucose transporter. E-Stim, relative to No E-Stim, fibers had greater (P glucose uptake. Copyright © 2015 the American Physiological Society.

  2. Contraction-by-contraction VO2 and computer-controlled pump perfusion as novel techniques to study skeletal muscle metabolism in situ.

    Science.gov (United States)

    Hernández, Andrés; Goodwin, Matthew L; Lai, Nicola; Cabrera, Marco E; McDonald, James R; Gladden, L Bruce

    2010-03-01

    The purpose of this research was to develop new techniques to 1) rapidly sample venous O(2) saturation to determine contraction-by-contraction oxygen uptake (Vo(2)), and 2) precisely control the rate and pattern of blood flow adjustment from one chosen steady state to another. An indwelling inline oximeter probe connected to an Oximetrix 3 meter was used to sample venous oxygen concentration ([O(2)]) (via fractional saturation of Hb with O(2)). Data from the Oximetrix 3 were filtered, deconvolved, and processed by a moving average second by second. Computer software and a program written in-house were used to control blood flow with a peristaltic pump. The isolated canine gastrocnemius muscle complex (GS) in situ was utilized to test these techniques. A step change in metabolic rate was elicited by stimulating GS muscles via their sciatic nerves (supramaximal voltage, 8 V; 50 Hz, 0.2-ms pulse width; train duration 200 ms) at a rate of either 1 contraction/2 s, or 2 contractions/3 s. With arterial [O(2)] maintained constant, blood flow and calculated venous [O(2)] were averaged over each contraction cycle and used in the Fick equation to calculate contraction-by-contraction Vo(2). About 5-8 times more data points were obtained with this method compared with traditional manual sampling. Software-controlled pump perfusion enabled the ability to mimic spontaneous blood flow on-kinetics (tau: 14.3 s) as well as dramatically speed (tau: 2.0 s) and slow (tau: 63.3 s) on-kinetics. These new techniques significantly improve on existing methods for mechanistically altering blood flow kinetics as well as accurately measuring muscle oxygen consumption kinetics during transitions between metabolic rates.

  3. Imaging mass spectrometry reveals fiber-specific distribution of acetylcarnitine and contraction-induced carnitine dynamics in rat skeletal muscles.

    Science.gov (United States)

    Furuichi, Yasuro; Goto-Inoue, Naoko; Manabe, Yasuko; Setou, Mitsutoshi; Masuda, Kazumi; Fujii, Nobuharu L

    2014-10-01

    Carnitine is well recognized as a key regulator of long-chain fatty acyl group translocation into the mitochondria. In addition, carnitine, as acetylcarnitine, acts as an acceptor of excess acetyl-CoA, a potent inhibitor of pyruvate dehydrogenase. Here, we provide a new methodology for accurate quantification of acetylcarnitine content and determination of its localization in skeletal muscles. We used matrix-assisted laser desorption/ionization imaging mass spectrometry (MALDI-IMS) to visualize acetylcarnitine distribution in rat skeletal muscles. MALDI-IMS and immunohistochemistry of serial cross-sections showed that acetylcarnitine was enriched in the slow-type muscle fibers. The concentration of ATP was lower in muscle regions with abundant acetylcarnitine, suggesting a relationship between acetylcarnitine and metabolic activity. Using our novel method, we detected an increase in acetylcarnitine content after muscle contraction. Importantly, this increase was not detected using traditional biochemical assays of homogenized muscles. We also demonstrated that acetylation of carnitine during muscle contraction was concomitant with glycogen depletion. Our methodology would be useful for the quantification of acetylcarnitine and its contraction-induced kinetics in skeletal muscles. Copyright © 2014 Elsevier B.V. All rights reserved.

  4. 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

  5. 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.

  6. Neuroprosthetic-enabled control of graded arm muscle contraction in a paralyzed human.

    Science.gov (United States)

    Friedenberg, David A; Schwemmer, Michael A; Landgraf, Andrew J; Annetta, Nicholas V; Bockbrader, Marcia A; Bouton, Chad E; Zhang, Mingming; Rezai, Ali R; Mysiw, W Jerry; Bresler, Herbert S; Sharma, Gaurav

    2017-08-21

    Neuroprosthetics that combine a brain computer interface (BCI) with functional electrical stimulation (FES) can restore voluntary control of a patients' own paralyzed limbs. To date, human studies have demonstrated an "all-or-none" type of control for a fixed number of pre-determined states, like hand-open and hand-closed. To be practical for everyday use, a BCI-FES system should enable smooth control of limb movements through a continuum of states and generate situationally appropriate, graded muscle contractions. Crucially, this functionality will allow users of BCI-FES neuroprosthetics to manipulate objects of different sizes and weights without dropping or crushing them. In this study, we present the first evidence that using a BCI-FES system, a human with tetraplegia can regain volitional, graded control of muscle contraction in his paralyzed limb. In addition, we show the critical ability of the system to generalize beyond training states and accurately generate wrist flexion states that are intermediate to training levels. These innovations provide the groundwork for enabling enhanced and more natural fine motor control of paralyzed limbs by BCI-FES neuroprosthetics.

  7. Tetanic contraction induces enhancement of fatigability and sarcomeric damage in atrophic skeletal muscle and its underlying molecular mechanisms.

    Science.gov (United States)

    Yu, Zhi-Bin

    2013-11-01

    Muscle unloading due to long-term exposure of weightlessness or simulated weightlessness causes atrophy, loss of functional capacity, impaired locomotor coordination, and decreased resistance to fatigue in the antigravity muscles of the lower limbs. Besides reducing astronauts' mobility in space and on returning to a gravity environment, the molecular mechanisms for the adaptation of skeletal muscle to unloading also play an important medical role in conditions such as disuse and paralysis. The tail-suspended rat model was used to simulate the effects of weightlessness on skeletal muscles and to induce muscle unloading in the rat hindlimb. Our series studies have shown that the maximum of twitch tension and the twitch duration decreased significantly in the atrophic soleus muscles, the maximal tension of high-frequency tetanic contraction was significantly reduced in 2-week unloaded soleus muscles, however, the fatigability of high-frequency tetanic contraction increased after one week of unloading. The maximal isometric tension of intermittent tetanic contraction at optimal stimulating frequency did not alter in 1- and 2-week unloaded soleus, but significantly decreased in 4-week unloaded soleus. The 1-week unloaded soleus, but not extensor digitorum longus (EDL), was more susceptible to fatigue during intermittent tetanic contraction than the synchronous controls. The changes in K+ channel characteristics may increase the fatigability during high-frequency tetanic contraction in atrophic soleus muscles. High fatigability of intermittent tetanic contraction may be involved in enhanced activity of sarcoplasmic reticulum Ca(2+)-ATPase (SERCA) and switching from slow to fast isoform of myosin heavy chain, tropomyosin, troponin I and T subunit in atrophic soleus muscles. Unloaded soleus muscle also showed a decreased protein level of neuronal nitric oxide synthase (nNOS), and the reduction in nNOS-derived NO increased frequency of calcium sparks and elevated

  8. Beneficial effects of serial contractions on muscle performance after a brief period of rest.

    Science.gov (United States)

    Green, Lara A; Parro, Justin J; Gabriel, David A

    2014-08-01

    The study investigated potential mechanisms underlying the beneficial effects of performing serial contractions for increasing muscle performance. Thirteen men performed maximal isometric dorsiflexion contractions to a limited amount of fatigue. The recovery pattern was monitored over 15 min. Force, surface electromyography (sEMG) of the agonist and antagonist, and skin temperature were observed. Evoked potentials were elicited. Force decreased to 206 ± 40 N and recovered to 243 ± 55 N (102 % of initial value). While full recovery is noteworthy, it was not significant (p = 0.24). Surface EMG root-mean-square (RMS) amplitude did not fully recover: tibialis anterior (219 ± 46 versus 242 ± 63 μV, 91 %) and soleus (13 ± 5 versus 16 ± 6 μV, 82 %). The result was an 11 % decrease in the co-activation ratio during recovery. Tibialis anterior and soleus mean power frequency (MPF) "over-recovered" to 117 % (144 ± 25 versus 124 ± 27 Hz) and 118 % (80 ± 14 versus 68 ± 11 Hz) of initial value, respectively. Peak rate of force development (RFD) during recovery was 146 % of initial (743 ± 246 versus 509 ± 271 N). Skin temperature increased 0.6 °C over the test session. Potentiation was not present during recovery, as assessed by twitch force. The return of force to initial values, rather than a persistent decrement was a result of several mechanisms operating simultaneously. The sEMG data indicate an increase in conduction velocity, while an increase in peak RFD suggests contraction-induced facilitation of ATPase pump activity. However, alterations in muscle coordination were observed as a reduction in antagonist co-activity.

  9. EMG control of a bionic knee prosthesis: exploiting muscle co-contractions for improved locomotor function.

    Science.gov (United States)

    Dawley, James A; Fite, Kevin B; Fulk, George D

    2013-06-01

    This paper presents the development and experimental evaluation of a volitional control architecture for a powered-knee transfemoral prosthesis that affords the amputee user with direct control of knee impedance using measured electromyogram (EMG) potentials of antagonist muscles in the residual limb. The control methodology incorporates a calibration procedure performed with each donning of the prosthesis that characterizes the co-contraction levels as the user performs volitional phantom-knee flexor and extensor contractions. The performance envelope for EMG control of impedance is then automatically shaped based on the flexor and extensor calibration datasets. The result is a control architecture that is optimized to the user's current co-contraction activity, providing performance robustness to variation in sensor placement or physiological changes in the residual-limb musculature. Experimental results with a single unilateral transfemoral amputee user demonstrate consistent and repeatable control performance for level walking at self-selected speed over a multi-week, multi-session period of evaluation.

  10. Age Related Differences in the Surface EMG Signals on Adolescent's Muscle during Contraction

    Science.gov (United States)

    Uddin Ahamed, Nizam; Taha, Zahari; Alqahtani, Mahdi; Altwijri, Omar; Rahman, Matiur; Deboucha, Abdelhakim

    2016-02-01

    The aim of this study was to investigate whether there are differences in the amplitude of the EMG signal among five different age groups of adolescent's muscle. Fifteen healthy adolescents participated in this study and they were divided into five age groups (13, 14, 15, 16 and 17 years). Subjects were performed dynamic contraction during lifting a standard weight (3-kg dumbbell) and EMG signals were recorded from their Biceps Brachii (BB) muscle. Two common EMG analysis techniques namely root mean square (RMS) and mean absolute values (MAV) were used to find the differences. The statistical analysis was included: linear regression to examine the relationships between EMG amplitude and age, repeated measures ANOVA to assess differences among the variables, and finally Coefficient of Variation (CoV) for signal steadiness among the groups of subjects during contraction. The result from RMS and MAV analysis shows that the 17-years age groups exhibited higher activity (0.28 and 0.19 mV respectively) compare to other groups (13-Years: 0.26 and 0.17 mV, 14-years: 0.25 and 0.23 mV, 15-Years: 0.23 and 0.16 mV, 16-years: 0.23 and 0.16 mV respectively). Also, this study shows modest correlation between age and signal activities among all age group's muscle. The experiential results can play a pivotal role for developing EMG prosthetic hand controller, neuromuscular system, EMG based rehabilitation aid and movement biomechanics, which may help to separate age groups among the adolescents.

  11. Non–Ca2+-conducting Ca2+ channels in fish skeletal muscle excitation-contraction coupling

    Science.gov (United States)

    Schredelseker, Johann; Shrivastav, Manisha; Dayal, Anamika; Grabner, Manfred

    2010-01-01

    During skeletal muscle excitation-contraction (EC) coupling, membrane depolarizations activate the sarcolemmal voltage-gated L-type Ca2+ channel (CaV1.1). CaV1.1 in turn triggers opening of the sarcoplasmic Ca2+ release channel (RyR1) via interchannel protein–protein interaction to release Ca2+ for myofibril contraction. Simultaneously to this EC coupling process, a small and slowly activating Ca2+ inward current through CaV1.1 is found in mammalian skeletal myotubes. The role of this Ca2+ influx, which is not immediately required for EC coupling, is still enigmatic. Interestingly, whole-cell patch clamp experiments on freshly dissociated skeletal muscle myotubes from zebrafish larvae revealed the lack of such Ca2+ currents. We identified two distinct isoforms of the pore-forming CaV1.1α1S subunit in zebrafish that are differentially expressed in superficial slow and deep fast musculature. Both do not conduct Ca2+ but merely act as voltage sensors to trigger opening of two likewise tissue-specific isoforms of RyR1. We further show that non-Ca2+ conductivity of both CaV1.1α1S isoforms is a common trait of all higher teleosts. This non-Ca2+ conductivity of CaV1.1 positions teleosts at the most-derived position of an evolutionary trajectory. Though EC coupling in early chordate muscles is activated by the influx of extracellular Ca2+, it evolved toward CaV1.1-RyR1 protein–protein interaction with a relatively small and slow influx of external Ca2+ in tetrapods. Finally, the CaV1.1 Ca2+ influx was completely eliminated in higher teleost fishes. PMID:20212109

  12. Disinhibition of upper limb motor area by voluntary contraction of the lower limb muscle.

    Science.gov (United States)

    Tazoe, Toshiki; Endoh, Takashi; Nakajima, Tsuyoshi; Sakamoto, Masanori; Komiyama, Tomoyoshi

    2007-03-01

    It is well known that monosynaptic spinal reflexes and motor evoked potentials following transcranial magnetic stimulation (TMS) are reinforced during phasic and intensive voluntary contraction in the remote segment (remote effect). However, the remote effect on the cortical silent period (CSP) is less known. The purpose of the present study is to determine to what extent the CSP in the intrinsic hand muscle following TMS is modified by voluntary ankle dorsiflexion and to elucidate the origin of the modulation of CSP by the remote effect. CSP was recorded in the right first dorsal interosseous while subjects performed phasic dorsiflexion in the ipsilateral side under self-paced and reaction-time conditions. Modulation of the peripherally-induced silent period (PSP) induced by electrical stimulation of the ulnar nerve was also investigated under the same conditions. In addition, modulation of the CSP was investigated during ischemic nerve block of the lower limb and during application of vibration to the tibialis anterior tendon. The duration of CSP was significantly shortened by phasic dorsiflexion, and the extent of shortening was proportional to dorsiflexion force. Shortening of the CSP duration was also observed during tonic dorsiflexion. In contrast, the PSP duration following ulnar nerve stimulation was not altered during phasic dorsiflexion. Furthermore, the remote effect on the CSP duration was seen during ischemic nerve block of the lower limb and the pre-movement period in the reaction-time paradigm, but shortening of the CSP was not observed during tendon vibration. These findings suggest that phasic muscle contraction in the remote segment results in a decrease in intracortical inhibitory pathways to the corticospinal tract innervating the muscle involved in reflex testing and that the remote effect on the CSP is predominantly cortical in origin.

  13. Role of M1 receptor in regulation of gastric fundus smooth muscle contraction

    Directory of Open Access Journals (Sweden)

    Marta Gajdus

    2011-09-01

    Full Text Available Background:The subject of this study is determination of the influence of drugs on gastric fundus smooth muscle contraction induced by activation of muscarinic receptors M1. Experiments tested interactions between a receptor agonist, carbachol and muscarinic receptor antagonists, atropine and pirenzepine.Material/Methods:Testing was conducted on tissues isolated from rat’s stomach. Male Wistar rats with weight between 220 g and 360 g were anesthetized by intraperitoneal injection of urethane (120 mg/kg. The stomach was dissected, and later the gastric fundus was isolated. Tissue was placed in a dish for insulated organs with 20 ml in capacity, filled with Krebs fluid. Results contained in the study are average values ± SE. In order to determine statistical significance, the principles of receptor theory were used (Kenakin modification.Results:According to tests, carbachol, in concentrations ranging between 10–8 M to 10–4 M, in a dosage-dependent way induces gastric fundus smooth muscle contraction. Presented results indicate that carbachol meets the conditions posed to full agonists. On the other hand, atropine, a non-selective muscarinic receptor antagonist, causes a concentration-dependent shift of concentration-effect curve (for carbachol to the right, maintaining maximum reaction. According to analysis of the curve determined, we can deduce that atropine meets the conditions posed to competitive antagonists. The use of pirenzepine, a competitive receptor agonist M1, causes shift of concentration-effect curve (for carbachol to the right, maintaining maximum reaction.Conclusions:From the testing conducted on the preparation of the gastric fundus we can deduce that atropine causes shift of concentration-effect curves for carbachol to the right. A similar effect is released by pirenzepine, selectively blocking muscarinic receptors of M1 type. The results indicate that in the preparation of the gastric fundus smooth muscle, M1 type

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

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    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

  15. 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

  16. Power spectral analysis of surface electromyography (EMG) at matched contraction levels of the first dorsal interosseous muscle in stroke survivors.

    Science.gov (United States)

    Li, Xiaoyan; Shin, Henry; Zhou, Ping; Niu, Xun; Liu, Jie; Rymer, William Zev

    2014-05-01

    The objective of this study was to help assess complex neural and muscular changes induced by stroke using power spectral analysis of surface electromyogram (EMG) signals. Fourteen stroke subjects participated in the study. They were instructed to perform isometric voluntary contractions by abducting the index finger. Surface EMG signals were collected from the paretic and contralateral first dorsal interosseous (FDI) muscles with forces ranging from 30% to 70% maximum voluntary contraction (MVC) of the paretic muscle. Power spectral analysis was performed to characterize features of the surface EMG in paretic and contralateral muscles at matched forces. A Linear Mixed Model was applied to identify the spectral changes in the hemiparetic muscle and to examine the relation between spectral parameters and contraction levels. Regression analysis was performed to examine the correlations between spectral characteristics and clinical features. Differences in power spectrum distribution patterns were observed in paretic muscles when compared with their contralateral pairs. Nine subjects showed increased mean power frequency (MPF) in the contralateral side (>15 Hz). No evident spectrum difference was observed in 3 subjects. Only 2 subjects had higher MPF in the paretic muscle than the contralateral muscle. Pooling all subjects' data, there was a significant reduction of MPF in the paretic muscle compared with the contralateral muscle (paretic: 168.7 ± 7.6 Hz, contralateral: 186.1 ± 8.7 Hz, mean ± standard error, F=36.56, pEMG power spectrum did not confirm a significant correlation between the MPF and contraction force in either hand (F=0.7, p>0.5). There was no correlation between spectrum difference and Fugl-Meyer or Chedoke scores, or ratio of paretic and contralateral MVC (p>0.2). There appears to be complex muscular and neural processes at work post stroke that may impact the surface EMG power spectrum. The majority of the tested stroke subjects had lower MPF in

  17. High-intensity stretch-shortening contraction training modifies responsivity of skeletal muscle in old male rats.

    Science.gov (United States)

    Rader, Erik P; Naimo, Marshall A; Ensey, James; Baker, Brent A

    2018-02-10

    Utilization of high-intensity resistance training to counter age-related sarcopenia is currently debated because of the potential for maladaptation when training design is inappropriate. Training design is problematic because the influence of various loading variables (e.g. contraction mode, repetition number, and training frequency) is still not well characterized at old age. To address this in a precisely controlled manner, we developed a rodent model of high-intensity training consisting of maximally-activated stretch-shortening contractions (SSCs), contractions typical during resistance training. With this model, we determined that at old age, high-repetition SSC training (80 SSCs: 8 sets of 10 repetitions) performed frequently (i.e. 3 days per week) for 4.5 weeks induced strength deficits with no muscle mass gain while decreasing frequency to 2 days per week promoted increases in muscle mass and muscle quality (i.e. performance normalized to muscle mass). This finding confirmed the popular notion that decreasing training frequency has a robust effect with age. Meanwhile, the influence of other loading variables remains contentious. The aim of the present study was to assess muscle adaptation following modulation of contraction mode and repetition number during high-intensity SSC training. Muscles of young (3 month old) and old (30 month old) male rats were exposed to 4.5 weeks of low-repetition static training of 4 (i.e. 4 sets of one repetition) isometric (ISO) contractions 3 days per week or a more moderate-repetition dynamic training of 40 SSCs (i.e. 4 sets of 10 repetitions) 3 days per week. For young rats, performance and muscle mass increased regardless of training protocol. For old rats, no muscle mass adaptation was observed for 4 ISO training while 40 SSC training induced muscle mass gain without improvement in muscle quality, an outcome distinct from modulating training frequency. Muscle mass gain for old rats was accompanied by

  18. Distinct Skeletal Muscle Gene Regulation from Active Contraction, Passive Vibration, and Whole Body Heat Stress in Humans.

    Directory of Open Access Journals (Sweden)

    Michael A Petrie

    Full Text Available Skeletal muscle exercise regulates several important metabolic genes in humans. We know little about the effects of environmental stress (heat and mechanical stress (vibration on skeletal muscle. Passive mechanical stress or systemic heat stress are often used in combination with many active exercise programs. We designed a method to deliver a vibration stress and systemic heat stress to compare the effects with active skeletal muscle contraction.The purpose of this study is to examine whether active mechanical stress (muscle contraction, passive mechanical stress (vibration, or systemic whole body heat stress regulates key gene signatures associated with muscle metabolism, hypertrophy/atrophy, and inflammation/repair.Eleven subjects, six able-bodied and five with chronic spinal cord injury (SCI participated in the study. The six able-bodied subjects sat in a heat stress chamber for 30 minutes. Five subjects with SCI received a single dose of limb-segment vibration or a dose of repetitive electrically induced muscle contractions. Three hours after the completion of each stress, we performed a muscle biopsy (vastus lateralis or soleus to analyze mRNA gene expression.We discovered repetitive active muscle contractions up regulated metabolic transcription factors NR4A3 (12.45 fold, PGC-1α (5.46 fold, and ABRA (5.98 fold; and repressed MSTN (0.56 fold. Heat stress repressed PGC-1α (0.74 fold change; p < 0.05; while vibration induced FOXK2 (2.36 fold change; p < 0.05. Vibration similarly caused a down regulation of MSTN (0.74 fold change; p < 0.05, but to a lesser extent than active muscle contraction. Vibration induced FOXK2 (p < 0.05 while heat stress repressed PGC-1α (0.74 fold and ANKRD1 genes (0.51 fold; p < 0.05.These findings support a distinct gene regulation in response to heat stress, vibration, and muscle contractions. Understanding these responses may assist in developing regenerative rehabilitation interventions to improve muscle cell

  19. 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

  20. Presence and Absence of Muscle Contraction Elicited by Peripheral Nerve Electrical Stimulation Differentially Modulate Primary Motor Cortex Excitability.

    Science.gov (United States)

    Sasaki, Ryoki; Kotan, Shinichi; Nakagawa, Masaki; Miyaguchi, Shota; Kojima, Sho; Saito, Kei; Inukai, Yasuto; Onishi, Hideaki

    2017-01-01

    Modulation of cortical excitability by sensory inputs is a critical component of sensorimotor integration. Sensory afferents, including muscle and joint afferents, to somatosensory cortex (S1) modulate primary motor cortex (M1) excitability, but the effects of muscle and joint afferents specifically activated by muscle contraction are unknown. We compared motor evoked potentials (MEPs) following median nerve stimulation (MNS) above and below the contraction threshold based on the persistence of M-waves. Peripheral nerve electrical stimulation (PES) conditions, including right MNS at the wrist at 110% motor threshold (MT; 110% MNS condition), right MNS at the index finger (sensory digit nerve stimulation [DNS]) with stimulus intensity approximately 110% MNS (DNS condition), and right MNS at the wrist at 90% MT (90% MNS condition) were applied. PES was administered in a 4 s ON and 6 s OFF cycle for 20 min at 30 Hz. In Experiment 1 (n = 15), MEPs were recorded from the right abductor pollicis brevis (APB) before (baseline) and after PES. In Experiment 2 (n = 15), M- and F-waves were recorded from the right APB. Stimulation at 110% MNS at the wrist evoking muscle contraction increased MEP amplitudes after PES compared with those at baseline, whereas DNS at the index finger and 90% MNS at the wrist not evoking muscle contraction decreased MEP amplitudes after PES. M- and F-waves, which reflect spinal cord or muscular and neuromuscular junctions, did not change following PES. These results suggest that muscle contraction and concomitant muscle/joint afferent inputs specifically enhance M1 excitability.

  1. Muscle Contraction Velocity: A Suitable Approach to Analyze the Functional Adaptations in Elite Soccer Players

    Science.gov (United States)

    Loturco, Irineu; Pereira, Lucas A.; Kobal, Ronaldo; Kitamura, Katia; Ramírez-Campillo, Rodrigo; Zanetti, Vinicius; Abad, Cesar C. Cal; Nakamura, Fabio Y.

    2016-01-01

    Tensiomyography (TMG) has been used as a simple and non-invasive tool to assess the mechanical properties of skeletal muscles. The TMG-derived velocity of contraction (Vc), which can be calculated from the ratio between maximal radial displacement and the sum of contraction time and delay time, has been proposed for evaluating athletes. However, its sensitivity to training effects and possible relation with changes in soccer players’ neuromuscular performance have not yet been addressed. To test this possibility, twenty-two male Brazilian elite soccer players were assessed using TMG-derived Vc, unloaded squat jump, countermovement jump and drop jump at 45 cm, loaded jump squat and linear (20 m) and change of direction (COD) sprint tests, prior to and after an 8-week period, between two consecutive official tournaments, during which the concurrency between endurance and strength-power training commonly impairs neuromuscular capacities. Magnitude-based inference was used to detect meaningful training effects. From pre- to post-tests, it was observed likely to almost certainly improvements in all modes of jumping tests. In addition, we could verify decrements in the 20-m and COD sprint performances, which were rated as very likely and almost certainly, respectively. Finally, both rectus femoris and biceps femoris muscles presented a likely reduction in Vc. Therefore, chronic decreases in sprinting speed are possibly accompanied by a reduced TMG-derived Vc. From a practical standpoint, the TMG-derived Vc can be used to monitor negative specific-soccer training effects related to potential impairments in maximum speed. Key points Tensiomyography (TMG) can be considered a useful technology for coaches and sport scientists seeking for non-invasive and practical tools to assess the muscle function of elite athletes; Velocity of contraction (Vc) is a single index able to integrate several of the reliable mechanical outcomes provided by TMG, which was shown to be sensitive

  2. Effect of 3-substituted 1,4-benzodiazepin-2-ones on bradykinin-induced smooth muscle contraction

    Directory of Open Access Journals (Sweden)

    P. A. Virych

    2017-02-01

    Full Text Available Biochemical properties of 3-substituted 1,4-benzodiazepine determined by the characteristics of their chemical structure. Influence of 3-substituted 1,4-benzodiazepin-2-ones on maximal normalized rate and amplitudes of isometric smooth muscle contraction in rats was investigated. Compounds MX-1775 and MX-1828 demonstrated the similar inhibition effect on bradykinin-induced contraction of smooth muscle like competitive inhibitor des-arg9-bradykinin-acetate to bradykinin B2-receptors. MX-1626 demonstrated unidirectional changes of maximal normalized rate and force of smooth muscle that proportionally depended on bradykinin concentration in the range 10-10-10-6 M. MX-1828 has statistically significant decrease of normalized rate of smooth muscle contraction for bradykinin concentrations 10-10 and 10-9 M by 20.7 and 8.6%, respectively, but for agonist concentration 10-6 M, this parameter increased by 10.7% and amplitude was reduced by 29.5%. Compounds MX-2011, MX-1785 and MX-2004 showed no natural effect on bradykinin-induced smooth muscle contraction. Compounds MX-1775, MX-1828, MX-1626 were selected for further research of their influence on kinin-kallikrein system and pain perception.

  3. The simultaneous collapse of both the swinging crossbridge theory of muscle contraction and the in vitro motility essays.

    Science.gov (United States)

    Oplatka, A

    2005-12-16

    In the early seventies we discovered that isolated, active, myosin fragments can induce movement and tension generation by actin filaments in both in vitro and in vivo systems, employing a variety of techniques. It was not in line with the domineering swinging crossbridge theory of muscle contraction. We then proposed an hydrodynamic mechanism which explained our results and was applied to muscle contraction and to other biological engines. Our discovery has been ignored for a long time until the so-called "in vitro motility essays" appeared. By using this artifact--laden technique the mechanochemical reactivity of the active myosin fragments was re-discovered without giving us any credit. The essays gave continuously changing values for fundamental parameters of muscle contraction; the values were appreciably different in different laboratories and decreased in a continuous fashion in the hands of one scientist. By analyzing recent experiments which derived the rate of ATP hydrolysis of active muscles as function of the applied load I calculated the value of the sliding distance resulting from the breakdown of one ATP molecule by each of the myosin heads in contracting muscle. According to the contemporary theory this should be the same for all muscles under any environmental conditions and determined by length of the myosin head's neck. My examination led to the conclusion that the sliding distance varies from one muscle to another and with different temperatures for the same muscle. This again, contradicts the current theory and should give the final blow to both this theory and the "essays". Furthermore: it can be explained by a hydrodynamic mechanism such as that proposed by us more than 30 years ago.

  4. 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.

  5. Effects of Duchenne muscular dystrophy on muscle stiffness and response to electrically-induced muscle contraction: A 12-month follow-up.

    Science.gov (United States)

    Lacourpaille, Lilian; Gross, Raphaël; Hug, François; Guével, Arnaud; Péréon, Yann; Magot, Armelle; Hogrel, Jean-Yves; Nordez, Antoine

    2017-03-01

    The present study aimed to assess the ability of muscle stiffness (shear modulus) and response to electrically-induced muscle contraction to detect changes in muscle properties over a 12-month period in children with Duchenne muscular dystrophy (DMD). Ten children with DMD and nine age-matched healthy male controls participated in two experimental sessions (T0 and T+12months) separated by 12.4 ± 0.9 months. Two contractions of the biceps brachii were electrically-induced during which an ultrasound probe was placed over the muscle. The resting shear modulus was measured using elastography from six muscles. Evoked maximal torque was increased at T+12months in controls (+11.2 ± 7.6%, P muscle stiffness at T+12months in children with DMD for tibialis anterior (+75.1 ± 93.5%, P= 0.043), gastrocnemius medialis (+144.8 ± 180.6%, P= 0.050) and triceps brachii (+35.5 ± 32.2%, P= 0.005). This 12-month follow-up study demonstrates that electromechanical delay and elastography may help detect subtle muscle impairments in patients with DMD. These sensitive outcomes may improve the follow-up of innovative therapeutic interventions within the field of DMD. Copyright © 2017 Elsevier B.V. All rights reserved.

  6. An Approach for Simulation of the Muscle Force Modeling It by Summation of Motor Unit Contraction Forces

    Directory of Open Access Journals (Sweden)

    Rositsa Raikova

    2013-01-01

    Full Text Available Muscle force is due to the cumulative effect of repetitively contracting motor units (MUs. To simulate the contribution of each MU to whole muscle force, an approach implemented in a novel computer program is proposed. The individual contraction of an MU (the twitch is modeled by a 6-parameter analytical function previously proposed; the force of one MU is a sum of its contractions due to an applied stimulation pattern, and the muscle force is the sum of the active MUs. The number of MUs, the number of slow, fast-fatigue-resistant, and fast-fatigable MUs, and their six parameters as well as a file with stimulation patterns for each MU are inputs for the developed software. Different muscles and different firing patterns can be simulated changing the input data. The functionality of the program is illustrated with a model consisting of 30 MUs of rat medial gastrocnemius muscle. The twitches of these MUs were experimentally measured and modeled. The forces of the MUs and of the whole muscle were simulated using different stimulation patterns that included different regular, irregular, synchronous, and asynchronous firing patterns of MUs. The size principle of MUs for recruitment and derecruitment was also demonstrated using different stimulation paradigms.

  7. The effect of motor control training on abdominal muscle contraction during simulated weight bearing in elite cricketers.

    Science.gov (United States)

    Hides, Julie A; Endicott, Timothy; Mendis, M Dilani; Stanton, Warren R

    2016-07-01

    To investigate whether motor control training alters automatic contraction of abdominal muscles in elite cricketers with low back pain (LBP) during performance of a simulated unilateral weight-bearing task. Clinical trial. 26 male elite-cricketers attended a 13-week cricket training camp. Prior to the camp, participants were allocated to a LBP or asymptomatic group. Real-time ultrasound imaging was used to assess automatic abdominal muscle response to axial loading. During the camp, the LBP group performed a staged motor control training program. Following the camp, the automatic response of the abdominal muscles was re-assessed. At pre-camp assessment, when participants were axially loaded with 25% of their own bodyweight, the LBP group showed a 15.5% thicker internal oblique (IO) muscle compared to the asymptomatic group (p = 0.009). The post-camp assessment showed that participants in the LBP group demonstrated less contraction of the IO muscle in response to axial loading compared with the asymptomatic group. A trend was found in the automatic recruitment pattern of the transversus abdominis (p = 0.08). Motor control training normalized excessive contraction of abdominal muscles in response to a low load task. This may be a useful strategy for rehabilitation of cricketers with LBP. Copyright © 2016 Elsevier Ltd. All rights reserved.

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

    DEFF Research Database (Denmark)

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

    2004-01-01

    4) yr] each performed a bout of 100 maximum voluntary eccentric contractions of the knee extensors. Muscle biopsies were taken before exercise and on days 4 and 22 afterward. Image analysis of stained tissue sections was used to quantify endomysial collagen staining intensity. Maximum voluntary...... contractile isometric force was recorded preexercise and on days 1, 2, 3, 4, 8, 11, and 14 postexercise. Venipuncture blood samples were also drawn on these days for measurement of serum creatine kinase activity and concentrations of MMP-9, TIMP-1, TIMP-2, and the MMP-2/TIMP-2 complex. Maximum voluntary...... contractile force declined by 39 +/- 23% (mean +/- SD) on day 2 postexercise and recovered thereafter. Serum creatine kinase activity peaked on day 4 postexercise (P day 22 postexercise to 126 +/- 29% (mean +/- SD) of preexercise values...

  9. Contraction intensity and feeding affect collagen and myofibrillar protein synthesis rates differently in human skeletal muscle

    DEFF Research Database (Denmark)

    Holm, Lars; van Hall, Gerrit; Rose, Adam

    2010-01-01

    with the fasting condition. The Rp-s6k-4E-binding protein-1 (BP1) and the mitogen-activated protein kinase (MAPk) pathways were activated by the HL intensity and were suggested to be responsible for regulating myofibrillar FSR in response to adequate contractile activity. Feeding predominantly affected Rp-s6k...... to contractile activity, whereas elongation mainly was found to respond to feeding. Furthermore, although functionally linked, the contractile and the supportive matrix structures upregulate their protein synthesis rate quite differently in response to feeding and contractile activity and intensity.......Exercise stimulates muscle protein fractional synthesis rate (FSR), but the importance of contractile intensity and whether it interplays with feeding is not understood. This was investigated following two distinct resistance exercise (RE) contraction intensities using an intrasubject design...

  10. Noninvasive 64Cu-ATSM and PET/CT Assessment of Hypoxia in Rat Skeletal Muscles and Tendons During Muscle Contractions

    DEFF Research Database (Denmark)

    Skovgaard, Dorthe; Kjaer, Michael; Madsen, Jacob

    2009-01-01

    the first PET/CT scan. Standardized uptake values (SUVs) were calculated for the Achilles tendons and triceps surae muscles and were correlated to gene expression of HIF1alpha and CAIII using real-time polymerase chain reaction. RESULTS: Immediately after the contractions, uptake of (64)Cu...

  11. 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.

  12. Muscle contraction induced arterial shear stress increases endothelial nitric oxide synthase phosphorylation in humans.

    Science.gov (United States)

    Casey, Darren P; Ueda, Kenichi; Wegman-Points, Lauren; Pierce, Gary L

    2017-10-01

    We determined if local increases in brachial artery shear during repetitive muscle contractions induce changes in protein expression of endothelial nitric oxide synthase (eNOS) and/or phosphorylated (p-)eNOS at Ser1177, the primary activation site on eNOS, in endothelial cells (ECs) of humans. Seven young male subjects (25 ± 1 yr) performed 20 separate bouts (3 min each) of rhythmic forearm exercise at 20% of maximum over a 2-h period. Each bout of exercise was separated by 3 min of rest. An additional six male subjects (24 ± 1 yr) served as time controls (no exercise). ECs were freshly isolated from the brachial artery using sterile J-wires through an arterial catheter at baseline and again after the 2-h exercise or time control period. Expression of eNOS or p-eNOS Ser1177 in ECs was determined via immunofluorescence. Brachial artery mean shear rate was elevated compared with baseline and the time control group throughout the 2-h exercise protocol (P 0.05 for both). Our novel results suggest that elevations in brachial artery shear increase eNOS Ser1177 phosphorylation in the absence of changes in total eNOS in ECs of young healthy male subjects, suggesting that this model is sufficient to alter posttranslational modification of eNOS activity in vivo in humans.NEW & NOTEWORTHY Elevations in brachial artery shear in response to forearm exercise increased endothelial nitric oxide synthase Ser1177 phosphorylation in brachial artery endothelial cells of healthy humans. Our present study provides the first evidence in humans that muscle contraction-induced increases in conduit arterial shear lead to in vivo posttranslational modification of endothelial nitric oxide synthase activity in endothelial cells. Copyright © 2017 the American Physiological Society.

  13. Skeletal muscle excitation-contraction coupling: who are the dancing partners?

    Science.gov (United States)

    Rebbeck, Robyn T; Karunasekara, Yamuna; Board, Philip G; Beard, Nicole A; Casarotto, Marco G; Dulhunty, Angela F

    2014-03-01

    There is an overwhelming body of work supporting the idea that excitation-contraction coupling in skeletal muscle depends on a physical interaction between the skeletal muscle isoform of the dihydropyridine receptor L-type Ca(2+) channel and the skeletal isoform of the ryanodine receptor Ca(2+) release channel. A general assumption is that this physical interaction is between "critical" residues that have been identified in the II-III loop of the dihydropyridine receptor alpha subunit and the ryanodine receptor. However, despite extensive searches, the complementary "critical" residues in the ryanodine receptor have not been identified. This raises the possibility that the coupling proceeds either through other subunits of the dihydropyridine receptor and/or other co-proteins within the large RyR1 protein complex. There have been some remarkable advances in recent years in identifying proteins in the RyR complex that impact on the coupling process, and these are considered in this review. A major candidate for a role in the coupling mechanism is the beta subunit of the dihydropyridine receptor, because specific residues in both the beta subunit and ryanodine receptor have been identified that facilitate an interaction between the two proteins and these also impact on excitation-contraction coupling. This role of beta subunit remains to be fully investigated as well as the degree to which it may complement any other direct or indirect voltage-dependent coupling interactions between the DHPR alpha II-III loop and the ryanodine receptor. Copyright © 2014. Published by Elsevier Ltd.

  14. Muscle Contraction Velocity: A Suitable Approach to Analyze the Functional Adaptations in Elite Soccer Players

    Directory of Open Access Journals (Sweden)

    Irineu Loturco, Lucas A. Pereira, Ronaldo Kobal, Katia Kitamura, Rodrigo Ramírez-Campillo, Vinicius Zanetti, Cesar C. Cal Abad, Fabio Y. Nakamura

    2016-09-01

    Full Text Available Tensiomyography (TMG has been used as a simple and non-invasive tool to assess the mechanical properties of skeletal muscles. The TMG-derived velocity of contraction (Vc, which can be calculated from the ratio between maximal radial displacement and the sum of contraction time and delay time, has been proposed for evaluating athletes. However, its sensitivity to training effects and possible relation with changes in soccer players’ neuromuscular performance have not yet been addressed. To test this possibility, twenty-two male Brazilian elite soccer players were assessed using TMG-derived Vc, unloaded squat jump, countermovement jump and drop jump at 45 cm, loaded jump squat and linear (20 m and change of direction (COD sprint tests, prior to and after an 8-week period, between two consecutive official tournaments, during which the concurrency between endurance and strength-power training commonly impairs neuromuscular capacities. Magnitude-based inference was used to detect meaningful training effects. From pre- to post-tests, it was observed likely to almost certainly improvements in all modes of jumping tests. In addition, we could verify decrements in the 20-m and COD sprint performances, which were rated as very likely and almost certainly, respectively. Finally, both rectus femoris and biceps femoris muscles presented a likely reduction in Vc. Therefore, chronic decreases in sprinting speed are possibly accompanied by a reduced TMG-derived Vc. From a practical standpoint, the TMG-derived Vc can be used to monitor negative specific-soccer training effects related to potential impairments in maximum speed.

  15. Non-muscle (NM) myosin heavy chain phosphorylation regulates the formation of NM myosin filaments, adhesome assembly and smooth muscle contraction.

    Science.gov (United States)

    Zhang, Wenwu; Gunst, Susan J

    2017-07-01

    Non-muscle (NM) and smooth muscle (SM) myosin II are both expressed in smooth muscle tissues, however the role of NM myosin in SM contraction is unknown. Contractile stimulation of tracheal smooth muscle tissues stimulates phosphorylation of the NM myosin heavy chain on Ser1943 and causes NM myosin filament assembly at the SM cell cortex. Expression of a non-phosphorylatable NM myosin mutant, NM myosin S1943A, in SM tissues inhibits ACh-induced NM myosin filament assembly and SM contraction, and also inhibits the assembly of membrane adhesome complexes during contractile stimulation. NM myosin regulatory light chain (RLC) phosphorylation but not SM myosin RLC phosphorylation is regulated by RhoA GTPase during ACh stimulation, and NM RLC phosphorylation is required for NM myosin filament assembly and SM contraction. NM myosin II plays a critical role in airway SM contraction that is independent and distinct from the function of SM myosin. The molecular function of non-muscle (NM) isoforms of myosin II in smooth muscle (SM) tissues and their possible role in contraction are largely unknown. We evaluated the function of NM myosin during contractile stimulation of canine tracheal SM tissues. Stimulation with ACh caused NM myosin filament assembly, as assessed by a Triton solubility assay and a proximity ligation assay aiming to measure interactions between NM myosin monomers. ACh stimulated the phosphorylation of NM myosin heavy chain on Ser1943 in tracheal SM tissues, which can regulate NM myosin IIA filament assembly in vitro. Expression of the non-phosphorylatable mutant NM myosin S1943A in SM tissues inhibited ACh-induced endogenous NM myosin Ser1943 phosphorylation, NM myosin filament formation, the assembly of membrane adhesome complexes and tension development. The NM myosin cross-bridge cycling inhibitor blebbistatin suppressed adhesome complex assembly and SM contraction without inhibiting NM myosin Ser1943 phosphorylation or NM myosin filament assembly. Rho

  16. Exposure to Radiofrequency Radiation Emitted from Common Mobile Phone Jammers Alters the Pattern of Muscle Contractions: an Animal Model Study

    Directory of Open Access Journals (Sweden)

    Rafati A.

    2015-09-01

    Full Text Available Introduction: The rapid growth of wireless communication technologies has caused public concerns regarding the biological effects of electromagnetic radiations on human health. Some early reports indicated a wide variety of non-thermal effects of electromagnetic radiation on amphibians such as the alterations of the pattern of muscle extractions. This study is aimed at investigating the effects of exposure to radiofrequency (RF radiation emitted from mobile phone jammers on the pulse height of contractions, the time interval between two subsequent contractions and the latency period of frog’s isolated gastrocnemius muscle after stimulation with single square pulses of 1V (1 Hz. Materials and Methods: Frogs were kept in plastic containers in a room. Animals in the jammer group were exposed to radiofrequency (RF radiation emitted from a common Jammer at a distance of 1m from the jammer’s antenna for 2 hours while the control frogs were only sham exposed. Then animals were sacrificed and isolated gastrocnemius muscles were exposed to on/off jammer radiation for 3 subsequent 10 minute intervals. Isolated gastrocnemius muscles were attached to the force transducer with a string. Using a PowerLab device (26-T, the pattern of muscular contractions was monitored after applying single square pulses of 1V (1 Hz as stimuli. Results: The findings of this study showed that the pulse height of muscle contractions could not be affected by the exposure to electromagnetic fields. However, the latency period was effectively altered in RF-exposed samples. However, none of the experiments could show an alteration in the time interval between two subsequent contractions after exposure to electromagnetic fields. Conclusion: These findings support early reports which indicated a wide variety of non-thermal effects of electromagnetic radiation on amphibians including the effects on the pattern of muscle extractions.

  17. Skeletal muscle contractions induce acute changes in cytosolic superoxide, but slower responses in mitochondrial superoxide and cellular hydrogen peroxide.

    Directory of Open Access Journals (Sweden)

    Timothy Pearson

    Full Text Available Skeletal muscle generation of reactive oxygen species (ROS is increased following contractile activity and these species interact with multiple signaling pathways to mediate adaptations to contractions. The sources and time course of the increase in ROS during contractions remain undefined. Confocal microscopy with specific fluorescent probes was used to compare the activities of superoxide in mitochondria and cytosol and the hydrogen peroxide content of the cytosol in isolated single mature skeletal muscle (flexor digitorum brevis fibers prior to, during, and after electrically stimulated contractions. Superoxide in mitochondria and cytoplasm were assessed using MitoSox red and dihydroethidium (DHE respectively. The product of superoxide with DHE, 2-hydroxyethidium (2-HE was acutely increased in the fiber cytosol by contractions, whereas hydroxy-MitoSox showed a slow cumulative increase. Inhibition of nitric oxide synthases increased the contraction-induced formation of hydroxy-MitoSox only with no effect on 2-HE formation. These data indicate that the acute increases in cytosolic superoxide induced by contractions are not derived from mitochondria. Data also indicate that, in muscle mitochondria, nitric oxide (NO reduces the availability of superoxide, but no effect of NO on cytosolic superoxide availability was detected. To determine the relationship of changes in superoxide to hydrogen peroxide, an alternative specific approach was used where fibers were transduced using an adeno-associated viral vector to express the hydrogen peroxide probe, HyPer within the cytoplasmic compartment. HyPer fluorescence was significantly increased in fibers following contractions, but surprisingly followed a relatively slow time course that did not appear directly related to cytosolic superoxide. These data demonstrate for the first time temporal and site specific differences in specific ROS that occur in skeletal muscle fibers during and after contractile

  18. Sources of calcium in agonist-induced contraction of rat distal colon smooth muscle in vitro.

    Science.gov (United States)

    Zhou, Hua; Kong, De-Hu; Pan, Qun-Wan; Wang, Hai-Hua

    2008-02-21

    To study the origin of calcium necessary for agonist-induced contraction of the distal colon in rats. The change in intracellular calcium concentration ([Ca2+]i) evoked by elevating external Ca2+ was detected by fura 2/AM fluorescence. Contractile activity was measured with a force displacement transducer. Tension was continuously monitored and recorded using a Powerlab 4/25T data acquisition system with an ML110 bridge bioelectric physiographic amplifier. Store depletion induced Ca2+ influx had an effect on [Ca2+]i. In nominally Ca2+-free medium, the sarco-endoplasmic reticulum Ca2+-ATPase inhibitor thapsigargin (1 mumol/L) increased [Ca2+]i from 68 to 241 nmol/L, and to 458 (P source of activator Ca2+ for the contractile response to agonist is extracellular Ca2+, and intracellular Ca2+ has little role to play in mediating excitation-contraction coupling by agonists in rat distal colon smooth muscle in vitro. The influx of extracellular Ca2+ is mainly mediated through voltage-, receptor- and store-operated Ca2+ channels, which can be used as an alternative to develop new drugs targeted on the dysfunction of digestive tract motility.

  19. Muscle fibers from senescent mice retain excitation-contraction coupling properties in culture.

    Science.gov (United States)

    Wang, Zhong-Min; Zheng, Zhenlin; Messi, María L; Delbono, Osvaldo

    2007-01-01

    In the present study, we test the hypothesis that mouse skeletal muscle in culture retains the fundamental properties of excitation-sarcoplasmic reticulum Ca(2+) release coupling reported for young-adult (3-4 mo) and senescent (22-23) mice. Dissociated flexor digitorum brevis (FDB) muscles from young-adult and senescent mice were cultured for 7 d in a serum-free medium. During this period, the overall morphology of cultured fibers resembled that exhibited by acutely dissociated cells. In addition, survival analysis revealed that more than 70% of the fibers from both young and old mice remained suitable for electrophysiological studies during this same culture period. Charge movement and intracellular Ca(2+) recordings in FDB fibers, voltage clamped in the whole cell configuration of the patch-clamp technique, reproduced the maximal values, and voltage dependence similarly displayed by acutely dissociated cells for both parameters in young-adult and senescent mice. The analysis of the dihydropyridine receptor by immunoblots confirmed, in the culture system, the age-dependent decrease in the expression of this protein. In conclusion, FDB fibers from young-adult and old mice retain the excitation-contraction coupling phenotype during the course of a week in serum-free medium culture.

  20. The multiple roles of titin in muscle contraction and force production.

    Science.gov (United States)

    Herzog, Walter

    2018-01-20

    Titin is a filamentous protein spanning the half-sarcomere, with spring-like properties in the I-band region. Various structural, signaling, and mechanical functions have been associated with titin, but not all of these are fully elucidated and accepted in the scientific community. Here, I discuss the primary mechanical functions of titin, including its accepted role in passive force production, stabilization of half-sarcomeres and sarcomeres, and its controversial contribution to residual force enhancement, passive force enhancement, energetics, and work production in shortening muscle. Finally, I provide evidence that titin is a molecular spring whose stiffness changes with muscle activation and actin-myosin-based force production, suggesting a novel model of force production that, aside from actin and myosin, includes titin as a "third contractile" filament. Using this three-filament model of sarcomeres, the stability of (half-) sarcomeres, passive force enhancement, residual force enhancement, and the decrease in metabolic energy during and following eccentric contractions can be explained readily.

  1. Effects of intracellular ruthenium red on excitation-contraction coupling in intact frog skeletal muscle fibres.

    Science.gov (United States)

    Baylor, S M; Hollingworth, S; Marshall, M W

    1989-01-01

    1. Ruthenium Red (RR) blocks sarcoplasmic reticulum (SR) Ca2+ release in disrupted muscle preparations and this block has been used as a marker for the physiological Ca2+ release pathway. To investigate whether RR can also affect SR Ca2+ release in living muscle, optical signals reflecting Ca2+ release have been measured in intact single frog twitch fibres microinjected with RR. 2. The total myoplasmic concentration of RR, [RRT], was obtained from measurements of RR-related absorbance and apparent diffusion constant, Dapp, of RR in myoplasm was estimated. The value of Dapp was about 1/30 of that expected and can be explained if the majority of RR (approximately 97%) was bound in myoplasm and free [RR] was only 1/30 of [RRT]. 3. Sarcoplasmic reticulum Ca2+ release following action potential stimulation was assessed from a Ca2+-related change in intrinsic birefringence. The birefringence signal was blocked in the presence of RR and the degree of block was clearly dependent upon [RRT]. At 16 degrees C the estimated [RRT] for half-block of the birefringence signal was 23 +/- 4 microM (+/- S.E. of mean; n = 3), and for half-block of the Ca2+ release process itself was 72 +/- 14 microM. The estimated free [RR] for half-block is then 0.8 +/- 0.1 and 2.4 +/- 0.5 microM, respectively. In the cold (6-8 degrees C), the half-blocking concentration of RR, referred to [RRT], appeared to be about 3-fold smaller than that observed at 16 degrees C. 4. The values estimated for the free [RR] which caused half-block of Ca2+ release in intact muscle fibres are in the range reported for RR's action in disrupted preparations, thus supporting the conclusion that the RR-blockable channel observed in disrupted muscle is the physiologically important Ca2+ release channel. 5. Intramembrane charge movements in skeletal muscle are thought to underlie the dependence of SR Ca2+ release on transverse tubular membrane potential. Charge movements were measured in RR-injected fibres at 4-6 degrees C

  2. Assessment of voluntary pelvic floor muscle contraction in continent and incontinent women using transperineal ultrasound, manual muscle testing and vaginal squeeze pressure measurements.

    Science.gov (United States)

    Thompson, Judith A; O'Sullivan, Peter B; Briffa, N Kathryn; Neumann, Patricia

    2006-11-01

    The aims of the study were: (1) to assess women performing voluntary pelvic floor muscle (PFM) contractions, on initial instruction without biofeedback teaching, using transperineal ultrasound, manual muscle testing, and perineometry and (2) to assess for associations between the different measurements of PFM function. Sixty continent (30 nulliparous and 30 parous) and 60 incontinent (30 stress urinary incontinence (SUI) and 30 urge urinary incontinence (UUI)) women were assessed. Bladder neck depression during attempts to perform an elevating pelvic floor muscle (PFM) contraction occurred in 17% of continent and 30% of incontinent women. The UUI group had the highest proportion of women who depressed the bladder neck (40%), although this was not statistically significant (p=0.060). The continent women were stronger on manual muscle testing (p=0.001) and perineometry (p=0.019) and had greater PFM endurance (pelevation than the incontinent women (p=0.051). There was a moderate correlation between bladder neck movement during PFM contraction measured by ultrasound and PFM strength assessed by manual muscle testing (r=0.58, p=0.01) and perineometry (r=0.43, p=0.01). The observation that many women were performing PFM exercises incorrectly reinforces the need for individual PFM assessment with a skilled practitioner. The significant correlation between the measurements of bladder neck elevation during PFM contraction and PFM strength measured using MMT and perineometry supports the use of ultrasound in the assessment of PFM function; however, the correlation was only moderate and, therefore, indicates that the different measurement tools assess different aspects of PFM function. It is recommended that physiotherapists use a combination of assessment tools to evaluate the different aspects of PFM function that are important for continence. Ultrasound is useful to determine the direction of pelvic floor movement in the clinical assessment of pelvic floor muscle function

  3. Effect of PDE5 inhibition on the modulation of sympathetic α-adrenergic vasoconstriction in contracting skeletal muscle of young and older recreationally active humans

    DEFF Research Database (Denmark)

    Nyberg, Michael Permin; Piil, Peter Bergmann; Egelund, Jon

    2015-01-01

    Aging is associated with an altered regulation of blood flow to contracting skeletal muscle; however, the precise mechanisms remain unclear. We recently demonstrated that inhibition of cGMP-binding phosphodiesterase 5 (PDE5) increased blood flow to contracting skeletal muscle of older but not you...

  4. Production of interleukin-6 in contracting human skeletal muscles can account for the exercise-induced increase in plasma interleukin-6

    DEFF Research Database (Denmark)

    Steensberg, A; Van Hall, Gerrit; Osada, T

    2000-01-01

    1. Plasma interleukin (IL)-6 concentration is increased with exercise and it has been demonstrated that contracting muscles can produce IL-The question addressed in the present study was whether the IL-6 production by contracting skeletal muscle is of such a magnitude that it can account for the ...

  5. MUSCLEMOTION : A Versatile Open Software Tool to Quantify Cardiomyocyte and Cardiac Muscle Contraction In Vitro and In Vivo

    NARCIS (Netherlands)

    Sala, Luca; van Meer, Berend J; Tertoolen, Leon T; Bakkers, Jeroen; Bellin, Milena; Davis, Richard P; Denning, Chris N; Dieben, Michel A; Eschenhagen, Thomas; Giacomelli, Elisa; Grandela, Catarina; Hansen, Arne; Holman, Eduard; Jongbloed, Monique R; Kamel, Sarah M; Koopman, Charlotte D; Lachaud, Quentin; Mannhardt, Ingra; Mol, Mervyn P; Mosqueira, Diogo; Orlova, Valeria V; Passier, Robert; Ribeiro, Marcelo C; Saleem, Umber; Smith, Godfrey; Burton, Francis L L; Mummery, Christine L

    2017-01-01

    Rationale: There are several methods to measure cardiomyocyte (CM) and muscle contraction but these require customized hardware, expensive apparatus and advanced informatics or can only be used in single experimental models. Consequently, data and techniques have been difficult to reproduce across

  6. Models to study airway smooth muscle contraction in vivo, ex vivo and in vitro : Implications in understanding asthma

    NARCIS (Netherlands)

    Wright, David; Sharma, Pawan; Ryu, Min-Hyung; Risse, Paul-Andre; Ngo, Melanie; Maarsingh, Harm; Koziol-White, Cynthia; Jha, Aruni; Halayko, Andrew J.; West, Adrian R.

    Asthma is a chronic obstructive airway disease characterised by airway hyperresponsiveness (AHR) and airway wall remodelling. The effector of airway narrowing is the contraction of airway smooth muscle (ASM), yet the question of whether an inherent or acquired dysfunction in ASM contractile function

  7. The effects of cannabidiol on the antigen-induced contraction of airways smooth muscle in the guinea-pig.

    Science.gov (United States)

    Dudášová, A; Keir, S D; Parsons, M E; Molleman, A; Page, C P

    2013-06-01

    (-)-Δ(9)-Tetrahydrocannabinol has been demonstrated to have beneficial effects in the airways, but its psychoactive effects preclude its therapeutic use for the treatment of airways diseases. In the present study we have investigated the effects of (-)-cannabidiol, a non-psychoactive component of cannabis for its actions on bronchial smooth muscle in vitro and in vivo. Guinea-pig bronchial smooth muscle contractions induced by exogenously applied spasmogens were measured isometrically. In addition, contractile responses of bronchial smooth muscle from ovalbumin-sensitized guinea-pigs were investigated in the absence or presence of (-)-cannabidiol. Furthermore, the effect of (-)-cannabidiol against ovalbumin-induced airway obstruction was investigated in vivo in ovalbumin-sensitized guinea-pigs. (-)-Cannabidiol did not influence the bronchial smooth muscle contraction induced by carbachol, histamine or neurokinin A. In contrast, (-)-cannabidiol inhibited anandamide- and virodhamine-induced responses of isolated bronchi. A fatty acid amide hydrolase inhibitor, phenylmethanesulfonyl fluoride reversed the inhibitory effect of (-)-cannabidiol on anandamide-induced contractions. In addition, (-)-cannabidiol inhibited the contractile response of bronchi obtained from allergic guinea-pigs induced by ovalbumin. In vivo, (-)-cannabidiol reduced ovalbumin-induced airway obstruction. In conclusion, our results suggest that cannabidiol can influence antigen-induced airway smooth muscle tone suggesting that this molecule may have beneficial effects in the treatment of obstructive airway disorders. Copyright © 2013. Published by Elsevier Ltd.

  8. Novel pentapeptide, PALAL, derived from a bony fish elicits contraction of the muscle in starfish Patiria pectinifera.

    Science.gov (United States)

    Go, Hye-Jin; Kim, Chan-Hee; Oh, Hye Young; Park, Nam Gyu

    2016-10-01

    A bioactive peptide mimicking peptide-signaling molecules has been isolated from the skin extract of fish Channa argus which caused contraction of the apical muscle of a starfish Patiria pectinifera, a deuterostomian invertebrate. The primary structure of the isolated pentapeptide comprises amino acid sequence of H-Pro-Ala-Leu-Ala-Leu-OH (PALAL) with a molecular mass of 483.7 Da. Pharmacological activity of PALAL, dosage ranging from 10(-9) to 10(-5) M, revealed concentration-dependent contraction of the apical muscles of P. pectinifera and Asterias amurensis. However, PALAL was not active on the intestinal smooth muscle of the goldfish Carassius auratus and has presumably other physiological roles in fish skin. Investigation of structure-activity relationship using truncated and substituted analogs of PALAL demonstrated that H-Ala-Leu-Ala-Leu-OH was necessary and should be sufficient to constrict apical muscle of P. pectinifera. Furthermore, the second alanine residue was required to display the activity, and the fifth leucine residue was responsible for its potency. Comparison with PALAL's primary structure with those of other known bioactive peptides from fish and starfish revealed that PALAL does not have any significant homology. Consequently, PALAL is a bioactive peptide that elicits a muscle contraction in starfish, and the isolation of PALAL may lead to develop other bioactive peptides sharing its similar sequence and/or activity. Copyright © 2016 European Peptide Society and John Wiley & Sons, Ltd. Copyright © 2016 European Peptide Society and John Wiley & Sons, Ltd.

  9. Change in Excitability of Corticospinal Pathway and GABA-Mediated Inhibitory Circuits of Primary Motor Cortex Induced by Contraction of Adjacent Hand Muscle.

    Science.gov (United States)

    Jono, Yasutomo; Iwata, Yasuyuki; Mizusawa, Hiroki; Hiraoka, Koichi

    2016-11-01

    The present study examined whether the excitability of the corticospinal pathway and the GABA-mediated inhibitory circuits of the primary motor cortex that project onto the corticospinal neurons in the tonically contracting hand muscle are changed by tonic contraction of the adjacent hand muscle. The motor evoked potential (MEP) and cortical silent period (CSP) in the tonically contracting hand muscle were obtained while the adjacent hand muscle was either tonically contracting or at rest. The MEP and CSP of the first dorsal interosseous (FDI) muscle elicited across the scalp sites where the MEP is predominantly elicited in the FDI muscle were decreased by tonic contraction of the abductor digiti minimi (ADM) muscle. The centers of the area of the MEP and the duration of the CSP in the FDI muscle elicited across the sites where the MEP is predominantly elicited in the FDI muscle were lateral to those in the FDI muscle elicited across the sites where the MEP is elicited in both the FDI and ADM muscles. They were also lateral to those in the ADM muscle elicited either across the sites where the MEP is predominantly elicited in the ADM muscle, or across the sites where the MEP is elicited in both the FDI and ADM muscles. The decrease in the corticospinal excitability and the excitability of the GABA-mediated inhibitory circuits of the primary motor cortex that project onto the corticospinal neurons in the FDI muscle may be due either to (1) the interaction between the activity of the lateral area of the FDI representation and the descending drive to the ADM muscle, or (2) the decreased susceptibility of the primary motor area that predominantly projects onto the corticospinal neurons in the FDI muscle, which also plays a role in independent finger movement when both the FDI and ADM muscles act together as synergists.

  10. Rats bred for low aerobic capacity become promptly fatigued and have slow metabolic recovery after stimulated, maximal muscle contractions.

    Directory of Open Access Journals (Sweden)

    Sira Torvinen

    Full Text Available Muscular fatigue is a complex phenomenon affected by muscle fiber type and several metabolic and ionic changes within myocytes. Mitochondria are the main determinants of muscle oxidative capacity which is also one determinant of muscle fatigability. By measuring the concentrations of intracellular stores of high-energy phosphates it is possible to estimate the energy production efficiency and metabolic recovery of the muscle. Low intrinsic aerobic capacity is known to be associated with reduced mitochondrial function. Whether low intrinsic aerobic capacity also results in slower metabolic recovery of skeletal muscle is not known. Here we studied the influence of intrinsic aerobic capacity on in vivo muscle metabolism during maximal, fatiguing electrical stimulation.Animal subjects were genetically heterogeneous rats selectively bred to differ for non-trained treadmill running endurance, low capacity runners (LCRs and high capacity runners (HCRs (n = 15-19. We measured the concentrations of major phosphorus compounds and force parameters in a contracting triceps surae muscle complex using (31P-Magnetic resonance spectroscopy ((31P-MRS combined with muscle force measurement from repeated isometric twitches.Our results demonstrated that phosphocreatine re-synthesis after maximal muscle stimulation was significantly slower in LCRs (p<0.05. LCR rats also became promptly fatigued and maintained the intramuscular pH poorly compared to HCRs. Half relaxation time (HRT of the triceps surae was significantly longer in LCRs throughout the stimulation protocol (p≤0.05 and maximal rate of torque development (MRTD was significantly lower in LCRs compared to HCRs from 2 min 30 s onwards (p≤0.05.We observed that LCRs are more sensitive to fatigue and have slower metabolic recovery compared to HCRs after maximal muscle contractions. These new findings are associated with reduced running capacity and with previously found lower mitochondrial content, increased

  11. RhoA kinase and protein kinase C participate in regulation of rabbit stomach fundus smooth muscle contraction

    Science.gov (United States)

    Ratz, Paul H; Meehl, Joel T; Eddinger, Thomas J

    2002-01-01

    The degree to which the RhoA kinase (ROK) blockers, Y-27632 (1 μM) and HA-1077 (10 μM), and the PKC blocker, GF-109203X (1 μM), reduced force produced by carbachol, a muscarinic receptor agonist, and phenylephrine, an α-adrenoceptor agonist, was examined in rabbit stomach fundus smooth muscle. When examining the effect on cumulative carbachol concentration-response curves (CRCs), ROK and PKC blockers shifted the potency (EC50) to the right but did not reduce the maximum response. In a single-dose carbachol protocol using moderate (∼EC50) and maximum carbachol concentrations, Y-27632 and HA-1077 reduced peak force, but GF-109203X had no effect. By contrast, all three agents inhibited the carbachol contractions of rabbit bladder (detrusor) smooth muscle. Compared to carbachol, phenylephrine produced a weaker maximum response that was not inhibited by phentolamine, atropine nor capsaicin but was inhibited by Y-27632 , HA-1077 and GF-109203X. In detrusor, classical down-regulation occurred, but in fundus, up-regulation of responsiveness occurred. This up-regulation in fundus may have been a post-receptor event, because a KCl-induced contraction produced after a carbachol CRC was stronger than one produced before the carbachol stimulus. In conclusion, these data suggest that ROK plays a critical role in the regulation of rabbit fundus smooth muscle contraction, which is distinct from chicken gizzard smooth muscle, where ROK is reported to exist but to not play a role in muscarinic receptor-induced contraction. Additional unique findings are that PKC participates in phenylephrine- but not carbachol-induced contraction in fundus, that carbachol does not activate identical subcellular signalling systems in fundus and detrusor, and that fundus, unlike detrusor, responds to carbachol stimulation with post-receptor up-regulation of contraction. PMID:12429570

  12. Effect of atrophy and contractions on myogenin mRNA concentration in chick and rat myoblast omega muscle cells

    Science.gov (United States)

    Krebs, J. M.; Denney, R. M.

    1997-01-01

    The skeletal rat myoblast omega (RMo) cell line forms myotubes that exhibit spontaneous contractions under appropriate conditions in culture. We examined if the RMo cells would provide a model for studying atrophy and muscle contraction. To better understand how to obtain contractile cultures, we examined levels of contraction under different growing conditions. The proliferation medium and density of plating affected the subsequent proportion of spontaneously contracting myotubes. Using a ribonuclease protection assay, we found that exponentially growing RMo myoblasts contained no detectable myogenin or herculin mRNA, while differentiating myoblasts contained high levels of myogenin mRNA but no herculin mRNA. There was no increase in myogenin mRNA concentration in either primary chick or RMo myotubes whose contractions were inhibited by depolarizing concentrations of potassium (K+). Thus, altered myogenin mRNA concentrations are not involved in atrophy of chick myotubes. Depolarizing concentrations of potassium inhibited spontaneous contractions in both RMo cultures and primary chick myotube cultures. However, we found that the myosin concentration of 6-d-old contracting RMo cells fed medium plus AraC was 11 +/- 3 micrograms myosin/microgram DNA, not significantly different from 12 +/- 4 micrograms myosin/microgram DNA (n = 3), the myosin concentration of noncontracting RMo cells (treated with 12 mM K+ for 6 d). Resolving how RMo cells maintained their myosin content when contraction is inhibited may be important for understanding atrophy.

  13. Ultrasonic Thickness of Lateral Abdominal Wall Muscles in Response to Pelvic Floor Muscle Contraction in women with stress incontinency with and without Chronic Low Back Pain

    Directory of Open Access Journals (Sweden)

    Farideh Dehghan-Manshadi

    2014-01-01

    Full Text Available Objective: Urinary Incontinence (UI as a common lower urinary tract dysfunction , results from Pelvic Floor Muscle's (PFM underactivity.Because of co-activation of PFM and the Lateral Abdominal Wall Muscles (LAWM, this study was aimed to investigate the changes in the ultrasonic thickness of the LAWM in response to PFM contraction in stress urinary incontinent (SUIwomen with and without Chronic Low Back Pain (CLBP. Materials & Methods: A total of 28 women, 10 healthy, 18 SUI with and without CLBP (9 in each group participated in this quasi-experimental study. After collecting demographic information and assessment of PFM function, changes in ultrasonic thickness of right LAWM were measured in response to PFM contraction. One way ANOVA, Kruskal-Wallis and Pearson’s correlation tests were performed to analyze the data. Values of P0.05. There was a significant increase in thickness of the Traversus Abdominis Muscle (TrA during PFM contraction in control group comparing experimental groups (P=0.03. Women in control group showed significantly higher PFM strength and more intravaginal pressure (P=0.001. Conclusion: Changes in ultrasonic thickness of the TrA during PFM contraction revealed disturbance of co-activation of the LAWM and the PFM in women with and without SUI CLBP.

  14. Do asymptomatic former high-impact sports practitioners maintain the ability to contract the pelvic floor muscles?

    Science.gov (United States)

    Brandão, S; Da Roza, T; Mascarenhas, T; Ramos, I; Natal Jorge, R

    2015-11-01

    Sports are associated with pelvic floor dysfunction. This work aimed to assess, in nulliparous asymptomatic women, whether previous intense practice of high-impact sports is associated with differences in morphology and contraction of the pelvic floor muscles, when compared to women who practiced low-level physical activity. In this prospective pilot study, 7 former high-impact sports practitioners and a control group (N.=7) were compared. Clinical evaluation and self-administered questionnaires were used to gather information about pelvic floor dysfunction and physical activity. Static and cine dynamic MR images were acquired. Morphological measures of the pubovisceral muscle area and thickness, and levator hiatus (LH) anterior-to-posterior diameter, width and area were taken in the static images. LH anterior-to-posterior diameter was again assessed in the dynamic acquisition (consecutive blocks of rest vs. maximal voluntary contraction). The relative variation between these two conditions was used as an indirect measure of contraction. No abnormal clinical or imaging findings were reported. Former high-impact sports practitioners evidenced decreased pubovisceral muscle thickness (right side P=0.005; left side P=0.004) and area (P=0.004), and larger levator hiatus width and area (P=0.045; P=0.005). Only its anterior-to-posterior diameter was similar (4.89cm±0.35 and 4.81cm±0.17, respectively). Their ability to perform maximum voluntary contractions seems to have decreased (8.03%±0.81 vs. 13.74%±0.95 for controls). The current results suggest that women who previously practiced high-impact sports, even being asymptomatic, may have suffered damage to the pelvic floor muscles due to the biomechanical impact of the sports. They may require pelvic floor muscle training to increase muscle thickness and hiatal closing capacity.

  15. Does the prevalence of levator ani muscle avulsion differ when assessed using tomographic ultrasound imaging at rest vs on maximum pelvic floor muscle contraction?

    Science.gov (United States)

    van Delft, K; Thakar, R; Sultan, A H; Kluivers, K B

    2015-07-01

    It has been suggested that transperineal ultrasound images obtained during maximum pelvic floor muscle contraction improve the diagnosis of levator ani muscle (LAM) avulsion by comparison with those obtained at rest. The objective of this study was to establish, using transperineal tomographic ultrasound imaging (TUI), the correlation between LAM avulsion diagnosed at rest and that on contraction. Primiparous women were examined 3 months postpartum by Pelvic Organ Prolapse Quantification (POP-Q) assessment and for LAM avulsion clinically by digital palpation and by transperineal TUI performed at rest and on pelvic floor muscle contraction. LAM avulsion was diagnosed on TUI when the three central slices were abnormal. A comparison was made between LAM avulsion diagnosed at rest and on maximum contraction. Two independent blinded investigators performed the analyses and a third investigator resolved discrepancies. One hundred and ninety primiparae were analyzed providing 380 results for comparison, as right and left LAM were analyzed independently. LAM avulsion was found in 36 (9.5%) images obtained at rest and in 35 (9.2%) on contraction, revealing moderate correlation between the two (ICC, 0.58 (95% CI, 0.51-0.64)). Twenty-two cases of LAM avulsion were identified both at rest and on contraction. One woman had LAM avulsion on palpation, which was seen on TUI as LAM avulsion on contraction, but not at rest. More cases of anterior and posterior compartment prolapse were found in women with LAM avulsion diagnosed on contraction only compared to LAM avulsion observed at rest only (POP-Q assessment point Ba, -1.8 vs -2.5 (P = 0.075) and point Bp, -2.5 vs -2.8 (P = 0.072)). Findings on transperineal TUI performed in women at rest and on contraction correlate reasonably well. However, given the trend towards an association with signs of pelvic floor dysfunction, diagnosis of LAM avulsion on contraction seems to be more reliable. Consistency in technique and

  16. Influence of exercise contraction mode and protein supplementation on human skeletal muscle satellite cell content and muscle fiber growth

    DEFF Research Database (Denmark)

    Farup, Jean; Rahbek, Stine Klejs; Riis, Simon

    2014-01-01

    Skeletal muscle satellite cells (SCs) are involved in remodeling and hypertrophy processes of skeletal muscle. However, little knowledge exists on extrinsic factors that influence the content of SCs in skeletal muscle. In a comparative human study, we investigated the muscle fiber type...... CSA increased exclusively with Whey-Conc (P hypertrophy correlated with whole muscle hypertrophy exclusively following Conc training (P ...-specific association between emergence of satellite cells (SCs), muscle growth, and remodeling in response to 12 wk unilateral resistance training performed as eccentric (Ecc) or concentric (Conc) resistance training ± whey protein (Whey, 19.5 g protein + 19.5 g glucose) or placebo (Placebo, 39 g glucose...

  17. Muscle co-contraction in elderly people change due to postural stability during single-leg standing.

    Science.gov (United States)

    Iwamoto, Yoshitaka; Takahashi, Makoto; Shinkoda, Koichi

    2017-12-16

    Muscle co-contraction is the simultaneous contraction of agonist and antagonist muscles crossing a joint, and it increases with age. This study primarily aimed to clarify the difference in the effect of a light fingertip contact to stationary surface on postural sway and muscle co-contraction during single-leg standing (SLS) between young and elderly groups; the secondary aim was to reveal the quantitative difference in the muscle co-contraction of the ankle joint among the three different support structure conditions in the elderly group. This study included eight young adults (age 23.4 ± 2.6 years) and nine community dwelling older adults (age 74.7 ± 3.4 years). The task was SLS under the following conditions: (1) no supporting structure, FR; (2) light index fingertip contact to a stationary supporting structure (to touch in force < 1 N), LT; and (3) dependence on a supporting structure for stabilization as desired, DO. Center of pressure (COP) variables [root-mean-square distance (RDIST), total excursion (TOTEX), mean velocity (MVELO), and standard deviation area (AREA-SD)] and the co-contraction index (CI) between the tibialis anterior and soleus were measured using surface electromyography. With regard to the effect of the light fingertip contact to stationary surface, in the young group, TOTEX, MVELO, AREA-SD, and CI during SLS were smaller under the LT condition than under the FR condition. However, in the elderly group, only AREA-SD and CI were smaller under the LT condition than under the FR condition. No significant difference was observed in COP variables and CI under the DO condition between the young and elderly groups. Both young and elderly groups could decrease muscle co-contraction using the light fingertip contact. On the other hand, in the elderly group, COP variables showed a limited effect from the light fingertip contact; only the "sway" domain measure (AREA-SD). Both young and elderly groups showed the smallest CI under the DO

  18. Influence of a valgus knee brace on muscle activation and co-contraction in patients with medial knee osteoarthritis.

    Science.gov (United States)

    Fantini Pagani, Cynthia H; Willwacher, Steffen; Kleis, Barbara; Brüggemann, Gert-Peter

    2013-04-01

    The purpose of this study was to analyse the effect of a valgus knee orthosis designed for patients with knee osteoarthritis on the electromyographic activity (EMG) of seven muscles of the lower limb during gait. Twelve patients with medial knee osteoarthritis walked on a treadmill in three different conditions: without orthosis, with a knee orthosis in 4° valgus adjustment and with an orthosis in a neutral flexible adjustment. Root-mean-square (RMS) was analysed in each condition during a 150 ms pre-activation phase and during the stance phase of gait, which was divided in four sub-phases. In addition, co-contraction ratios (CCRs) were calculated between extensor/flexor, medial/lateral muscles and between agonist and antagonist muscle pairs. Significant decreases in muscle activity and CCRs were observed with the use of the knee orthosis in both adjustments compared to the condition without orthosis. Using the valgus brace, medial/lateral CCR decreased significantly during the late stance and the flexor/extensor CCR decreased significantly during the loading phase and late stance. Decreases of muscle pairs CCRs were observed with the neutral flexible adjustment. The results support the theory of a possible beneficial effect of knee braces in reducing knee loading by decreasing muscle activation and co-contraction levels, which could contribute to decelerate disease progression in patients with knee osteoarthritis. Copyright © 2012 Elsevier Ltd. All rights reserved.

  19. Lubiprostone Increases Small Intestinal Smooth Muscle Contractions Through a Prostaglandin E Receptor 1 (EP1)-mediated Pathway.

    Science.gov (United States)

    Chan, Walter W; Mashimo, Hiroshi

    2013-07-01

    Lubiprostone, a chloride channel type 2 (ClC-2) activator, was thought to treat constipation by enhancing intestinal secretion. It has been associated with increased intestinal transit and delayed gastric emptying. Structurally similar to prostones with up to 54% prostaglandin E2 activity on prostaglandin E receptor 1 (EP1), lubiprostone may also exert EP1-mediated procontractile effect on intestinal smooth muscles. We investigated lubiprostone's effects on intestinal smooth muscle contractions and pyloric sphincter tone. Isolated murine small intestinal (longitudinal and circular) and pyloric tissues were mounted in organ baths with modified Krebs solution for isometric recording. Basal muscle tension and response to electrical field stimulation (EFS; 2 ms pulses/10 V/6 Hz/30 sec train) were measured with lubiprostone (10(-10)-10(-5) M) ± EP1 antagonist. Significance was established using Student t test and P Lubiprostone had no effect on the basal tension or EFS-induced contractions of longitudinal muscles. With circular muscles, lubiprostone caused a dose-dependent increase in EFS-induced contractions (2.11 ± 0.88 to 4.43 ± 1.38 N/g, P = 0.020) that was inhibited by pretreatment with EP1 antagonist (1.69 ± 0.70 vs. 4.43 ± 1.38 N/g, P = 0.030). Lubiprostone had no effect on circular muscle basal tension, but it induced a dose-dependent increase in pyloric basal tone (1.07 ± 0.01 to 1.97 ± 0.86 fold increase, P lubiprostone caused a dose-dependent and EP1-mediated increase in contractility of circular but not longitudinal small intestinal smooth muscles, and in basal tone of the pylorus. These findings suggest another mechanism for lubiprostone's observed clinical effects on gastrointestinal motility.

  20. Brain activity during bladder filling and pelvic floor muscle contractions: a study using functional magnetic resonance imaging and synchronous urodynamics.

    Science.gov (United States)

    Krhut, Jan; Holy, Petr; Tintera, Jaroslav; Zachoval, Roman; Zvara, Peter

    2014-02-01

    To map the brain activity during bladder filling by functional magnetic resonance imaging using a refined scanning protocol including synchronous urodynamics and pelvic floor muscle contractions. A total of 23 healthy female volunteers (age 20-68 years) were enrolled. Participants were asked to contract their pelvic floor muscles. This was followed by a urodynamic examination consisting of repeated filling cycles. Brain activity was measured by functional magnetic resonance imaging using a 3T magnetic resonance system. Measurements of brain activity consisted of 120 functional scans during pelvic floor contractions and 210 scans during bladder filling. Each functional magnetic resonance imaging scan covered the brain with 35 slices. Statistical analyses used the general linear model and independent component analysis. Areas of activation were visualized using group statistics. The following main clusters of activation were observed during pelvic floor muscle contractions: medial surface of the frontal lobe (primary motor area), bilaterally; supplementary motor area, bilaterally; and left gyrus precentralis. During bladder filling, activation was detected in the inferior frontal lobe bordering the frontal cingulum, left gyrus parietalis superior, left central area, right insula, brainstem and thalamus with subcortical gray matter nuclei. Our work extends an existing functional magnetic resonance imaging protocol for researching the neural control of the lower urinary tract. The present results are consistent with the available literature and agree with the present hypothetical functional model of lower urinary tract neural control. © 2013 The Japanese Urological Association.

  1. Transverse Strains in Muscle Fascicles during Voluntary Contraction: A 2D Frequency Decomposition of B-Mode Ultrasound Images

    Directory of Open Access Journals (Sweden)

    James M. Wakeling

    2014-01-01

    Full Text Available When skeletal muscle fibres shorten, they must increase in their transverse dimensions in order to maintain a constant volume. In pennate muscle, this transverse expansion results in the fibres rotating to greater pennation angle, with a consequent reduction in their contractile velocity in a process known as gearing. Understanding the nature and extent of this transverse expansion is necessary to understand the mechanisms driving the changes in internal geometry of whole muscles during contraction. Current methodologies allow the fascicle lengths, orientations, and curvatures to be quantified, but not the transverse expansion. The purpose of this study was to develop and validate techniques for quantifying transverse strain in skeletal muscle fascicles during contraction from B-mode ultrasound images. Images were acquired from the medial and lateral gastrocnemii during cyclic contractions, enhanced using multiscale vessel enhancement filtering and the spatial frequencies resolved using 2D discrete Fourier transforms. The frequency information was resolved into the fascicle orientations that were validated against manually digitized values. The transverse fascicle strains were calculated from their wavelengths within the images. These methods showed that the transverse strain increases while the longitudinal fascicle length decreases; however, the extent of these strains was smaller than expected.

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

    Directory of Open Access Journals (Sweden)

    Joachim Nielsen

    Full Text Available Unaccustomed eccentric exercise is accompanied by muscle damage and impaired glucose uptake and glycogen synthesis during subsequent recovery. Recently, it was shown that the role and regulation of glycogen in skeletal muscle are dependent on its subcellular localization, and that glycogen synthesis, as described by the product of glycogen particle size and number, is dependent on the time course of recovery after exercise and carbohydrate availability. In the present study, we investigated the subcellular distribution of glycogen in fibers with high (type I and low (type II mitochondrial content during post-exercise recovery from eccentric contractions. Analysis was completed on five male subjects performing an exercise bout consisting of 15 x 10 maximal eccentric contractions. Carbohydrate-rich drinks were subsequently ingested throughout a 48 h recovery period and muscle biopsies for analysis included time points 3, 24 and 48 h post exercise from the exercising leg, whereas biopsies corresponding to prior to and at 48 h after the exercise bout were collected from the non-exercising, control leg. Quantitative imaging by transmission electron microscopy revealed an early (post 3 and 24 h enhanced storage of intramyofibrillar glycogen (defined as glycogen particles located within the myofibrils of type I fibers, which was associated with an increase in the number of particles. In contrast, late in recovery (post 48 h, intermyofibrillar, intramyofibrillar and subsarcolemmal glycogen in both type I and II fibers were lower in the exercise leg compared with the control leg, and this was associated with a smaller size of the glycogen particles. We conclude that in the carbohydrate-supplemented state, the effect of eccentric contractions on glycogen metabolism depends on the subcellular localization, muscle fiber's oxidative capacity, and the time course of recovery. The early enhanced storage of intramyofibrillar glycogen after the eccentric

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

    DEFF Research Database (Denmark)

    Caserotti, Paolo; Aagaard, Per; Puggaard, Lis

    2008-01-01

    with increasing age. Exercise has been recommended to prevent loss of muscle power and function and recent guidelines indicate training program for increasing muscle power highly relevant for elderly subjects. This study examined the differences in muscle power, force and movement pattern during concentric......-alone and coupled eccentric-concentric contraction and selected functional motor performances before and after 36-week multicomponent training including aerobic, strength, balance, flexibility and coordination components in elderly males. Vertical force, excursion, velocity, power and acceleration of the body......). Nevertheless, pre-stretch enhancement occurred as for similar SQJ and CMJ maximal performance, elderly people employed lower mechanical work, higher mean muscle power (P (mean)), shorter concentric phase duration and shorter body center of mass displacement during CMJ. Post training, CMJ P(peak), P (mean...

  4. Human Skeletal Muscle Stem Cells in Adaptations to Exercise; Effects of Resistance Exercise Contraction Mode and Protein Supplementation

    DEFF Research Database (Denmark)

    Farup, Jean

    2014-01-01

    SUMMARY Human skeletal muscle has a remarkable capability of adapting to a change in demands. The preservation of this adaptability relies partly on a pool of resident myogenic stem cells (satellite cells, SCs). Extrinsic factors such as mechanical load (e.g. resistance exercise) and dietary...... protein constitute key factors in regulation of human skeletal muscle mass; however, the influence of divergent resistance exercise contraction modes and protein supplementation on SC content, is not well described. The overall aim of the present thesis was to investigate whether eccentric versus...... concentric resistance training and ingestion of protein influence myocellular adaptations, with special emphasis on muscle stem cell adaptations, during both acute and prolonged resistance exercise in human skeletal muscle. Paper I. Whey protein supplementation accelerates satellite cell proliferation during...

  5. Contraction type influences the human ability to use the available torque capacity of skeletal muscle during explosive efforts.

    Science.gov (United States)

    Tillin, Neale A; Pain, Matthew T G; Folland, Jonathan P

    2012-06-07

    The influence of contraction type on the human ability to use the torque capacity of skeletal muscle during explosive efforts has not been documented. Fourteen male participants completed explosive voluntary contractions of the knee extensors in four separate conditions: concentric (CON) and eccentric (ECC); and isometric at two knee angles (101°, ISO101 and 155°, ISO155). In each condition, torque was measured at 25 ms intervals up to 150 ms from torque onset, and then normalized to the maximum voluntary torque (MVT) specific to that joint angle and angular velocity. Explosive voluntary torque after 50 ms in each condition was also expressed as a percentage of torque generated after 50 ms during a supramaximal 300 Hz electrically evoked octet in the same condition. Explosive voluntary torque normalized to MVT was more than 60 per cent larger in CON than any other condition after the initial 25 ms. The percentage of evoked torque expressed after 50 ms of the explosive voluntary contractions was also greatest in CON (ANOVA; p muscle's torque capacity explosively is influenced by contraction type, with concentric contractions being more conducive to explosive performance due to a more effective neural strategy.

  6. Efficient Structure-Based Models for the McKibben Contraction Pneumatic Muscle Actuator: The Full Description of the Behaviour of the Contraction PMA

    Directory of Open Access Journals (Sweden)

    Alaa Al-Ibadi

    2017-10-01

    Full Text Available To clarify the advantages of using soft robots in all aspects of life, the effective behaviour of the pneumatic muscle actuator (PMA must be known. In this work, the performances of the PMA are explained and modelled with three formulas. The first formula describes the pulling force of the actuator based on the structure parameters; furthermore, the formula presented is the generalised contraction force for wholly-pneumatic muscle actuators. The second important model is the length formula, which is modified to our previous work to fit different actuator structures. Based on these two models, the stiffness of the actuator is formulated to illustrate its variability at different air pressure amounts. In addition, these formulas will make the selection of proper actuators for any robot arm structure easier using the knowledge gained from their performance. On the other hand, the desired behaviour of this type of actuator will be predefined and controlled.

  7. 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.

  8. Secophalloidin and phalloidin-(S)-sulfoxide as contraction modifiers for comparative study of skeletal and cardiac muscles.

    Science.gov (United States)

    Bukatina, A E; Kirkpatrick, R D; Campbell, K B

    2000-01-01

    Phalloidin, a toxic product of the mushroom Amanita phalloides, binds specifically to F-actin resulting in strong stabilization of F-actin structure (for review, see; Wieland, 1986). Binding to a specific site on the muscle thin filament F-actin, phalloidin modifies contraction in a tissue specific manner. Phalloidin induced changes depend on functionally important parameters (thin filament activation, cross-bridge kinetics), indicating changes in essential steps of the contractile mechanism. Moreover, there is a different action with different phalloidin derivatives. Such properties make phallotoxins (phalloidin and its derivatives) powerful modifiers for muscle research (for review, see: Bukatina, 1996). Phalloidin-induced changes vary qualitatively with muscle types. In all types of skinned skeletal muscle preparations that have been studied (fast and slow muscles from evolutionarily distant animals), the most general effect of phalloidin is to cause a decrease in tension (Bukatina, Morozov, 1979; Alievskaya et al., 1987; Bukatina et al., 1993). In mammalian skeletal muscles, this decrease in tension may be followed by a slowly developing increase in tension. The resulting tension may considerably exceed the tension before phalloidin administration. In contrast, skinned cardiac muscle responds to phalloidin only by increasing isometric tension from the onset of the response. Moreover, the phalloidin response is completed in approximately one-tenth the time in cardiac muscle that it takes in skeletal muscle. These phalloidin effects in cardiac muscle result in an enhanced Ca2+ responsiveness (Boels, Pfitzer, 1992) with an increase in both the force at maximum Ca2+ activation and the Ca2+ sensitivity (Bukatina et al., 1995).

  9. Vibration-induced extra torque during electrically-evoked contractions of the human calf muscles

    Directory of Open Access Journals (Sweden)

    Kohn André F

    2010-06-01

    Full Text Available Abstract Background High-frequency trains of electrical stimulation applied over the lower limb muscles can generate forces higher than would be expected from a peripheral mechanism (i.e. by direct activation of motor axons. This phenomenon is presumably originated within the central nervous system by synaptic input from Ia afferents to motoneurons and is consistent with the development of plateau potentials. The first objective of this work was to investigate if vibration (sinusoidal or random applied to the Achilles tendon is also able to generate large magnitude extra torques in the triceps surae muscle group. The second objective was to verify if the extra torques that were found were accompanied by increases in motoneuron excitability. Methods Subjects (n = 6 were seated on a chair and the right foot was strapped to a pedal attached to a torque meter. The isometric ankle torque was measured in response to different patterns of coupled electrical (20-Hz, rectangular 1-ms pulses and mechanical stimuli (either 100-Hz sinusoid or gaussian white noise applied to the triceps surae muscle group. In an additional investigation, Mmax and F-waves were elicited at different times before or after the vibratory stimulation. Results The vibratory bursts could generate substantial self-sustained extra torques, either with or without the background 20-Hz electrical stimulation applied simultaneously with the vibration. The extra torque generation was accompanied by increased motoneuron excitability, since an increase in the peak-to-peak amplitude of soleus F waves was observed. The delivery of electrical stimulation following the vibration was essential to keep the maintained extra torques and increased F-waves. Conclusions These results show that vibratory stimuli applied with a background electrical stimulation generate considerable force levels (up to about 50% MVC due to the spinal recruitment of motoneurons. The association of vibration and electrical

  10. AMP-activated protein kinase in contraction regulation of skeletal muscle metabolism: necessary and/or sufficient?

    DEFF Research Database (Denmark)

    Jensen, Thomas Elbenhardt; Wojtaszewski, Jørgen; Richter, Erik

    2009-01-01

    . These include glucose uptake, glycogen synthesis, post-exercise insulin sensitivity, fatty acid (FA) uptake, intramuscular triacylglyceride hydrolysis, FA oxidation, suppression of protein synthesis, proteolysis, autophagy and transcriptional regulation of genes relevant to promoting an oxidative phenotype.......In skeletal muscle, the contraction-activated heterotrimeric 5'-AMP-activated protein kinase (AMPK) protein is proposed to regulate the balance between anabolic and catabolic processes by increasing substrate uptake and turnover in addition to regulating the transcription of proteins involved...

  11. 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

  12. 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

  13. Rem uncouples excitation–contraction coupling in adult skeletal muscle fibers

    Science.gov (United States)

    Beqollari, Donald; Romberg, Christin F.; Filipova, Dilyana; Meza, Ulises; Papadopoulos, Symeon

    2015-01-01

    In skeletal muscle, excitation–contraction (EC) coupling requires depolarization-induced conformational rearrangements in L-type Ca2+ channel (CaV1.1) to be communicated to the type 1 ryanodine-sensitive Ca2+ release channel (RYR1) of the sarcoplasmic reticulum (SR) via transient protein–protein interactions. Although the molecular mechanism that underlies conformational coupling between CaV1.1 and RYR1 has been investigated intensely for more than 25 years, the question of whether such signaling occurs via a direct interaction between the principal, voltage-sensing α1S subunit of CaV1.1 and RYR1 or through an intermediary protein persists. A substantial body of evidence supports the idea that the auxiliary β1a subunit of CaV1.1 is a conduit for this intermolecular communication. However, a direct role for β1a has been difficult to test because β1a serves two other functions that are prerequisite for conformational coupling between CaV1.1 and RYR1. Specifically, β1a promotes efficient membrane expression of CaV1.1 and facilitates the tetradic ultrastructural arrangement of CaV1.1 channels within plasma membrane–SR junctions. In this paper, we demonstrate that overexpression of the RGK protein Rem, an established β subunit–interacting protein, in adult mouse flexor digitorum brevis fibers markedly reduces voltage-induced myoplasmic Ca2+ transients without greatly affecting CaV1.1 targeting, intramembrane gating charge movement, or releasable SR Ca2+ store content. In contrast, a β1a-binding–deficient Rem triple mutant (R200A/L227A/H229A) has little effect on myoplasmic Ca2+ release in response to membrane depolarization. Thus, Rem effectively uncouples the voltage sensors of CaV1.1 from RYR1-mediated SR Ca2+ release via its ability to interact with β1a. Our findings reveal Rem-expressing adult muscle as an experimental system that may prove useful in the definition of the precise role of the β1a subunit in skeletal-type EC coupling. PMID:26078055

  14. Rem uncouples excitation-contraction coupling in adult skeletal muscle fibers.

    Science.gov (United States)

    Beqollari, Donald; Romberg, Christin F; Filipova, Dilyana; Meza, Ulises; Papadopoulos, Symeon; Bannister, Roger A

    2015-07-01

    In skeletal muscle, excitation-contraction (EC) coupling requires depolarization-induced conformational rearrangements in L-type Ca(2+) channel (Ca(V)1.1) to be communicated to the type 1 ryanodine-sensitive Ca(2+) release channel (RYR1) of the sarcoplasmic reticulum (SR) via transient protein-protein interactions. Although the molecular mechanism that underlies conformational coupling between Ca(V)1.1 and RYR1 has been investigated intensely for more than 25 years, the question of whether such signaling occurs via a direct interaction between the principal, voltage-sensing α(1S) subunit of Ca(V)1.1 and RYR1 or through an intermediary protein persists. A substantial body of evidence supports the idea that the auxiliary β(1a) subunit of Ca(V)1.1 is a conduit for this intermolecular communication. However, a direct role for β(1a) has been difficult to test because β(1a) serves two other functions that are prerequisite for conformational coupling between Ca(V)1.1 and RYR1. Specifically, β(1a) promotes efficient membrane expression of Ca(V)1.1 and facilitates the tetradic ultrastructural arrangement of Ca(V)1.1 channels within plasma membrane-SR junctions. In this paper, we demonstrate that overexpression of the RGK protein Rem, an established β subunit-interacting protein, in adult mouse flexor digitorum brevis fibers markedly reduces voltage-induced myoplasmic Ca(2+) transients without greatly affecting Ca(V)1.1 targeting, intramembrane gating charge movement, or releasable SR Ca(2+) store content. In contrast, a β(1a)-binding-deficient Rem triple mutant (R200A/L227A/H229A) has little effect on myoplasmic Ca(2+) release in response to membrane depolarization. Thus, Rem effectively uncouples the voltage sensors of Ca(V)1.1 from RYR1-mediated SR Ca(2+) release via its ability to interact with β(1a). Our findings reveal Rem-expressing adult muscle as an experimental system that may prove useful in the definition of the precise role of the β(1a) subunit in

  15. Involvement of sarcoplasmic reticulum 'Ca2+ release channels' in excitation-contraction coupling in vertebrate skeletal muscle.

    Science.gov (United States)

    Brunder, D G; Györke, S; Dettbarn, C; Palade, P

    1992-01-01

    1. Pharmacological blockers of calcium-induced calcium release from isolated skeletal sarcoplasmic reticulum (SR) vesicles have been introduced into frog skeletal muscle fibres to determine their effects on excitation-contraction coupling. 2. Among the blockers tested, Ruthenium Red, neomycin, gentamicin and 9-aminoacridine inhibited the SR Ca2+ release associated with excitation-contraction (E-C) coupling as much as they inhibited caffeine potentiation of that release. Protamine, certain of its derivatives, and spermine were ineffective in both in situ tests. 3. Alternative sites of polyamine action on the contractile proteins, SR Ca2+ uptake or charge movements were ruled out. 4. All polyamines tested required considerably higher concentrations to inhibit excitation-contraction coupling than to block Ca2+ release from isolated SR vesicles. 5. The quantitative pharmacological difference in sensitivity between isolated and intact systems serves as a reminder that results on isolated systems cannot generally be used to predict results of the same substances on more physiological systems. 6. Since caffeine is known to open the SR 'Ca2+ release channels' (the ryanodine receptors that mediate Ca(2+)-induced Ca2+ release), the equal effectiveness of these blockers at inhibiting excitation-contraction (E-C) coupling and its potentiation by caffeine suggests that the SR 'Ca2+ release channels' are indeed involved in excitation-concentration coupling in skeletal muscle, although the results do not indicate how the channel is gated open during E-C coupling. PMID:1380087

  16. Ca2+ oscillations, Ca2+ sensitization, and contraction activated by protein kinase C in small airway smooth muscle.

    Science.gov (United States)

    Mukherjee, Seema; Trice, Jacquelyn; Shinde, Paurvi; Willis, Ray E; Pressley, Thomas A; Perez-Zoghbi, Jose F

    2013-02-01

    Protein kinase C (PKC) has been implicated in the regulation of smooth muscle cell (SMC) contraction and may contribute to airway hyperresponsiveness. Here, we combined optical and biochemical analyses of mouse lung slices to determine the effects of PKC activation on Ca(2+) signaling, Ca(2+) sensitivity, protein phosphorylation, and contraction in SMCs of small intrapulmonary airways. We found that 10 µM phorbol-12-myristate-13-acetate or 1 µM phorbol 12,13-dibutyrate induced repetitive, unsynchronized, and transient contractions of the SMCs lining the airway lumen. These contractions were associated with low frequency Ca(2+) oscillations in airway SMCs that resulted from Ca(2+) influx through L-type voltage-gated Ca(2+) channels and the subsequent release of Ca(2+) from intracellular stores through ryanodine receptors. Phorbol ester stimulation of lung slices in which SMC intracellular Ca(2+) concentration ([Ca(2+)](i)) was "clamped" at a high concentration induced strong airway contraction, indicating that PKC mediated sensitization of the contractile response to [Ca(2+)](i). This Ca(2+) sensitization was accompanied by phosphorylation of both the PKC-potentiated PP1 inhibitory protein of 17 kD (CPI-17) and the regulatory myosin light chain. Thrombin, like the phorbol esters, induced a strong Ca(2+) sensitization that was inhibited by the PKC inhibitor GF-109203X and also potentiated airway contraction to membrane depolarization with KCl. In conclusion, we suggest that PKC activation in small airways leads to both the generation of Ca(2+) oscillations and strong Ca(2+) sensitization; agents associated with airway inflammation, such as thrombin, may activate this pathway to sensitize airway smooth muscle to agonists that cause membrane depolarization and Ca(2+) entry and induce airway hyperresponsiveness.

  17. Concentration-dependent effects of tetracaine on excitation-contraction coupling in frog skeletal muscle fibres.

    Science.gov (United States)

    Sárközi, S; Szentesi, P; Cseri, J; Kovács, L; Csernoch, L

    1996-12-01

    The effects of low (10-100 microM) concentrations of tetracaine on intermembrane charge movement and on the rate of calcium release (Rrel) from the sarcoplasmic reticulum (SR) were studied in cut skeletal muscle fibres of the frog using the voltage clamp technique. The fibres were mounted in a single or double vaseline gap chamber to study the events near the contraction threshold or in a wide membrane potential range. Although the 'hump' component of charge movement (Q gamma) was suppressed to some extent, the voltage dependence and the parameters of the Boltzmann distribution were not modified significantly at tetracaine concentrations below 50 microM. At 50 and 100 microM of tetracaine the midpoint voltage of the Boltzmann distribution was shifted to higher membrane potentials and the steepness was decreased. The total available charge remained the same at all concentrations tested. Using fura-2 to measure calcium transients at 100 microM tetracaine the threshold for calcium release was found to be significantly shifted to more positive membrane potentials. Tetracaine reversibly suppressed both the early inactivating peak and the steady-level of Rrel but the concentration dependence of the effects was markedly different. The inactivation component of calcium release was decreased with a Hill coefficient of approximately 1 and half effective concentration of 11.8 microM while the steady-level was decreased with a Hill coefficient of greater than 2 and a half effective concentration of 47.0 microM. These results favour two sites of action where tetracaine would suppress the calcium release from the SR.

  18. The effect of in vivo rotator cuff muscle contraction on glenohumeral joint translation: An ultrasonographic and electromyographic study.

    Science.gov (United States)

    Rathi, Sangeeta; Taylor, Nicholas F; Green, Rodney A

    2016-12-08

    The proposed stabilizing mechanism of rotator cuff muscles is to limit excessive humeral head translation. However, an accurate measurement of glenohumeral joint translation in vivo has been challenging. We aimed to measure the effect of rotator cuff muscle contraction on glenohumeral joint translation using real time ultrasound (RTUS) and electromyography. Twenty healthy adults with no history of shoulder pathology were recruited. Six intramuscular electrodes were inserted in the rotator cuff muscles (supraspinatus, upper and lower infraspinatus, teres minor, upper and lower subscapularis). Anterior and posterior glenohumeral translations were measured in testing conditions (with and without translation force, with and without isometric internal and external rotation), in two positions (shoulder neutral, abduction) and views (anterior, posterior). There was reduced glenohumeral translation with rotator cuff muscle contraction in the neutral anterior (F 2,38 =17.8, pmuscles in response to anterior and posterior translation forces (pmuscles, infraspinatus and teres minor, appeared to tether anterior translation of the humeral head. Our results confirm that the rotator cuff functions as a stabilizer of the glenohumeral joint by limiting humeral head translation and this is likely to be in a direction-specific manner. Copyright © 2016 Elsevier Ltd. All rights reserved.

  19. Effectiveness of adding voluntary pelvic floor muscle contraction to a Pilates exercise program: an assessor-masked randomized controlled trial.

    Science.gov (United States)

    Torelli, Luiza; de Jarmy Di Bella, Zsuzsanna Ilona Katalin; Rodrigues, Claudinei Alves; Stüpp, Liliana; Girão, Manoel João Batista Castello; Sartori, Marair Gracio Ferreira

    2016-11-01

    The purpose of this study was to evaluate the effectiveness of adding voluntary pelvic floor muscle contraction (PFMC) to a Pilates exercise program in sedentary nulliparous women. Fifty-seven healthy nulliparous and physically inactive women were randomized to a Pilates exercise program (PEP) with or without PFMC. Forty-eight women concluded this study (24 participants for each group). Each woman was evaluated before and after the PEP, by a physiotherapist and an urogynecologist (UG). Neither of the professionals was revealed to them. This physiotherapist measured their pelvic floor muscle strength by using both a perineometer (Peritron) and vaginal palpation (Oxford Scale). The UG, who performed 3D perineal ultrasound examinations, collected their data and evaluated the results for pubovisceral muscle thickness and the levator hiatus area (LA). Both professionals were blinded to the group allocation. The protocol for both groups consisted of 24 bi-weekly 1-h individual sessions of Pilates exercises, developed by another physiotherapist who specializes in PFM rehabilitation and the Pilates technique. The PEP+ PFMC group showed significantly greater strength improvements than the PEP group when comparing the Oxford scale, vaginal pressure and pubovisceral muscle thickness during contraction measurements at baseline and post-treatment. Our findings suggest that adding a voluntary PFMC to a Pilates exercise program is more effective than Pilates alone in improving PFM strength in sedentary nulliparous women.

  20. Exercise training improves blood flow to contracting skeletal muscle of older men via enhanced cGMP signaling

    DEFF Research Database (Denmark)

    Piil, Peter Bergmann; Smith Jørgensen, Tue; Egelund, Jon

    2018-01-01

    -induced adaptations in the regulation of skeletal muscle blood flow and oxidative metabolism during exercise in aging humans. We measured leg hemodynamics and oxidative metabolism during exercise engaging the knee-extensor muscles in young (n=15, 25 ± 1 years) and older (n=15, 72 ± 1 years) subjects before and after...... a period of aerobic high-intensity exercise training. To determine the role of cGMP signaling, pharmacological inhibition of phosphodiesterase 5 (PDE5) was performed. Before training, inhibition of PDE5 increased (Polder...... group; however, these effects of PDE5 inhibition were not detected after training. These findings suggest a role for enhanced cGMP signaling in the training-induced improvement of regulation of blood flow in contracting skeletal muscle of older men....

  1. Decrease in intramuscular lipid droplets and translocation of HSL in response to muscle contraction and epinephrine

    DEFF Research Database (Denmark)

    Prats, Clara; Donsmark, Morten; Qvortrup, Klaus

    2006-01-01

    A better understanding of skeletal muscle lipid metabolism is needed to identify the molecular mechanisms relating intramuscular triglyceride (IMTG) to muscle metabolism and insulin sensitivity. An increasing number of proteins have been reported to be associated with intracellular triglyceride (...

  2. A comparative study of embedded and anesthetized zebrafish in vivo on myocardiac calcium oscillation and heart muscle contraction

    Directory of Open Access Journals (Sweden)

    Brian eMuntean

    2010-12-01

    Full Text Available The zebrafish (Danio rerio has been used as a model for studying vertebrate development in the cardiovascular system. In order to monitor heart contraction and cytosolic calcium oscillations, fish were either embedded in methylcellulose or anesthetized with tricaine. Using high-resolution differential interference contrast (DIC and calcium imaging microscopy, we here show that dopamine and verapamil alter calcium signaling and muscle contraction in anesthetized zebrafish, but not in embedded zebrafish. In anesthetized fish, dopamine increases the amplitude of cytosolic calcium oscillation with a subsequent increase in heart contraction, whereas verapamil decreases the frequency of calcium oscillation and heart rate. Interestingly, verapamil also increases myocardial contraction. Our data further indicate that verapamil can increase myocardial calcium sensitivity in anesthetized fish. Taken together, our data reinforce in vivo cardiac responses to dopamine and verapamil. Furthermore, effects of dopamine and verapamil on myocardial calcium and contraction are greater in anesthetized than embedded fish. We suggest that while the zebrafish is an excellent model for a cardiovascular imaging study, the cardio-pharmacological profiles are very different between anesthetized and embedded fish.

  3. A Comparative Study of Embedded and Anesthetized Zebrafish in vivo on Myocardiac Calcium Oscillation and Heart Muscle Contraction.

    Science.gov (United States)

    Muntean, Brian S; Horvat, Christine M; Behler, James H; Aboualaiwi, Wissam A; Nauli, Andromeda M; Williams, Frederick E; Nauli, Surya M

    2010-01-01

    The zebrafish (Danio rerio) has been used as a model for studying vertebrate development in the cardiovascular system. In order to monitor heart contraction and cytosolic calcium oscillations, fish were either embedded in methylcellulose or anesthetized with tricaine. Using high-resolution differential interference contrast and calcium imaging microscopy, we here show that dopamine and verapamil alter calcium signaling and muscle contraction in anesthetized zebrafish, but not in embedded zebrafish. In anesthetized fish, dopamine increases the amplitude of cytosolic calcium oscillation with a subsequent increase in heart contraction, whereas verapamil decreases the frequency of calcium oscillation and heart rate. Interestingly, verapamil also increases myocardial contraction. Our data further indicate that verapamil can increase myocardial calcium sensitivity in anesthetized fish. Taken together, our data reinforce in vivo cardiac responses to dopamine and verapamil. Furthermore, effects of dopamine and verapamil on myocardial calcium and contraction are greater in anesthetized than embedded fish. We suggest that while the zebrafish is an excellent model for a cardiovascular imaging study, the cardio-pharmacological profiles are very different between anesthetized and embedded fish.

  4. Contraction-stimulated glucose transport in muscle is controlled by AMPK and mechanical stress but not sarcoplasmatic reticulum Ca2+ release

    Directory of Open Access Journals (Sweden)

    Thomas E. Jensen

    2014-10-01

    Full Text Available Understanding how muscle contraction orchestrates insulin-independent muscle glucose transport may enable development of hyperglycemia-treating drugs. The prevailing concept implicates Ca2+ as a key feed forward regulator of glucose transport with secondary fine-tuning by metabolic feedback signals through proteins such as AMPK. Here, we demonstrate in incubated mouse muscle that Ca2+ release is neither sufficient nor strictly necessary to increase glucose transport. Rather, the glucose transport response is associated with metabolic feedback signals through AMPK, and mechanical stress-activated signals. Furthermore, artificial stimulation of AMPK combined with passive stretch of muscle is additive and sufficient to elicit the full contraction glucose transport response. These results suggest that ATP-turnover and mechanical stress feedback are sufficient to fully increase glucose transport during muscle contraction, and call for a major reconsideration of the established Ca2+ centric paradigm.

  5. [Effect of arotinolol on the incomplete tetanic contractions of the cat soleus muscle--relation to its anti-tremorgenic action].

    Science.gov (United States)

    Hara, Y; Sugimoto, S; Ono, H

    1993-08-01

    The effect of arotinolol on the incomplete tetanic contractions of the cat soleus muscle was studied. Isoproterenol and epinephrine injected intravenously decreased the tension and degree of fusion of incomplete tetanic contractions of the soleus muscle in anesthetized cats. Intravenous arotinolol (> 3 micrograms/kg), propranolol (> 30 micrograms/kg) and pindolol (> 3 micrograms/kg) blocked the effects of isoproterenol and epinephrine, but atenolol (-300 micrograms/kg), prazosin (0.1-10 micrograms/kg) and phentolamine (10, 30 micrograms/kg) did not block them. These results indicate that the receptors involved can be classified as of the beta 2-type. It is proposed that arotinolol may inhibit beta 2-adrenoceptors in the extrafusal muscle fibers of slow muscle, and thereby reduces the amplitude of tremor by changing the incomplete tetanic contractions of the muscle to the complete ones.

  6. 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.

  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. Energy conservation attenuates the loss of skeletal muscle excitability during intense contractions

    DEFF Research Database (Denmark)

    Macdonald, W A; Ørtenblad, N; Nielsen, Ole Bækgaard

    2007-01-01

    changes in muscle metabolites. However, the role of metabolites in the loss of muscle excitability is not clear. The metabolic state of isolated rat extensor digitorum longus muscles at 30 degrees C was manipulated by decreasing energy expenditure and thereby allowed investigation of the effects of energy...... conservation on skeletal muscle excitability. Muscle ATP utilization was reduced using a combination of the cross-bridge cycling blocker N-benzyl-p-toluene sulfonamide (BTS) and the SR Ca2+ release channel blocker Na-dantrolene, which reduce activity of the myosin ATPase and SR Ca2+-ATPase. Compared...

  10. 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...

  11. Effect of antioxidants on airway smooth muscle contraction: action of lipoic acid and some of its novel derivatives on guinea pig tracheal smooth muscle.

    Science.gov (United States)

    Assem, E S K; Mann, S; Wan, B Y C; Marson, C M

    2010-03-01

    The aim of this study was to investigate the ability of (a) antioxidants, some related to alpha-lipoic acid (LA), (b) histone deacetylase (HDAC) inhibitors, and (c) hybrid compounds possessing both alpha-lipoic acid-derived antioxidant properties and HDAC inhibitory activity to inhibit guinea pig smooth muscle contraction. Guinea pig isolated tracheal rings (GPTR) were prepared and their isometric tension measured using a transducer. Histamine, carbachol and 5-hydroxytryptamine (5-HT) served as agonists. Tests with antigen (ovalbumin) used GPTR from sensitised guinea pigs or rings from non-sensitised animals that had been incubated for at least 2 h with diluted serum from sensitised animals. All antioxidants tested showed a relaxant effect on resting tension and on tension induced by histamine or carbachol, with EC(50)(s) of 0.2-5.0 mM and a rank order of potency: LA derivatives > glutathione (GSH) > ascorbic acid (AA). However, low concentrations (MGCD0103 inhibited mast cell activation and GPTR contraction produced by antigen and certain agonists, although a 2-6 h pre-incubation was required for those effects to be apparent. Two LA-benzamide HDAC hybrid compounds, UCL M084 and UCL M109 inhibited GPTR contraction after 30 min pre-incubation; however, even after long pre-incubation (up to 6 h) those hybrid compounds showed less potent inhibition of agonist-induced contraction than did MGCD0103. The results showed that GSH more potently inhibited contraction induced by histamine than that induced by 5-HT or carbachol, whereas LA, and especially UCL M084 and UCL M109, more potently blocked contraction induced by carbachol and 5-HT than that induced by histamine. For GSH, and possibly also for LA-type compounds, the inhibition of agonist-induced tracheal smooth muscle contractions may be due to NO formation. This study did not detect a synergistic relaxant effect in two compounds incorporating the structural union of a benzamide HDAC inhibitor terminus with a LA

  12. External Ca2+-dependent excitation–contraction coupling in a population of ageing mouse skeletal muscle fibres

    Science.gov (United States)

    Payne, Anthony Michael; Zheng, Zhenlin; González, Estela; Wang, Zhong-Min; Messi, María Laura; Delbono, Osvaldo

    2004-01-01

    In the present work, we investigate whether changes in excitation–contraction (EC) coupling mode occur in skeletal muscles from ageing mammals by examining the dependence of EC coupling on extracellular Ca2+. Single intact muscle fibres from flexor digitorum brevis muscles from young (2–6 months) and old (23–30 months) mice were subjected to tetanic contractile protocols in the presence and absence of external Ca2+. Contractile experiments in the absence of external Ca2+ show that about half of muscle fibres from old mice are dependent upon external Ca2+ for maintaining maximal tetanic force output, while young fibres are not. Decreased force in the absence of external Ca2+ was not due to changes in charge movement as revealed by whole-cell patch-clamp experiments. Ca2+ transients, measured by fluo-4 fluorescence, declined in voltage-clamped fibres from old mice in the absence of external Ca2+. Similarly, Ca2+ transients declined in parallel with tetanic contractile force in single intact fibres. Examination of inward Ca2+ current and of mRNA and protein assays suggest that these changes in EC coupling mode are not due to shifts in dihydropyridine receptor (DHPR) and/or ryanodine receptor (RyR) isoforms. These results indicate that a change in EC coupling mode occurs in a population of fibres in ageing skeletal muscle, and is responsible for the age-related dependence on extracellular Ca2+. PMID:15297570

  13. External Ca(2+)-dependent excitation--contraction coupling in a population of ageing mouse skeletal muscle fibres.

    Science.gov (United States)

    Payne, Anthony Michael; Zheng, Zhenlin; González, Estela; Wang, Zhong-Min; Messi, María Laura; Delbono, Osvaldo

    2004-10-01

    In the present work, we investigate whether changes in excitation-contraction (EC) coupling mode occur in skeletal muscles from ageing mammals by examining the dependence of EC coupling on extracellular Ca(2+). Single intact muscle fibres from flexor digitorum brevis muscles from young (2-6 months) and old (23-30 months) mice were subjected to tetanic contractile protocols in the presence and absence of external Ca(2+). Contractile experiments in the absence of external Ca(2+) show that about half of muscle fibres from old mice are dependent upon external Ca(2+) for maintaining maximal tetanic force output, while young fibres are not. Decreased force in the absence of external Ca(2+) was not due to changes in charge movement as revealed by whole-cell patch-clamp experiments. Ca(2+) transients, measured by fluo-4 fluorescence, declined in voltage-clamped fibres from old mice in the absence of external Ca(2+). Similarly, Ca(2+) transients declined in parallel with tetanic contractile force in single intact fibres. Examination of inward Ca(2+) current and of mRNA and protein assays suggest that these changes in EC coupling mode are not due to shifts in dihydropyridine receptor (DHPR) and/or ryanodine receptor (RyR) isoforms. These results indicate that a change in EC coupling mode occurs in a population of fibres in ageing skeletal muscle, and is responsible for the age-related dependence on extracellular Ca(2+).

  14. Anaesthetic tricaine acts preferentially on neural voltage-gated sodium channels and fails to block directly evoked muscle contraction.

    Directory of Open Access Journals (Sweden)

    Seetharamaiah Attili

    Full Text Available Movements in animals arise through concerted action of neurons and skeletal muscle. General anaesthetics prevent movement and cause loss of consciousness by blocking neural function. Anaesthetics of the amino amide-class are thought to act by blockade of voltage-gated sodium channels. In fish, the commonly used anaesthetic tricaine methanesulphonate, also known as 3-aminobenzoic acid ethyl ester, metacaine or MS-222, causes loss of consciousness. However, its role in blocking action potentials in distinct excitable cells is unclear, raising the possibility that tricaine could act as a neuromuscular blocking agent directly causing paralysis. Here we use evoked electrical stimulation to show that tricaine efficiently blocks neural action potentials, but does not prevent directly evoked muscle contraction. Nifedipine-sensitive L-type Cav channels affecting movement are also primarily neural, suggesting that muscle Nav channels are relatively insensitive to tricaine. These findings show that tricaine used at standard concentrations in zebrafish larvae does not paralyse muscle, thereby diminishing concern that a direct action on muscle could mask a lack of general anaesthesia.

  15. Invertebrate muscles: thin and thick filament structure; molecular basis of contraction and its regulation, catch and asynchronous muscle.

    Science.gov (United States)

    Hooper, Scott L; Hobbs, Kevin H; Thuma, Jeffrey B

    2008-10-01

    This is the second in a series of canonical reviews on invertebrate muscle. We cover here thin and thick filament structure, the molecular basis of force generation and its regulation, and two special properties of some invertebrate muscle, catch and asynchronous muscle. Invertebrate thin filaments resemble vertebrate thin filaments, although helix structure and tropomyosin arrangement show small differences. Invertebrate thick filaments, alternatively, are very different from vertebrate striated thick filaments and show great variation within invertebrates. Part of this diversity stems from variation in paramyosin content, which is greatly increased in very large diameter invertebrate thick filaments. Other of it arises from relatively small changes in filament backbone structure, which results in filaments with grossly similar myosin head placements (rotating crowns of heads every 14.5 nm) but large changes in detail (distances between heads in azimuthal registration varying from three to thousands of crowns). The lever arm basis of force generation is common to both vertebrates and invertebrates, and in some invertebrates this process is understood on the near atomic level. Invertebrate actomyosin is both thin (tropomyosin:troponin) and thick (primarily via direct Ca(++) binding to myosin) filament regulated, and most invertebrate muscles are dually regulated. These mechanisms are well understood on the molecular level, but the behavioral utility of dual regulation is less so. The phosphorylation state of the thick filament associated giant protein, twitchin, has been recently shown to be the molecular basis of catch. The molecular basis of the stretch activation underlying asynchronous muscle activity, however, remains unresolved.

  16. Fatigue and contraction of slow and fast muscles in hypokinetic/hypodynamic rats

    Science.gov (United States)

    Fell, R. D.; Gladden, L. B.; Steffen, J. M.; Musacchia, X. J.

    1985-01-01

    The effects of hypokinesia/hypodynamia (H/H) on the fatigability and contractile properties of the rat soleus (S) and gastrocnemius (G) muscles have been investigated experimentally. Whole body suspension for one week was used to induce H/H, and fatigue was brought on by train stimulation for periods of 45 and 16 minutes. Following stimulation, rapid rates of fatigue were observed in the G-muscles of the suspended rats, while minimal fatigue was observed in the S-muscles. The twitch and tetanic contractile properties of the muscles were measured before and after train stimulation. It is found that H/H suspension increased twitch tension in the G-muscles, but did not change any contractile properties in the S-muscles. The peak twitch, train, tetanic tensions and time to peak were unchanged in the S-muscles of the suspended rats. On the basis of the experimental results, it is concluded that 1 wk of muscle atropy induced by H/H significantly increases fatigability in G-muscles, but does not affect the contractile properties of fast-twitch and slow-twitch muscles.

  17. Two inhibitors of store operated Ca2+ entry suppress excitation contraction coupling in frog skeletal muscle.

    Science.gov (United States)

    Olivera, J Fernando; Fernando Olivera, J; Pizarro, Gonzalo

    2010-08-01

    Two drugs, 2-APB and SKF-96365, commonly used to block Store Operated Ca(2+) Entry (SOCE) were found to have inhibitory effects at different levels of the Excitation Contraction Coupling (ECC) process in frog skeletal muscle fibers. Treatment with either drug suppressed Ca(2+) release from the Sarcoplasmic Reticulum, but this effect was not due to inhibition of SOCE as it occurred in Ca(2+)-free conditions. 2-APB applied extracellularly at 100 microM, the usual concentration to suppress SOCE, reversibly reduced the charge movement elicited by pulses in the range between -45 and -35 mV from 7.99 +/- 0.73 nC/microF (N = 17) before drug application to 6.27 +/- 0.68 nC/microF in the presence of 2-APB. This effect was mostly on the delayed Q(gamma) component. In fibers treated with the SERCA ATPase inhibitor CPA the Q(gamma) component disappeared, under this condition the application of 2-APB did not suppress the remaining charge movement. Thus the effect of 2-APB on charge movement currents seemed to be secondary to the suppression of Ca(2+) release, likely occurring directly on the release channels. No significant suppression of ECC was observed for concentration below 20 muM. 2-APB also inhibited the L-type Ca(2+) current (20 +/- 4%, N = 8). On the other hand SKF-96365 had a direct effect on the voltage sensor promoting its voltage dependent inactivation. Applied at 20 muM, a typical concentration used for inhibiting SOCE, to fibers held at -80 mV inhibited the charge moved in response to pulses ranging -45 to -30 mV from 7.95 +/- 2.59 nC/microF to 3.48 +/- 0.9 nC/microF (N = 12). A parallel reduction of Ca(2+) release was observed. Wash out was drastically increased by hyperpolarization of the holding potential to -100 mV. SKF-96365 also inhibited the L-type Ca(2+) current (41 +/- 8%, N = 4) and increased its rate of inactivation.

  18. Effects of membrane cholesterol manipulation on excitation-contraction coupling in skeletal muscle of the toad.

    Science.gov (United States)

    Launikonis, B S; Stephenson, D G

    2001-07-01

    1. Single mechanically skinned fibres and intact bundles of fibres from the twitch region of the iliofibularis muscle of cane toads were used to investigate the effects of membrane cholesterol manipulation on excitation-contraction (E-C) coupling. The cholesterol content of membranes was manipulated with methyl-beta-cyclodextrin (MbetaCD). 2. In mechanically skinned fibres, depletion of membrane cholesterol with MbetaCD caused a dose- and time-dependent decrease in transverse tubular (t)-system depolarization-induced force responses (TSDIFRs). TSDIFRs were completely abolished within 2 min in the presence of 10 mM MbetaCD but were not affected after 2 min in the presence of a 10 mM MbetaCD-1 mM cholesterol complex. There was a very steep dependence between the change in TSDIFRs and the MbetaCD : cholesterol ratio at 10 mM MbetaCD, indicating that the inhibitory effect of MbetaCD was due to membrane cholesterol depletion and not to a pharmacological effect of the agent. Tetanic responses in bundles of intact fibres were abolished after 3-4 h in the presence of 10 mM MbetaCD. 3. The duration of TSDIFRs increased markedly soon (laser scanning microscopy revealed that the integrity of the t-system was not compromised by either intra- or extracellular application of 10 mM MbetaCD and that a large [Ca(2+)] gradient was maintained across the t-system. 5. Membrane cholesterol depletion caused rapid depolarization of the polarized t-system as shown independently by spontaneous TSDIFRs induced by MbetaCD and by changes in the fluorescence intensity of an anionic potentiometric dye (DiBAC(4)(3)) in the presence of MbetaCD. This rapid depolarization of the t-system by cholesterol depletion was not prevented by blocking the Na(+) channels with TTX (10 microM) or the L-type Ca(2+) channels with Co(2+) (5 mM). 6. The results demonstrate that cholesterol is important for maintaining the functional integrity of the t-system and sarcoplasmic reticulum, probably by having specific

  19. Impact of detubulation on force and kinetics of cardiac muscle contraction.

    Science.gov (United States)

    Ferrantini, Cecilia; Coppini, Raffaele; Sacconi, Leonardo; Tosi, Benedetta; Zhang, Mei Luo; Wang, Guo Liang; de Vries, Ewout; Hoppenbrouwers, Ernst; Pavone, Francesco; Cerbai, Elisabetta; Tesi, Chiara; Poggesi, Corrado; ter Keurs, Henk E D J

    2014-06-01

    Action potential-driven Ca(2+) currents from the transverse tubules (t-tubules) trigger synchronous Ca(2+) release from the sarcoplasmic reticulum of cardiomyocytes. Loss of t-tubules has been reported in cardiac diseases, including heart failure, but the effect of uncoupling t-tubules from the sarcolemma on cardiac muscle mechanics remains largely unknown. We dissected intact rat right ventricular trabeculae and compared force, sarcomere length, and intracellular Ca(2+) in control trabeculae with trabeculae in which the t-tubules were uncoupled from the plasma membrane by formamide-induced osmotic shock (detubulation). We verified disconnection of a consistent fraction of t-tubules from the sarcolemma by two-photon fluorescence imaging of FM4-64-labeled membranes and by the absence of tubular action potential, which was recorded by random access multiphoton microscopy in combination with a voltage-sensitive dye (Di-4-AN(F)EPPTEA). Detubulation reduced the amplitude and prolonged the duration of Ca(2+) transients, leading to slower kinetics of force generation and relaxation and reduced twitch tension (1 Hz, 30°C, 1.5 mM [Ca(2+)]o). No mechanical changes were observed in rat left atrial trabeculae after formamide shock, consistent with the lack of t-tubules in rodent atrial myocytes. Detubulation diminished the rate-dependent increase of Ca(2+)-transient amplitude and twitch force. However, maximal twitch tension at high [Ca(2+)]o or in post-rest potentiated beats was unaffected, although contraction kinetics were slower. The ryanodine receptor (RyR)2 Ca-sensitizing agent caffeine (200 µM), which increases the velocity of transverse Ca(2+) release propagation in detubulated cardiomyocytes, rescued the depressed contractile force and the slower twitch kinetics of detubulated trabeculae, with negligible effects in controls. We conclude that partial loss of t-tubules leads to myocardial contractile abnormalities that can be rescued by enhancing and accelerating the

  20. 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

  1. Impairment of Excitation-Contraction Coupling in Right Ventricular Hypertrophied Muscle with Fibrosis Induced by Pulmonary Artery Banding.

    Directory of Open Access Journals (Sweden)

    Yoichiro Kusakari

    Full Text Available Interstitial myocardial fibrosis is one of the factors responsible for dysfunction of the heart. However, how interstitial fibrosis affects cardiac function and excitation-contraction coupling (E-C coupling has not yet been clarified. We developed an animal model of right ventricular (RV hypertrophy with fibrosis by pulmonary artery (PA banding in rats. Two, four, and six weeks after the PA-banding operation, the tension and intracellular Ca2+ concentration of RV papillary muscles were simultaneously measured (n = 33. The PA-banding rats were clearly divided into two groups by the presence or absence of apparent interstitial fibrosis in the papillary muscles: F+ or F- group, respectively. The papillary muscle diameter and size of myocytes were almost identical between F+ and F-, although the RV free wall weight was heavier in F+ than in F-. F+ papillary muscles exhibited higher stiffness, lower active tension, and lower Ca2+ responsiveness compared with Sham and F- papillary muscles. In addition, we found that the time to peak Ca2+ had the highest correlation coefficient to percent of fibrosis among other parameters, such as RV weight and active tension of papillary muscles. The phosphorylation level of troponin I in F+ was significantly higher than that in Sham and F-, which supports the idea of lower Ca2+ responsiveness in F+. We also found that connexin 43 in F+ was sparse and disorganized in the intercalated disk area where interstitial fibrosis strongly developed. In the present study, the RV papillary muscles obtained from the PA-banding rats enabled us to directly investigate the relationship between fibrosis and cardiac dysfunction, the impairment of E-C coupling in particular. Our results suggest that interstitial fibrosis worsens cardiac function due to 1 the decrease in Ca2+ responsiveness and 2 the asynchronous activation of each cardiac myocyte in the fibrotic preparation due to sparse cell-to-cell communication.

  2. Differences of muscle co-contraction of the ankle joint between young and elderly adults during dynamic postural control at different speeds.

    Science.gov (United States)

    Iwamoto, Yoshitaka; Takahashi, Makoto; Shinkoda, Koichi

    2017-08-02

    Agonist and antagonist muscle co-contractions during motor tasks are greater in the elderly than in young adults. During normal walking, muscle co-contraction increases with gait speed in young adults, but not in elderly adults. However, no study has compared the effects of speed on muscle co-contraction of the ankle joint during dynamic postural control in young and elderly adults. We compared muscle co-contractions of the ankle joint between young and elderly subjects during a functional stability boundary test at different speeds. Fifteen young adults and 16 community-dwelling elderly adults participated in this study. The task was functional stability boundary tests at different speeds (preferred and fast). Electromyographic evaluations of the tibialis anterior and soleus were recorded. The muscle co-contraction was evaluated using the co-contraction index (CI). There were no statistically significant differences in the postural sway parameters between the two age groups. Elderly subjects showed larger CI in both speed conditions than did the young subjects. CI was higher in the fast speed condition than in the preferred speed condition in the young subjects, but there was no difference in the elderly subjects. Moreover, after dividing the analytical range into phases (acceleration and deceleration phases), the CI was larger in the deceleration phase than in the acceleration phase in both groups, except for the young subjects in the fast speed conditions. Our results showed a greater muscle co-contraction of the ankle joint during dynamic postural control in elderly subjects than in young subjects not only in the preferred speed condition but also in the fast speed condition. In addition, the young subjects showed increased muscle co-contraction in the fast speed condition compared with that in the preferred speed condition; however, the elderly subjects showed no significant difference in muscle co-contraction between the two speed conditions. This indicates

  3. 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.

  4. Muscle Cramps

    Science.gov (United States)

    Muscle cramps are sudden, involuntary contractions or spasms in one or more of your muscles. They often occur after exercise or at night, ... to several minutes. It is a very common muscle problem. Muscle cramps can be caused by nerves ...

  5. Na+-K+ pump location and translocation during muscle contraction  in rat skeletal muscle

    DEFF Research Database (Denmark)

    Kristensen, Michael; Rasmussen, Martin Krøyer; Juel, Carsten

    2008-01-01

    the translocation. Electrical stimulation and biotin labeling of rat muscle revealed a 40% and 18% increase in the amounts of the Na+-K+ pump a2 subunit and caveolin-3 (Cav-3), respectively, in the sarcolemma. Exercise induced a 36% and 19% increase in the relative amounts of the a2 subunit and Cav-3, respectively...

  6. Rac1 and AMPK account for the majority of muscle glucose uptake stimulated by ex vivo contraction but not in vivo exercise

    DEFF Research Database (Denmark)

    Sylow, Lykke; Møller, Lisbeth Liliendal Valbjørn; Kleinert, Maximilian

    2017-01-01

    by Rac1 mKO with no additive effect of α2KD. It is concluded that Rac1 and α2AMPK together account for almost the entire ex vivo contraction-response in muscle glucose transport, while only Rac1, but not α2AMPK, regulates muscle glucose uptake during submaximal exercise in vivo....... but whether those two signaling pathways jointly account for the entire signal to glucose transport is unknown. We therefore studied the ability of contraction and exercise to stimulate glucose transport in isolated muscles with AMPK loss-of-function combined with either pharmacological inhibition or genetic...

  7. 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.

  8. The influence of temperature on muscle velocity and sustained performance in swimming carp.

    Science.gov (United States)

    Rome, L C; Funke, R P; Alexander, R M

    1990-11-01

    The aim of this study was to evaluate how fish locomote at different muscle temperatures. Sarcomere length excursion and muscle shortening velocity, V, were determined from high-speed motion pictures of carp, Cyprinus carpio (11-14 cm), swimming steadily at various sustained speeds at 10, 15 and 20 degrees C. In the middle and posterior regions of the carp, sarcomeres of the lateral red muscle underwent cyclical excursions of 0.31 microns, centered around the resting length of 2.06 microns (i.e. from 1.91 to 2.22 microns). The amplitudes of the sarcomere length excursions were essentially independent of swimming speed and temperature. As tail-beat frequency increased linearly with swimming speed regardless of temperature, the sarcomeres underwent the same length changes in a shorter time. Thus, V increased in a linear and temperature-independent manner with swimming speed. Neither temperature nor swimming speed had an influence on tail-beat amplitude or tail height. Our findings indicate that muscle fibres are used only over a narrow, temperature-independent range of V/Vmax (0.17-0.36) where power and efficiency are maximal. Carp start to recruit their white muscles at swimming speeds where the red muscle V/Vmax becomes too high (and thus power output declines). When the V/Vmax of the active muscle falls too low during steady swimming, carp switch to 'burst-and-coast' swimming, apparently to keep V/Vmax high. Because Vmax (maximum velocity of shortening) of carp red muscle has a Q10 of 1.63, the transition speeds between swimming styles are lower at lower temperatures. Thus, carp recruit their white anaerobic muscle at a lower swimming speed at lower temperatures (verified by electromyography), resulting in a lower maximum sustainable swimming speed. The present findings also indicate that, to generate the same total force and power to swim at a given speed, carp at 10 degrees C must recruit about 50% greater fibre cross-sectional area than they do at 20 degrees C.

  9. Individuals with chronic low back pain do not modulate the level of transversus abdominis muscle contraction across different postures.

    Science.gov (United States)

    Miura, Takuya; Yamanaka, Masanori; Ukishiro, Kengo; Tohyama, Harukazu; Saito, Hiroshi; Samukawa, Mina; Kobayashi, Takumi; Ino, Takumi; Takeda, Naoki

    2014-12-01

    The aim of this study was to evaluate the thickness of the transversus abdominis (TrA) muscle in three basic postures in subjects with and without chronic low back pain. Subjects were classified into a chronic low back pain group (n = 27) and a healthy control group (n = 23). The thickness of the TrA muscle was measured at rest and during the abdominal drawing-in manoeuvre (ADIM) in supine, sitting and standing postures using B-mode ultrasound imaging. Contraction ratio (TrA thickness during the ADIM/TrA thickness at rest) was calculated for each posture. At rest, the TrA thickness in the sitting and standing postures was significantly greater than in the supine posture (p postures in the low back pain group. TrA thickness was similar in the low back pain and control group in all three postures. During the ADIM, TrA thickness was significantly greater in the control group than in the chronic low back pain group in all three postures. The contraction ratio was also significantly higher in the control group than in the chronic low back pain group in all three postures. These results indicate that the automatic postural contraction of the TrA observed in the control subjects in the sitting and standing postures was not demonstrated in subjects with chronic low back pain. The present study revealed the one aspect of different response of the TrA muscle to changing posture between two groups. Copyright © 2014 Elsevier Ltd. All rights reserved.

  10. PTHrP is endogenous relaxant for spontaneous smooth muscle contraction in urinary bladder of female rat.

    Science.gov (United States)

    Nishikawa, Nobuyuki; Kanematsu, Akihiro; Negoro, Hiromitsu; Imamura, Masaaki; Sugino, Yoshio; Okinami, Takeshi; Yoshimura, Koji; Hashitani, Hikaru; Ogawa, Osamu

    2013-06-01

    Acute bladder distension causes various morphologic and functional changes, in part through altered gene expression. We aimed to investigate the physiologic role of PTHrP, which is up-regulated in an acute bladder distension model in female rats. In the control Empty group, bladders were kept empty for 6 hours, and in the Distension group, bladders were kept distended for 3 hours after an artificial storing-voiding cycle for 3 hours. In the Distention group bladder, up-regulation of transcripts was noted for 3 genes reported to be up-regulated by stretch in the cultured bladder smooth muscle cells in vitro. Further transcriptome analysis by microarray identified PTHrP as the 22nd highest gene up-regulated in Distension group bladder, among more than 27,000 genes. Localization of PTHrP and its functional receptor, PTH/PTHrP receptor 1 (PTH1R), were analyzed in the untreated rat bladders and cultured bladder cells using real-time RT-PCR and immunoblotting, which revealed that PTH1R and PTHrP were more predominantly expressed in smooth muscle than in urothelium. Exogenous PTHrP peptide (1-34) increased intracellular cAMP level in cultured bladder smooth muscle cells. In organ bath study using bladder strips, the PTHrP peptide caused a marked reduction in the amplitude of spontaneous contraction but caused only modest suppression for carbachol-induced contraction. In in vivo functional study by cystometrogram, the PTHrP peptide decreased voiding pressure and increased bladder compliance. Thus, PTHrP is a potent endogenous relaxant of bladder contraction, and autocrine or paracrine mechanism of the PTHrP-PTH1R axis is a physiologically relevant pathway functioning in the bladder.

  11. Impaired excitation-contraction coupling in muscle fibres from the dynamin2R465W mouse model of centronuclear myopathy.

    Science.gov (United States)

    Kutchukian, Candice; Szentesi, Peter; Allard, Bruno; Trochet, Delphine; Beuvin, Maud; Berthier, Christine; Tourneur, Yves; Guicheney, Pascale; Csernoch, Laszlo; Bitoun, Marc; Jacquemond, Vincent

    2017-12-15

    Dynamin 2 is a ubiquitously expressed protein involved in membrane trafficking processes. Mutations in the gene encoding dynamin 2 are responsible for a congenital myopathy associated with centrally located nuclei in the muscle fibres. Using muscle fibres from a mouse model of the most common mutation responsible for this disease in humans, we tested whether altered Ca2+ signalling and excitation-contraction coupling contribute to muscle weakness. The plasma membrane network that carries the electrical excitation is moderately perturbed in the diseased muscle fibres. The excitation-activated Ca2+ input fluxes across both the plasma membrane and the membrane of the sarcoplasmic reticulum are defective in the diseased fibres, which probably contributes to muscle weakness in patients. Mutations in the gene encoding dynamin 2 (DNM2) are responsible for autosomal dominant centronuclear myopathy (AD-CNM). We studied the functional properties of Ca2+ signalling and excitation-contraction (EC) coupling in muscle fibres isolated from a knock-in (KI) mouse model of the disease, using confocal imaging and the voltage clamp technique. The transverse-tubule network organization appeared to be unaltered in the diseased fibres, although its density was reduced by ∼10% compared to that in control fibres. The density of Ca2+ current through CaV1.1 channels and the rate of voltage-activated sarcoplasmic reticulum Ca2+ release were reduced by ∼60% and 30%, respectively, in KI vs. control fibres. In addition, Ca2+ release in the KI fibres reached its peak value 10-50 ms later than in control ones. Activation of Ca2+ transients along the longitudinal axis of the fibres was more heterogeneous in the KI than in the control fibres, with the difference being exacerbated at intermediate membrane voltages. KI fibres exhibited spontaneous Ca2+ release events that were almost absent from control fibres. Overall, the results of the present study demonstrate that Ca2+ signalling and EC

  12. Vascular Function and Regulation of Blood Flow in Resting and Contracting Skeletal Muscle

    DEFF Research Database (Denmark)

    Nyberg, Michael Permin

    The precise matching of blood flow, oxygen delivery and metabolism is essential as it ensures that any increase in muscle work is precisely matched by increases in oxygen delivery. Therefore, understanding the control mechanisms of skeletal muscle blood flow regulation is of great biological impo...

  13. Hand-Held Model of a Sarcomere to Illustrate the Sliding Filament Mechanism in Muscle Contraction

    Science.gov (United States)

    Jittivadhna, Karnyupha; Ruenwongsa, Pintip; Panijpan, Bhinyo

    2009-01-01

    From our teaching of the contractile unit of the striated muscle, we have found limitations in using textbook illustrations of sarcomere structure and its related dynamic molecular physiological details. A hand-held model of a striated muscle sarcomere made from common items has thus been made by us to enhance students' understanding of the…

  14. Supplementation with vitamins C and E inhibits the release of interleukin-6 from contracting human skeletal muscle

    DEFF Research Database (Denmark)

    Fischer, Christian P; Hiscock, Natalie J; Penkowa, Milena

    2004-01-01

    (6 h). Leg blood flow was measured using Doppler ultrasonography. Plasma IL-6 concentration was measured in blood sampled from the femoral artery and vein. The net release of IL-6 was calculated using Fick's principle. Plasma vitamin C and E concentrations were elevated in Treatment compared...... in Control, but not in Treatment. In conclusion, our results show that supplementation with vitamins C and E attenuated the systemic IL-6 response to exercise primarily via inhibition of the IL-6 protein release from the contracting skeletal muscle per se....

  15. Development of muscle fatigue as assessed by electromyography and mechanomyography during continuous and intermittent low-force contractions: effects of the feedback mode

    DEFF Research Database (Denmark)

    Madeleine, Pascal; Jørgensen, Lars Vincents; Søgaard, Karen

    2002-01-01

    The goal of the present study was to investigate the significance of low-force continuous or intermittent static contraction and feedback mode (visual or proprioceptive) on the development of muscle fatigue as assessed by electromyography (EMG) and mechanomyography (MMG). Visual (force control...... and MPF values versus time were observed with proprioceptive feedback compared with visual feedback. The findings suggest that (1) the EMG and MMG signals give complementary information about localised muscle fatigue at low-level contraction: they responded differently in terms of changes in the time...... and frequency domain during continuous contraction, while they responded in concert in the frequency domain during intermittent contractions, and (2) the different centrally mediated motor control strategies used during fatiguing contraction may be dependent upon the feedback modality....

  16. Rac1 and AMPK Account for the Majority of Muscle Glucose Uptake Stimulated by Ex Vivo Contraction but Not In Vivo Exercise.

    Science.gov (United States)

    Sylow, Lykke; Møller, Lisbeth L V; Kleinert, Maximilian; D'Hulst, Gommaar; De Groote, Estelle; Schjerling, Peter; Steinberg, Gregory R; Jensen, Thomas E; Richter, Erik A

    2017-06-01

    Exercise bypasses insulin resistance to increase glucose uptake in skeletal muscle and therefore represents an important alternative to stimulate glucose uptake in insulin-resistant muscle. Both Rac1 and AMPK have been shown to partly regulate contraction-stimulated muscle glucose uptake, but whether those two signaling pathways jointly account for the entire signal to glucose transport is unknown. We therefore studied the ability of contraction and exercise to stimulate glucose transport in isolated muscles with AMPK loss of function combined with either pharmacological inhibition or genetic deletion of Rac1.Muscle-specific knockout (mKO) of Rac1, a kinase-dead α2 AMPK (α2KD), and double knockout (KO) of β1 and β2 AMPK subunits (β1β2 KO) each partially decreased contraction-stimulated glucose transport in mouse soleus and extensor digitorum longus (EDL) muscle. Interestingly, when pharmacological Rac1 inhibition was combined with either AMPK β1β2 KO or α2KD, contraction-stimulated glucose transport was almost completely inhibited. Importantly, α2KD+Rac1 mKO double-transgenic mice also displayed severely impaired contraction-stimulated glucose transport, whereas exercise-stimulated glucose uptake in vivo was only partially reduced by Rac1 mKO with no additive effect of α2KD. It is concluded that Rac1 and AMPK together account for almost the entire ex vivo contraction response in muscle glucose transport, whereas only Rac1, but not α2 AMPK, regulates muscle glucose uptake during submaximal exercise in vivo. © 2017 by the American Diabetes Association.

  17. 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.

  18. Increased muscle tension and reduced elasticity of affected muscles in recent-onset Graves' disease caused primarily by active muscle contraction

    NARCIS (Netherlands)

    H.J. Simonsz (Huib); G. Kommerell (Guntram)

    1989-01-01

    textabstractIn 3 patients with Graves' disease of recent onset, length-tension diagrams were made during surgery for squint under eyedrop anesthesia. The affected muscles were found to be very stiff when the other eye looked straight ahead. It was expected that these stiff muscles would be able to

  19. 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.

  20. Ultrasound Imaging of Muscle Contraction of the Tibialis Anterior in Patients with Facioscapulohumeral Dystrophy

    NARCIS (Netherlands)

    Gijsbertse, K.; Goselink, R.J.M.; Lassche, S.; Nillesen, M.M.; Sprengers, A.M.; Verdonschot, N.J.; Alfen, N. van; Korte, C.L. de

    2017-01-01

    A need exists for biomarkers to diagnose, quantify and longitudinally follow facioscapulohumeral muscular dystrophy (FSHD) and many other neuromuscular disorders. Furthermore, the pathophysiological mechanisms leading to muscle weakness in most neuromuscular disorders are not completely understood.

  1. Muscle force loss and soreness subsequent to maximal eccentric contractions depend on the amount of fascicle strain in vivo.

    Science.gov (United States)

    Guilhem, G; Doguet, V; Hauraix, H; Lacourpaille, L; Jubeau, M; Nordez, A; Dorel, S

    2016-06-01

    Defining the origins of muscle injury has important rehabilitation and exercise applications. However, current knowledge of muscle damage mechanics in human remains unclear in vivo. This study aimed to determine the relationships between muscle-tendon unit mechanics during maximal eccentric contractions and the extent of subsequent functional impairments induced by muscle damage. The length of the muscle-tendon unit, fascicles and tendinous tissues was continuously measured on the gastrocnemius medialis using ultrasonography, in time with torque, during 10 sets of 30 maximal eccentric contractions of plantar flexors at 45°s(-1) , in seventeen participants. Muscle-tendon unit, fascicles and tendinous tissues were stretched up to 4.44 ± 0.33 cm, 2.31 ± 0.64 cm and 1.92 ± 0.61 cm respectively. Fascicle stretch length, lengthening amplitude and negative fascicle work beyond slack length were significantly correlated with the force decrease 48 h post-exercise (r = 0.51, 0.47 and 0.68, respectively; P muscle fibres during eccentric contractions strongly influences the magnitude of muscle damage in vivo. Achilles tendon compliance decreases the amount of strain, while architectural gear ratio may moderately contribute to attenuating muscle fascicle lengthening and hence muscle damage. Further studies are necessary to explore the impact of various types of task to fully understand the contribution of muscle-tendon interactions during active lengthening to muscle damage. © 2016 Scandinavian Physiological Society. Published by John Wiley & Sons Ltd.

  2. Effects of isoprenaline on contractions of directly stimulated fast and slow skeletal muscles of the guinea-pig.

    Science.gov (United States)

    Tashiro, N

    1973-05-01

    1. The actions of isoprenaline on the contraction and the resting potential of the isolated extensor digitorum longus (EDL), a fast contracting muscle, and the soleus, a slow contracting muscle, of the guinea-pig were investigated. Twitch tension was elicited by direct supramaximal stimulation and recorded isometrically.2. The twitch tension of EDL elicited by pulses of 0.5-10 ms duration was increased in the presence of isoprenaline (1 mug/ml). Isoprenaline increased the twitch tension of the soleus elicited by a pulse of more than 5 ms duration, but decreased it when elicited by a pulse of less than 1 millisecond. These effects were blocked by propranolol (1-3 mug/ml) but not by phentolamine (1-5 mug/ml).3. In EDL, isoprenaline prolonged the time to peak tension and the half-relaxation time. The twitch of the soleus was shortened by isoprenaline due to an acceleration of relaxation. These findings were independent of stimulus duration.4. The potentiating effects of isoprenaline on the twitch tension of EDL and the soleus were not observed in K(+)-free Krebs solution and were abolished by ouabain (1 mug/ml) and by reduction of the temperature from 33 degrees to 18 degrees C. The effects of isoprenaline on the relaxation proces were not affected by these treatments.5. In EDL, the resting potential increased from 77.3 mV to 78.5 mV after isoprenaline, whereas in the soleus it increased from 69.1 to 74.7 mV. These effects were blocked by propranolol, K(+)-deficiency, ouabain, and cooling to 18 degrees C. Hyperpolarization by isoprenaline was increased by substitution of isethionate for the external chloride.6. There was a good correlation between the potentiation of the mechanical response and the hyperpolarization of the membrane by isoprenaline. The hyperpolarization seems to be due to activation of the Na(+)-K(+) pump.

  3. Supralaryngeal muscle activity during sustained vibrato in four sopranos: surface EMG findings.

    Science.gov (United States)

    Sapir, S; Larson, K K

    1993-09-01

    Four classically trained sopranos, aged 22-41 years, sustained a vibrato at a comfortable loudness level, and at different vowels (/u/, /i/, or /a/) and pitch levels (220, 277, 349, 440, 554, 698, or 880 Hz). Pairs of surface electrodes were placed on each singer's right side over the submandibular region, the thyroid cartilage, mandibular ramus, and upper lip to record electromyographic (EMG) activity from the anterior suprahyoid (ASH), extralaryngeal (ELAR), massetter (MAS), and perioral (PER) muscles, respectively. A headset-mounted miniature microphone transduced the voice, and a Kay Visi-Pitch extracted the voice fundamental frequency (F0). The output of the Visi-Pitch, a voltage analog of the F0 (VF0), and the EMG signals were digitized, the EMG signals rectified and smoothed, and the VF0 and smoothed EMG signals were subjected to Fast Fourier Transform (FFT) analysis. Spectral peaks in the FFT records indicated vibrato-related activity in the ASH and ELAR muscles, with occasional vibrato-related activity in the MAS and PER muscles. The role of supralaryngeal muscles in vibrato is discussed.

  4. Caloric restriction induces energy-sparing alterations in skeletal muscle contraction, fiber composition and local thyroid hormone metabolism that persist during catch-up fat upon refeeding

    Directory of Open Access Journals (Sweden)

    Paula Bresciani M. De Andrade

    2015-09-01

    Full Text Available Weight regain after caloric restriction results in accelerated fat storage in adipose tissue. This catch-up fat phenomenon is postulated to result partly from suppressed skeletal muscle thermogenesis, but the underlying mechanisms are elusive. We investigated whether the reduced rate of skeletal muscle contraction-relaxation cycle that occurs after caloric restriction persists during weight recovery and could contribute to catch-up fat. Using a rat model of semistarvation-refeeding, in which fat recovery is driven by suppressed thermogenesis, we show that contraction and relaxation of leg muscles are slower after both semistarvation and refeeding. These effects are associated with (i higher expression of muscle deiodinase type 3 (DIO3 which inactivates tri-iodothyronine (T3, and lower expression of T3-activating enzyme, deiodinase type 2 (DIO2, (ii slower net formation of T3 from its T4 precursor in muscles, and (iii accumulation of slow fibers at the expense of fast fibers. These semistarvation-induced changes persisted during recovery and correlated with impaired expression of transcription factors involved in slow-twitch muscle development.We conclude that diminished muscle thermogenesis following caloric restriction results from reduced muscle T3 levels, alteration in muscle-specific transcription factors, and fast-to-slow fiber shift causing slower contractility. Energy-sparing effects persist during weight recovery and likely contribute to catch-up fat.

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

    Science.gov (United States)

    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…

  6. Electrically Stimulated Antagonist Muscle Contraction Increased Muscle Mass and Bone Mineral Density of One Astronaut - Initial Verification on the International Space Station.

    Directory of Open Access Journals (Sweden)

    Naoto Shiba

    Full Text Available Musculoskeletal atrophy is one of the major problems of extended periods of exposure to weightlessness such as on the International Space Station (ISS. We developed the Hybrid Training System (HTS to maintain an astronaut's musculoskeletal system using an electrically stimulated antagonist to resist the volitional contraction of the agonist instead of gravity. The present study assessed the system's orbital operation capability and utility, as well as its preventative effect on an astronaut's musculoskeletal atrophy.HTS was attached to the non-dominant arm of an astronaut staying on the ISS, and his dominant arm without HTS was established as the control (CTR. 10 sets of 10 reciprocal elbow curls were one training session, and 12 total sessions of training (3 times per week for 4 weeks were performed. Pre and post flight ground based evaluations were performed by Biodex (muscle performance, MRI (muscle volume, and DXA (BMD, lean [muscle] mass, fat mass. Pre and post training inflight evaluations were performed by a hand held dynamometer (muscle force and a measuring tape (upper arm circumference.The experiment was completed on schedule, and HTS functioned well without problems. Isokinetic elbow extension torque (Nm changed -19.4% in HTS, and -21.7% in CTR. Isokinetic elbow flexion torque changed -23.7% in HTS, and there was no change in CTR. Total Work (Joule of elbow extension changed -8.3% in HTS, and +0.3% in CTR. For elbow flexion it changed -23.3% in HTS and -32.6% in CTR. Average Power (Watts of elbow extension changed +22.1% in HTS and -8.0% in CTR. For elbow flexion it changed -6.5% in HTS and -4.8% in CTR. Triceps muscle volume according to MRI changed +11.7% and that of biceps was +2.1% using HTS, however -0.1% and -0.4% respectively for CTR. BMD changed +4.6% in the HTS arm and -1.2% for CTR. Lean (muscle mass of the arm changed only +10.6% in HTS. Fat mass changed -12.6% in HTS and -6.4% in CTR.These results showed the orbital

  7. Reduced glycogen availability is associated with an elevation in HSP72 in contracting human skeletal muscle

    DEFF Research Database (Denmark)

    Febbraio, Mark A; Steensberg, Adam; Walsh, Rory

    2002-01-01

    To test the hypothesis that a decrease in intramuscular glycogen availability may stimulate heat shock protein expression, seven men depleted one leg of muscle glycogen the day before performing 4-5 h of exhaustive, two-legged knee extensor exercise at 40 % of leg peak power output. Subjects...... then rested for a further 3 h. Muscle biopsies were obtained from the depleted and control leg before, immediately after and 3 h into recovery from exercise. These samples were analysed for muscle glycogen, and HSP72 gene and protein expression. In addition, catheters were placed in one femoral artery...... glycogen content was 40 % lower in the depleted compared with the control leg and this difference was maintained throughout the experiment (P

  8. Satellite cell activity is differentially affected by contraction mode in human muscle following a work-matched bout of exercise

    Directory of Open Access Journals (Sweden)

    Robert D Hyldahl

    2014-12-01

    Full Text Available Optimal repair and adaptation of skeletal muscle is facilitated by resident stem cells (satellite cells. To understand how different exercise modes influence satellite cell dynamics, we measured satellite cell activity in conjunction with markers of muscle damage and inflammation in human skeletal muscle following a single work- and intensity-matched bout of eccentric (ECC or concentric contractions (CON. Participants completed a single bout of ECC (n=7 or CON (n=7 of the knee extensors. A muscle biopsy was obtained before and 24 h after exercise. Functional measures and immunohistochemical analyses were used to determine the extent of muscle damage and indices of satellite cell activity. Cytokine concentrations were measured using a multiplexed magnetic bead assay. Isokinetic peak torque decreased following ECC (p<0.05 but not CON. Greater histological staining of the damage marker Xin was observed in muscle samples of ECC vs CON. Tenasin C immunoreactivity increased 15 fold (P<0.01 following ECC and was unchanged following CON. The inflammatory cytokines interferon gamma-induced protein 10 (IP-10 and monocyte chemotactic protein 1 (MCP-1 increased pre- to post-ECC (4.26 ± 1.4 vs. 10.49 ± 5.8 pg/ml, and 3.06 ± 0.7 vs. 6.25 ± 4.6 pg/ml, respectively; p<0.05. There was no change in any cytokine post-CON. Satellite cell content increased 27% pre- to post-ECC (0.10 ± 0.031 vs. 0.127 ± 0.041, respectively; p<0.05. There was no change in satellite cell number in CON (0.099 ± 0.027 vs. 0.102 ± 0.029, respectively. There was no fiber type-specific satellite cell response following either exercise mode. ECC but not CON resulted in an increase in MyoD positive nuclei per myofiber pre- to post-exercise (p<0.05, but there was no change in MyoD DNA binding activity in either condition. In conclusion, ECC but not CON results in functional and histological evidence of muscle damage that is accompanied by increased satellite cell activity 24 h post-exercise.

  9. NS309 decreases rat detrusor smooth muscle membrane potential and phasic contractions by activating SK3 channels

    Science.gov (United States)

    Parajuli, Shankar P; Hristov, Kiril L; Soder, Rupal P; Kellett, Whitney F; Petkov, Georgi V

    2013-01-01

    Background and Purpose Overactive bladder (OAB) is often associated with abnormally increased detrusor smooth muscle (DSM) contractions. We used NS309, a selective and potent opener of the small or intermediate conductance Ca2+-activated K+ (SK or IK, respectively) channels, to evaluate how SK/IK channel activation modulates DSM function. Experimental Approach We employed single-cell RT-PCR, immunocytochemistry, whole cell patch-clamp in freshly isolated rat DSM cells and isometric tension recordings of isolated DSM strips to explore how the pharmacological activation of SK/IK channels with NS309 modulates DSM function. Key Results We detected SK3 but not SK1, SK2 or IK channels expression at both mRNA and protein levels by RT-PCR and immunocytochemistry in DSM single cells. NS309 (10 μM) significantly increased the whole cell SK currents and hyperpolarized DSM cell resting membrane potential. The NS309 hyperpolarizing effect was blocked by apamin, a selective SK channel inhibitor. NS309 inhibited the spontaneous phasic contraction amplitude, force, frequency, duration and tone of isolated DSM strips in a concentration-dependent manner. The inhibitory effect of NS309 on spontaneous phasic contractions was blocked by apamin but not by TRAM-34, indicating no functional role of the IK channels in rat DSM. NS309 also significantly inhibited the pharmacologically and electrical field stimulation-induced DSM contractions. Conclusions and Implications Our data reveal that SK3 channel is the main SK/IK subtype in rat DSM. Pharmacological activation of SK3 channels with NS309 decreases rat DSM cell excitability and contractility, suggesting that SK3 channels might be potential therapeutic targets to control OAB associated with detrusor overactivity. PMID:23145946

  10. Antispasmodic effects of Pycnocycla spinosa seed and aerial part extracts on rat ileum and uterus smooth muscle contractions

    Directory of Open Access Journals (Sweden)

    2008-08-01

    Full Text Available Background and the purpose of study: Hydroalcoholic extract of Pycnocycla spinosa has a relaxant effect on ileum and inhibits castor oil induced diarrhoea in mice. However, effects of P. spinosa seed extracts on ileum and uterus hasn't been investigated.  The aim of this study was to investigate effect of P. spinosa seed and extracts of the aerial part on rat ileum and uterus smooth muscle contraction. Methods: A 70% ethanol extract of seed and aerial parts of P. spinosa was prepared by a percolation method. Uterine horns or ileum were dissected from non-pregnant female Wistar rats (200-230g and cut into longitudinal strips and mounted for isotonic recording under 1g tension in Tyrode's solution. Effects of the extracts were examined on tonic contractions induced by KCl (80mM on both tissues and on phasic spasm induced by oxytocin (0.002iu/ml on the uterus. Results: The aerial part extract inhibited rat ileum contractions induced by 80mM KCl (IC50=42±3.4mg/ml in a concentration dependent manner and it also inhibited rat uterus contraction induced by 80 mM KCl. However, its inhibitory effects were observed with higher concentration of the extract (IC50=420±90mg/ml and at concentration of 1.28mg/ml of the extract in the bath the response was 19±7%.  The aerial part extract (40-640mg/ml also reduced the evoked phasic response of uterus by oxytocin (IC50=71±17.3mg/ml. The seed extract reduced the uterus response to oxytocin in a concentration-dependent manner, and inhibited tissue response completely at 160mg/ml (IC50=27±4mg/ml.  Major conclusion: From this study it was concluded that the seed extract of P. spinosa have similar inhibitory properties on rat isolated uterus and ileum contractions, while the extract of the aerial part of P. spinosa is more selective inhibitor of ileum contraction, and at higher concentrations it also inhibits uterus spasm.

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

    Science.gov (United States)

    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.

  12. 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.

  13. 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 ...

  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. Role of calcium influx through voltage-operated calcium channels and of calcium mobilization in the physiology of Schistosoma mansoni muscle contractions.

    Science.gov (United States)

    Mendonça-Silva, D L; Novozhilova, E; Cobbett, P J R; Silva, C L M; Noël, F; Totten, M I J; Maule, A G; Day, T A

    2006-07-01

    We tested the hypothesis that voltage-operated Ca2+ channels mediate an extracellular Ca2+ influx in muscle fibres from the human parasite Schistosoma mansoni and, along with Ca2+ mobilization from the sarcoplasmic reticulum, contribute to muscle contraction. Indeed, whole-cell voltage clamp revealed voltage-gated inward currents carried by divalent ions with a peak current elicited by steps to +20 mV (from a holding potential of -70 mV). Depolarization of the fibres by elevated extracellular K+ elicited contractions that were completely dependent on extracellular Ca2+ and inhibited by nicardipine (half inhibition at 4.1 microM). However these contractions were not very sensitive to other classical blockers of voltage-gated Ca2+ channels, indicating that the schistosome muscle channels have an atypical pharmacology when compared to their mammalian counterparts. Futhermore, the contraction induced by 5 mM caffeine was inhibited after depletion of the sarcoplasmic reticulum either with thapsigargin (10 microM) or ryanodine (10 microM). These data suggest that voltage-operated Ca2+ channels do contribute to S. mansoni contraction as does the mobilization of stored Ca2+, despite the small volume of sarcoplasmic reticulum in schistosome smooth muscles.

  16. AMPK alpha1 activation is required for stimulation of glucose uptake by twitch contraction, but not by H2O2, in mouse skeletal muscle

    DEFF Research Database (Denmark)

    Jensen, Thomas Elbenhardt; Schjerling, Peter; Viollet, Benoit

    2008-01-01

    , in wildtype and alpha-AMPK transgenic mouse muscles, this study aimed to define conditions where alpha(1) AMPK is required to increase muscle glucose uptake. METHODOLOGY/PRINCIPAL FINDINGS: Following stimulation with H(2)O(2) (3 mM, 20 min) or twitch-contraction (0.1 ms pulse, 2 Hz, 2 min), signaling and 2...... uptake was not reduced in any of the AMPK transgenic mouse models compared with wild type. In contrast, twitch-contraction increased the activity of alpha(1) AMPK, but not alpha(2) AMPK activity nor Akt or AS160 phosphorylation. Glucose uptake was markedly lower in alpha(1) AMPK knockout and KD AMPK...

  17. Homologous muscle contraction during unilateral movement does not show a dominant effect on leg representation of the ipsilateral primary motor cortex.

    Directory of Open Access Journals (Sweden)

    Shin-Yi Chiou

    Full Text Available Co-activation of homo- and heterotopic representations in the primary motor cortex (M1 ipsilateral to a unilateral motor task has been observed in neuroimaging studies. Further analysis showed that the ipsilateral M1 is involved in motor execution along with the contralateral M1 in humans. Additionally, transcranial magnetic stimulation (TMS studies have revealed that the size of the co-activation in the ipsilateral M1 has a muscle-dominant effect in the upper limbs, with a prominent decline of inhibition within the ipsilateral M1 occurring when a homologous muscle contracts. However, the homologous muscle-dominant effect in the ipsilateral M1 is less clear in the lower limbs. The present study investigates the response of corticospinal output and intracortical inhibition in the leg representation of the ipsilateral M1 during a unilateral motor task, with homo- or heterogeneous muscles. We assessed functional changes within the ipsilateral M1 and in corticospinal outputs associated with different contracting muscles in 15 right-handed healthy subjects. Motor tasks were performed with the right-side limb, including movements of the upper and lower limbs. TMS paradigms were measured, consisting of short-interval intracortical inhibition (SICI and recruitment curves (RCs of motor evoked potentials (MEPs in the right M1, and responses were recorded from the left rectus femoris (RF and left tibialis anterior (TA muscles. TMS results showed that significant declines in SICI and prominent increases in MEPs of the left TA and left RF during unilateral movements. Cortical activations were associated with the muscles contracting during the movements. The present data demonstrate that activation of the ipsilateral M1 on leg representation could be increased during unilateral movement. However, no homologous muscle-dominant effect was evident in the leg muscles. The results may reflect that functional coupling of bilateral leg muscles is a reciprocal

  18. Nicotinic acetylcholine receptors containing the α7-like subunit mediate contractions of muscles responsible for space positioning of the snail, Helix pomatia L. tentacle.

    Directory of Open Access Journals (Sweden)

    Tibor Kiss

    Full Text Available Three recently discovered tentacle muscles are crucial to perform patterned movements of upper tentacles of the terrestrial snail, Helix pomatia. The muscles receive central and peripheral excitatory cholinergic innervation lacking inhibitory innervation. Here, we investigate the pharmacology of acetylcholine (ACh responses in muscles to determine the properties of the ACh receptor (AChR, the functional availability of which was assessed using isotonic contraction measurement. Using broad spectrum of nicotinic and muscarinic ligands, we provide the evidence that contractions in the muscles are attributable to the activation of nAChRs that contain the α7-like subunit. Contractions could be evoked by nicotine, carbachol, succinylchloride, TMA, the selective α7-nAChR agonist choline chloride, 3-Bromocytisine and PNU-282987, and blocked by nAChR selective antagonists such as mytolon, hexamethonium, succinylchloride, d-tubocurarine, hemicholinium, DMDA (decamethonium, methyllycaconitine, α-Bungarotoxin (αBgTx and α-Conotoxin IMI. The specific muscarinic agonist oxotremorine and arecoline failed to elicit contractions. Based on these pharmacological properties we conclude that the Na+ and Ca2+ permeable AChRs of the flexor muscle are nicotinic receptors that contain the α7-like subunit. Immunodetection experiments confirmed the presence of α7- or α7-like AChRs in muscle cells, and α4-AChRs in nerves innervating the muscle. These results support the conclusion that the slowly desensitizing αBgTx-sensitive responses obtained from flexor muscles are produced by activation of α7- like AChRs. This is the first demonstration of postsynaptic expression and an obligatory role for a functional α7-like nAChR in the molluscan periphery.

  19. Novel excitation-contraction coupling related genes reveal aspects of muscle weakness beyond atrophy-new hopes for treatment of musculoskeletal diseases.

    Science.gov (United States)

    Manring, Heather; Abreu, Eduardo; Brotto, Leticia; Weisleder, Noah; Brotto, Marco

    2014-01-01

    Research over the last decade strengthened the understanding that skeletal muscles are not only the major tissue in the body from a volume point of view but also function as a master regulator contributing to optimal organismal health. These new contributions to the available body of knowledge triggered great interest in the roles of skeletal muscle beyond contraction. The World Health Organization, through its Global Burden of Disease (GBD) report, recently raised further awareness about the key importance of skeletal muscles as the GDB reported musculoskeletal (MSK) diseases have become the second greatest cause of disability, with more than 1.7 billion people in the globe affected by a diversity of MSK conditions. Besides their role in MSK disorders, skeletal muscles are also seen as principal metabolic organs with essential contributions to metabolic disorders, especially those linked to physical inactivity. In this review, we have focused on the unique function of new genes/proteins (i.e., MTMR14, MG29, sarcalumenin, KLF15) that during the last few years have helped provide novel insights about muscle function in health and disease, muscle fatigue, muscle metabolism, and muscle aging. Next, we provide an in depth discussion of how these genes/proteins converge into a common function of acting as regulators of intracellular calcium homeostasis. A clear link between dysfunctional calcium homeostasis is established and the special role of store-operated calcium entry is analyzed. The new knowledge that has been generated by the understanding of the roles of previously unknown modulatory genes of the skeletal muscle excitation-contraction coupling (ECC) process brings exciting new possibilities for treatment of MSK diseases, muscle regeneration, and skeletal muscle tissue engineering. The next decade of skeletal muscle and MSK research is bound to bring to fruition applied knowledge that will hopefully offset the current heavy and sad burden of MSK diseases on the

  20. Novel excitation-contraction coupling related genes reveal aspects of muscle weakness beyond atrophy – New hopes for treatment of musculoskeletal diseases

    Directory of Open Access Journals (Sweden)

    Heather eManring

    2014-02-01

    Full Text Available Research over the last decade strengthened the understanding that skeletal muscles are not only the major tissue in the body from a volume point of view but also function as a master regulator contributing to optimal organismal health. These new contributions to the available body of knowledge triggered great interest in the roles of skeletal muscle beyond contraction. The World Health Organization, through its Global Burden of Disease (GBD report, recently raised further awareness about the key importance of skeletal muscles as the GDB reported musculoskeletal (MSK diseases have become the second greatest cause of disability, with more than 1.7 billion people in the globe affected by a diversity of MSK conditions. Besides their role in MSK disorders, skeletal muscles are also seen as principal metabolic organs with essential contributions to metabolic disorders, especially those linked to physical inactivity. In this review, we have focused on the unique function of new genes/proteins (i.e. MTMR14, MG29, sarcalumenin, KFL15 that during the last few years have helped provide novel insights about muscle function in health and disease, muscle fatigue, muscle metabolism, and muscle aging. Next, we provide an in depth discussion of how these genes/proteins converge into a common function of acting as regulators of intracellular calcium homeostasis. A clear link between dysfunctional calcium homeostasis is established and the special role of store-operated calcium entry is analyzed. The new knowledge that has been generated by the understanding of the roles of previously unknown modulatory genes of the skeletal muscle excitation-contraction coupling (ECC process brings exciting new possibilities for treatment of MSK diseases, muscle regeneration, and skeletal muscle tissue engineering. The next decade of skeletal muscle and MSK research is bound to bring to fruition applied knowledge that will hopefully offset the current heavy and sad burden of MSK

  1. Novel excitation-contraction coupling related genes reveal aspects of muscle weakness beyond atrophy—new hopes for treatment of musculoskeletal diseases

    Science.gov (United States)

    Manring, Heather; Abreu, Eduardo; Brotto, Leticia; Weisleder, Noah; Brotto, Marco

    2013-01-01

    Research over the last decade strengthened the understanding that skeletal muscles are not only the major tissue in the body from a volume point of view but also function as a master regulator contributing to optimal organismal health. These new contributions to the available body of knowledge triggered great interest in the roles of skeletal muscle beyond contraction. The World Health Organization, through its Global Burden of Disease (GBD) report, recently raised further awareness about the key importance of skeletal muscles as the GDB reported musculoskeletal (MSK) diseases have become the second greatest cause of disability, with more than 1.7 billion people in the globe affected by a diversity of MSK conditions. Besides their role in MSK disorders, skeletal muscles are also seen as principal metabolic organs with essential contributions to metabolic disorders, especially those linked to physical inactivity. In this review, we have focused on the unique function of new genes/proteins (i.e., MTMR14, MG29, sarcalumenin, KLF15) that during the last few years have helped provide novel insights about muscle function in health and disease, muscle fatigue, muscle metabolism, and muscle aging. Next, we provide an in depth discussion of how these genes/proteins converge into a common function of acting as regulators of intracellular calcium homeostasis. A clear link between dysfunctional calcium homeostasis is established and the special role of store-operated calcium entry is analyzed. The new knowledge that has been generated by the understanding of the roles of previously unknown modulatory genes of the skeletal muscle excitation-contraction coupling (ECC) process brings exciting new possibilities for treatment of MSK diseases, muscle regeneration, and skeletal muscle tissue engineering. The next decade of skeletal muscle and MSK research is bound to bring to fruition applied knowledge that will hopefully offset the current heavy and sad burden of MSK diseases on the

  2. Effects of combined strength and sprint training on regulation of muscle contraction at the whole-muscle and single-fibre levels in elite master sprinters.

    Science.gov (United States)

    Cristea, A; Korhonen, M T; Häkkinen, K; Mero, A; Alén, M; Sipilä, S; Viitasalo, J T; Koljonen, M J; Suominen, H; Larsson, L

    2008-07-01

    This study aims at examining the effects of progressive strength and sprint training on regulation of muscle contraction at the whole-muscle and single-fibre levels in older sprint-trained athletes. Eleven men (52-78 years) were randomized to a training (EX, n = 7) or control (CTRL, n = 4) group. EX participated in a 20-week programme that combined sprint training with heavy and explosive strength exercises, while CTRL maintained their usual run-based training schedules. EX improved maximal isometric and dynamic leg strength, explosive jump performance and force production in running. Specific tension and maximum shortening velocity of single fibres from the vastus lateralis were not altered in EX or CTRL. Fibre type and myosin heavy chain isoform distributions remained unchanged in the two groups. There was a general increase in fibre areas in EX, but this was significant only in IIa fibres. The 10% increase in squat jump in EX was accompanied by a 9% increase in the integrated EMG (iEMG) of the leg extensors but the 21-40% increases in isometric and dynamic strength were not paralleled by changes in iEMG. Adding strength training stimulus to the training programme improved maximal, explosive and sport-specific force production in elite master sprinters. These improvements were primarily related to hypertrophic muscular adaptations.

  3. Non-Adrenergic, Tamsulosin-Insensitive Smooth Muscle Contraction is Sufficient to Replace α1 -Adrenergic Tension in the Human Prostate.

    Science.gov (United States)

    Hennenberg, Martin; Acevedo, Alice; Wiemer, Nicolas; Kan, Aysenur; Tamalunas, Alexander; Wang, Yiming; Yu, Qingfeng; Rutz, Beata; Ciotkowska, Anna; Herlemann, Annika; Strittmatter, Frank; Stief, Christian G; Gratzke, Christian

    2017-05-01

    Lower urinary tract symptoms (LUTS) suggestive of benign prostatic hyperplasia may be caused by prostate smooth muscle contraction. Although α1 -blockers may improve symptoms by prostate smooth muscle relaxation, their efficacy is limited. This may be explained by non-adrenergic mediators causing contraction in parallel to α1 -adrenoceptors. However, little is known about the relevance and cooperative actions of non-adrenergic mediators in the prostate. Prostate tissues were obtained from radical prostatectomy (n = 127 patients). Contractile responses were studied in an organ bath. Endothelin-1 and noradrenaline induced contractions of similar magnitude (116 ± 23 and 117 ± 18% of KCl-induced contractions). Endothelin-2- and -3-induced maximum contractions of 63 ± 8.6 and 71 ± 19% of KCl, while contractions by the thromboxane analog U46619 amounted up to 63 ± 9.4%. Dopamine-induced contractions averaged to 22 ± 4.5% of KCl, while maximum contractions by serotonin, histamine, and carbachol stayed below 10% of KCl-induced. While noradrenaline-induced contractions were inhibited by tamsulosin (300 nM), endothelin-1-, -2-, or -3-induced contraction were not. No additive effects were observed if endothelins and noradrenaline were applied consecutively to the same samples. If endothelin-1 was applied after U46619, resulting tension (172 ± 43% of KCl) significantly exceeded noradrenaline-induced contraction. Tensions following combined application of endothelin-2 or -3 with U46619 stayed below noradrenaline-induced contractions. Tension following combined application of all three endothelins with U46619 resembled maximum noradrenaline-induced tone. Contractions following concomitant confrontation of human prostate tissue with noradrenaline and endothelin-1 are not additive. Endothelin-1 is sufficient to induce a smooth muscle tone resembling that of noradrenaline. This may replace lacking α1 -adrenergic tone under therapy with

  4. Adaptation of Slow Myofibers: The Effect of Sustained BDNF Treatment of Extraocular Muscles in Infant Nonhuman Primates

    Science.gov (United States)

    Willoughby, Christy L.; Fleuriet, Jérome; Walton, Mark M.; Mustari, Michael J.; McLoon, Linda K.

    2015-01-01

    Purpose. We evaluated promising new treatment options for strabismus. Neurotrophic factors have emerged as a potential treatment for oculomotor disorders because of diverse roles in signaling to muscles and motor neurons. Unilateral treatment with sustained release brain-derived neurotrophic factor (BDNF) to a single lateral rectus muscle in infant monkeys was performed to test the hypothesis that strabismus would develop in correlation with extraocular muscle (EOM) changes during the critical period for development of binocularity. Methods. The lateral rectus muscles of one eye in two infant macaques were treated with sustained delivery of BDNF for 3 months. Eye alignment was assessed using standard photographic methods. Muscle specimens were analyzed to examine the effects of BDNF on the density, morphology, and size of neuromuscular junctions, as well as myofiber size. Counts were compared to age-matched controls. Results. No change in eye alignment occurred with BDNF treatment. Compared to control muscle, neuromuscular junctions on myofibers expressing slow myosins had a larger area. Myofibers expressing slow myosin had larger diameters, and the percentage of myofibers expressing slow myosins increased in the proximal end of the muscle. Expression of BDNF was examined in control EOM, and observed to have strongest immunoreactivity outside the endplate zone. Conclusions. We hypothesize that the oculomotor system adapted to sustained BDNF treatment to preserve normal alignment. Our results suggest that BDNF treatment preferentially altered myofibers expressing slow myosins. This implicates BDNF signaling as influencing the slow twitch properties of EOM. PMID:26030102

  5. No effect of menstrual cycle on myofibrillar and connective tissue protein synthesis in contracting skeletal muscle

    DEFF Research Database (Denmark)

    Miller, Benjamin F; Hansen, Mette; Olesen, Jens L

    2006-01-01

    in the follicular (FP, n=8) or the luteal phase (LP, n=7, n=1 out of phase) 24 h after an acute bout of one-legged exercise (60 min of kicking at 67% W(max)), samples being taken from the vastus lateralis in both the exercised and resting legs. Rates of synthesis of myofibrillar and muscle collagen proteins were...... measured by incorporation of [(13)C]leucine. Myofibrillar protein synthesis (means+/-SD; rest FP: 0.053+/-0.009%/h, LP: 0.055+/-0.013%/h) was increased at 24-h postexercise (FP: 0.131+/-0.018%/h, Pmuscle collagen synthesis...... of exercise, on myofibrillar protein synthesis and muscle collagen synthesis in women....

  6. Muscle fatigue resistance during stimulated contractions is reduced in young male smokers.

    NARCIS (Netherlands)

    Morse, C.I.; Wust, R.C.I.; Jones, D.A.; de Haan, A.; Degens, H.

    2007-01-01

    Aim: To determine whether muscle function is compromised in healthy smokers in comparison with activity-matched non-smokers. Methods: Nine male smokers (aged 22.2 ± 2.5 years: mean ± SD) with a smoking history of 2.5 ± 3.1 pack years, and ten male control participants (25.4 ± 2.9 years) matched for

  7. An allosteric model of the molecular interactions of excitation- contraction coupling in skeletal muscle

    OpenAIRE

    1993-01-01

    A contact interaction is proposed to exist between the voltage sensor of the transverse tubular membrane of skeletal muscle and the calcium release channel of the sarcoplasmic reticulum. This interaction is given a quantitative formulation inspired in the Monod, Wyman, and Changeux model of allosteric transitions in hemoglobin (Monod, J., J. Wyman, and J.-P. Changeux. 1965. Journal of Molecular Biology. 12:88- 118), and analogous to one proposed by Marks and Jones for voltage- dependent Ca ch...

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

    DEFF Research Database (Denmark)

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

    2007-01-01

    % and 16/100 Hz force ratio by 33%. The eSRCa2+ in fibres from non-stimulated muscles was 45 +/- 5% of the maximal loading capacity. After EC, eSRCa2+ per fibre CSA decreased by 38% (P = 0.05), and the maximal capacity of SR Ca2+ loading was depressed by 32%. There were no effects of EC on either...

  9. Sarcoplasmic-reticulum biogenesis in contraction-inhibited skeletal-muscle cultures.

    OpenAIRE

    Charuk, J H; Guerin, C.; Holland, P.C.

    1992-01-01

    We have previously shown that inhibition of the spontaneous contractile activity of cultured embryonic-chick skeletal-muscle fibres with tetrodotoxin (TTX) leads to decreased sarcoplasmic-reticulum Ca(2+)-transport rates and steady-state concentrations of the high-energy Ca(2+)-ATPase phosphoenzyme intermediate [Charuk & Holland (1983) Exp. Cell Res. 144, 143-157]. In the present study we used a monoclonal antibody to the Ca(2+)-ATPase to show that there is a decreased amount of enzyme accumu...

  10. Alpha and beta adrenergic effects on metabolism in contracting, perfused muscle

    DEFF Research Database (Denmark)

    Richter, Erik; Ruderman, N B; Galbo, H

    1982-01-01

    was obtained by epinephrine in a physiological concentration (2.4 X 10(-8) M) and alpha- and beta-adrenergic blockade by 10(-5) M phentolamine and propranolol, respectively. Epinephrine enhanced net glycogenolysis during contractions most markedly in slow-twitch red fibers. In these fibers the effect...... was mediated by alpha- as well as by beta-adrenergic stimulation, the latter involving production of cAMP, phosphorylase activation and synthase inactivation. In contrast, in fast-twitch fibers only beta-adrenergic mechanisms were involved in the glycogenolytic effect of epinephrine. Moreover, inactivation...

  11. Effect of pelvic floor muscle contraction on vesical and rectal function with identification of puborectalis-rectovesical inhibitory reflex and levator-rectovesical excitatory reflex.

    Science.gov (United States)

    Shafik, A; El-Sibai, O

    2001-08-01

    The effects of pelvic floor muscle contraction on rectal and vesical function were studied in 19 healthy volunteers with the aim of shedding light on some of the hitherto vague aspects of the mechanisms involved in micturition and defecation and their disorders. Rectal and vesical pressures were recorded during puborectalis (PR) and levator ani (LA) muscle stimulation with the rectum or urinary bladder empty and full. Muscle stimulation was effected by needle EMG electrode. The pressure responses to stimulation of the PR and LA muscles were also recorded with these muscles and the rectum and urinary bladder individually anesthetized in 12 of the 19 subjects. The test was repeated using saline instead of xylocaine. PR and LA muscle stimulation produced no pressure response in the empty rectum or bladder. Upon rectal balloon distension with a mean of 156.6+/-34.2 ml of carbon dioxide the mean rectal pressure was 64.6+/-18.7 cm H2O, the subject felt the urge to evacuate and the balloon was expelled to the exterior. On PR muscle stimulation at rectal distension with the above volume, the subject did not feel the urge to evacuate, the rectal pressure was 8.2+/-1.6 cm H2O and the balloon was not expelled. Upon LA stimulation at the same volume, the urge persisted, the rectal pressure was higher and the balloon was expelled. Vesical filling with a mean of 378.2+/-23.6 ml of saline initiated the urge to urinate and elevated the vesical pressure. PR muscle stimulation at this volume aborted the urge and pressure elevation, while LA stimulation caused more elevation of the vesical pressure and spontaneous micturition. Bladder filling with a mean of 423.6+/-38.2 ml produced high vesical pressure and spontaneous urination, both of which were prevented by PR muscle stimulation but not by LA muscle stimulation. Stimulation of the PR and LA muscles during individual anesthetization of the rectum, bladder or PR and LA muscles resulted in no significant rectal or vesical pressure

  12. Rat whisker movement after facial nerve lesion: evidence for autonomic contraction of skeletal muscle.

    Science.gov (United States)

    Heaton, James T; Sheu, Shu Hsien; Hohman, Marc H; Knox, Christopher J; Weinberg, Julie S; Kleiss, Ingrid J; Hadlock, Tessa A

    2014-04-18

    Vibrissal whisking is often employed to track facial nerve regeneration in rats; however, we have observed similar degrees of whisking recovery after facial nerve transection with or without repair. We hypothesized that the source of non-facial nerve-mediated whisker movement after chronic denervation was from autonomic, cholinergic axons traveling within the infraorbital branch of the trigeminal nerve (ION). Rats underwent unilateral facial nerve transection with repair (N=7) or resection without repair (N=11). Post-operative whisking amplitude was measured weekly across 10weeks, and during intraoperative stimulation of the ION and facial nerves at ⩾18weeks. Whisking was also measured after subsequent ION transection (N=6) or pharmacologic blocking of the autonomic ganglia using hexamethonium (N=3), and after snout cooling intended to elicit a vasodilation reflex (N=3). Whisking recovered more quickly and with greater amplitude in rats that underwent facial nerve repair compared to resection (Pnerve-mediated whisking was elicited by electrical stimulation of the ION, temporarily diminished following hexamethonium injection, abolished by transection of the ION, and rapidly and significantly (Precovery period (indicative of reinnervation), but re-appeared in the resected rats after undergoing ION transection (indicative of motor denervation). Cholinergic, parasympathetic axons traveling within the ION innervate whisker pad vasculature, and immunohistochemistry for vasoactive intestinal peptide revealed these axons branching extensively over whisker pad muscles and contacting neuromuscular junctions after facial nerve resection. This study provides the first behavioral and anatomical evidence of spontaneous autonomic innervation of skeletal muscle after motor nerve lesion, which not only has implications for interpreting facial nerve reinnervation results, but also calls into question whether autonomic-mediated innervation of striated muscle occurs naturally in

  13. Lead Acetate Induces Epithelium-Dependent Contraction of Airway Smooth Muscle

    OpenAIRE

    , Ramadan B. Sopi; , Kemajl Bislimi; , Fetah Halili; , Mentor Sopjani; , Burim Neziri; , Muharrem Jakupi

    2016-01-01

    The effect of lead acetate on tracheal smooth muscle (TSM) of dog pups was investigated in this study. In addition we studied the role of epithelium and involvement of nitric oxide (NO) in counteracting the effects of lead acetate on TSM as well as the modifying effects of lead acetate on contractile responses of TSM to acetylcholine (ACh) . Tracheal rings were excised and placed in in vitro organ baths. In vitro administration of lead acetate in increasing concentrations(10-7–10-3 M) induced...

  14. 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

  15. The functional coupling of the deep abdominal and paraspinal muscles: the effects of simulated paraspinal muscle contraction on force transfer to the middle and posterior layer of the thoracolumbar fascia.

    Science.gov (United States)

    Vleeming, A; Schuenke, M D; Danneels, L; Willard, F H

    2014-10-01

    The thoracolumbar fascia (TLF) consists of aponeurotic and fascial layers that interweave the paraspinal and abdominal muscles into a complex matrix stabilizing the lumbosacral spine. To better understand low back pain, it is essential to appreciate how these muscles cooperate to influence lumbopelvic stability. This study tested the following hypotheses: (i) pressure within the TLF's paraspinal muscular compartment (PMC) alters load transfer between the TLF's posterior and middle layers (PLF and MLF); and (ii) with increased tension of the common tendon of the transversus abdominis (CTrA) and internal oblique muscles and incremental PMC pressure, fascial tension is primarily transferred to the PLF. In cadaveric axial sections, paraspinal muscles were replaced with inflatable tubes to simulate paraspinal muscle contraction. At each inflation increment, tension was created in the CTrA to simulate contraction of the deep abdominal muscles. Fluoroscopic images and load cells captured changes in the size, shape and tension of the PMC due to inflation, with and without tension to the CTrA. In the absence of PMC pressure, increasing tension on the CTrA resulted in anterior and lateral movement of the PMC. PMC inflation in the absence of tension to the CTrA resulted in a small increase in the PMC perimeter and a larger posterior displacement. Combining PMC inflation and tension to the CTrA resulted in an incremental increase in PLF tension without significantly altering tension in the MLF. Paraspinal muscle contraction leads to posterior displacement of the PLF. When expansion is combined with abdominal muscle contraction, the CTrA and internal oblique transfers tension almost exclusively to the PLF, thereby girdling the paraspinal muscles. The lateral border of the PMC is restrained from displacement to maintain integrity. Posterior movement of the PMC represents an increase of the PLF extension moment arm. Dysfunctional paraspinal muscles would reduce the posterior

  16. The functional coupling of the deep abdominal and paraspinal muscles: the effects of simulated paraspinal muscle contraction on force transfer to the middle and posterior layer of the thoracolumbar fascia

    Science.gov (United States)

    Vleeming, A; Schuenke, M D; Danneels, L; Willard, F H

    2014-01-01

    The thoracolumbar fascia (TLF) consists of aponeurotic and fascial layers that interweave the paraspinal and abdominal muscles into a complex matrix stabilizing the lumbosacral spine. To better understand low back pain, it is essential to appreciate how these muscles cooperate to influence lumbopelvic stability. This study tested the following hypotheses: (i) pressure within the TLF's paraspinal muscular compartment (PMC) alters load transfer between the TLF's posterior and middle layers (PLF and MLF); and (ii) with increased tension of the common tendon of the transversus abdominis (CTrA) and internal oblique muscles and incremental PMC pressure, fascial tension is primarily transferred to the PLF. In cadaveric axial sections, paraspinal muscles were replaced with inflatable tubes to simulate paraspinal muscle contraction. At each inflation increment, tension was created in the CTrA to simulate contraction of the deep abdominal muscles. Fluoroscopic images and load cells captured changes in the size, shape and tension of the PMC due to inflation, with and without tension to the CTrA. In the absence of PMC pressure, increasing tension on the CTrA resulted in anterior and lateral movement of the PMC. PMC inflation in the absence of tension to the CTrA resulted in a small increase in the PMC perimeter and a larger posterior displacement. Combining PMC inflation and tension to the CTrA resulted in an incremental increase in PLF tension without significantly altering tension in the MLF. Paraspinal muscle contraction leads to posterior displacement of the PLF. When expansion is combined with abdominal muscle contraction, the CTrA and internal oblique transfers tension almost exclusively to the PLF, thereby girdling the paraspinal muscles. The lateral border of the PMC is restrained from displacement to maintain integrity. Posterior movement of the PMC represents an increase of the PLF extension moment arm. Dysfunctional paraspinal muscles would reduce the posterior

  17. Muscle contraction velocity, strength and power output changes following different degrees of hypohydration in competitive olympic combat sports.

    Science.gov (United States)

    Pallarés, J G; Martínez-Abellán, A; López-Gullón, J M; Morán-Navarro, R; De la Cruz-Sánchez, E; Mora-Rodríguez, R

    2016-01-01

    It is habitual for combat sports athletes to lose weight rapidly to get into a lower weight class. Fluid restriction, dehydration by sweating (sauna or exercise) and the use of diuretics are among the most recurrent means of weight cutting. Although it is difficult to dissuade athletes from this practice due to the possible negative effect of severe dehydration on their health, athletes may be receptive to avoid weight cutting if there is evidence that it could affect their muscle performance. Therefore, the purpose of the present study was to investigate if hypohydration, to reach a weight category, affects neuromuscular performance and combat sports competition results. We tested 163 (124 men and 39 woman) combat sports athletes during the 2013 senior Spanish National Championships. Body mass and urine osmolality (UOSM) were measured at the official weigh-in (PRE) and 13-18 h later, right before competing (POST). Athletes were divided according to their USOM at PRE in euhydrated (EUH; UOSM 250-700 mOsm · kgH2O(-1)), hypohydrated (HYP; UOSM 701-1080 mOsm · kgH2O(-1)) and severely hypohydrated (S-HYP; UOSM 1081-1500 mOsm · kgH2O(-1)). Athletes' muscle strength, power output and contraction velocity were measured in upper (bench press and grip) and lower body (countermovement jump - CMJ) muscle actions at PRE and POST time-points. At weigh-in 84 % of the participants were hypohydrated. Before competition (POST) UOSM in S-HYP and HYP decreased but did not reach euhydration levels. However, this partial rehydration increased bench press contraction velocity (2.8-7.3 %; p sports athletes at weigh-in and not fully reversed in the 13-18 h from weigh-in to competition. Nonetheless, partial rehydration recovers upper and lower body neuromuscular performance in the severely hypohydrated participants. Our data suggest that the advantage of competing in a lower weight category could compensate the declines in neuromuscular performance at the onset of competition, since 69

  18. Survey of the Effects of Exposure to 900 MHz Radiofrequency Radiation Emitted by a GSM Mobile Phone on the Pattern of Muscle Contractions in an Animal Model.

    Science.gov (United States)

    Mortazavi, S M J; Rahimi, S; Talebi, A; Soleimani, A; Rafati, A

    2015-09-01

    The rapid development of wireless telecommunication technologies over the past decades, has led to significant changes in the exposure of the general public to electromagnetic fields. Nowadays, people are continuously exposed to different sources of electromagnetic fields such as mobile phones, mobile base stations, cordless phones, Wi-Fi routers, and power lines. Therefore, the last decade witnessed a rapidly growing concern about the possible health effects of exposure to electromagnetic fields emitted by these sources. In this study that was aimed at investigating the effects of exposure to radiofrequency (RF) radiation emitted by a GSM mobile phone on the pattern of contraction in frog's isolated gastrocnemius muscle after stimulation with single square pulses of 1V (1 Hz), pulse height of contractions, the time interval between two subsequent contractions and the latency period were measured. Our findings showed that the pulse height of contractions muscle could be affected by the exposure to electromagnetic fields. Especially, the latency period was effectively altered in RF-exposed samples. However, none of the experiments could show an alteration in the time interval between two subsequent contractions after exposure to electromagnetic fields. These findings support early reports which indicated a wide variety of non-thermal effects of electromagnetic radiation on amphibians including the effects on the pattern of muscle extractions.

  19. Survey of the Effects of Exposure to 900 MHz Radiofrequency Radiation Emitted by a GSM Mobile Phone on the Pattern of Muscle Contractions in an Animal Model

    Directory of Open Access Journals (Sweden)

    Mortazavi S. M. J.

    2015-09-01

    Full Text Available Background: The rapid development of wireless telecommunication technologies over the past decades, has led to significant changes in the exposure of the general public to electromagnetic fields. Nowadays, people are continuously exposed to different sources of electromagnetic fields such as mobile phones, mobile base stations, cordless phones, Wi-Fi routers, and power lines. Therefore, the last decade witnessed a rapidly growing concern about the possible health effects of exposure to electromagnetic fields emitted by these sources. Materials and Methods: In this study that was aimed at investigating the effects of exposure to radiofrequency (RF radiation emitted by a GSM mobile phone on the pattern of contraction in frog’s isolated gastrocnemius muscle after stimulation with single square pulses of 1V (1 Hz, pulse height of contractions, the time interval between two subsequent contractions and the latency period were measured. Results: Our findings showed that the pulse height of contractions muscle could be affected by the exposure to electromagnetic fields. Especially, the latency period was effectively altered in RF-exposed samples. However, none of the experiments could show an alteration in the time interval between two subsequent contractions after exposure to electromagnetic fields. Conclusion: These findings support early reports which indicated a wide variety of non-thermal effects of electromagnetic radiation on amphibians including the effects on the pattern of muscle extractions

  20. Central common drive to antagonistic ankle muscles in relation to short-term co-contraction training in non-dancers and professional ballet dancers

    DEFF Research Database (Denmark)

    Geertsen, Svend Sparre; Kjær, Majken; Pedersen, Kasper Karhu

    2013-01-01

    Optimization of co-contraction of antagonistic muscles around the ankle joint has been shown to involve plastic changes in spinal and cortical neural circuitries. Such changes may explain the ability of elite ballet dancers to maintain a steady balance during various ballet postures. Here we...... investigated whether short-term co-contraction training in ballet dancers and non-dancers leads to changes in the coupling between antagonistic ankle motor units. Eleven ballet dancers and ten non-dancers were recruited for the study. Prior to training, ballet dancers and non-dancers showed an equal amount...... of coherence in the 15-35 Hz frequency band and short-term synchronization between antagonistic tibialis anterior and soleus motor units. The ballet dancers tended to be better at maintaining a stable co-contraction of the antagonistic muscles, but this difference was not significant (P = 0.09). Following 27...

  1. 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.

  2. From single molecule fluctuations to muscle contraction: a Brownian model of A.F. Huxley's hypotheses.

    Directory of Open Access Journals (Sweden)

    Lorenzo Marcucci

    Full Text Available Muscular force generation in response to external stimuli is the result of thermally fluctuating, cyclical interactions between myosin and actin, which together form the actomyosin complex. Normally, these fluctuations are modelled using transition rate functions that are based on muscle fiber behaviour, in a phenomenological fashion. However, such a basis reduces the predictive power of these models. As an alternative, we propose a model which uses direct single molecule observations of actomyosin fluctuations reported in the literature. We precisely estimate the actomyosin potential bias and use diffusion theory to obtain a brownian ratchet model that reproduces the complete cross-bridge cycle. The model is validated by simulating several macroscopic experimental conditions, while its interpretation is compatible with two different force-generating scenarios.

  3. Structural and functional aspects of the myosin essential light chain in cardiac muscle contraction

    Energy Technology Data Exchange (ETDEWEB)

    Muthu, Priya; Wang, Li; Yuan, Chen-Ching; Kazmierczak, Katarzyna; Huang, Wenrui; Hernandez, Olga M.; Kawai, Masataka; Irving, Thomas C.; Szczesna-Cordary, Danuta (IIT); (Iowa); (Miami-MED)

    2012-04-02

    The myosin essential light chain (ELC) is a structural component of the actomyosin cross-bridge, but its function is poorly understood, especially the role of the cardiac specific N-terminal extension in modulating actomyosin interaction. Here, we generated transgenic (Tg) mice expressing the A57G (alanine to glycine) mutation in the cardiac ELC known to cause familial hypertrophic cardiomyopathy (FHC). The function of the ELC N-terminal extension was investigated with the Tg-{Delta}43 mouse model, whose myocardium expresses a truncated ELC. Low-angle X-ray diffraction studies on papillary muscle fibers in rigor revealed a decreased interfilament spacing ({approx} 1.5 nm) and no alterations in cross-bridge mass distribution in Tg-A57G mice compared to Tg-WT, expressing the full-length nonmutated ELC. The truncation mutation showed a 1.3-fold increase in I{sub 1,1}/I{sub 1,0}, indicating a shift of cross-bridge mass from the thick filament backbone toward the thin filaments. Mechanical studies demonstrated increased stiffness in Tg-A57G muscle fibers compared to Tg-WT or Tg-{Delta}43. The equilibrium constant for the cross-bridge force generation step was smallest in Tg-{Delta}43. These results support an important role for the N-terminal ELC extension in prepositioning the cross-bridge for optimal force production. Subtle changes in the ELC sequence were sufficient to alter cross-bridge properties and lead to pathological phenotypes.

  4. Function of the medial red muscle during sustained swimming in common thresher sharks: contrast and convergence with thunniform swimmers.

    Science.gov (United States)

    Bernal, Diego; Donley, Jeanine M; McGillivray, David G; Aalbers, Scott A; Syme, Douglas A; Sepulveda, Chugey

    2010-04-01

    Through convergent evolution tunas and lamnid sharks share thunniform swimming and a medial position of the red, aerobic swimming musculature. During continuous cruise swimming these muscles move uniformly out of phase with local body curvature and the surrounding white muscle tissue. This design results in thrust production primarily from the caudal fin rather than causing whole-body undulations. The common thresher shark (Family Alopiidae) is the only other fish known to share the same medial red muscle anatomy as the thunniform swimmers. However, the overall body shape and extremely heterocercal caudal fin of the common thresher is not shared with the thunniform swimmers, which have both fusiform bodies and high aspect-ratio, lunate caudal fins. Our study used sonomicrometry to measure the dynamics of red and white muscle movement in common thresher sharks swimming in the ocean to test whether the medial position of red muscle is associated with uncoupling of muscle shortening and local body bending as characteristic of thunniform swimmers. Common threshers ( approximately 60-100kg) instrumented with sonomicrometric and electromyographic (EMG) leads swam alongside of the vessel with a tail-beat frequency of approximately 0.5Hz. EMG signals confirmed that only the red muscle was active during sustained swimming. Despite the more medial position of the red muscle relative to the white muscle, its strain was approximately 1.5-times greater than that of the overlying white muscle, and there was a notable phase shift between strain trajectories in the red muscle and adjacent white muscle. These results suggest an uncoupling (shearing) of the red muscle from the adjacent white muscle. Although the magnitude of the phase shift between red and white muscle strain was relatively constant within individuals, it varied among sharks, ranging from near zero (red and white in phase) to almost 180 degrees out of phase. This extent in variability has not been documented

  5. 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

  6. Enhanced maximal exercise capacity, vasodilation to electrical muscle contraction, and hind limb vascular density in ASIC1a null mice.

    Science.gov (United States)

    Drummond, Heather A; Xiang, Lusha; Chade, Alejandro R; Hester, Robert

    2017-08-01

    Acid-sensing ion channel (ASIC) proteins form extracellular proton-gated, cation-selective channels in neurons and vascular smooth muscle cells and are proposed to act as extracellular proton sensors. However, their importance to vascular responses under conditions associated with extracellular acidosis, such as strenuous exercise, is unclear. Therefore, the purpose of this study was to determine if one ASIC protein, ASIC1a, contributes to extracellular proton-gated vascular responses and exercise tolerance. To determine if ASIC1a contributes to exercise tolerance, we determined peak oxygen (O2) uptake in conscious ASIC1a-/- mice during exhaustive treadmill running. Loss of ASIC1a was associated with a greater peak running speed (60 ± 2 vs. 53 ± 3 m·min-1, P = 0.049) and peak oxygen (O2) uptake during exhaustive treadmill running (9563 ± 120 vs. 8836 ± 276 mL·kg-1·h-1, n = 6-7, P = 0.0082). There were no differences in absolute or relative lean body mass, as determined by EchoMRI. To determine if ASIC1a contributes to vascular responses during muscle contraction, we measured femoral vascular conductance (FVC) during a stepwise electrical stimulation (0.5-5.0 Hz at 3 V for 60 sec) of the left major hind limb muscles. FVC increased to a greater extent in ASIC1a-/- versus ASIC1a+/+ mice (0.44 ± 0.03 vs. 0.30 ± 0.04 mL·min-1·100 g hind limb mass-1 · mmHg-1, n = 5 each, P = 0.0009). Vasodilation following local application of external protons in the spinotrapezius muscle increased the duration, but not the magnitude, of the vasodilatory response in ASIC1a-/- mice. Finally, we examined hind limb vascular density using micro-CT and found increased density of 0-80 μm vessels (P < 0.05). Our findings suggest an increased vascular density and an enhanced vasodilatory response to local protons, to a lesser degree, may contribute to the enhanced vascular conductance and increased peak exercise capacity in ASIC1a-/- mice. © 2017 The

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

    Science.gov (United States)

    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.

  8. The Effects of Ibogaine on Uterine Smooth Muscle Contractions: Relation to the Activity of Antioxidant Enzymes

    Directory of Open Access Journals (Sweden)

    Zorana Oreščanin-Dušić

    2018-01-01

    Full Text Available Ibogaine is an indole alkaloid originally extracted from the root bark of the African rainforest shrub Tabernanthe iboga. It has been explored as a treatment for substance abuse because it interrupts drug addiction and relieves withdrawal symptoms. However, it has been shown that ibogaine treatment leads to a sharp and transient fall in cellular ATP level followed by an increase of cellular respiration and ROS production. Since contractile tissues are sensitive to changes in the levels of ATP and ROS, here we investigated an ibogaine-mediated link between altered redox homeostasis and uterine contractile activity. We found that low concentrations of ibogaine stimulated contractile activity in spontaneously active uteri, but incremental increase of doses inhibited it. Inhibitory concentrations of ibogaine led to decreased SOD1 and elevated GSH-Px activity, but doses that completely inhibited contractions increased CAT activity. Western blot analyses showed that changes in enzyme activities were not due to elevated enzyme protein concentrations but posttranslational modifications. Changes in antioxidant enzyme activities point to a vast concentration-dependent increase in H2O2 level. Knowing that extracellular ATP stimulates isolated uterus contractility, while H2O2 has an inhibitory effect, this concentration-dependent stimulation/inhibition could be linked to ibogaine-related alterations in ATP level and redox homeostasis.

  9. Effect of 3-substituted 1,4-benzodiazepin-2-ones on maximal normalized rate of bradykinin-induced smooth muscle contraction in the presence of calcium channel blockers

    Directory of Open Access Journals (Sweden)

    P. A. Virych

    2017-05-01

    Full Text Available The development of modern organic chemistry and molecular modeling technologies simplify the search for potential inhibitors of various receptor systems and biological processes. The one of the directions is the development of analgesics of broad spectrum and low toxicity. It is important to search for inhibitors of the kinin-kallikrein system that regulates many functions: inflammation, pain, carcinogenesis, vascular tone, smooth muscle contraction and other. Derivatives of 3-substituted 1,4-benzodiazepine-2-ones have a unique spatial conformation that allows one to simulate β-structures of bioactive peptides. The functional activity of compounds is determined by properties of their peripheral chemical radicals. We analyzed the effect of 3-substituted 1,4-benzodiazepin-2-ones derivatives on the normalized maximal rate of bradykinin-induced smooth muscle contraction and relaxation of the stomach in the presence of calcium channel blockers: verapamil (1 μM, gadolinium (300 μM and 2-aminoethyl diphenylborinate (0.1 μM. The levels of bradykinin and 3-arylamino-1,2-dihydro-3H-1,4-benzodiazepine-2-ones in incubation solution were 10–6 M. Data processing on dynamics of contraction was performed according to the method of Burdyha and Kosterin. Compounds MX-1775 and MX-1925 reduced maximal normalized rate (Vn of bradykinin-induced smooth muscle contraction in the presence of Gd3+ by 21.2% and 31.0% respectively. Compound MX-1925 increased Vn of relaxation by 11.6%. A similar effect is typical for MX-2011, where there is an increase by 34.6%. In the presence of verapamil this compound additionally decreased Vn contraction by 20.5%. Substances MX-1775, MX-2004 and MX-1925 restored maximal normalized rate of relaxation to original values of bradykinin-induced contraction. In the presence of 2-aminoethyldiphenylborinate MX-1775 additionally reduced Vn of contractions by 7.5%. 3-substituted 1,4-benzo­diazepine-2-ones did not change the maximal

  10. Omega-3 and omega-6 DPA equally inhibit the sphingosylphosphorylcholine-induced Ca2+-sensitization of vascular smooth muscle contraction via inhibiting Rho-kinase activation and translocation

    Science.gov (United States)

    Zhang, Ying; Zhang, Min; Lyu, Bochao; Kishi, Hiroko; Kobayashi, Sei

    2017-01-01

    We previously reported that eicosapentaenoic acid (EPA), an omega-3 polyunsaturated fatty acid (n-3 PUFA), effectively inhibits sphingosylphosphorylcholine (SPC)-induced Ca2+-sensitization of vascular smooth muscle (VSM) contraction which is a major cause of cardiovascular and cerebrovascular vasospasm, and EPA is utilized clinically to prevent cerebrovascular vasospasm. In this study, we clearly demonstrate that docosapentaenoic acid (DPA), which exists in two forms as omega-3 (n-3) and omega-6 (n-6) PUFA, strongly inhibits SPC-induced contraction in VSM tissue and human coronary artery smooth muscle cells (CASMCs), with little effect on Ca2+-dependent contraction. Furthermore, n-3 and n-6 DPA inhibited the activation and translocation of Rho-kinase from cytosol to cell membrane. Additionally, SPC-induced phosphorylation of myosin light chain (MLC) was inhibited in n-3 and n-6 DPA pretreated smooth muscleVSM cells and tissues. In summary, we provide direct evidence that n-3 and n-6 DPA effectively equally inhibits SPC-induced contraction by inhibiting Rho-kinase activation and translocation to the cell membrane. PMID:28169288

  11. Pulse variations of a conducted energy weapon (similar to the TASER X26 device): effects on muscle contraction and threshold for ventricular fibrillation*.

    Science.gov (United States)

    Beason, Charles W; Jauchem, James R; Clark, C D; Parker, James E; Fines, David A

    2009-09-01

    Conducted energy weapons (such as the Advanced TASER X26 model produced by TASER International), incapacitate individuals by causing muscle contractions. To provide information relevant to development of future potential devices, a "Modifiable Electronic Stimulator" was used to evaluate the effects of changing various parameters of the stimulating pulse. Muscle contraction was affected by pulse power, net/gross charge, pulse duration, and pulse repetition frequency. The contraction force increased linearly as each of these factors was increased. Elimination of a precursor pulse from X26-like pulses did not have a significant effect on the normalized force measured. Muscle-contraction force increased as the spacing increased from 5 to 20 cm, with no further change in force above 20 cm of spacing. Therefore, it is suggested that any future developments of new conducted energy weapons should include placement of electrodes a minimum of 20 cm apart so that efficiency of the system is not degraded. In the current study, the 50% probability of fibrillation level of X26-like pulses ranged from 4 to 5 times higher than the X26 itself. Relatively large variations about the X26 operating level were found not to result in fibrillation or asystole. Therefore, it should be possible to design and build an X26-type device that operates efficiently at levels higher than the X26.

  12. A computational model of the ionic currents, Ca2+ dynamics and action potentials underlying contraction of isolated uterine smooth muscle.

    Directory of Open Access Journals (Sweden)

    Wing-Chiu Tong

    2011-04-01

    Full Text Available Uterine contractions during labor are discretely regulated by rhythmic action potentials (AP of varying duration and form that serve to determine calcium-dependent force production. We have employed a computational biology approach to develop a fuller understanding of the complexity of excitation-contraction (E-C coupling of uterine smooth muscle cells (USMC. Our overall aim is to establish a mathematical platform of sufficient biophysical detail to quantitatively describe known uterine E-C coupling parameters and thereby inform future empirical investigations of physiological and pathophysiological mechanisms governing normal and dysfunctional labors. From published and unpublished data we construct mathematical models for fourteen ionic currents of USMCs: Ca2+ currents (L- and T-type, Na+ current, an hyperpolarization-activated current, three voltage-gated K+ currents, two Ca2+-activated K+ current, Ca2+-activated Cl current, non-specific cation current, Na+-Ca2+ exchanger, Na+-K+ pump and background current. The magnitudes and kinetics of each current system in a spindle shaped single cell with a specified surface area:volume ratio is described by differential equations, in terms of maximal conductances, electrochemical gradient, voltage-dependent activation/inactivation gating variables and temporal changes in intracellular Ca2+ computed from known Ca2+ fluxes. These quantifications are validated by the reconstruction of the individual experimental ionic currents obtained under voltage-clamp. Phasic contraction is modeled in relation to the time constant of changing [Ca2+]i. This integrated model is validated by its reconstruction of the different USMC AP configurations (spikes, plateau and bursts of spikes, the change from bursting to plateau type AP produced by estradiol and of simultaneous experimental recordings of spontaneous AP, [Ca2+]i and phasic force. In summary, our advanced mathematical model provides a powerful tool to

  13. The Effect of Ratio of Contraction to Relaxation Durations in PNF Exercises on the Muscle Strength and Range of Motion of Hip Joint

    Directory of Open Access Journals (Sweden)

    Hossein Rashedi

    2015-09-01

    Full Text Available Objective: The aim of the present study was to compare the effect of ratios of contraction- Relaxation on the muscle strength and range of motion of hip joint in PNF exercises. Methods: Thirty nine nonathletic male students (Mean±SD; age, 13±1.2 years; body mass, 55±9.8 kg were assigned .Three groups designated as I, II and III groups. The ratios of contraction to relaxation periods for groups were 1, 2 and 3 respectively. Training program included three sessions per week (CR-PNF for 6 weeks. Measurements of hip extensors muscles stretch and strength were performed at the beginning and at the end of training using an inclinometer (during leg raise test and dynamometer. Data were analyzed using dependent samples t-test and one-way ANOVA. Results: The results of the present study showed significant increases in hip extensor muscles flexibility and strength for three groups. This increase the in the strength in group I equaled 6 kg, in group II 4 kg and in group III 7 kg. The amount of increase in the hip extensor muscles flexibility in group I, II and II were 15, 8 and 12 degrees, respectively. The increase in these two variables was significant and similar in all three groups. Conclusion: Different contraction to relaxation ratio normally, 0.5, 1 and 2, did not show any meaningful differences on hip extensor muscular strength and hip range of motion.

  14. Ultrasound imaging of the serratus anterior muscle at rest and during contraction.

    Science.gov (United States)

    Talbott, Nancy R; Witt, Dexter W

    2013-05-01

    The purpose of this study is to describe a clinically feasible method for measuring the thickness of the serratus anterior (SA) muscle using rehabilitative ultrasound imaging (RUSI) and to determine the reliability of repeated measures of that method. An exploratory clinical measurement study using a test-retest methodology was utilized to determine the reliability of the measurements in a sample of 20 healthy subjects. While sitting with the arm flexed 120°, the SA of each subject was imaged at rest, during an active hold and while holding a three pound weight. On Day 1, images were repeated three times for each condition by the same examiner. On Day 2, Examiner 1 and Examiner 2 repeated the scans. Images were examined offline by Examiner 1 with SA thickness measured superior to the most distal rib in the image. Reliability was evaluated using intraclass correlation coefficients (ICCs) and Bland-Altman plots. The intra-examiner reliability (same day) during rest, active hold and active hold with resistance was ICC3,3  = 0·892; ICC3,3  = 0·951; and ICC3,3  = 0·869-0·971, respectively. Intra-examiner reliability between days ranged from ICC3,2  = 0·613 at rest to ICC3,2  = 0·736 during active hold with resistance. Interexaminer reliability was moderate during active hold (ICC2,2  = 0·526) and active hold with resistance (ICC2,2  = 0·535) and poor during rest (ICC2,2  = 0·425). This study demonstrates that SA thickness can be measured reliably using RUSI by the same examiner and suggests that active movements may increase that reliability. © 2012 The Authors Clinical Physiology and Functional Imaging © 2012 Scandinavian Society of Clinical Physiology and Nuclear Medicine.

  15. Brain-derived neurotrophic factor is produced by skeletal muscle cells in response to contraction and enhances fat oxidation via activation of AMP-activated protein kinase

    DEFF Research Database (Denmark)

    Matthews, V B; Åström, Maj-Brit; Chan, M H S

    2009-01-01

    C12 skeletal muscle cells were electrically stimulated to mimic contraction. L6 myotubes and isolated rat extensor digitorum longus muscles were treated with BDNF and phosphorylation of the proteins AMP-activated protein kinase (AMPK) (Thr(172)) and acetyl coenzyme A carboxylase beta (ACCbeta) (Ser...... into the circulation. Bdnf mRNA and protein expression was increased in muscle cells that were electrically stimulated. BDNF increased phosphorylation of AMPK and ACCbeta and enhanced FAO both in vitro and ex vivo. The effect of BDNF on FAO was AMPK-dependent, since the increase in FAO was abrogated in cells infected......AIMS/HYPOTHESIS: Brain-derived neurotrophic factor (BDNF) is produced in skeletal muscle, but its functional significance is unknown. We aimed to determine the signalling processes and metabolic actions of BDNF. METHODS: We first examined whether exercise induced BDNF expression in humans. Next, C2...

  16. A Ca2+-calmodulin-eEF2K-eEF2 signalling cascade, but not AMPK, contributes to the suppression of skeletal muscle protein synthesis during contractions

    DEFF Research Database (Denmark)

    Rose, Adam John; Alsted, Thomas Junker; Jensen, Thomas Elbenhardt

    2009-01-01

    Skeletal muscle protein synthesis rate decreases during contractions but the underlying regulatory mechanisms are poorly understood. It was hypothesised that there would be a coordinated regulation of eukaryotic elongation factor 2 (eEF2) and eukaryotic initiation factor 4E-binding protein 1 (4EBP1......-turnover related mechanisms. Furthermore, eEF2 kinase inhibition completely blunted increases in eEF2 phosphorylation and partially blunted (i.e. 30-40%) the suppression of protein synthesis during contractions. The 3-5 fold increase in skeletal muscle eEF2 phosphorylation during contractions in situ was rapid......) phosphorylation by signalling cascades downstream of rises in intracellular [Ca(2+)] and decreased energy charge via AMP activated protein kinase (AMPK) in contracting skeletal muscle. When fast-twitch skeletal muscles were contracted ex vivo using different protocols, the suppression of protein synthesis...

  17. An allosteric model of the molecular interactions of excitation-contraction coupling in skeletal muscle.

    Science.gov (United States)

    Ríos, E; Karhanek, M; Ma, J; González, A

    1993-09-01

    A contact interaction is proposed to exist between the voltage sensor of the transverse tubular membrane of skeletal muscle and the calcium release channel of the sarcoplasmic reticulum. This interaction is given a quantitative formulation inspired in the Monod, Wyman, and Changeux model of allosteric transitions in hemoglobin (Monod, J., J. Wyman, and J.-P. Changeux. 1965. Journal of Molecular Biology. 12:88-118), and analogous to one proposed by Marks and Jones for voltage-dependent Ca channels (Marks, T. N., and S. W. Jones. 1992. Journal of General Physiology. 99:367-390). The allosteric protein is the calcium release channel, a homotetramer, with two accessible states, closed and open. The kinetics and equilibrium of this transition are modulated by voltage sensors (dihydropyridine receptors) pictured as four units per release channel, each undergoing independent voltage-driven transitions between two states (resting and activating). For each voltage sensor that moves to the activating state, the tendency of the channel to open increases by an equal (large) factor. The equilibrium and kinetic equations of the model are solved and shown to reproduce well a number of experimentally measured relationships including: charge movement (Q) vs. voltage, open probability of the release channel (Po) vs. voltage, the transfer function relationship Po vs. Q, and the kinetics of charge movement, release activation, and deactivation. The main consequence of the assumption of allosteric coupling is that primary effects on the release channel are transmitted backward to the voltage sensor and give secondary effects. Thus, the model reproduces well the effects of perchlorate, described in the two previous articles, under the assumption that the primary effect is to increase the intrinsic tendency of the release channel to open, with no direct effects on the voltage sensor. This modification of the open-closed equilibrium of the release channel causes a shift in the equilibrium

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

    Directory of Open Access Journals (Sweden)

    Y.C. Chang

    1998-10-01

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

  19. 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.

  20. Evidence that the contraction-induced rapid hyperemia in rabbit masseter muscle is based on a mechanosensitive mechanism, not shared by cutaneous vascular beds.

    Science.gov (United States)

    Turturici, Marco; Mohammed, Mazher; Roatta, Silvestro

    2012-08-15

    Several mechanisms have been hypothesized to contribute to the rapid hyperemia at the onset of exercise. The aim of the present study was to investigate the role played by the mechanosensitivity of the vascular network. In 12 anesthetized rabbits blood flow was recorded from the exclusively muscular masseteric artery in response to brief spontaneous contractions (BSC) of the masseter muscle, artery occlusion (AO), muscle compression (MC), and muscle stretch (MS). Activation of masseter muscle was monitored by electromyography (EMG). Responses to AO were also recorded from the mostly cutaneous facial and the central ear arteries. Five animals were also tested in the awake condition. The hyperemic response to BSC (peak amplitude of 394 ± 82%; time to peak of 1.8 ± 0.8 s) developed with a latency of 300-400 ms from the beginning of the EMG burst and 200-300 ms from the contraction-induced transient flow reduction. This response was neither different from the response to AO (peak amplitude = 426 ± 158%), MC, and MS (P = 0.23), nor from the BSC response in the awake condition. Compared with the masseteric artery, the response to AO was markedly smaller both in the facial (83 ± 18%,) and in the central ear artery (68 ± 20%) (P < 0.01). In conclusion, the rapid contraction-induced hyperemia can be replicated by a variety of stimuli affecting transmural pressure in muscle blood vessels and is thus compatible with the Bayliss effect. This prominent mechanosensitivity appears to be a characteristic of muscle and not cutaneous vascular beds.

  1. Design of a myo-seismic transducer for non-invasive transcutaneous vectorial recording of locally fast muscle-fibre micro-contractions.

    Science.gov (United States)

    Journée, H L; de Jonge, A B

    1995-01-01

    Mechanical recording usually concerns the analysis of movements in bio-mechanical research projects. Mechanical recording of locally fast muscle-fibre micro-contractions, however, is a little-developed and rarely-applied myographic technique. In the last decade, acoustic or myophonic measurements came increasingly into the picture when they were also applied to research on general muscle activity, such as in muscle fatigue studies. In this paper, a new micro-seismic recording technique is introduced. The technique registers extremely local activity in the velocity and force vector of skin movement as a function in time. The recording method is sensitive to micro excursions caused by muscle fibres under the skin. The resolution in time is at least 100 us, which is demonstrated in an experiment where a mechanical contraction is provoked by electrical stimulation of the median nerve. This indicates a seismic variant, refered to as seismic-myography (SMG), of surface EMG's, and offers complementary features. The most important features are: 1. Insensitivity to low frequent, large movement artefacts. 2. Sensitivity to fast mechanical micro-excursions and velocities. 3. Fast and precise discrimination of local mechanical events. 4. Vectorial reconstruction of superficial mechanic activity which can be used for the identification and functional behaviour of subcutaneous muscle fibres and, in addition, for the localisation of motor endplate zones. 5. The method is easy to use.(ABSTRACT TRUNCATED AT 250 WORDS)

  2. Genetic disruption of AMPK signaling abolishes both contraction- and insulin-stimulated TBC1D1 phosphorylation and 14-3-3 binding in mouse skeletal muscle

    OpenAIRE

    Pehmøller, Christian; Treebak, Jonas T.; Birk, Jesper B.; Chen, Shuai; MacKintosh, Carol; Hardie, D. Grahame; Richter, Erik A.; Wojtaszewski, Jørgen F.P.

    2009-01-01

    TBC1D1 is a Rab-GTPase-activating protein (GAP) known to be phosphorylated in response to insulin, growth factors, pharmacological agonists that activate 5′-AMP-activated protein kinase (AMPK), and muscle contraction. Silencing TBC1D1 in L6 muscle cells by siRNA increases insulin-stimulated GLUT4 translocation, and overexpression of TBC1D1 in 3T3-L1 adipocytes with low endogenous TBC1D1 expression inhibits insulin-stimulated GLUT4 translocation, suggesting a role of TBC1D1 in regulating GLUT4...

  3. Contraction-stimulated glucose transport in muscle is controlled by AMPK and mechanical stress but not sarcoplasmatic reticulum Ca2+ release

    DEFF Research Database (Denmark)

    Jensen, Thomas Elbenhardt; Sylow, Lykke; Rose, Adam John

    2014-01-01

    signals through proteins such as AMPK. Here, we demonstrate in incubated mouse muscle that Ca(2+) release is neither sufficient nor strictly necessary to increase glucose transport. Rather, the glucose transport response is associated with metabolic feedback signals through AMPK, and mechanical stress......-activated signals. Furthermore, artificial stimulation of AMPK combined with passive stretch of muscle is additive and sufficient to elicit the full contraction glucose transport response. These results suggest that ATP-turnover and mechanical stress feedback are sufficient to fully increase glucose transport...

  4. Low force contractions induce fatigue consistent with muscle mRNA expression in people with spinal cord injury

    OpenAIRE

    Petrie, Michael A.; Suneja, Manish; Faidley, Elizabeth; Shields, Richard K.

    2014-01-01

    Abstract Spinal cord injury (SCI) is associated with muscle atrophy, transformation of muscle fibers to a fast fatigable phenotype, metabolic inflexibility (diabetes), and neurogenic osteoporosis. Electrical stimulation of paralyzed muscle may mitigate muscle metabolic abnormalities after SCI, but there is a risk for a fracture to the osteoporotic skeletal system. The goal of this study was to determine if low force stimulation (3 Hz) causes fatigue of chronically paralyzed muscle consistent ...

  5. Carbachol induces a rapid and sustained hydrolysis of polyphosphoinositide in bovine tracheal smooth muscle measurements of the mass of polyphosphoinositides, 1,2-diacylglycerol, and phosphatidic acid.

    Science.gov (United States)

    Takuwa, Y; Takuwa, N; Rasmussen, H

    1986-11-05

    The effects of carbachol on polyphosphoinositides and 1,2-diacylglycerol metabolism were investigated in bovine tracheal smooth muscle by measuring both lipid mass and the turnover of [3H]inositol-labeled phosphoinositides. Carbachol induces a rapid reduction in the mass of phosphatidylinositol 4,5-bisphosphate and phosphatidylinositol 4-monophosphate and a rapid increase in the mass of 1,2-diacylglycerol and phosphatidic acid. These changes in lipid mass are sustained for at least 60 min. The level of phosphatidylinositol shows a delayed and progressive decrease during a 60-min period of carbachol stimulation. The addition of atropine reverses these responses completely. Carbachol stimulates a rapid loss in [3H]inositol radioactivity from phosphatidylinositol 4,5-bisphosphate and phosphatidylinositol 4-monophosphate associated with production of [3H]inositol trisphosphate. The carbachol-induced change in the mass of phosphoinositides and phosphatidic acid is not affected by removal of extracellular Ca2+ and does not appear to be secondary to an increase in intracellular Ca2+. These results indicate that carbachol causes phospholipase C-mediated polyphosphoinositide breakdown, resulting in the production of inositol trisphosphate and a sustained increase in the actual content of 1,2-diacylglycerol. These results strongly suggest that carbachol-induced contraction is mediated by the hydrolysis of polyphosphoinositides with the resulting generation of two messengers: inositol 1,4,5-trisphosphate and 1,2-diacylglycerol.

  6. Carbachol induces a rapid and sustained hydrolysis of polyphosphoinositide in bovine tracheal smooth muscle measurements of the mass of polyphosphoinositides, 1,2-diacylglycerol, and phosphatidic acid

    Energy Technology Data Exchange (ETDEWEB)

    Takuwa, Y.; Takuwa, N.; Rasmussen, H.

    1986-11-05

    The effects of carbachol on polyphosphoinositides and 1,2-diacylglycerol metabolism were investigated in bovine tracheal smooth muscle by measuring both lipid mass and the turnover of (/sup 3/H)inositol-labeled phosphoinositides. Carbachol induces a rapid reduction in the mass of phosphatidylinositol 4,5-bisphosphate and phosphatidylinositol 4-monophosphate and a rapid increase in the mass of 1,2-diacylglycerol and phosphatidic acid. These changes in lipid mass are sustained for at least 60 min. The level of phosphatidylinositol shows a delayed and progressive decrease during a 60-min period of carbachol stimulation. The addition of atropine reverses these responses completely. Carbachol stimulates a rapid loss in (/sup 3/H)inositol radioactivity from phosphatidylinositol 4,5-bisphosphate and phosphatidylinositol 4-monophosphate associated with production of (/sup 3/H)inositol trisphosphate. The carbachol-induced change in the mass of phosphoinositides and phosphatidic acid is not affected by removal of extracellular Ca/sup 2 +/ and does not appear to be secondary to an increase in intracellular Ca/sup 2 +/. These results indicate that carbachol causes phospholipase C-mediated polyphosphoinositide breakdown, resulting in the production of inositol trisphosphate and a sustained increase in the actual content of 1,2-diacylglycerol. These results strongly suggest that carbachol-induced contraction is mediated by the hydrolysis of polyphosphoinositides with the resulting generation of two messengers: inositol 1,4,5-trisphosphate and 1,2-diacylglycerol.

  7. Maximum swimming speeds of sailfish and three other large marine predatory fish species based on muscle contraction time and stride length

    DEFF Research Database (Denmark)

    Svendsen, Morten Bo Søndergaard; Domenici, Paolo; Marras, Stefano

    2016-01-01

    , and three other large marine pelagic predatory fish species, by measuring the twitch contraction time of anaerobic swimming muscle. The highest estimated maximum swimming speeds were found in sailfish (8.3±1.4 m s(-1)), followed by barracuda (6.2±1.0 m s(-1)), little tunny (5.6±0.2 m s(-1)) and dorado (4...

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

    Directory of Open Access Journals (Sweden)

    Mariana O. Gois

    2014-01-01

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

  9. Mirror illusion reduces motor cortical inhibition in the ipsilateral primary motor cortex during forceful unilateral muscle contractions

    NARCIS (Netherlands)

    Zult, Tjerk; Goodall, Stuart; Thomas, Kevin; Hortobagyi, Tibor; Howatson, Glyn

    2015-01-01

    Forceful, unilateral contractions modulate corticomotor paths targeting the resting, contralateral hand. However, it is unknown whether mirror-viewing of a slowly moving but forcefully contracting hand would additionally affect these paths. Here we examined corticospinal excitability and

  10. The effects of dehydroepiandrosterone (DHEA)/DHEA-sulfate (DHEAS) on the contraction responses of the clitoral cavernous smooth muscle from female rabbits.

    Science.gov (United States)

    Lee, Shin Young; Myung, Soon Chul; Lee, Moo Yeol; Kim, Tae Hyoung; Kim, Sae Chul; Kim, Kyung Do; Park, Soo Hyun; Kim, Won Yong

    2009-10-01

    Dehydroepiandrosterone (DHEA) is a multifunctional steroid that is increasingly available as a supplement aimed at improving libido and well-being in postmenopausal women in the recent times. Together with its sulfate version, DHEA-sulfate (DHEAS), it is the most abundant steroid in humans. The clitoris is an important component of the female sexual response, with its increased vascular response during sexual arousal that results in erection. To elucidate the direct effects of DHEA/DHEAS on the vasomotor reactivity of the rabbit clitoral cavernosum. Twenty New Zealand white female rabbits weighing approximately 2.5-3 kg were used in the study. The contractile response of clitoral cavernous smooth muscle strips in response to phenylephrine (PE; 10(-9)-10(-4) M) were observed in rabbits. Additionally, DHEA/DHEAS effects on phenylephrine-induced contraction and/or acetylcholine-induced relaxation of phenylephrine-induced contraction were measured. DHEA/DHEAS did not elicit any remarkable response in the resting state. However, both DHEA and DHEAS evoked dose-dependent relaxations of PE-induced contraction. The contractile responses to high potassium were significantly decreased in the DHEA/DHEAS-pretreated strips, compared with the DHEA/DHEAS-nontreated strips. Additionally, contractions by Bay K 8644 (10(-7)-10(-6) M) treatment were also significantly inhibited by DHEA/DHEAS. DHEA-induced relaxation responses were stronger than DHEAS-induced relaxation responses. Various K channel blockers, tetraethylammonium (TEA; 1 mM, 10 mM), 4-aminopyridine (10 microM) and glibenclamide (10 microM) did not affect the DHEA/DHEAS-induced relaxation on muscle strips contracted by PE. Relaxation responses by acetylcholine or sodium nitroprusside (SNP) were not changed after DHEA/DHEAS pretreatment. DHEA/DHEAS was found to induce a relaxation response in rabbit clitoral cavernosal smooth muscle, and this is thought to be mediated by direct inhibition of a voltage-dependent calcium

  11. Muscle contraction during electro-muscular incapacitation: A comparison between square-wave pulses and the TASER(®) X26 Electronic control device.

    Science.gov (United States)

    Comeaux, James A; Jauchem, James R; Cox, D Duane; Crane, Carrie C; D'Andrea, John A

    2011-01-01

    Electronic control devices (including the Advanced TASER(®) X26 model produced by TASER International) incapacitate individuals by causing muscle contractions. To provide information relevant to development of future potential devices, effects of monophasic square waves with different parameters were compared with those of the X26 electronic control device, using two animal models (frogs and swine). Pulse power, electrical pulse charge, pulse duration, and pulse repetition frequency affected muscle contraction. There was no difference in the charge required, between the square waveform and the X26 waveform, to cause approximately the same muscle-contraction response (in terms of the strength-duration curve). Thus, on the basis of these initial studies, the detailed shape of a waveform may not be important in terms of generating electro-muscular incapacitation. More detailed studies, however, may be required to thoroughly test all potential waveforms to be considered for future use in ECDs. 2010 American Academy of Forensic Sciences. Published 2010. This article is a U.S. Government work and is in the public domain in the U.S.A.

  12. 40-Hz square-wave stimulation requires less energy to produce muscle contraction: compared with the TASER® X26 conducted energy weapon.

    Science.gov (United States)

    Comeaux, James A; Jauchem, James R; Cox, D Duane; Crane, Carrie C; D'Andrea, John A

    2013-07-01

    Conducted energy weapons (CEWs) (including the Advanced TASER(®) X26 model produced by TASER International, Inc.) incapacitate individuals by causing muscle contractions. In this study using anesthetized swine, the potential incapacitating effect of primarily monophasic, 19-Hz voltage imposed by the commercial CEW was compared with the effect of voltages imposed by a laboratory device that created 40-Hz square waves. Forces of muscle contraction were measured with the use of strain gauges. Stimulation with 40-Hz square waves required less pulse energy than stimulation with the commercial CEW to produce similar muscle contraction. The square-pulse stimulation, at the higher repetition rate, caused a more complete tetanus at a lower energy. Use of such a simple shape of waveform may be used to make future nonlethal weapon devices more efficient. © 2013 American Academy of Forensic Sciences Published 2013. This article is a U.S. Government work and is in the public domain in the U.S.A.

  13. H2O2 generated from mitochondrial electron transport chain in thoracic perivascular adipose tissue is crucial for modulation of vascular smooth muscle contraction.

    Science.gov (United States)

    Costa, Rafael M; Filgueira, Fernando P; Tostes, Rita C; Carvalho, Maria Helena C; Akamine, Eliana H; Lobato, Nubia S

    2016-09-01

    The perivascular adipose tissue (PVAT) releases a variety of factors that affect vascular function. PVAT in the thoracic aorta shares characteristics with the brown adipose tissue, including a large amount of mitochondria. PVAT-derived factors influence both endothelial and smooth muscle function via several signaling mechanisms including the release/generation of reactive nitrogen and oxygen species. Considering the importance of reactive oxygen species (ROS) on vascular function and that mitochondria are an important source of ROS, we hypothesized that mitochondria-derived ROS in the PVAT modulates vascular reactivity. Vascular reactivity to norephinephrine (NE) was evaluated in thoracic aortic rings, with or without endothelium and/or PVAT, from male Wistar rats. Mitochondrial uncoupling, as well as hydrogen peroxide (H2O2) removal, increased the contraction in vessels surrounded by PVAT. PVAT stimulated with NE exhibited increased protein expression, determined by Western blot analysis, of manganese superoxide dismutase (Mn-SOD) and decreased protein expression of catalase. Ultimately, NE increased superoxide anion (O2(-)) generation in PVAT via increases in intracellular calcium. These results clearly demonstrate that mitochondrial electron transport chain (mETC) in PVAT contributes to modulation of aortic muscle contraction by generating higher amounts of O2(-) that is, in turn, dismutated to hydrogen peroxide, which then acts as a pivotal signaling molecule regulating vascular smooth muscle contraction. Copyright © 2015 Elsevier Inc. All rights reserved.

  14. Distribution of motor unit potential velocities in the biceps brachii muscle of sprinters and endurance athletes during short static contractions at low force levels.

    Science.gov (United States)

    Klaver-Król, Ewa G; Henriquez, Nizare R; Oosterloo, Sebe J; Klaver, Peter; Kuipers, Harm; Zwarts, Machiel J

    2010-12-01

    In surface electromyography (sEMG), the distribution of motor unit potential (MUP) velocities has been shown to reflect the proportion of faster and slower propagating MUPs. This study investigated whether the distribution of MUP velocities could distinguish between sprinters and endurance athletes in not-specifically trained muscle (biceps brachii). sEMG results were acquired from 15 sprinters and 18 endurance athletes during short static contractions (3.8s) at three force levels: unloaded, 10% and 20% of maximum voluntary contraction. The features extracted from the sEMG were: the mean muscle conduction velocity (CV) - estimated using the inter-peak latency and the cross-correlation methods, the within-subject skewness of MUP velocities (expressing the relative proportions of faster and slower propagating MUPs), and the within-subject standard deviation of MUP velocities. Sprinters had a higher CV than endurance athletes using both methods. Sprinters also demonstrated a greater proportion of fast propagating MUPs, as indicated by the skewness. Thus, the distribution of MUP velocities was able to demonstrate physiological differences between sprinters and endurance athletes during short contractions at low forces. The findings can be extrapolated to the motor unit level. Since the investigated muscle was not involved in specific training, the differences seem to reflect inherited properties. Copyright © 2010 Elsevier Ltd. All rights reserved.

  15. 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.

  16. Cortical and spinal excitability during and after lengthening contractions of the human plantar flexor muscles performed with maximal voluntary effort.

    Directory of Open Access Journals (Sweden)

    Daniel Hahn

    Full Text Available This study was designed to investigate the sites of potential specific modulations in the neural control of lengthening and subsequent isometric maximal voluntary contractions (MVCs versus purely isometric MVCs of the plantar flexor muscles, when there is enhanced torque during and following stretch. Ankle joint torque during maximum voluntary plantar flexion was measured by a dynamometer when subjects (n = 10 lay prone on a bench with the right ankle tightly strapped to a foot-plate. Neural control was analysed by comparing soleus motor responses to electrical nerve stimulation (M-wave, V-wave, electrical stimulation of the cervicomedullary junction (CMEP and transcranial magnetic stimulation of the motor cortex (MEP. Enhanced torque of 17 ± 8% and 9 ± 8% was found during and 2.5-3 s after lengthening MVCs, respectively. Cortical and spinal responsiveness was similar to that in isometric conditions during the lengthening MVCs, as shown by unchanged MEPs, CMEPs and V-waves, suggesting that the major voluntary motor pathways are not subject to substantial inhibition. Following the lengthening MVCs, enhanced torque was accompanied by larger MEPs (p ≤ 0.05 and a trend to greater V-waves (p ≤ 0.1. In combination with stable CMEPs, increased MEPs suggest an increase in cortical excitability, and enlarged V-waves indicate greater motoneuronal output or increased stretch reflex excitability. The new results illustrate that neuromotor pathways are altered after lengthening MVCs suggesting that the underlying mechanisms of the enhanced torque are not purely mechanical in nature.

  17. In vivo pH and metabolite changes during a single contraction in rat uterine smooth muscle

    Science.gov (United States)

    Larcombe-McDouall, Jacky; Buttell, Naomi; Harrison, Norma; Wray, Susan

    1999-01-01

    We have used 31P NMR spectroscopy to measure metabolites and pHi at three periods during a phasic contraction of the uterus, in vivo, to determine whether they change as a consequence of contraction. The regular uterine contractions were recorded via a balloon catheter in the uterine lumen. Each phasic contraction was divided into three parts: the period between contractions (rest), the development of force (up) and the relaxation of force (down). The NMR data were summed separately from each of these three periods over 20-40 successive contractions.Significant changes in ATP, phosphocreatine (PCr) and inorganic phosphate (Pi) occurred during the contraction. [ATP] fell from 2.0 to 1.6 mM and [PCr] from 2.6 to 2.0 mM during the up period, while [Pi] increased from 2.2 to 2.8 mM. Recovery of ATP and PCr occurred during the relaxation part of the contraction, whereas Pi did not fully recover until the contraction was complete.Significant acidification from pH 7.28 ± 0.02 at rest to 7.16 ± 0.02, occurred with contraction. This acidification is greater than that previously reported for in vitro uterine preparations. Measurements of uterine blood flow show that it decreased with contraction. Therefore, ischaemia, in addition to the metabolic consequences of contraction, may account for the larger acidification observed in vivo.Lowering pHi in an in vitro uterine preparation by a similar level to that found in vivo produced a significant reduction of the phasic contractions. Thus we propose that these changes, especially the fall in pHi during force development, feed back negatively on the contraction to limit its strength, and may help prevent uterine ischaemia and fetal hypoxia during labour. PMID:10420014

  18. Cholesterol Removal from Adult Skeletal Muscle impairs Excitation-Contraction Coupling and Aging reduces Caveolin-3 and alters the Expression of other Triadic Proteins

    Directory of Open Access Journals (Sweden)

    Genaro eBarrientos

    2015-04-01

    Full Text Available Cholesterol and caveolin are integral membrane components that modulate the function/location of many cellular proteins. Skeletal muscle fibers, which have unusually high cholesterol levels in transverse tubules, express the caveolin-3 isoform but its association with transverse tubules remains contentious. Cholesterol removal impairs excitation-contraction coupling in amphibian and mammalian fetal skeletal muscle fibers. Here, we show that treating single muscle fibers from adult mice with the cholesterol removing agent methyl-β-cyclodextrin decreased fiber cholesterol by 26%, altered the location pattern of caveolin-3 and of the voltage dependent calcium channel Cav1.1, and suppressed or reduced electrically evoked Ca2+ transients without affecting membrane integrity or causing sarcoplasmic reticulum calcium depletion. We found that transverse tubules from adult muscle and triad fractions that contain ~10% attached transverse tubules, but not sarcoplasmic reticulum membranes, contained caveolin-3 and Cav1.1; both proteins partitioned into detergent-resistant membrane fractions highly enriched in cholesterol. Aging entails significant deterioration of skeletal muscle function. We found that triad fractions from aged rats had similar cholesterol and RyR1 protein levels compared to triads from young rats, but had lower caveolin-3 and glyceraldehyde 3-phosphate dehydrogenase and increased Na+/K+-ATPase protein levels. Both triad fractions had comparable NADPH oxidase (NOX activity and protein content of NOX2 subunits (p47phox and gp91phox, implying that NOX activity does not increase during aging. These findings show that partial cholesterol removal impairs excitation-contraction coupling and alters caveolin-3 and Cav1.1 location pattern, and that aging reduces caveolin-3 protein content and modifies the expression of other triadic proteins. We discuss the possible implications of these findings for skeletal muscle function in young and aged

  19. Psychometric Properties of the Deep Muscle Contraction Scale for Assessment of the Drawing-in Maneuver in Patients With Chronic Nonspecific Low Back Pain.

    Science.gov (United States)

    Oliveira, Crystian B; Negrão Filho, Ruben F; Franco, Márcia R; Morelhão, Priscila K; Araujo, Amanda C; Pinto, Rafael Z

    2017-06-01

    Study Design A prospective cohort study. Background Motor control dysfunctions have been commonly reported in patients with chronic nonspecific low back pain (LBP). Physical therapists need clinical tools with adequate psychometric properties t