Literatura académica sobre el tema "Maximal voluntary contraction"
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Artículos de revistas sobre el tema "Maximal voluntary contraction"
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Todd, Gabrielle, Janet L. Taylor, Jane E. Butler, Peter G. Martin, Robert B. Gorman y Simon C. Gandevia. "Use of motor cortex stimulation to measure simultaneously the changes in dynamic muscle properties and voluntary activation in human muscles". Journal of Applied Physiology 102, n.º 5 (mayo de 2007): 1756–66. http://dx.doi.org/10.1152/japplphysiol.00962.2006.
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Force responses to transcranial magnetic stimulation of motor cortex (TMS) during exercise provide information about voluntary activation and contractile properties of the muscle. Here, TMS-generated twitches and muscle relaxation during the TMS-evoked silent period were measured in fresh, heated, and fatigued muscle. Subjects performed isometric contractions of elbow flexors in two studies. Torque and EMG were recorded from elbow flexor and extensor muscles. One study ( n = 6) measured muscle contraction times and relaxation rates during brief maximal and submaximal contractions in fresh and fatigued muscle. Another study ( n = 7) aimed to 1) assess the reproducibility of muscle contractile properties during brief voluntary contractions in fresh muscle, 2) validate the technique for contractile properties in passively heated muscle, and 3) apply the technique to study contractile properties during sustained maximal voluntary contractions. In both studies, muscle contractile properties during voluntary contractions were compared with the resting twitch evoked by motor nerve stimulation. Measurement of muscle contractile properties during voluntary contractions is reproducible in fresh muscle and reveals faster and slower muscle relaxation rates in heated and fatigued muscle, respectively. The technique is more sensitive to altered muscle state than the traditional motor nerve resting twitch. Use of TMS during sustained maximal contractions reveals slowing of muscle contraction and relaxation with different time courses and a decline in voluntary activation. Voluntary output from the motor cortex becomes insufficient to maintain complete activation of muscle, although slowing of muscle contraction and relaxation indicates that lower motor unit firing rates are required for fusion of force.
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Froyd, Christian, Fernando Gabe Beltrami, Jørgen Jensen y Timothy David Noakes. "Potentiation Increases Peak Twitch Torque by Enhancing Rates of Torque Development and Relaxation". Journal of Human Kinetics 38 (1 de septiembre de 2013): 83–94. http://dx.doi.org/10.2478/hukin-2013-0048.
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Abstract The aim of this study was to measure the extent to which potentiation changes in response to an isometric maximal voluntary contraction. Eleven physically active subjects participated in two separate studies. Single stimulus of electrical stimulation of the femoral nerve was used to measure torque at rest in unpotentiated quadriceps muscles (study 1 and 2), and potentiated quadriceps muscles torque in a 10 min period after a 5 s isometric maximal voluntary contraction of the quadriceps muscles (study 1). Additionally, potentiated quadriceps muscles torque was measured every min after a further 10 maximal voluntary contractions repeated every min (study 2). Electrical stimulation repeated several times without previous maximal voluntary contraction showed similar peak twitch torque. Peak twitch torque 4 s after a 5 s maximal voluntary contraction increased by 45±13% (study 1) and by 56±10% (study 2), the rate of torque development by 53±13% and 82±29%, and the rate of relaxation by 50±17% and 59±22%, respectively, but potentiation was lost already two min after a 5 s maximal voluntary contraction. There was a tendency for peak twitch torque to increase for the first five repeated maximal voluntary contractions, suggesting increased potentiation with additional maximal voluntary contractions. Correlations for peak twitch torque vs the rate of torque development and for the rate of relaxation were r2= 0.94 and r2=0.97. The correlation between peak twitch torque, the rate of torque development and the rate of relaxation suggests that potentiation is due to instantaneous changes in skeletal muscle contractility and relaxation.
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Chapman, Neil, John William Whitting, Suzanne Broadbent, Zachary Crowley-McHattan y Rudi Meir. "Poststretch Isometric Contractions of the Hamstrings: Just a Brief Stretch to Achieve Supramaximal Isometric Force". Journal of Applied Biomechanics 37, n.º 4 (1 de agosto de 2021): 320–26. http://dx.doi.org/10.1123/jab.2020-0236.
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Hamstring strain injuries are common in sport. Supramaximal eccentric or high-intensity isometric contractions are favored in hamstring strain injury prevention. The effect of combining these contraction modes in such prevention programs as a poststretch isometric contraction is unknown. Poststretch isometric contractions incorporate an active stretch and result in greater final isometric force than isometric contractions at comparable joint angles. This study compared torque and muscle activation levels between maximal voluntary isometric contraction and maximal poststretch isometric contractions of the knee flexors. Participants (n = 9) completed baseline maximal voluntary isometric contraction at 150° knee flexion and maximal poststretch isometric contractions at 120° knee flexion actively stretching at 60°/s to 150° knee flexion for final isometric contraction. Torque of the knee flexors and surface electromyography root mean square (sEMGRMS) of biceps femoris long head were simultaneously recorded and compared between baseline and poststretch isometric at 150° knee flexion. Torque was 14% greater in the poststretch isometric condition compared with baseline maximal voluntary isometric contraction (42.45 [20.75] N·m, 14% [22.18%], P < .001) without increase in sEMGRMS of biceps femoris long head (−.03 mV, ±.06, P = .130, d = .93). Poststretch isometric contractions resulted in supramaximal levels of poststretch isometric torque without increased activation of biceps femoris long head.
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Duchateau, J. y K. Hainaut. "Electrical and mechanical changes in immobilized human muscle". Journal of Applied Physiology 62, n.º 6 (1 de junio de 1987): 2168–73. http://dx.doi.org/10.1152/jappl.1987.62.6.2168.
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After forearm fracture, the human thumb was unilaterally immobilized in eight subjects for 6 wk in a standard plaster cast. Changes of contraction properties were studied in the adductor pollicis muscle. The contralateral muscle remained unrestrained and served as control. After immobilization, the maximal voluntary contraction was reduced by 55% (P less than 0.05), and the electrically evoked maximal tetanic contraction (Po) was reduced by 33% (P less than 0.05). The decrease of Po was associated with increased maximal rate of tension development (10%) and decreased maximal rate of tension relaxation (22%). The twitch times to peak and to half relaxation were increased by 16 and 14%, respectively, but the twitch tension (Pt) was not significantly changed and the Pt/Po ratio was increased by 43% after immobilization. The muscle surface action potential presented an increase of its duration (19%) and a decrease of the amplitude and the total area (15 and 26%, respectively). The comparison of the electrical and mechanical alterations recorded during voluntary contractions, and in contractions evoked by electrical stimulation of the motor nerve, suggests that immobilization not only modifies the peripheral processes associated with contraction but also changes central and/or neural command of the contraction. At peripheral sites, it is proposed that the intracellular processes of contraction play the major role in the contractile impairment recorded during immobilization.
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Ushiyama, Junichi, Yoshihisa Masakado, Toshiyuki Fujiwara, Tetsuya Tsuji, Kimitaka Hase, Akio Kimura, Meigen Liu y Junichi Ushiba. "Contraction level-related modulation of corticomuscular coherence differs between the tibialis anterior and soleus muscles in humans". Journal of Applied Physiology 112, n.º 8 (15 de abril de 2012): 1258–67. http://dx.doi.org/10.1152/japplphysiol.01291.2011.
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The sensorimotor cortex activity measured by scalp EEG shows coherence with electromyogram (EMG) activity within the 15- to 35-Hz frequency band (β-band) during weak to moderate intensity of isometric voluntary contraction. This coupling is known to change its frequency band to the 35- to 60-Hz band (γ-band) during strong contraction. This study aimed to examine whether such contraction level-related modulation of corticomuscular coupling differs between muscles with different muscle compositions and functions. In 11 healthy young adults, we quantified the coherence between EEG over the sensorimotor cortex and rectified EMG during tonic isometric voluntary contraction at 10–70% of maximal voluntary contraction of the tibialis anterior (TA) and soleus (SOL) muscles, respectively. In the TA, the EEG-EMG coherence shifted from the β-band to the γ-band with increasing contraction level. Indeed, the magnitude of β-band EEG-EMG coherence was significantly decreased, whereas that of γ-band coherence was significantly increased, when the contraction level was above 60% of maximal voluntary contraction. In contrast to the TA, the SOL showed no such frequency changes of EEG-EMG coherence with alterations in the contraction levels. In other words, the maximal peak of EEG-EMG coherence in the SOL existed within the β-band, irrespective of the contraction levels. These findings suggest that the central nervous system regulates the frequency of corticomuscular coupling to exert the desired levels of muscle force and, notably, that the applicable rhythmicity of the coupling for performing strong contractions differs between muscles, depending on the physiological muscle compositions and functions of the contracting muscle.
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Baudry, Stéphane y Jacques Duchateau. "Postactivation potentiation in a human muscle: effect on the load-velocity relation of tetanic and voluntary shortening contractions". Journal of Applied Physiology 103, n.º 4 (octubre de 2007): 1318–25. http://dx.doi.org/10.1152/japplphysiol.00403.2007.
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Recently it was demonstrated that postactivation potentiation (PAP), which refers to the enhancement of the muscle twitch torque as a result of a prior conditioning contraction, increased the maximal rate of torque development of tetanic and voluntary isometric contractions ( 3 ). In this study, we investigated the effects of PAP and its decay over time on the load-velocity relation. To that purpose, angular velocity of thumb adduction in response to a single electrical stimulus (twitch), a high-frequency train of 15 pulses at 250 Hz (HFT250), and during ballistic voluntary shortening contractions, performed against loads ranging from 10 to 50% of the maximum torque, were recorded before and after a conditioning 6-s maximal voluntary contraction (MVC). The results showed an increase of the peak angular velocity for the different loads tested after the conditioning MVC ( P < 0.001), but the effect was greatest for the twitch (∼182%) compared with the HFT250 or voluntary contractions (∼14% for both contraction types). The maximal potentiation occurred immediately following the conditioning MVC for the twitch, whereas it was reached 1 min later for the tetanic and ballistic voluntary contractions. At that time, the load-velocity relation was significantly shifted upward, and the maximal power of the muscle was increased (∼13%; P < 0.001). Furthermore, the results also indicated that the effect of PAP on shortening contractions was not related to the modality of muscle activation. In conclusion, the findings suggest a functional significance of PAP in human movements by improving muscle performance of voluntary dynamic contractions.
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Kavanagh, Justin J., Matthew R. Feldman y Michael J. Simmonds. "Maximal intermittent contractions of the first dorsal interosseous inhibits voluntary activation of the contralateral homologous muscle". Journal of Neurophysiology 116, n.º 5 (1 de noviembre de 2016): 2272–80. http://dx.doi.org/10.1152/jn.00367.2016.
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The aim of this study was to investigate how maximal intermittent contractions for a hand muscle influence cortical and reflex activity, as well as the ability to voluntarily activate the homologous muscle in the opposite limb. Twelve healthy subjects (age 24 ± 3 yr, all right-hand dominant) performed maximal contractions of the dominant limb first dorsal interosseous (FDI), and activity of the contralateral FDI was examined in a series of experiments. Index finger abduction force, FDI electromyography (EMG), motor evoked potentials, and heteronomous reflexes were obtained from the contralateral limb during brief, nonfatiguing contractions. The same measures, as well as the ability to voluntarily activate the contralateral FDI, were then assessed in an extended intermittent contraction protocol that elicited fatigue. Brief contractions under nonfatigued conditions increased index finger abduction force, FDI EMG, and motor evoked potential amplitude of the contralateral limb. However, when intermittent maximal contractions were continued until fatigue, there was an inability to produce maximal force with the contralateral limb (∼30%), which was coupled to a decrease in the level of voluntary activation (∼20%). These declines were present without changes in reflex activity and regardless of whether cortical or motor point stimulation was used to assess voluntary activation. It is concluded that performing maximal intermittent contractions with a single limb causes an inability of the central nervous system to maximally drive the homologous muscle of the contralateral limb. This is, in part, mediated by mechanisms that involve the motor cortex ipsilateral to the contracting limb.
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Kern, Mark K., Ronald C. Arndorfer, James S. Hyde y Reza Shaker. "Cerebral cortical representation of external anal sphincter contraction: effect of effort". American Journal of Physiology-Gastrointestinal and Liver Physiology 286, n.º 2 (febrero de 2004): G304—G311. http://dx.doi.org/10.1152/ajpgi.00201.2003.
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The external anal sphincter (EAS) plays a critical role in maintaining fecal continence; however, cerebral cortical control of voluntary EAS contraction is not completely understood. Our aims were to determine the cortical areas associated with voluntary EAS contraction and to determine the effect of two levels of sphincter contraction effort on brain activity. Seventeen asymptomatic adults (ages 21-48, 9 male) were studied using functional magnetic resonance imaging (fMRI) to detect brain activity. Studies were done in two stages. In stage 1 (10 subjects, 5 male), anal sphincter pressure was monitored from a catheter-affixed bag. Subjects performed maximal and submaximal EAS contractions during two fMRI scanning sessions consisting of alternating 10-s intervals of sustained contraction and rest. In stage 2 studies, seven subjects (4 male) performed only maximum effort sphincter contractions without a catheter. EAS contraction was associated with multifocal fMRI activity in sensory/motor, anterior cingulate, prefrontal, parietal, occipital, and insular regions. Total cortical activity volume was significantly larger ( P < 0.05) for maximal (5,175 ± 720 μl) compared with submaximal effort contractions (2,558 ± 306 μl). Similarly, percent fMRI signal change was significantly higher ( P < 0.05) for maximal (4.8 ± 0.1%) compared with submaximal effort contractions (2.2 ± 0.1%). Cortical region-of-interest analysis showed the incidence of insular activation to be more common in women compared with men. Other cortical regions showed no such gender differences. fMRI activity detected in stage 2 showed similar regions of cortical activation to those of the stage 1 study. Willful contraction of the EAS is associated with multifocal cerebral cortical activity. The volume and intensity of cerebral cortical activation is commensurate with the level of contractile effort.
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Dalton, Brian H., Brad Harwood, Andrew W. Davidson y Charles L. Rice. "Recovery of Motoneuron Output Is Delayed in Old Men Following High-Intensity Fatigue". Journal of Neurophysiology 103, n.º 2 (febrero de 2010): 977–85. http://dx.doi.org/10.1152/jn.00908.2009.
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Despite an age-related slowing in the contractile properties of the triceps surae, inherently low maximal motor unit firing rates (MUFRs) in the soleus are unchanged. Fatigue following high-intensity contractions is characterized by contractile slowing in conjunction with a reduction in MUFRs in young adults. Here we exploit the ageing model of the soleus to assess changes in neuromuscular function during fatigue and short-term recovery. We hypothesize that a high-intensity sustained contraction will cause minimal reductions in MUFRs in young and old subjects but that recovery of MUFRs will be delayed in aged subjects. We compared the effects of a high-intensity sustained task on the MUFRs of the soleus and triceps surae contractile properties in six young (∼24 yr) and six old (∼75 yr) men. Various measures of the contractile function of the triceps surae were tested during two to six sessions via maximal voluntary isometric contractions (MVCs) and tibial nerve stimulation. Populations of MUFR trains were recorded from the soleus during brief (∼7 s) MVCs, a high-intensity (75% MVC) sustained fatiguing task, and brief MVCs following task failure at 1, 2, 5, and 10 min. Old men had greater time to task failure than the young (∼138 and ∼100 s, respectively). Voluntary activation was near maximal (>99%) for all subjects but at task failure, decreased to ∼89% in both groups. Maximal MUFRs, for both groups, were reduced by ∼44% and twitch contraction duration slowed by ∼30% following task failure. Contraction duration recovered equally for both groups within 2 min, but maximal MUFRs did not recover until 5 min in the old compared with 1 min for the young. The surprising fatigue-induced reduction in MUFRs was similar for both groups, but despite a similar recovery of contractile properties for both, recovery of MUFRs was impaired in the old subjects.
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Latash, M., E. Kalugina, J. Nicholas, C. Orpett, D. Stefoski y F. Davis. "Myogenic and Central Neurogenic Factors in Fatigue in Multiple Sclerosis". Multiple Sclerosis Journal 1, n.º 4 (febrero de 1996): 236–41. http://dx.doi.org/10.1177/135245859600100409.
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Short episodes of electrical stimulation were applied to the right quadriceps muscle of patients with multiple sclerosis (MS) and healthy subjects at different times during 60 sec sustained voluntary muscle contractions at 0 to 100% levels of maximal voluntarily generated joint torque. The amplitude of electrically induced increments of torque (ΔT) has been shown to depend upon both the level of muscular contraction and time from the beginning of the contraction. The dependence of ΔT upon the time from the beginning of contraction has been assumed to reflect muscle fatigue. Patients with MS demonstrated an apparent involvement of central neurogenic mechanisms in fatigue manifested as a drop in muscle torque during sustained contractions at 75 and 100% levels when electrical stimulation was able to induce considerable increments in muscle torque. These patients also demonstrated a dependence of ΔT upon the contraction level suggesting that they did not produce maximal voluntary contraction torque in the pre-trial. Fatigue in MS is due to central, neurogenic factors and does not seem to involve any myogenic factors such as might be related to secondary muscle changes due to the long-standing disorder. The subjective feeling of tiredness (‘fatigue’) may be related to a dissociation between central motor commands (‘effort’) and their mechanical consequences.
Tesis sobre el tema "Maximal voluntary contraction"
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Perez, Diana. "Can humans fully activate the motor units of the quadriceps femoris muscle when performing a maximal voluntary contraction?" Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=69743.
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The ability to fully activate the motor units of the quadriceps femoris muscle when performing an isometric maximal voluntary contraction (MVC) was assessed in 30 subjects. The twitch interpolation technique (TIT) was used to measure the increase in force superimposed on the MVC by a supramaximal shock to the femoral nerve. The superimposed force was compared to the potentiated twitch (PtP) force, and an activation ratio (A.R.) was calculated. The resting twitch (PtR) force, MVC force, and the inverse relationship between the level of voluntary force and the superimposed twitch force were also measured. Subjects were compared on the basis of activity level (15 sedentary and 15 trained) and gender (14 males and 16 females). The mean A.R. was 95% regardless of activity level or gender. Males were stronger than females but there was no difference in strength between the sedentary and trained groups. PtR and PtP force values showed the same pattern of results. The nature of the relationship between the level of voluntary force and the superimposed twitch force was curvilinear, and indicates that the TIT may not be accurate in measuring the amount of activation for a muscle as large as the quadriceps when voluntary contractions greater than 70% of the MVC are performed. The intra-subject reliability of the TIT used in this lab was acceptable (ICC = 0.78).
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Fry, Adam. "A neurophysiological examination of voluntary isometric contractions : modulations in sensorimotor oscillatory dynamics with contraction force and physical fatigue, and peripheral contributions to maximal force production". Thesis, Loughborough University, 2016. https://dspace.lboro.ac.uk/2134/20392.
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Human motor control is a complex process involving both central and peripheral components of the nervous system. Type Ia afferent input contributes to both motor unit recruitment and firing frequency, however, whether maximal force production is dependent on this input is unclear. Therefore, chapter 2 examined maximal and explosive force production of the knee extensors following prolonged infrapatellar tendon vibration; designed to attenuate the efficacy of the homonymous Ia afferent-α-motoneuron pathway. Despite a marked decrease in H-reflex amplitude, indicating an attenuated efficacy of the Ia afferent-α-motoneuron pathway, both maximal and explosive force production were unaffected after vibration. This suggested that maximal and explosive isometric quadriceps force production was not dependent upon Ia afferent input to the homonymous motor unit pool. Voluntary movements are linked with various modulations in ongoing neural oscillations within the supraspinal sensorimotor system. Despite considerable interest in the oscillatory responses to movements per se, the influence of the motor parameters that define these movements is poorly understood. Subsequently, chapters 3 and 4 investigated how the motor parameters of voluntary contractions modulated the oscillatory amplitude. Chapter 3 recorded electroencephalography from the leg area of the primary sensorimotor cortex in order to investigate the oscillatory responses to isometric unilateral contractions of the knee-extensors at four torque levels (15, 30, 45 and 60% max.). An increase in movement-related gamma (30-50 Hz) activity was observed with increments in knee-extension torque, whereas oscillatory power within the delta (0.5-3 Hz), theta (3-7 Hz), alpha (7-13 Hz) and beta (13-30 Hz) bands were unaffected. Chapter 4 examined the link between the motor parameters of voluntary contraction and modulations in beta (15-30 Hz) oscillations; specifically, movement-related beta decrease (MRBD) and post-movement beta rebound (PMBR). Magnetoencephalography (MEG) was recorded during isometric ramp and constant-force wrist-flexor contractions at distinct rates of force development (10.4, 28.9 and 86.7% max./s) and force output (5, 15, 35 and 60%max.), respectively. MRBD was unaffected by RFD or force output, whereas systematic modulation of PMBR by both contraction force and RFD was identified for the first time. Specifically, increments in isometric contraction force increased PMBR amplitude, and increments in RFD increased PMBR amplitude but decreased PMBR duration. Physical fatigue arises not only from peripheral processes within the active skeletal muscles but also from supraspinal mechanisms within the brain. However, exactly how cortical activity is modulated during fatigue has received a paucity of attention. Chapter 5 investigated whether oscillatory activity within the primary sensorimotor cortex was modulated when contractions were performed in a state of physical fatigue. MEG was recorded during submaximal isometric contractions of the wrist-flexors performed both before and after a fatiguing series of isometric wrist-flexions or a time matched control intervention. Physical fatigue offset the attenuation in MRBD observed during the control trial, whereas PMBR was increased when submaximal contractions were performed in a fatigued state.
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Kan, Benjamin. "Effect of transcranial direct current stimulation (tDCS) on maximal voluntary isometric strength and endurance of the elbow flexors". Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2011. https://ro.ecu.edu.au/theses/375.
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The present study investigated the effects of transcranial direct current stimulation (tDCS) on maximal voluntary contraction strength (MVC) and the time to failure (TTF) of an isometric muscle endurance test of the elbow flexors. Prior to the main study, the test-retest reliability of MVC and TTF measures was investigated using 10 men (33.2 ± 9.4 y) for the measurements separated by 60 min (within-day) and one week (between-day). Coefficient of variation (CV), Intraclass correlation (ICC, R), a paired t-test and the Bland-Altman plots revealed that TTF at 30% MVC task was reliable, and was able to detect a possible effect of tDCS on TTF, if the magnitude of effect was greater than 11%. Based on the reliability study results, it was hypothesised that tDCS would increase TTF from the first test to the second test separated by 60 min, when a tDCS treatment was administered immediately before the second test. Fifteen men (27.7 ± 8.4 y) were tested for MVC and TTF at 30%-MVC before and immediately after tDCS or sham intervention (10 min) in three separate sessions. In two sessions direct current (2 mA) was delivered through saline-soaked sponge electrodes, with the anode placed on the scalp overlying the right motor cortical representation of the left arm and the cathode secured over the right shoulder. One session was a sham intervention (current delivery for the first 30s). The order of the intervention sessions was randomised and counterbalanced amongst the subjects and subjects who were blinded to intervention type. Changes in MVC strength and TTF from pre to post intervention were compared between the interventions by a two-way repeated measures ANOVA. No significant differences were evident for the two tDCS sessions. MVC strength (baseline: 66.0 ± 11.4 Nm) decreased by 5.9 ± 4.2 % (P
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Ruas, Cassio V. "Neuromuscular characteristics of eccentric contractions of the knee extensors and their muscle damage profiles". Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2021. https://ro.ecu.edu.au/theses/2437.
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Muscle can generate greater force with lower muscle activation during eccentric (ECC) than isometric (ISO) and concentric (CON) contractions (actions). Unaccustomed ECC exercise induces muscle damage represented by prolonged impairment of muscle function and delayed onset muscle soreness (DOMS), but also confers protection from muscle damage, known as the repeated bout effect (RBE). However, the neuromuscular characteristics of ECC contractions, and the mechanisms involved in the muscle damage and RBE induced by ECC are not fully understood. Therefore, the purpose of this PhD thesis was to examine the neuromuscular characteristics of ECC contractions of the knee extensors in relation to muscle damage and the RBE profiles. This thesis consisted of five studies as summarised below.
Study 1: Short-interval intracortical inhibition (SICI) is often used to examine inhibitory responses in the primary motor cortex representation of the quadriceps, but appropriate pairedpulse transcranial magnetic stimulation (TMS) parameters to optimise SICI measurement were not clear. Using 9 men and 6 women (26.6 ± 4.4 y), responses to single and paired-pulse (3-ms interval) TMS were recorded from vastus lateralis (VL), rectus femoris (RF) and vastus medialis (VM). Test stimulus intensity was 140% of active motor threshold (AMT), and conditioning stimulus intensities (CSIs) ranged from 55-90% (eight intensities) of AMT (5 test and 5 paired responses for each intensity). With CSI of 55% AMT, SICI was minimal (conditioned:test motor evoked potential [MEP]; 1.00, 0.96 and 0.95 for VL, RF and VM, respectively, -1.00 indicates inhibition). Inhibition was greater at 70-90% AMT for VL (0.67- 0.85), at 75-90% AMT for RF (0.70-0.78) and at 80-90% AMT for VM (0.59-0.68) when compared to 55% AMT. The CSIs that elicited maximal and 50% maximal inhibition were ~84% and ~75% AMT, respectively. This method was shown to provide a practical approach to investigate quadriceps inhibitory networks.
Study 2: Responses to TMS, twitch forces (TF) and voluntary drive were compared between ECC, ISO and CON contractions of the knee extensors. Sixteen participants (20-33 y) performed submaximal and maximal voluntary contractions (MVCs) for ISO and isokinetic (30˚/s) CON and ECC of knee extensors. EMG was recorded from VL. Supramaximal femoral nerve stimulation during and after MVCs evoked superimposed (ST) and resting TF to calculate voluntary activation (VA). Maximal M-waves (MMAX) were recorded. During 30% MVCs, single- and paired-pulse TMS elicited MEPs and assessed SICI. MVC torque was greater (P
Study 3: ECC-only and coupled concentric-eccentric contractions (CON-ECC) of the knee extensors were compared for changes in neurophysiological indices before, immediately after and 1-3 days post-exercise. Twenty participants (19-36 y) were randomly assigned to ECC (n=10) or CON-ECC (n=10) group. ECC group performed 6 sets of 8 ECC-only contractions at 80% of ECC one-repetition maximum (1-RMecc), while CON-ECC group performed 6 sets of 8 alternating CON and ECC (i.e., 8 CON and 8 ECC) contractions at 80% of CON 1-RM and 1-RMecc, respectively. Maximal voluntary isometric contraction (MVIC) force, rate of force development (RFD), TF elicited by femoral nerve stimulation, VA, MEPs, corticospinal silent period (CSP) and SICI assessed by single- and paired-pulse TMS, and muscle soreness were measured before, immediately after, and 1-3 days post-exercise. No significant (p>0.05) differences between ECC and CON-ECC were evident for the changes in any variables post3 exercise. MVIC force decreased immediately post-exercise compared to baseline (ECC: -20.7 ± 12.8%, CON-ECC: -23.6 ± 23.3%) and remained low at 3 days post-exercise (-13.6 ± 13.4%, -3.3 ± 21.2%), and changes in RFD were greater than those of MVIC force (immediately postexercise: ECC: -38.3 ± 33.9%, CON-ECC: -30.7 ± 38.3%). VA, TF and MEP/MMAX decreased and CSP increased post-exercise (p
Study 4: Since the participants from Study 3 responded similarly for indirect indicators of muscle damage, the 20 participants were used to examine whether the magnitude of muscle damage indicated by changes in MVIC force 1-3 days after ECC could be predicted by changes in central and peripheral neuromuscular parameters immediately post-ECC. The criterion measures were the same as those in Study 2, and additional analyses of the rate of force development (RFDRT) and rate of relaxation (RRRT) of the TF were performed. Relationships between changes in the variables immediately post-ECC and changes in MVIC force at 1-3 days post-ECC were examined by Pearson product-moment (r) or Spearman correlations. MVIC force decreased (-22.2 ± 18.4%) immediately post-exercise, and remained below baseline at 1 (-16.3 ± 15.2%), 2 (-14.7 ± 13.2%) and 3 days post-ECC (-8.6 ± 15.7%). Immediately post-ECC, RFD (0-30-ms: -38.3 ± 31.4%), TF (-45.9 ± 22.4%), RFDRT (-32.5±40.7%), RRRT (-38.0±39.7%), VA (-21.4 ± 16.5%) and MEP/MMAX at rest (-42.5 ± 23.3%) also decreased, while CSP at 10%-MVIC increased by 26.0 ± 12.2% (p
Study 5: Among the 20 participants described in Study 4, 10 participants (6 from the eccentriconly exercise group and 4 from the concentric-eccentric exercise group) returned two weeks after the first exercise bout to perform the second bout of the same exercise. Changes in MVIC force, RFD, muscle soreness, TF, VA, MMAX, MEPs, and SICI before, immediately after and 1–3 days post-exercise were compared between the first (ECC1) and the second bouts (ECC2). ECC2 induced less (P=0.01) muscle soreness (peak: 27.5 ± 26.6 mm) than ECC1 (50.7 ± 31.8 mm), and MVIC force decreased more immediately post-ECC1 (-21.6 ± 23.3%) than ECC2 (-11.0 ± 11.3%) and recovered faster to the baseline after ECC2 than ECC1. RFD decreased immediately after ECC1 (e.g. 0-50-ms: -50.5 ± 52.5%, P0.05). The non-significant differences in VA and MEPs between ECC1 and ECC2, and lack of changes in MMAX and SICI suggest that changes in neural factors after eccentric exercise do not explain the repeated bout effect.
Collectively, these studies advance understanding of the characteristics of ECC muscle contractions and their relationship to muscle damage and the RBE, and can be used to inform future research directions.
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Kluka, Virginie. "Etude des propriétés neuromusculaires chez l'enfant : approche par la stimulation magnétique périphérique". Thesis, Clermont-Ferrand 2, 2015. http://www.theses.fr/2015CLF22649/document.
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L’objectif de ce travail était de comparer l’importance de la composante nerveuse dans les différences de production de force entre les enfants et les adultes en tenant compte des conditions mécaniques qui sont susceptibles de l’influencer (longueur musculaire, mode et vitesse de contraction) et des effets de la fatigue. Trente et un garçons pré-pubères de 8-12 ans et 37 hommes de 18-30 ans ont été recrutés et répartis dans les 3 études composant ce projet. La première étude portait sur les effets de la longueur musculaire et de la fatigue sur la production de force et le niveau d’activation maximal volontaire (VA) des extenseurs du genou.La seconde traitait des effets de la longueur musculaire sur la production de force et le VA des fléchisseurs plantaires. Enfin, la troisième portait sur les effets du mode et de la vitesse de contraction sur le VA des extenseurs du genou. Les propriétés neuromusculaires ont été évaluées à l’aide de stimulations magnétiques périphériques et de contractions maximales volontaires. Les résultats montrent un VA des extenseurs du genou supérieur chez l’adulte lors de grande longueur musculaire (90°-100° de flexion) (étude 1), mais aucune différence avec l’enfant à courte longueur musculaire (20° de flexion). En revanche, sur des groupes musculaires tels que les fléchisseurs plantaires, aucun effet de la longueur sur le VA n’a été observé chez les enfants et les adultes (étude 2). En ce qui concerne les effets du mode de contraction, nos résultats montrent que le VA est inférieur en conditions excentrique et concentrique par rapport à la condition isométrique, mais aucune différence n’était observée entre les groupes (étude 3). Toutefois, l’effet de cette baisse de VA sur la production de force variait entre les groupes ; une diminution de force accompagnant la diminution de VA n’était retrouvée que chez l’adulte. Enfin,nous avons montré que la baisse du VA au cours d’un protocole de fatigue est plus conséquente chez les enfants par rapport aux adultes (étude 1), ce qui témoigne de l’existence d’une fatigue centrale majorée chez l’enfant. Une maturation inaboutie et les propriétés musculo-tendineuses particulières de l’enfant (compliance supérieure) pourraient expliquer les résultats obtenus au cours de ce travailThe purpose of this PhD thesis was to compare the contribution of the maximal voluntary activation level (VA) of the motor units to force production differences between children and adults in various mechanical conditions that affect force production (muscle length, contraction mode and velocity), and in fatigue condition. Thirty one pre-pubertal 8 to 12-year old boys and 37 men (18-30 years) were recruited and allocated into the 3 studies ofthis project. The first study was devoted to compare the effects of muscle length and fatigue on the VA and force generating capacity of the knee extensors between children and adults. In the second study, we compared the effects of muscle length on the VA and force generating capacity of the plantar flexors between children and adults. The third study analysed the effect of contraction mode and velocity on the VA and force generating capacity of the knee extensors between children and adults. Neuromuscular properties were assessed with peripheral magnetic stimulation and maximal voluntary contractions. Results showed a higher VA of the knee extensors in adults at long muscle length (90° and 100° knee flexion) but no difference between children and adults at short length (20° knee flexion; study 1). However, the VA of the plantar flexors was not affected by muscle length changes whatever the age group considered (study 2). Results also showed a higher VA in isometric mode compared to eccentric and concentric conditions whatever the age group (study 3). However, the effect of this VA reduction on force generating capacity differed between groups, a concomitant force reduction being observed in adults, but not in children. Finally, we observed a greater VA reduction and therefore greater central fatigue in children during the fatiguing protocol (study 1). A relative immaturity and the particular musculo-tendinous properties of children (higher compliance) may account for the reported results
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Barrue-Belou, Simon. "Contrôle nerveux de la contraction volontaire excentrique chez l'homme : approche neurophysiologique et plasticité à l'entraînement". Thesis, Toulouse 3, 2017. http://www.theses.fr/2017TOU30201/document.
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L'objectif de ce travail de thèse est d'étudier d'une part les spécificités de la commande nerveuse lors de la contraction excentrique en explorant les mécanismes impliqués au niveau spinal et d'autre part d'examiner les mécanismes nerveux responsables de la plasticité du système neuromusculaire après un entraînement de force excentrique sous-maximal. A travers ce travail de thèse, nous mettons en évidence la contribution de l'inhibition récurrente à la réduction de l'activation musculaire classiquement observée lors de la contraction excentrique. Par ailleurs, nous montrons que l'inhibition récurrente est majorée lors des contractions sous-maximales indépendamment du mode de contraction. Ces résultats soulignent le rôle important de l'inhibition récurrente dans la spécificité de la commande nerveuse lors de la contraction excentrique. Nous confirmons que le pilotage nerveux de la contraction excentrique peut être modulé par l'entraînement de force excentrique même si les modulations de l'excitabilité spinale semblent dépendre des caractéristiques de l'entraînementThe purpose of this PhD research is, on the one hand, to study the neural drive specificities during eccentric contractions by exploring the neural mechanisms involved at spinal level and, on the other hand, to examine the neural mechanisms responsible for the modulations of neuromuscular system following a strength submaximal eccentric training. Through this PhD research we highlight the contribution of recurrent inhibition by the Renshaw cell to the decrease of muscular activation typically observed during eccentric contraction. Furthermore, we show that recurrent inhibition is enhanced during submaximal contractions regardless of the contraction type. These results emphasize the important role of recurrent inhibition in the specificity of neural control during eccentric contractions. We confirm that the neural drive of the eccentric contraction may be modulated by eccentric strength training although modulations of spinal excitability seem to depend on the characteristics of training
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Aldayel, Abdulaziz A. "Comparison of acute physiological effects between alternating current and pulsed current electrical muscle stimulation". Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2010. https://ro.ecu.edu.au/theses/131.
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Electrical muscle stimulation (EMS) is widely used in rehabilitation and sport training, and alternating current and pulsed current EMS are commonly used. However, no systematic comparison between alternating and pulsed current EMS has been made in the previous studies. The main aim of this research was to compare acute physiological responses between the alternating and pulsed current EMS. The secondary purpose of the research was to investigate further muscle damage induced by EMS-evoked isometric contractions. Three experimental studies were conducted in the thesis project together with literature review about EMS.
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Garbašauskaitė, Inga. "Judamųjų gebėjimų ugdymas taikant skirtingus treniravimo modelius". Bachelor's thesis, Lithuanian Academic Libraries Network (LABT), 2014. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2014~D_20140619_113432-16728.
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Darbo objektai – 1) skirtingiems fiziniams krūviams adaptuotų sportininkų maksimalios valingos jėgos įtaka greitumo jėgos rodikliams. 2) krepšininkų parengimas taikant skirtingus treniruočių modelius.
Keliame hipotezes, kad turintys didesnę maksimalią valingąją jėgą tiriamieji greičiau bėgs 30 m distancijos pirmą atkarpą (0-10 m.), o adaptuoti maksimaliajam bėgimo greičiui – greičiau bėgs nuotolio pabaigoje ir pasieks geresnius rezultatus. Taikant koncentruotą treniruočių sistemą didelio meistriškumo krepšininkai pasiekia geresnių galingumo rodiklių ir sugeba juos išlaikyti rungtynių metu.
Tikslai Nustatyti taikytų skirtingų treniravimo modelių įtaką judamųjų gebėjimų ugdymui.
Uždaviniai: 1. Nustatyti ir palyginti skirtingam fiziniam krūviui adaptuotų sportininkų maksimalios valingosios jėgos (MVJ) ir 30 m bėgimo rezultatus bei bėgimo greičio prieaugio tempą. 2. Nustatyti ir palyginti vertikalaus šuolio rezultatus krepšininkų grupėms, besitreniruojančioms pagal skirtingus treniruočių modelius.
Išvados: 1. Turėdami didžiausią MVJ pirmus 10 m greičiausiai įveikia sunkiaatlečiai, tačiau likusias bėgimo atkarpas greičiausiai įveikia elito sprinteriai, taip pat pasiekdami didžiausią bėgimo greičio prieaugį nuo 10 iki 30 bėgimo metro – 29,74 % (p<0,05). 2. Koncentruotas skirtingų judamųjų gebėjimų ugdymo modelis labiau pagerina krepšininkų vertikalaus šuolio rezultatus bei jų atsistatymą po rungtynių nei mišraus režimo modelis.
Praktinės rekomendacijos: tyrimo metu gauti duomenys... [toliau žr. visą tekstą]The objects of the study: 1) the impact of maximum voluntary contraction force to speed values for the athletes who are adapted to different physical loads. 2) the physical preparation of the basketball players using different training models. It is possible to make a hypothesis that athletes who have greater maximum voluntary contraction force runs faster in the first 10 meters (0-10 meters.) in the distance of 30 meters. However, the sprinters who are adapted to maximum speed of running runs faster in the end of the distance and achieves better results. Applying concentrated training model, the results of professional basketball players achieve greater power indicators and are able to keep them during the mach. The aim – To identify the influence of the different training models applied to the training of the moving abilities. Scopes: 1. To identify and compare the maximal voluntary contraction force and 30 meters of running results. Although to identify and compare the rate of increment for the speed of running. 2. To identify and compare the rates of vertical leap for the groups of basketball players who are trained using different training models. Conclusions: 1. Weightlifters who have the greatest maximum voluntary contraction force pass the first 10 meters faster. However, the other meters of the distance are passed faster by elite sprinters. In addition, the elite sprinters achieve the greatest increment of running speed (from 10 to 30 running meter – 29.74 % (p<0.0... [to full text]
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Chan, Roy Y. H. "The influence of set-repetition configuration in eccentric exercise on muscle damage and repeated bout effect". Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2011. https://ro.ecu.edu.au/theses/382.
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It is well known that maximal eccentric exercise induces muscle damage, especially when it is performed for the first time. However, muscle damage is attenuated in subsequent bouts of the same or similar exercise, which is known as the repeated bout effect. One of the factors affecting the magnitude of muscle damage and the repeated bout effect is the number of eccentric contractions; however, it is unknown if different set-repetition configurations with the same number of eccentric contractions would result in different magnitudes of muscle damage and adaptation. This study investigated changes in muscle strength, range of motion (ROM), muscle cross sectional area (CSA), muscle soreness and plasma creatine kinase (CK) activity following an initial bout of maximal eccentric contractions with the same total number of contractions but different set-repetition configurations (e.g. 3 sets of 10 reps vs. 10 sets of 3 reps) and a second bout (20 sets of 3 repetitions) separated by four weeks. Since the present study was the first to use the ultrasound extended field of view (EFOV) technique to quantify bicep brachii CSA for an indication of muscle swelling, the reliability and validity of the technique were assessed in a separate study using 6 men (27.5 ± 1.9 y). In the main study, 10 non-resistance trained men (26.1 ± 4.1 y) performed two bouts of eccentric exercise of the elbow flexors for each arm (4 bouts in total). One arm performed 3 sets of 10 maximal eccentric contractions (3x10) followed 4 weeks later by 20 sets of 3 maximal eccentric contractions (20x3). The contralateral arm performed 10 sets of 3 maximal eccentric contractions (10x3) followed 4 weeks later by 20x3. The order of the exercise (3x10, 10x3) and the use of arm (dominant, non-dominant) were counterbalanced amongst subjects. Changes in the criterion measures over time and peak torque were compared among the initial bouts (3x10 vs. 10x3) and the repeated bouts (20x3 vs. 20x3) by a factorial repeatedmeasures analysis of variance (ANOVA) with two factors. Significance level was set at P
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Matkowski, Boris. "Adaptations neuromusculaires des muscles extenseurs du genou : contractions fatigantes uni- vs bi-latérales". Phd thesis, Université de Bourgogne, 2010. http://tel.archives-ouvertes.fr/tel-00796850.
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L'objectif de ce travail était de déterminer i) l'influence du niveau de force absolue sur la durée du temps de maintien, et les altérations neuromusculaires subséquentes chez un même individu à l'issue d'un exercice réalisé à la même intensité relative, avec un ou deux membres ; ii) l'influence de la commande nerveuse sur la capacité de production de force de chacun des muscles extenseurs du genou lors de contractions unilatérales (UL) vs. bilatérales (BL); iii) l'évolution des mécanismes d'activation pendant une série de contractions sous-maximales évoquées par électromyostimulation (EMS).Les résultats de la première étude confirment que le temps limite est dépendant du niveau de force absolu pour un même individu, la durée de la contraction en UL étant 20% plus longue qu'en BL. De plus, une corrélation a été trouvée entre la force lors d'une contraction maximale volontaire (CMV) et le temps limite en UL et BL. Toutefois, d'autres mécanismes semblent être également mis en jeu, car dans un cas les mécanismes sont d'origine nerveux et musculaire (UL), alors que dans l'autre cas les mécanismes sont seulement nerveux (BL). Les résultats de la deuxième étude montrent que la force maximale développée lors d'une contraction BL est inférieure à la somme des forces des contractions UL (i.e. présence d'un déficit bilatéral). Les temps d'apparition des pics de force lors des CMV de chacune des jambes ne sont pas différents de celui de la CMV BL, mais la force développée au cours de celle-ci est inférieure à la somme des CMV de chacune des jambes durant la CMV BL, c'est-à-dire à la force maximale produite par chacune des jambes lors de la CMV BL. Néanmoins, aucune différence d'activité EMG, d'amplitude d'onde M, de doublet et de niveau d'activation n'a été observée entre les conditions UL et BL. Les résultats de la troisième étude montrent que l'estimation de la commande descendante, par la technique de la secousse surimposée, lors d'un effort sous-maximal fatigant présente des biais méthodologiques. Toutefois, l'estimation des mécanismes nerveux par les deux méthodes classiques (niveau d'activation volontaire (NAV) et ratio d'activation centrale (CAR)) reste néanmoins pertinente pendant des contractions maximales volontaires. L'ensemble de nos travaux met en évidence l'intervention de mécanismes d'origine nerveux différents entre les contractions UL et BL
Libros sobre el tema "Maximal voluntary contraction"
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The effect of imaginary maximal muscle contraction training on the voluntary neural drive to muscle. 1990.
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Ratel, Sébastien y Craig A. Williams. Neuromuscular fatigue. Editado por Neil Armstrong y Willem van Mechelen. Oxford University Press, 2017. http://dx.doi.org/10.1093/med/9780198757672.003.0009.
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Scientific evidence supports the proposition that prepubertal children fatigue less than adults when performing whole-body dynamic activities like maximal cycling, running bouts, and maximal voluntary isometric/isokinetic muscle contractions. Although the mechanisms underpinning differences in fatigue between children and adults are not all fully understood, there is a consensus that children experience less peripheral fatigue (i.e. muscular fatigue) than their older counterparts. Central factors may also account for the lower fatigability in children. Some studies report a higher reduction of muscle voluntary activation during fatiguing exercise in prepubertal children compared to adults. This could reflect a strategy of the central nervous system aimed at limiting the recruitment of motor units, in order to prevent any extensive peripheral fatigue. Further studies are required to clarify this proposition.
Capítulos de libros sobre el tema "Maximal voluntary contraction"
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Andreis, F. R., M. A. Favretto, S. Cossul, P. A. Barbetta y J. L. B. Marques. "Reliability of Maximal Voluntary Isometric Contraction of Ankle Dorsiflexion in Male Subjects". En XXVI Brazilian Congress on Biomedical Engineering, 353–57. Singapore: Springer Singapore, 2019. http://dx.doi.org/10.1007/978-981-13-2119-1_55.
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De Blasi, R. A., M. Cope y M. Ferrari. "Oxygen Consumption of Human Skeletal Muscle by Near Infrared Spectroscopy during Tourniquet-Induced Ischemia in Maximal Voluntary Contraction". En Oxygen Transport to Tissue XIV, 771–77. Boston, MA: Springer US, 1992. http://dx.doi.org/10.1007/978-1-4615-3428-0_94.
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Gallegos Ledezma, Angel, Ivett Quiñones Uriostegui, Virginia Bueyes-Roiz y Rafael Zepeda Mora. "Algorithm to Quantify Maximum Isometric Voluntary Contraction in Subjects with Osteoporosis". En IFMBE Proceedings, 42–46. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-30648-9_6.
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Chang, Jing, Damien Chablat, Fouad Bennis y Liang Ma. "Estimating the EMG Response Exclusively to Fatigue During Sustained Static Maximum Voluntary Contraction". En Advances in Intelligent Systems and Computing, 29–39. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-41694-6_4.
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Cannan, James A. R. y Huosheng Hu. "Automatic Circumference Measurement for Aiding in the Estimation of Maximum Voluntary Contraction (MVC) in EMG Systems". En Intelligent Robotics and Applications, 202–11. Berlin, Heidelberg: Springer Berlin Heidelberg, 2011. http://dx.doi.org/10.1007/978-3-642-25486-4_21.
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Khong, T. K., V. S. Selvanayagam, S. H. Hamzah, P. J. Lim y A. Yusof. "Effect of High and Low Carbohydrate Meals on Sustained Maximum Voluntary Contraction (MVC) after Prolonged Exercise". En IFMBE Proceedings, 133–35. Singapore: Springer Singapore, 2017. http://dx.doi.org/10.1007/978-981-10-3737-5_27.
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Rodrick, David, Santosh Erupaka, Rohit Sasidharan y Waldemar Karwowsk. "Nonlinear synchronization of biceps and triceps muscles during maximum voluntary contraction". En Advances in Human Factors, Ergonomics, and Safety in Manufacturing and Service Industries, 511–20. CRC Press, 2010. http://dx.doi.org/10.1201/ebk1439834992-53.
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Makaram, Navaneethakrishna, Sridhar P. Arjunan, Dinesh Kumar y Ramakrishnan Swaminathan. "Spatial Intensity Map of HDEMG Based Classification of Muscle Fatigue". En Studies in Health Technology and Informatics. IOS Press, 2021. http://dx.doi.org/10.3233/shti210218.
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In this, study, we have investigated to identify the muscle fatigue using spatial maps of High-Density Electromyography (HDEMG). The experiment involves subjects performing plantar flexion at 40% maximum voluntary contraction until fatigue. During the experiment, HDEMG signal was recorded from the tibialis anterior muscle. The monopolar and bipolar spatial intensity maps were extracted from the HDEMG signal. The random forest classifier with different tree configurations was tested to distinguish nonfatigue and fatigue condition. The results indicate that selected electrodes from the differential intensity map results in an accuracy of 83.3% with the number of trees set at 17. This method of spatial analysis of HDEMG signals may be extended to assess fatigue in real life scenarios.
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"The suitable sampling duration for performing consecutive maximum voluntary contraction gripping exertions without fatigue". En Advances in Physical Ergonomics and Safety, 523–32. CRC Press, 2012. http://dx.doi.org/10.1201/b12323-64.
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Jordan, David, Louise Mawn y Richard L. Anderson. "The Extraocular Muscles". En Surgical Anatomy of the Ocular Adnexa. Oxford University Press, 2012. http://dx.doi.org/10.1093/oso/9780199744268.003.0011.
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Whereas skeletal muscles generally perform specific limited roles, extraocular muscles (EOMs) have to be responsive over a wider dynamic range. As a result, EOMs have fundamentally distinct structural, functional, biochemical, and immunological properties as compared to other skeletal muscles. At birth, the extraocular muscles are at approximately 50 % to 60 % of their final dimension. Their relative growth within the enlarging orbit and their angular relations with the globe remain nearly constant from infancy to adulthood. The adult rectus muscles are approximately the same length (40 mm) but differ in thickness and in the length of their tendons. There are six extrinsic, or extraocular, muscles of the eye: four recti and two obliques. Only the horizontal and vertical recti insert on the eyeball in front of its equator. Both obliques have their insertions behind the equator of the globe. All six muscles consist of striated muscle fibers with abundant elastic fibers. The EOMs have muscle fibers and innervations that differ from those of skeletal muscle. There are three distinct types of muscle fibers (fine, granular, and coarse) that contribute to the action of the EOMs. The fine fibers are thought to be responsible for slow twitch movements, the granular fibers for fast twitch movements, and the coarse fibers for slow tonic movements. The EOMs are more richly innervated than other voluntary muscles of the body and have three types of nerve terminals: single endplate (driving eye movements), multiple endplates (tonic tension), and palisade endings (can be sensory receptors). In addition, there are both singly and multiply innervated nerve fibers present. EOMs are able to vary their contractile force by small increments. The maximum firing frequency of ocular motor units is about four times greater than those of limb muscle motor units. To allow them to operate at a higher frequency, EOMs also have faster contractile properties, with their time to peak tension and their one-half relaxation time being at least half of those in limb muscles.
Actas de conferencias sobre el tema "Maximal voluntary contraction"
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Niijima, Arinobu, Takashi Isezaki, Ryosuke Aoki, Tomoki Watanabe y Tomohiro Yamada. "Controlling Maximal Voluntary Contraction of the Upper Limb Muscles by Facial Electrical Stimulation". En CHI '18: CHI Conference on Human Factors in Computing Systems. New York, NY, USA: ACM, 2018. http://dx.doi.org/10.1145/3173574.3173968.
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Macnab, Andrew J., Emily Deegan y Lynn Stothers. "Application of a NIRS-derived measure to quantify reoxygenation of the pelvic floor muscles in women following sustained maximal voluntary contraction". En Therapeutics and Diagnostics in Urology 2020, editado por Hyun Wook Kang. SPIE, 2020. http://dx.doi.org/10.1117/12.2543649.
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Santos, Wanderson, Vitor Marques, Naiany Silva, Gabriel Siqueira, Raquel Schincaglia y Carlos Vieira. "HANDGRIP STRENGTH AND ISOMETRIC BILATERAL BENCH PRESS FOR UPPER INTERLIMB STRENGTH ASYMMETRY IN BREAST CANCER WOMEN, WITH OR WITHOUT LYMPHEDEMA". En Abstracts from the Brazilian Breast Cancer Symposium - BBCS 2021. Mastology, 2021. http://dx.doi.org/10.29289/259453942021v31s2058.
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Purpose: The aim of this study is to compare upper interlimb strength asymmetry in breast cancer women (BCW), with or without lymphedema, using the handgrip strength test and the isometric bilateral bench press (IBBP) test. Methodology: Twenty-two BCW (age 52.04±8.62 years) were enrolled in a cross-sectional study, with a single-day testing. Ten participants with self-reported breast cancer – related lymphedema (BCRL) and 12 participants without BCRL were evaluated for the interlimb strength asymmetry. The average of the best three of four attempts of the handgrip strength and the IBBP was used to compare the maximal voluntary isometric contraction of each limb. To calculate the interlimb strength asymmetry, we used the following formula as a percentage: the modulus of left minus right side divided by the average between sides, then multiplied by 100. For the statistical analysis, we used the nonparametric Mann–Whitney U test for the handgrip strength and the independent t-test for IBBP. Results: The handgrip strength in BCW with lymphedema (27.62%±15.5%) showed a higher interlimb strength asymmetry than BCW without lymphedema (12.37%±16.29%; p=0.021). However, there was no difference in IBBP (with lymphedema 8.89%±5.81% versus without lymphedema 9.84%±7.98%, p=0.759). Conclusion: BCW with lymphedema might have higher interlimb strength asymmetry assessed by the handgrip strength test compared with BCW without lymphedema, but not in a multi-compound movement such as IBBP. More studies are necessary to confirm our findings.
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Hickman, Stephen, Rocio Alba-Flores y Mohammad Ahad. "EMG based classification of percentage of maximum voluntary contraction using artificial neural networks". En 2014 IEEE Dallas Circuits and Systems Conference (DCAS). IEEE, 2014. http://dx.doi.org/10.1109/dcas.2014.6965337.
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Pusapati, Vamsi. "Effect of Task Characteristics on Maximum Voluntary Contraction Recovery Time during a Lifting Task". En 33rd Annual International Occupational Ergonomics and Safety Conference. International Society for Occupational Ergonomics and Safety, 2021. http://dx.doi.org/10.47461/isoes.2021_065.
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Touge, Tetsuo, Yoshimitsu Urai y Mieko Shimamura. "Excitability changes of corticospinal pathways by magnetic brain stimulation during the maximum voluntary muscle contraction". En 2009 ICME International Conference on Complex Medical Engineering - CME 2009. IEEE, 2009. http://dx.doi.org/10.1109/iccme.2009.4906609.
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Arıtan, Serdar, S. Olutunde Oyadiji y Roger M. Bartlett. "In Vivo Mechanical Properties of Muscular Bulk Tissue: Mechanical Model Representation of Stress-Relaxation Behavior". En ASME 2008 International Mechanical Engineering Congress and Exposition. ASMEDC, 2008. http://dx.doi.org/10.1115/imece2008-68547.
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In Vivo mechanical properties of bulk tissue have not been yet investigated sufficiently. One of the major problems the researchers confront is the lack of agreement for the constitutive models and standardized methodology for experimental studies (1). Despite the fact that the tissue properties are non-linear, many modeling studies preferred to adopt linear isotropic models. The object of this study was to obtain bulk modulus of the upper arm under relax and controlled contraction that was 25% of the maximum voluntary contraction (MVC).
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Mazumdar, Sushmi, Angana Saikia, Nitin Sahai, Sudip Paul y Dinesh Bhatia. "Determination of significant muscle in movement of upper limb using maximum voluntary contraction of EMG signal". En 2017 4th International Conference on Signal Processing and Integrated Networks (SPIN). IEEE, 2017. http://dx.doi.org/10.1109/spin.2017.8049923.
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Cahyadi, B. N., I. Zunaidi, S. A. Bakar, Wan Khairunizam, S. H. Majid, Z. M. Razlan, M. Nor Muhammad, M. N. Rudzuan y W. A. Mustafa. "Upper Limb Muscle Strength Analysis For Movement Sequence Based on Maximum Voluntary Contraction Using EMG Signal". En 2018 International Conference on Computational Approach in Smart Systems Design and Applications (ICASSDA). IEEE, 2018. http://dx.doi.org/10.1109/icassda.2018.8477638.
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Knop, Lauren, Guilherme Aramizo Ribeiro y Mo Rastgaar. "Towards a Generalized Model of Multivariable Ankle Impedance During Standing Based on the Lower Extremity Muscle EMG". En 2019 Design of Medical Devices Conference. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/dmd2019-3315.
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The ankle mechanical impedance of healthy subjects was estimated during the standing pose while they co-contracted their lower-leg muscles. Subsequently, the impedance parameters were modeled as a function of the level of co-contraction using machine learning regression methods. From the experimental results, the average ankle stiffness coefficients in dorsi-plantar flexion (DP) showed more dependence to the muscle contraction than stiffness in inversion-eversion (IE): 4.6 Nm/rad per %MVC (percent of the maximum voluntary contraction) and 1.1 Nm/rad per %MVC, respectively. To accurately estimate the ankle impedance parameters as a function of the electromyography (EMG) signals, multiple EMG feature selection methods, regression models, and types of models were evaluated. Using a 1-vs-All model validation approach, the best regression model to fit the stiffness and damping in DP was the Least Square method with Regularization, and the best IE stiffness was the Gaussian Process Regression. No model was able to estimate the IE damping well, possibly because this parameter is not modulated with a changing co-contraction of the lower-leg muscles.