scholarly journals Effects of whole-body vibrations on neuromuscular fatigue: a study with sets of different durations

PeerJ ◽  
2020 ◽  
Vol 8 ◽  
pp. e10388
Author(s):  
Miloš Kalc ◽  
Ramona Ritzmann ◽  
Vojko Strojnik
Keyword(s):  
High Frequency ◽  
Maximum Voluntary Contraction ◽  
Peak Torque ◽  
Voluntary Contraction ◽  
Neuromuscular Fatigue ◽  
Voluntary Activation ◽  
Whole Body ◽  
Peripheral Fatigue ◽  
Single Twitch ◽  
Whole Body Vibrations

Background Whole body vibrations have been used as an exercise modality or as a tool to study neuromuscular integration. There is increasing evidence that longer WBV exposures (up to 10 minutes) induce an acute impairment in neuromuscular function. However, the magnitude and origin of WBV induced fatigue is poorly understood. Purpose The study aimed to investigate the magnitude and origin of neuromuscular fatigue induced by half-squat long-exposure whole-body vibration intervention (WBV) with sets of different duration and compare it to non-vibration (SHAM) conditions. Methods Ten young, recreationally trained adults participated in six fatiguing trials, each consisting of maintaining a squatting position for several sets of the duration of 30, 60 or 180 seconds. The static squatting was superimposed with vibrations (WBV30, WBV60, WBV180) or without vibrations (SHAM30, SHAM60, SHAM180) for a total exercise exposure of 9-minutes in each trial. Maximum voluntary contraction (MVC), level of voluntary activation (%VA), low- (T20) and high-frequency (T100) doublets, low-to-high-frequency fatigue ratio (T20/100) and single twitch peak torque (TWPT) were assessed before, immediately after, then 15 and 30 minutes after each fatiguing protocol. Result Inferential statistics using RM ANOVA and post hoc tests revealed statistically significant declines from baseline values in MVC, T20, T100, T20/100 and TWPT in all trials, but not in %VA. No significant differences were found between WBV and SHAM conditions. Conclusion Our findings suggest that the origin of fatigue induced by WBV is not significantly different compared to control conditions without vibrations. The lack of significant differences in %VA and the significant decline in other assessed parameters suggest that fatiguing protocols used in this study induced peripheral fatigue of a similar magnitude in all trials.

Neuromuscular Fatigue in Individuals With Intellectual Disability: Comparison Between Sedentary Individuals and Athletes

Motor Control ◽  
2021 ◽  
Vol 25 (2) ◽  
pp. 264-282
Author(s):  
Rihab Borji ◽  
Firas Zghal ◽  
Nidhal Zarrouk ◽  
Sonia Sahli ◽  
Haithem Rebai
Keyword(s):  
Intellectual Disability ◽  
Recovery Period ◽  
Voluntary Contraction ◽  
Neuromuscular Fatigue ◽  
Voluntary Activation ◽  
Peripheral Fatigue ◽  
Typical Development ◽  
Activation Level ◽  
Voluntary Activation Level ◽  
Voluntary Contractions

The authors explored neuromuscular fatigue in athletes with intellectual disability (AID) compared with sedentary individuals with intellectual disability (SID) and individuals with typical development. Force, voluntary activation level, potentiated resting twitch, and electromyography signals were assessed during isometric maximal voluntary contractions performed before and immediately after an isometric submaximal exhaustive contraction (15% isometric maximal voluntary contractions) and during recovery period. AID presented shorter time to task failure than SID (p < .05). The three groups presented similar isometric maximal voluntary contraction decline and recovery kinetic. Both groups with intellectual disability presented higher voluntary activation level and root mean square normalized to peak-to-peak M-wave amplitude declines (p < .05) compared with individuals with typical development. These declines were more pronounced in SID (p < .05) than in AID. The AID recovered their initial voluntary activation level later than controls, whereas SID did not. SID presented lower potentiated resting twitch decline compared with AID and controls with faster recovery (p < .05). AID presented attenuated central fatigue and accentuated peripheral fatigue compared with their sedentary counterparts, suggesting a neuromuscular profile close to that of individuals with typical development.

scholarly journals The Physiological and Perceptual Effects of Stochastic Simulated Rugby League Match Play

2021 ◽  
Vol 16 (1) ◽  
pp. 73-79
Author(s):  
Thomas Mullen ◽  
Craig Twist ◽  
Jamie Highton
Keyword(s):  
Perceived Exertion ◽  
Maximum Voluntary Contraction ◽  
Peak Torque ◽  
Team Sport ◽  
Rugby League ◽  
Stroop Test ◽  
Voluntary Contraction ◽  
Rating Of Perceived Exertion ◽  
Voluntary Activation ◽  
Cognitive Responses

Purpose: To examine responses to a simulated rugby league protocol designed to include more stochastic commands, and therefore require greater vigilance, than traditional team-sport simulation protocols. Methods: Eleven male university rugby players completed 2 trials (randomized and control [CON]) of a rugby league movement simulation protocol, separated by 7 to 10 d. The CON trial consisted of 48 repeated ∼115-s cycles of activity. The stochastic simulation (STOCH) was matched for the number and types of activity performed every 5.45 min in CON but included no repeated cycles of activity. Movement using GPS, heart rate, rating of perceived exertion, and Stroop test performance was assessed throughout. Maximum voluntary contraction peak torque, voluntary activation (in percentage), and global task load were assessed after exercise. Results: The mean mental demand of STOCH was higher than CON (effect size [ES] = 0.56; ±0.69). Mean sprint speed was higher in STOCH (22.5 [1.4] vs 21.6 [1.6] km·h−1, ES = 0.50; ±0.55), which was accompanied by a higher rating of perceived exertion (14.3 [1.0] vs 13.0 [1.4], ES = 0.87; ±0.67) and a greater number of errors in the Stroop test (10.3 [2.5] vs 9.3 [1.4] errors; ES = 0.65; ±0.83). Maximum voluntary contraction peak torque (CON = −48.4 [31.6] N·m and STOCH = −39.6 [36.6] N·m) and voluntary activation (CON = −8.3% [4.8%] and STOCH = −6.0% [4.1%]) was similarly reduced in both trials. Conclusions: Providing more stochastic commands, which requires greater vigilance, might alter performance and associated physiological, perceptual, and cognitive responses to team-sport simulations.

Nonlinear behavior of muscle reflexes at the human ankle joint

1995 ◽  
Vol 73 (1) ◽  
pp. 65-72 ◽  
Author(s):  
R. B. Stein ◽  
R. E. Kearney
Keyword(s):  
Ankle Joint ◽  
Stretch Reflex ◽  
Maximum Voluntary Contraction ◽  
Voluntary Contraction ◽  
Voluntary Activation ◽  
Random Perturbations ◽  
Hydraulic Actuator ◽  
Voluntary Activity ◽  
Highly Nonlinear ◽  
Human Ankle

1. Pulse inputs (similar to tendon jerks) were applied to the human ankle joint with the use of a hydraulic actuator. Inputs of only 1-2 degrees could elicit large responses (> 20% of maximum voluntary contraction). The magnitude of the response depended nonlinearly on a number of factors: the amplitude, direction, and duration of the pulse; the angle of the ankle; and the level of voluntary activation of the ankle muscles. 2. Pulses that flexed or extended the ankle could both produce reflex torques in the same direction (extensor torque). Although an extension of the ankle did not itself produce a response, it could affect the response to a subsequent flexion for up to 1 s. 3. The influence of random perturbations on the stretch reflex at the ankle was assessed. Responses to pulse displacements alone and to pulses superimposed on random perturbations were compared at the same level of voluntary activity. Reflex responses decreased in a graded manner with increasing amplitude or bandwidth of the random perturbations. 4. These results demonstrate that stretch reflexes can generate substantial torques, but in a highly nonlinear manner. In particular, passive joint movements markedly alter stretch reflex gain, and these changes must be considered in interpreting the functional significance of reflex actions.

scholarly journals Child-adult differences in neuromuscular fatigue are muscle dependent

2018 ◽  
Vol 125 (4) ◽  
pp. 1246-1256 ◽  
Author(s):  
Enzo Piponnier ◽  
Vincent Martin ◽  
Bastien Bontemps ◽  
Emeric Chalchat ◽  
Valérie Julian ◽  
...  
Keyword(s):  
Near Infrared ◽  
Knee Extensor ◽  
Central Fatigue ◽  
Neuromuscular Fatigue ◽  
Muscle Group ◽  
Voluntary Activation ◽  
Peripheral Fatigue ◽  
Plantar Flexor ◽  
Significant Difference ◽  
Lower Extent

The aim of the present study was to compare the development and etiology of neuromuscular fatigue of the knee extensor (KE) and plantar flexor (PF) muscles during repeated maximal voluntary isometric contractions (MVICs) between children and adults. Prepubertal boys ( n = 21; 9–11 yr) and men ( n = 24; 18–30 yr) performed two fatigue protocols consisting of a repetition of 5-s isometric MVIC of the KE or PF muscles interspersed with 5-s passive recovery periods until MVIC reached 60% of its initial value. The etiology of neuromuscular fatigue of the KE and PF muscles was investigated by means of noninvasive methods, such as the surface electromyography, single and doublet magnetic stimulation, twitch interpolation technique, and near-infrared spectroscopy. The number of repetitions performed was significantly lower in men (15.4 ± 3.8) than boys (38.7 ± 18.8) for the KE fatigue test. In contrast, no significant difference was found for the PF muscles between boys and men (12.1 ± 4.9 and 13.8 ± 4.9 repetitions, respectively). Boys displayed a lower reduction in potentiated twitch torque, low-frequency fatigue, and muscle oxygenation than men whatever the muscle group considered. In contrast, voluntary activation level and normalized electromyography data decreased to a greater extent in boys than men for both muscle groups. To conclude, boys experienced less peripheral and more central fatigue during repeated MVICs than men whatever the muscle group considered. However, child-adult differences in neuromuscular fatigue were muscle-dependent since boys fatigued similarly to men with the PF muscles and to a lower extent with the KE muscles. NEW & NOTEWORTHY Child-adult differences in neuromuscular fatigue during repeated maximal voluntary contractions are specific to the muscle group since children fatigue similarly to adults with the plantar flexor muscles and to a lower extent with the knee extensor muscles. Children experience less peripheral fatigue and more central fatigue than adults, regardless of the muscle group considered.

Neuromuscular fatigue

2017 ◽  
Author(s):  
Sébastien Ratel ◽  
Craig A Williams
Keyword(s):  
Scientific Evidence ◽  
Motor Units ◽  
Voluntary Activation ◽  
Whole Body ◽  
Peripheral Fatigue ◽  
Prepubertal Children ◽  
The Central Nervous System ◽  
Fatiguing Exercise ◽  
Body Dynamic ◽  
Central Factors

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.

scholarly journals Pre-Exercise Rehydration Attenuates Central Fatigability during 2-Min Maximum Voluntary Contraction in Hyperthermia

Medicina ◽  
2019 ◽  
Vol 55 (3) ◽  
pp. 66
Author(s):  
Kazys Vadopalas ◽  
Aivaras Ratkevičius ◽  
Albertas Skurvydas ◽  
Saulė Sipavičienė ◽  
Marius Brazaitis
Keyword(s):  
Body Weight ◽  
Physiological Stress ◽  
Maximum Voluntary Contraction ◽  
Thermal Strain ◽  
Plasma Osmolality ◽  
Voluntary Contraction ◽  
Whole Body ◽  
Knee Extensors ◽  
Lower Body ◽  
Whole Body Hyperthermia

Background and objectives: Hyperthermia with dehydration alters several brain structure volumes, mainly by changing plasma osmolality, thus strongly affecting neural functions (cognitive and motor). Here, we aimed to examine whether the prevention of significant dehydration caused by passively induced whole-body hyperthermia attenuates peripheral and/or central fatigability during a sustained 2-min isometric maximal voluntary contraction (MVC). Materials and Methods: Ten healthy and physically active adult men (21 ± 1 years of age) performed an isometric MVC of the knee extensors for 2 min (2-min MVC) under control (CON) conditions, after passive lower-body heating that induced severe whole-body hyperthermia (HT, Tre > 39 °C) with dehydration (HT-D) and after HT with rehydration (HT-RH). Results: In the HT-D trial, the subjects lost 0.94 ± 0.15 kg (1.33% ± 0.13%) of their body weight; in the HT-RH trial, their body weight increased by 0.1 ± 0.42 kg (0.1% ± 0.58%). After lower-body heating, the HT-RH trial (vs. HT-D trial) was accompanied by a significantly lower physiological stress index (6.77 ± 0.98 vs. 7.40 ± 1.46, respectively), heart rate (47.8 ± 9.8 vs. 60.8 ± 13.2 b min−1, respectively), and systolic blood pressure (−12.52 ± 5.1 vs. +2.3 ± 6.4, respectively). During 2-min MVC, hyperthermia (HT-D; HT-RH) resulted in greater central fatigability compared with the CON trial. The voluntary activation of exercising muscles was less depressed in the HT-RH trial compared with the HT-D trial. Over the exercise period, electrically (involuntary) induced torque decreased less in the HT-D trial than in the CON and HT-RH trials. Conclusions: Our results suggest that pre-exercise rehydration might have the immediate positive effect of reducing physiological thermal strain, thus attenuating central fatigability even when exercise is performed during severe (Tre > 39 °C) HT, induced by passive warming of the lower body.

scholarly journals Maximum Voluntary Activation in Nonfatigued and Fatigued Muscle of Young and Elderly Individuals

2001 ◽  
Vol 81 (5) ◽  
pp. 1102-1109 ◽  
Author(s):  
Scott K Stackhouse ◽  
Jennifer E Stevens ◽  
Samuel CK Lee ◽  
Karen M Pearce ◽  
Lynn Snyder-Mackler ◽  
...  
Keyword(s):  
Maximum Voluntary Contraction ◽  
Quadriceps Femoris ◽  
Voluntary Contraction ◽  
Voluntary Activation ◽  
Elderly Subjects ◽  
Central Activation ◽  
Quadriceps Femoris Muscle ◽  
Age Related ◽  
Young Subjects ◽  
Femoris Muscle

Abstract Background and Purpose. Researchers studying central activation of muscles in elderly subjects (≥65 years of age) have investigated activation in only the nonfatigued state. This study examined the ability of young and elderly people to activate their quadriceps femoris muscles voluntarily under both fatigued and nonfatigued conditions to determine the effect of central activation failure on age-related loss of force. Subjects and Methods. Twenty young subjects (11 men, 9 women; mean age=22.67 years, SD=4.14, range=18–32 years) and 17 elderly subjects (8 men, 9 women; mean age=71.5 years, SD=5.85, range=65–84 years) participated in this study. Subjects were seated on a dynamometer and stabilized. Central activation was quantified, based on the change in force produced by a 100-Hz, 12-pulse electrical train that was delivered during a 3- to 5-second isometric maximum voluntary contraction (MVC) of the quadriceps femoris muscle. Next, subjects performed 25 MVCs (a 5-second contraction with 2 seconds of rest) to fatigue the muscle. During the last MVC, central activation was measured again. Results. In the nonfatigued state, elderly subjects had lower central activation than younger subjects. In the fatigued state, this difference became larger. Discussion and Conclusion. Central activation of the quadriceps femoris muscle in elderly subjects was reduced in both the fatigued and nonfatigued states when compared with young subjects. Some part of age-related weakness, therefore, may be attributed to failure of central activation in both the fatigued and nonfatigued states.

scholarly journals Motor planning perturbation: muscle activation and reaction time

2018 ◽  
Vol 120 (4) ◽  
pp. 2059-2065
Author(s):  
Stefan Delmas ◽  
Agostina Casamento-Moran ◽  
Seoung Hoon Park ◽  
Basma Yacoubi ◽  
Evangelos A. Christou
Keyword(s):  
Reaction Time ◽  
Muscle Activity ◽  
Muscle Activation ◽  
Maximum Voluntary Contraction ◽  
Motor Planning ◽  
Reaction Time Task ◽  
Voluntary Contraction ◽  
Voluntary Activation ◽  
Time Interval ◽  
Voluntary Activity

Reaction time (RT) is the time interval between the appearance of a stimulus and initiation of a motor response. Within RT, two processes occur, selection of motor goals and motor planning. An unresolved question is whether perturbation to the motor planning component of RT slows the response and alters the voluntary activation of muscle. The purpose of this study was to determine how the modulation of muscle activity during an RT response changes with motor plan perturbation. Twenty-four young adults (20.5 ±1.1 yr, 13 women) performed 15 trials of an isometric RT task with ankle dorsiflexion using a sinusoidal anticipatory strategy (10–20% maximum voluntary contraction). We compared the processing part of the RT and modulation of muscle activity from 10 to 60 Hz of the tibialis anterior (primary agonist) when the stimulus appeared at the trough or at the peak of the sinusoidal task. We found that RT ( P = 0.003) was longer when the stimulus occurred at the peak compared with the trough. During the time of the reaction, the electromyography (EMG) power from 10 to 35 Hz was less at the peak than the trough ( P = 0.019), whereas the EMG power from 35 to 60 Hz was similar between the peak and trough ( P = 0.92). These results suggest that perturbation to motor planning lengthens the processing part of RT and alters the voluntary activation of the muscle by decreasing the relative amount of power from 10 to 35 Hz. NEW & NOTEWORTHY We aimed to determine whether perturbation to motor planning would alter the speed and muscle activity of the response. We compared trials when a stimulus appeared at the peak or trough of an oscillatory reaction time task. When the stimulus occurred at the trough, participants responded faster, with greater force, and less EMG power from 10-35 Hz. We provide evidence that motor planning perturbation slows the response and alters the voluntary activity of the muscle.

scholarly journals Effect of Elbow Flexion Angle on Cortical Voluntary Activation of the Non-Impaired Biceps: A 3 Days Repeated Sessions Study

2020 ◽  
Author(s):  
Thibault Roumengous ◽  
Paul A. Howell ◽  
Carrie L. Peterson
Keyword(s):  
Cortical Neurons ◽  
Maximum Voluntary Contraction ◽  
Motor Evoked Potential ◽  
Elbow Flexion ◽  
Voluntary Contraction ◽  
Voluntary Activation ◽  
Elbow Angle ◽  
Flexion Extension ◽  
Minimal Stimulation ◽  
Stimulation Of

ABSTRACTMeasurement of cortical voluntary activation (VA) with transcranial magnetic stimulation (TMS) is limited by technical challenges. One challenge is the difficulty in preferential stimulation of cortical neurons projecting to the target muscle and minimal stimulation of cortical neurons projecting to antagonists. Thus, the motor evoked potential (MEP) response to TMS in the target muscle compared to its primary antagonist may be an important parameter in the assessment of cortical VA. Modulating isometric elbow angle alters the magnitude of MEPs at rest. The purpose of this study was to evaluate the effect of isometric elbow flexion-extension angle on: 1) the ratio of biceps MEP relative to the triceps MEP amplitude across a range of voluntary efforts, and 2) cortical VA. Ten non-impaired participants completed three sessions wherein VA was determined using TMS at 45°, 90° and 120° of isometric elbow flexion, and peripheral electrical stimulation at 90° of elbow flexion. The biceps/triceps MEP ratio was greater in the more flexed elbow angle (120° flexion) compared to 90° during contractions of 50% and 75% of maximum voluntary contraction. Cortical VA assessed in the more extended elbow angle (45° flexion) was lower relative to 90° elbow flexion; this effect was dependent on the biceps/triceps MEP ratio. Cortical VA was sensitive to small changes in the linearity of the voluntary torque and superimposed twitch relationship, regardless of the elbow angle. Peripheral and cortical VA measures at 90° of elbow flexion were repeatable across three days. In conclusion, although the biceps/triceps MEP ratio was increased at a more flexed elbow angle relative to 90°, there was not a corresponding difference in cortical VA. Thus, increasing the MEP ratio via elbow angle did not affect estimation of cortical VA.

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