scholarly journals Neuromuscular Adaptations after an Altitude Training Camp in Elite Judo Athletes

2021 ◽  
Vol 18 (13) ◽  
pp. 6777
Author(s):  
Katja Tomazin ◽  
Filipa Almeida ◽  
Igor Stirn ◽  
Paulino Padial ◽  
Juan Bonitch-Góngora ◽  
...  
Keyword(s):  
Knee Extensor ◽  
Voluntary Activation ◽  
Peripheral Fatigue ◽  
Altitude Training ◽  
Neuromuscular Adaptations ◽  
Judo Athletes ◽  
The Difference ◽  
Neuromuscular Assessment ◽  
Level Training ◽  
Torque Development

The aim of this study was to investigate neuromuscular adaptations in elite judo athletes after three weeks of power-oriented strength training at terrestrial altitude (2320 m). Nineteen men were assigned to altitude training (AL) (22.1 ± 2.3 years) and sea level training (SL) (22.6 ± 4.1 years). Neuromuscular assessment consisted of: (1) maximal isometric knee extensor (KE) torque, (2) KE rate of torque development (RTD), (3) quadriceps activity and voluntary activation, (4) soleus H-reflex, (5) quadriceps single (TTW) and double twitch torque (TDB100) and contraction time (CTTW). There were no significant differences between groups at baseline for any of the observed parameters. Significant differences were found between groups in terms of change in RTD (p = 0.04). Cohen’s d showed a positive significant effect (0.43) in the SL group and a negative significant effect (−0.58) in the AL group. The difference between groups in changes in CTTW as a function of altitude was on the edge of significance (p = 0.077). CTTW increased by 8.1 ± 9.0% in the AL group (p = 0.036) and remained statistically unchanged in the SL group. Only the AL group showed a relationship between changes in TTW and TDB100 and changes in RTD at posttest (p = 0.022 and p = 0.016, respectively). Altitude induced differences in muscular adaptations likely due to greater peripheral fatigue.

Initial phase of maximal voluntary and electrically stimulated knee extension torque development at different knee angles

2004 ◽  
Vol 97 (5) ◽  
pp. 1693-1701 ◽  
Author(s):  
C. J. de Ruiter ◽  
R. D. Kooistra ◽  
M. I. Paalman ◽  
A. de Haan
Keyword(s):  
Muscle Activation ◽  
Knee Extensor ◽  
Surface Emg ◽  
Knee Extension ◽  
Voluntary Contraction ◽  
Voluntary Activation ◽  
Knee Angle ◽  
Time Integral ◽  
Voluntary Contractions ◽  
Torque Development

We investigated the capacity for torque development and muscle activation at the onset of fast voluntary isometric knee extensions at 30, 60, and 90° knee angle. Experiments were performed in subjects ( n = 7) who had high levels (>90%) of activation at the plateau of maximal voluntary contractions. During maximal electrical nerve stimulation (8 pulses at 300 Hz), the maximal rate of torque development (MRTD) and torque time integral over the first 40 ms (TTI40) changed in proportion with torque at the different knee angles (highest values at 60°). At each knee angle, voluntary MRTD and stimulated MRTD were similar ( P < 0.05), but time to voluntary MRTD was significantly longer. Voluntary TTI40 was independent ( P > 0.05) of knee angle and on average (all subjects and angles) only 40% of stimulated TTI40. However, among subjects, the averaged (across knee angles) values ranged from 10.3 ± 3.1 to 83.3 ± 3.2% and were positively related ( r2 = 0.75, P < 0.05) to the knee-extensor surface EMG at the start of torque development. It was concluded that, although all subjects had high levels of voluntary activation at the plateau of maximal voluntary contraction, among subjects and independent of knee angle, the capacity for fast muscle activation varied substantially. Moreover, in all subjects, torque developed considerably faster during maximal electrical stimulation than during maximal voluntary effort. At different knee angles, stimulated MRTD and TTI40 changed in proportion with stimulated torque, but voluntary MRTD and TTI40 changed less than maximal voluntary torque.

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.

Etiology of Neuromuscular Fatigue After Repeated Sprints Depends on Exercise Modality

2017 ◽  
Vol 12 (7) ◽  
pp. 878-885 ◽  
Author(s):  
Katja Tomazin ◽  
Jean-Benoit Morin ◽  
Guillaume Y. Millet
Keyword(s):  
Vastus Lateralis ◽  
Knee Extensor ◽  
Compound Action Potential ◽  
Neuromuscular Fatigue ◽  
Voluntary Activation ◽  
Peak Power Output ◽  
Peripheral Fatigue ◽  
M Wave ◽  
Sprint Running ◽  
Repeated Sprint

Purpose:To compare neuromuscular fatigue induced by repeated-sprint running vs cycling.Methods:Eleven active male participants performed 2 repeated-maximal-sprint protocols (5×6 s, 24-s rest periods, 4 sets, 3 min between sets), 1 in running (treadmill) and 1 in cycling (cycle ergometer). Neuromuscular function, evaluated before (PRE); 30 s after the first (S1), the second (S2), and the last set (LAST); and 5 min after the last set (POST5) determined the knee-extensor maximal voluntary torque (MVC); voluntary activation (VA); single-twitch (Tw), high- (Db100), and low- (Db10) frequency torque; and maximal muscle compound action potential (M-wave) amplitude and duration of vastus lateralis.Results:Peak power output decreased from 14.6 ± 2.2 to 12.4 ± 2.5 W/kg in cycling (P < .01) and from 21.4 ± 2.6 to 15.2 ± 2.6 W/kg in running (P < .001). MVC declined significantly from S1 in running but only from LAST in cycling. VA decreased after S2 (~–7%, P < .05) and LAST (~–9%, P < .01) set in repeated-sprint running and did not change in cycling. Tw, Db100, and Db10/Db100 decreased to a similar extent in both protocols (all P < .001 post-LAST). Both protocols induced a similar level of peripheral fatigue (ie, low-frequency peripheral fatigue, no changes in M-wave characteristics), while underlying mechanisms probably differed. Central fatigue was found only after running.Conclusion:Findings about neuromuscular fatigue resulting from RS cycling cannot be transferred to RS running.

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.

Effect of voluntary vs. artificial activation on the relationship of muscle torque to speed

1990 ◽  
Vol 69 (6) ◽  
pp. 2215-2221 ◽  
Author(s):  
G. A. Dudley ◽  
R. T. Harris ◽  
M. R. Duvoisin ◽  
B. M. Hather ◽  
P. Buchanan
Keyword(s):  
Knee Extensor ◽  
Voluntary Activation ◽  
Knee Extensors ◽  
Angular Velocities ◽  
The Central Nervous System ◽  
The Right ◽  
Artificial Activation ◽  
Relationship Of ◽  
The Relationship ◽  
Eccentric Actions

The speed-torque relationship of the right knee extensor muscle group was investigated in eight untrained subjects (28 +/- 2 yr old). Torque was measured at a specific knee angle during isokinetic concentric or eccentric actions at nine angular velocities (0.17-3.66 rad/s) and during isometric actions. Activation was by "maximal" voluntary effort or by transcutaneous tetanic electrical stimulation that induced an isometric torque equal to 60% (STIM 1) or 45% (STIM 2) of the voluntary isometric value. Torque increased (P less than 0.05) to 1.4 times isometric as the speed of eccentric actions increased to 1.57 rad/s for STIM 1 and STIM 2. Thereafter, increases in eccentric speed did not further increase torque. Torque did not increase (P greater than 0.05) above isometric for voluntary eccentric actions. As the speed of concentric actions increased from 0.00 to 3.66 rad/s, torque decreased (P less than 0.05) more (P less than 0.05) for both STIM 1 and STIM 2 (two-thirds) than for voluntary activation (one-half). As a result of these responses, torque changed three times as much (P less than 0.05) across speeds of concentric and eccentric actions with artificial (3.4-fold) than voluntary (1.1-fold) activation. The results indicate that with artificial activation the normalized speed-torque relationship of the knee extensors in situ is remarkably similar to that of isolated muscle. The relationship for voluntary activation, in contrast, suggests that the ability of the central nervous system to activate the knee extensors during maximal efforts depends on the speed and type of muscle action performed.

scholarly journals Fatigue reduces the complexity of knee extensor torque during fatiguing sustained isometric contractions

2018 ◽  
Author(s):  
Jamie Pethick ◽  
Mark Burnley ◽  
Samantha Lee Winter
Keyword(s):  
Temporal Structure ◽  
Femoral Nerve ◽  
Knee Extensor ◽  
Approximate Entropy ◽  
Task Demands ◽  
Peripheral Fatigue ◽  
Knee Extensors ◽  
Fluctuation Analysis ◽  
Isometric Contractions ◽  
Scaling Exponent

The temporal structure, or complexity, of muscle torque output reflects the adaptability of motor control to changes in task demands. This complexity is reduced by neuromuscular fatigue during intermittent isometric contractions. We tested the hypothesis that sustained fatiguing isometric contractions would result in a similar loss of complexity. To that end, nine healthy participants performed, on separate days, sustained isometric contractions of the knee extensors at 20% MVC to task failure and at 100% MVC for 60 seconds. Torque and surface EMG signals were sampled continuously. Complexity and fractal scaling were quantified by calculating approximate entropy (ApEn) and the detrended fluctuation analysis (DFA) α scaling exponent. Global, central and peripheral fatigue were quantified using maximal voluntary contractions (MVCs) with femoral nerve stimulation. Fatigue reduced the complexity of both submaximal (ApEn from 1.02 ± 0.06 to 0.41 ± 0.04, P &lt; 0.05) and maximal contractions (ApEn from 0.34 ± 0.05 to 0.26 ± 0.04, P &lt; 0.05; DFA α from 1.41 ± 0.04 to 1.52 ± 0.03, P &lt; 0.05). The losses of complexity were accompanied by significant global, central and peripheral fatigue (all P &lt; 0.05). These results demonstrate that a fatigue-induced loss of torque complexity is evident not only during fatiguing intermittent isometric contractions, but also during sustained fatiguing contractions.

scholarly journals Acute effect of tendon vibration applied during isometric contraction at two knee angles on maximal knee extension force production

PLoS ONE ◽  
2020 ◽  
Vol 15 (11) ◽  
pp. e0242324
Author(s):  
Jonathan Harnie ◽  
Thomas Cattagni ◽  
Christophe Cornu ◽  
Peter McNair ◽  
Marc Jubeau
Keyword(s):  
Isometric Contraction ◽  
Vastus Lateralis ◽  
Force Production ◽  
Knee Extensor ◽  
Acute Effect ◽  
Knee Extension ◽  
Voluntary Contraction ◽  
Voluntary Activation ◽  
Tendon Vibration ◽  
Knee Angle

The aim of the current study was to investigate the effect of a single session of prolonged tendon vibration combined with low submaximal isometric contraction on maximal motor performance. Thirty-two young sedentary adults were assigned into two groups that differed based on the knee angle tested: 90° or 150° (180° = full knee extension). Participants performed two fatigue-inducing exercise protocols: one with three 10 min submaximal (10% of maximal voluntary contraction) knee extensor contractions and patellar tendon vibration (80 Hz) another with submaximal knee extensor contractions only. Before and after each fatigue protocol, maximal voluntary isometric contractions (MVC), voluntary activation level (assessed by the twitch interpolation technique), peak-to-peak amplitude of maximum compound action potentials of vastus medialis and vastus lateralis (assessed by electromyography with the use of electrical nerve stimulation), peak twitch amplitude and peak doublet force were measured. The knee extensor fatigue was significantly (P<0.05) greater in the 90° knee angle group (-20.6% MVC force, P<0.05) than the 150° knee angle group (-8.3% MVC force, P = 0.062). Both peripheral and central alterations could explain the reduction in MVC force at 90° knee angle. However, tendon vibration added to isometric contraction did not exacerbate the reduction in MVC force. These results clearly demonstrate that acute infrapatellar tendon vibration using a commercial apparatus operating at optimal conditions (i.e. contracted and stretched muscle) does not appear to induce knee extensor neuromuscular fatigue in young sedentary subjects.

Estimation of critical torque using intermittent isometric maximal voluntary contractions of the quadriceps in humans

2009 ◽  
Vol 106 (3) ◽  
pp. 975-983 ◽  
Author(s):  
Mark Burnley
Keyword(s):  
Laboratory Tests ◽  
Mean Squared Error ◽  
Voluntary Activation ◽  
Peripheral Fatigue ◽  
Contraction Time ◽  
Twitch Interpolation ◽  
Squared Error ◽  
The Mean ◽  
Duration Relationship ◽  
Voluntary Contractions

To determine whether the asymptote of the torque-duration relationship (critical torque) could be estimated from the torque measured at the end of a series of maximal voluntary contractions (MVCs) of the quadriceps, eight healthy men performed eight laboratory tests. Following familiarization, subjects performed two tests in which they were required to perform 60 isometric MVCs over a period of 5 min (3 s contraction, 2 s rest), and five tests involving intermittent isometric contractions at ∼35–60% MVC, each performed to task failure. Critical torque was determined using linear regression of the torque impulse and contraction time during the submaximal tests, and the end-test torque during the MVCs was calculated from the mean of the last six contractions of the test. During the MVCs voluntary torque declined from 263.9 ± 44.6 to 77.8 ± 17.8 N·m. The end-test torque was not different from the critical torque (77.9 ± 15.9 N·m; 95% paired-sample confidence interval, −6.5 to 6.2 N·m). The root mean squared error of the estimation of critical torque from the end-test torque was 7.1 N·m. Twitch interpolation showed that voluntary activation declined from 90.9 ± 6.5% to 66.9 ± 13.1% ( P < 0.001), and the potentiated doublet response declined from 97.7 ± 23.0 to 46.9 ± 6.7 N·m ( P < 0.001) during the MVCs, indicating the development of both central and peripheral fatigue. These data indicate that fatigue during 5 min of intermittent isometric MVCs of the quadriceps leads to an end-test torque that closely approximates the critical torque.

Intent-Related Differences in Surface EMG of Maximum Eccentric and Concentric Contractions

2003 ◽  
Vol 19 (2) ◽  
pp. 99-105 ◽  
Author(s):  
Mark D. Grabiner ◽  
Tammy M. Owings
Keyword(s):  
Muscle Activation ◽  
Vastus Lateralis ◽  
Knee Extensor ◽  
Eccentric Contraction ◽  
Surface Emg ◽  
Vastus Lateralis Muscle ◽  
Concentric Contractions ◽  
Concentric Contraction ◽  
Contraction Condition ◽  
The Difference

For this study it was hypothesized that when participants intended to perform a maximum voluntary concentric (or eccentric) contraction but had an eccentric (or concentric) contraction imposed upon them, the initial EMG measured during the isometric phase preceding the onset of the dynamometer motion would reflect the intended contraction condition. The surface EMG of the vastus lateralis muscle was measured in 24 participants performing isokinetic concentric and eccentric maximum voluntary knee extensor contractions. The contractions were initiated from rest and from the same knee flexion angle and required the same level of external force to trigger the onset of dynamometer motion. Vastus lateralis EMG were quantified during the isometric phase preceding the onset of the dynamometer motion. When participants intended to perform a concentric contraction but had an eccentric contraction imposed upon them, the initial EMG resembled that of a concentric contraction. When they intended to perform an eccentric contraction but had a concentric contraction imposed upon them, the initial EMG resembled that of an eccentric contraction. Overall, the difference between concentric and eccentric contractions observed during the period of theinitialmuscle activation implies that descending signals include information that distinguishes between eccentric and concentric contractions.

scholarly journals Mechanisms for the increased fatigability of the lower limb in people with type 2 diabetes

2018 ◽  
Vol 125 (2) ◽  
pp. 553-566 ◽  
Author(s):  
Jonathon Senefeld ◽  
Steven B. Magill ◽  
April Harkins ◽  
Alison R. Harmer ◽  
Sandra K. Hunter
Keyword(s):  
Physical Activity ◽  
Type 2 Diabetes ◽  
Body Mass Index ◽  
Magnetic Stimulation ◽  
Knee Extensor ◽  
Voluntary Activation ◽  
Men And Women ◽  
Extensor Muscles ◽  
Knee Extensor Muscles

Fatiguing exercise is the basis of exercise training and a cornerstone of management of type 2 diabetes mellitus (T2D); however, little is known about the fatigability of limb muscles and the involved mechanisms in people with T2D. The purpose of this study was to compare fatigability of knee extensor muscles between people with T2D and controls without diabetes and determine the neural and muscular mechanisms for a dynamic fatiguing task. Seventeen people with T2D [ten men and seven women: 59.6 (9.0) yr] and twenty-one age-, body mass index-, and physical activity-matched controls [eleven men and ten women: 59.5 (9.6) yr] performed one hundred twenty high-velocity concentric contractions (one contraction/3 s) with a load equivalent to 20% maximal voluntary isometric contraction (MVIC) torque with the knee extensors. Transcranial magnetic stimulation (TMS) and electrical stimulation of the quadriceps were used to assess voluntary activation and contractile properties. People with T2D had larger reductions than controls in power during the fatiguing task [42.8 (24.2) vs. 26.4 (15.0)%; P < 0.001] and MVIC torque after the fatiguing task [37.6 (18.2) vs. 26.4 (12.1)%; P = 0.04]. People with T2D had greater reductions than controls in the electrically evoked twitch amplitude after the fatiguing task [44.0 (20.4) vs. 35.4 (12.1)%, respectively; P = 0.01]. However, the decrease in voluntary activation was similar between groups when assessed with electrical stimulation [12.1 (2.6) vs. 12.4 (4.4)% decrease; P = 0.84] and TMS ( P = 0.995). A greater decline in MVIC torque was associated with larger reductions of twitch amplitude ( r2 = 0.364, P = 0.002). Although neural mechanisms contributed to fatigability, contractile mechanisms were responsible for the greater knee extensor fatigability in men and women with T2D compared with healthy controls. NEW & NOTEWORTHY Transcranial magnetic stimulation and percutaneous muscle stimulation were used to determine the contributions of neural and contractile mechanisms of fatigability of the knee extensor muscles after a dynamic fatiguing task in men and women with type 2 diabetes (T2D) and healthy age-, body mass index-, and physical activity-matched controls. Although neural and contractile mechanisms contributed to greater fatigability of people with T2D, fatigability was primarily associated with impaired contractile mechanisms and glycemic control.

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