The Effects of Fatigue of the Plantar Flexors on Peak Torque and Voluntary Activation in Untrained and Resistance-Trained Men

The purpose of the present research was to identify the contribution of central vs. peripheral factors to the force loss after passive muscle stretching. Thirteen men randomly performed both a 5-min constant-torque stretch of the plantar flexors on an isokinetic dynamometer and a resting condition on 2 separate days. The triceps surae electromyogram (EMG) was recorded simultaneously with plantar flexor isometric torque. Measures of central drive, including the EMG amplitude normalized to the muscle compound action potential amplitude (EMG/M), percent voluntary activation and first volitional wave amplitude, and measures of peripheral function, including the twitch peak torque, 20-to-80-Hz tetanic torque ratio and torque during 20-Hz stimulation preceded by a doublet, were taken before and immediately and 15 min after each condition. Peak torque (−15.7%), EMG/M (−8.2%), and both twitch (−9.4%) and 20-Hz peak torques (−11.5%) were reduced immediately after stretch but recovered by 15 min. There were strong correlations between the torque loss and the reductions in central drive parameters ( r = 0.65–0.93). Torque recovery was also strongly correlated with the recovery in EMG/M and percent voluntary activation ( r = 0.77–0.81). The moderate decreases in measures of peripheral function were not related to the torque loss or recovery. These results suggest that 1) central factors were strongly related to the torque reduction immediately after stretch and during torque recovery; and 2) the muscle's contractile capacity was moderately reduced, although these changes were not associated with the torque reduction, and changes in excitation-contraction coupling efficiency were not observed.

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Velocity of the muscle tendon unit is sex-dependent and not altered with acute static stretch

Applied Physiology Nutrition and Metabolism ◽

10.1139/apnm-2017-0289 ◽

2018 ◽

Vol 43 (3) ◽

pp. 227-232 ◽

Cited By ~ 2

Author(s):

Carey L. Simpson ◽

Rowan R. Smart ◽

Dylan E.E. Melady ◽

Jennifer M. Jakobi

Keyword(s):

Plantar Flexion ◽

Voluntary Contraction ◽

Voluntary Activation ◽

Plantar Flexors ◽

Shortening Velocity ◽

Static Stretch ◽

Twitch Interpolation ◽

Tendon Lengthening ◽

The Individual ◽

The Relationship

Contraction velocity of a muscle tendon unit (MTU) is dependent upon the interrelationship between fascicles shortening and the tendon lengthening. Altering the mechanical properties of these tissues through a perturbation such as static stretching slows force generation. Females, who have inherently greater compliance compared with males, have slower velocity of MTU components. The addition of a static stretch might further exacerbate this sex difference. The purpose of this study was to investigate the velocity of fascicle shortening and tendon lengthening in males and females during isometric maximal voluntary contraction (MVC) of the plantar flexors prior to and following an acute static stretch. The MTU was imaged with ultrasound and voluntary activation tested with twitch interpolation for the 5-s plantar flexion MVC, which proceeded and followed an acute stretch. For the 3-min stretch the ankle was passively rotated to maximal dorsi-flexion. The males were stronger (128.71 ± 7.88 Nm) than the females (89.92 ± 4.70 Nm) but voluntary activation did not differ. Tendon lengthening velocity (p = 0.001) and fascicle shortening velocity (p = 0.01) were faster in males than females. Tendon velocity was positively and significantly correlated with fascicle velocity, (r2 = 0.307, p = 0.02). Although sex was significant as a predictor (p = 0.05) time was not independently significant. Thus, stretch did not alter this relationship in either sex (p = 0.6). The velocity of the individual components of the MTU is slower in females when compared with males; however, acute stretch does not alter the relationship between these components in males or females.

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EFFECTS OF ADDING BIOFEEDBACK TRAINING TO ACTIVE EXERCISES AFTER TOTAL KNEE ARTHROPLASTY

Journal of Musculoskeletal Research ◽

10.1142/s0218957714500018 ◽

2014 ◽

Vol 17 (01) ◽

pp. 1450001 ◽

Cited By ~ 3

Author(s):

Al-Sayed A. Shanb ◽

Enas F. Youssef

Keyword(s):

Total Knee Arthroplasty ◽

Exercise Training ◽

Training Program ◽

Knee Arthroplasty ◽

Functional Activity ◽

Peak Torque ◽

Biofeedback Training ◽

Voluntary Activation ◽

Exercise Training Program ◽

Total Knee

The purpose of this study was to evaluate the effects of adding biofeedback training to active exercise training on quadriceps torque, voluntary activation and functional activity after total knee arthroplasty (TKA). A total of 45 patients with unilateral TKA participated in this study; their ages ranged from 58 to 67 years. They were assigned randomly to two groups. Group I comprised 21 patients who practiced an active exercise training program for 30 to 45 min/session, two sessions/week, for 4 months. Group II contained 24 patients who practiced biofeedback training in addition to the active exercise training program for 30 to 45 min/session, two sessions/week, for 4 months. Isometric peak torque of the quadriceps, voluntary activation and knee functional activity were measured. The results revealed significant improvements in quadriceps torque, voluntary activation and knee functional activity for both groups, with more improvement in knee functional activities in group II. There were nonsignificant differences between the two groups in both quadriceps peak torque and voluntary activation after training (p > 0.05). Conclusion: An active exercise program can enhance quadriceps peak torque, voluntary activation and knee functional activity after unilateral TKA. The addition of biofeedback training increases the benefits for the knee functional activity of a patient.

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

PeerJ ◽

10.7717/peerj.10388 ◽

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.

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Sex differences in central and peripheral fatigue induced by sustained isometric ankle plantar flexion

10.1101/2021.09.03.458912 ◽

2021 ◽

Author(s):

Donguk Jo ◽

Miriam Goubran ◽

Martin Bilodeau

Keyword(s):

Sex Differences ◽

Plantar Flexion ◽

Recovery Period ◽

Isometric Exercise ◽

Voluntary Contraction ◽

Voluntary Activation ◽

Peripheral Fatigue ◽

Plantar Flexors ◽

Maximal Voluntary Isometric Contraction ◽

Males And Females

The main aim of this study was to determine sex differences in central and peripheral fatigue produced by a sustained isometric exercise of ankle plantar flexors in healthy young adults. Ten males and fourteen females performed a sustained isometric ankle exercise until task failure. Maximal voluntary isometric contraction torque (plantarflexion), voluntary activation level (using the twitch interpolation technique), and twitch contractile properties (twitch peak torque, twitch half relaxation time, and low frequency fatigue index) were measured before, immediately after, and throughout a recovery period (1, 2, 5, and 10 min) following the exercise protocol in order to characterize neuromuscular fatigue. Fatigue had a significant effect (p £ 0.05) on all dependent variables. Other than for the maximal voluntary contraction torque, where males showed a greater fatigue-related decrease than females, males and females showed generally similar changes with fatigue. Altogether, our findings indicate no major differences in central or peripheral fatigue mechanisms between males and females to explain a somewhat greater fatigability in males.

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Characterization of performance fatigability during a self-paced exercise

Journal of Applied Physiology ◽

10.1152/japplphysiol.00090.2019 ◽

2019 ◽

Vol 127 (3) ◽

pp. 838-846 ◽

Cited By ~ 4

Author(s):

Rafael de Almeida Azevedo ◽

Ramon Cruz ◽

Patrícia Couto ◽

Marcos David Silva-Cavalcante ◽

Daniel Boari ◽

...

Keyword(s):

Time Course ◽

Muscle Activation ◽

Contractile Function ◽

Time Trial ◽

Peak Torque ◽

Voluntary Activation ◽

Knee Extensors ◽

Electromyographic Activity ◽

Cycling Time Trial ◽

Fast Start

Pacing during a high-intensity cycling time trial (TT) appears to prevent premature task failure, but the performance fatigability during a self-paced exercise is currently unknown. Therefore, the current study characterized the time course of performance fatigability during a 4-km TT. Eleven male cyclists performed three separated TTs in a crossover, counterbalanced design. The TTs lasted until the end of the fast-start (FS; 600 ± 205 m), even-pace (EP; 3,600 ± 190 m), and end-spurt (ES; 4,000 m) phases. Performance fatigability was characterized by using isometric maximal voluntary contractions (IMVCs), whereas the muscle activation [i.e., voluntary activation (VA)] and contractile function of knee extensors [e.g., peak torque of potentiated twitches (TwPt)] were evaluated using electrically evoked contractions performed before and 1 min after each specific part of the trial. Gas exchange, power output (PO), and electromyographic activity (EMG) were also recorded. EMG/PO showed an abrupt increase followed by a continuous decrease toward the end of FS, resulting in a drop in IMVC (−12%), VA (−8%), and TwPt (−23%). EMG/PO was stable during EP, with no additional drop on IMVC, VA, or TwPt (−12%, −6%, and −22%, respectively). EMG/PO increased abruptly during the ES, but there was no change in IMVCs, VA, or TwPt (−13%, −8%, and −26%, respectively). These findings demonstrate that the performance fatigability during a self-paced exercise is characterized by a large drop in contractile function and muscle activation at the beginning of the trial (i.e., FS), without additional change during the middle and end phases (i.e., EP and ES). NEW & NOTEWORTHY The time course of performance fatigability throughout a self-paced exercise is currently unknown. The results showed that a large amount of muscle activation and contractile function impairments are attained early on a self-paced exercise (first ∼15% of the total time trial distance) and maintained throughout the test. This novel finding characterizes the performance fatigability from a contractile function and muscle activation perspective, which brings new insights for future studies focused on real-world exercise training and competition.

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Comparison of neuromuscular adjustments associated with sustained isometric contractions of four different muscle groups

Journal of Applied Physiology ◽

10.1152/japplphysiol.01539.2012 ◽

2013 ◽

Vol 114 (10) ◽

pp. 1426-1434 ◽

Cited By ~ 26

Author(s):

Daria Neyroud ◽

Jennifer Rüttimann ◽

Anne F. Mannion ◽

Guillaume Y. Millet ◽

Nicola A. Maffiuletti ◽

...

Keyword(s):

Muscle Fatigue ◽

Upper Limb ◽

Voluntary Contraction ◽

Voluntary Activation ◽

Knee Extensors ◽

Elbow Flexors ◽

Plantar Flexors ◽

Task Failure ◽

Before And After ◽

Muscle Groups

The extent and characteristics of muscle fatigue of different muscle groups when subjected to a similar fatiguing task may differ. Thirteen healthy young men performed sustained contractions at 50% maximal voluntary contraction (MVC) force until task failure, with four different muscle groups, over two sessions. Per session, one upper limb and one lower limb muscle group were tested (knee extensors and thumb adductor, or plantar and elbow flexors). Changes in voluntary activation level and contractile properties were derived from doublet responses evoked during and after MVCs before and after exercise. Time to task failure differed ( P < 0.05) between muscle groups (220 ± 64 s for plantar flexors, 114 ± 27 s for thumb adductor, 77 ± 25 s for knee extensors, and 72 ± 14 s for elbow flexors). MVC force loss immediately after voluntary task failure was similar (−30 ± 11% for plantar flexors, −37 ± 13% for thumb adductor, −34 ± 15% for knee extensors, and −40 ± 12% for elbow flexors, P > 0.05). Voluntary activation was decreased for plantar flexors only (from 95 ± 5% to 82 ± 9%, P < 0.05). Potentiated evoked doublet amplitude was more depressed for upper limb muscles (−59.3 ± 14.7% for elbow flexors and −60.1 ± 24.1% for thumb adductor, P < 0.05) than for knee extensors (−28 ± 15%, P < 0.05); no reduction was found in plantar flexors (−7 ± 12%, P > 0.05). In conclusion, despite different times to task failure when sustaining an isometric contraction at 50% MVC force for as long as possible, diverse muscle groups present similar loss of MVC force after task failure. Thus the extent of muscle fatigue is not affected by time to task failure, whereas this latter determines the etiology of fatigue.

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Eccentric Loading Increases Peak Torque Angle of the Ankle Plantar Flexors in Healthy Volunteers

International Journal of Sports and Exercise Medicine ◽

10.23937/2469-5718/1510009 ◽

2015 ◽

Vol 1 (5) ◽

Cited By ~ 1

Author(s):

Matthew Wellisch

Keyword(s):

Healthy Volunteers ◽

Peak Torque ◽

Plantar Flexors ◽

Torque Angle

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Unilateral Knee and Ankle Joint Fatigue Induce Similar Impairment to Bipedal Balance in Judo Athletes

Journal of Human Kinetics ◽

10.2478/hukin-2018-0063 ◽

2019 ◽

Vol 66 (1) ◽

pp. 7-18 ◽

Cited By ~ 1

Author(s):

Amine Ghram ◽

James D Young ◽

Rahman Soori ◽

David G Behm

Keyword(s):

Postural Control ◽

Plantar Flexion ◽

National Level ◽

Peak Torque ◽

Knee Extension ◽

Plantar Flexors ◽

Training Experience ◽

Eyes Closed ◽

Eyes Open ◽

Judo Athletes

Abstract The purpose of this study was to compare the effects of unilateral ankle fatigue versus the knee muscles with and without vision on bipedal postural control. Elite judo athletes who competed at the national level with at least 10 years of training experience, were randomised into KNEE (n = 10; 20 ± 2 years) and ANKLE (n = 9; 20 ± 3 years) groups, who performed dynamic isokinetic fatiguing contractions (force decreased to 50% of initial peak torque for three consecutive movements) of the knee flexors and extensors or ankle dorsiflexors and plantar flexors, respectively. Static bipedal postural control (French Posturology Association normative standards) with eyes open and eyes closed was examined before and immediately after the fatiguing task. Postural variables examined were the centre of pressure (CoP) sway in the medio-lateral and antero-posterior directions, total CoP area sway and CoP sway velocity. Although unilateral ankle and knee fatigue adversely affected all bipedal postural measures, with greater disturbances with eyes closed, there were no significant main group or interaction effects between KNEE and ANKLE groups. Unilateral lower limb fatigue adversely affected bipedal balance, with knee extension/flexion fatigue affecting bipedal postural control to a similar extent as unilateral ankle dorsiflexion/plantar flexion fatigue. Hence unilateral fatigue can affect subsequent bilateral performance or also have implications for rehabilitation exercise techniques. Our findings may be limited to judo athletes as other populations were not tested.

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