scholarly journals Study of muscle fatigue in isokinetic exercise with estimated conduction velocity and traditional electromyographic indicators

2014 ◽  
Vol 30 (4) ◽  
pp. 312-321 ◽  
Author(s):  
Fabiano Peruzzo Schwartz ◽  
Martim Bottaro ◽  
Rodrigo Souza Celes ◽  
Maria Claudia Pereira ◽  
Valdinar de Araújo Rocha Júnior ◽  
...  
Keyword(s):  
Muscle Fatigue ◽  
Conduction Velocity ◽  
Isokinetic Exercise

scholarly journals Sex differences in muscle fatigue following isokinetic muscle contractions

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Miguel Gomes ◽  
Paulo Santos ◽  
Paulo Correia ◽  
Pedro Pezarat-Correia ◽  
Goncalo V. Mendonca
Keyword(s):  
Sex Differences ◽  
Muscle Fatigue ◽  
Human Performance ◽  
Knee Extension ◽  
Muscle Contractions ◽  
Limiting Factor ◽  
Maximal Voluntary Isometric Contraction ◽  
Isokinetic Exercise ◽  
Isokinetic Contractions ◽  
The Impact

AbstractMuscle fatigue is a limiting factor of human performance. It is unclear whether sex-based differences in fatigability exist during dynamic exercise of varying velocities of contraction. We aimed at exploring sex differences in muscle fatigue elicited by maximal isokinetic muscle contractions performed at different angular velocities. Twenty-six healthy participants (13 men: 23.2 ± 1.5; 13 women: 21.9 ± 3.0 years) were tested for concentric knee-extension at slow, moderate and fast angular isokinetic velocity (60, 180 and 300º.s−1, respectively), on non-consecutive days. The impact of sex on fatigue resistance and consecutive recovery for each isokinetic condition was explored by calculating the percent change in maximal voluntary isometric contraction (MVIC) and in rate of torque development (RTD), from pre- to post-isokinetic exercise (30 repetitions). The isokinetic fatigue index was also determined. No sex differences were obtained in response to isokinetic contractions completed at 60º.s−1. After performing muscle contractions at 300º.s−1, women had a significantly greater loss in MVIC than men (− 18.4 ± 5.5 vs. − 12.9 ± 3.8%; p = 0.009) and larger decreases in work output during isokinetic exercise (− 34.2 ± 8.9 vs − 27.5 ± 10.6%; p = 0.017). Recovery of initial MVIC strength was greater for women post-exercise at 180º.s−1 (15.6 ± 4.1% vs. 6.7 ± 9.5; p = 0.003). No differences were found between sexes in any condition for RTD from pre- to post-fatigue. These results suggest the presence of a sexually dimorphic fatigability in response to dynamic (isokinetic) contractions favouring men at higher absolute velocities of contraction.

Myoelectric manifestations of fatigue in voluntary and electrically elicited contractions

1990 ◽  
Vol 69 (5) ◽  
pp. 1810-1820 ◽  
Author(s):  
R. Merletti ◽  
M. Knaflitz ◽  
C. J. De Luca
Keyword(s):  
Muscle Fatigue ◽  
Root Mean Square ◽  
Conduction Velocity ◽  
Time Course ◽  
Tibialis Anterior Muscle ◽  
Median Frequency ◽  
Mean Square ◽  
Myoelectric Signal ◽  
Physiological Factor ◽  
Voluntary Contractions

The time course of muscle fiber conduction velocity and surface myoelectric signal spectral (mean and median frequency of the power spectrum) and amplitude (average rectified and root-mean-square value) parameters was studied in 20 experiments on the tibialis anterior muscle of 10 healthy human subjects during sustained isometric voluntary or electrically elicited contractions. Voluntary contractions at 20% maximal voluntary contraction (MVC) and at 80% MVC with duration of 20 s were performed at the beginning of each experiment. Tetanic electrical stimulation was then applied to the main muscle motor point for 20 s with surface electrodes at five stimulation frequencies (20, 25, 30, 35, and 40 Hz). All subjects showed myoelectric manifestations of muscle fatigue consisting of negative trends of spectral variables and conduction velocity and positive trends of amplitude variables. The main findings of this work are 1) myoelectric signal variables obtained from electrically elicited contractions show fluctuations smaller than those observed in voluntary contractions, 2) spectral variables are more sensitive to fatigue than conduction velocity and the average rectified value is more sensitive to fatigue than the root-mean-square value, 3) conduction velocity is not the only physiological factor affecting spectral variables, and 4) contractions elicited at supramaximal stimulation and frequencies greater than 30 Hz demonstrate myoelectric manifestations of muscle fatigue greater than those observed at 80% MVC sustained for the same time.

scholarly journals Sex Differences in Muscle Fatigue Following Isokinetic Muscle Contractions

2020 ◽  
Author(s):  
Miguel Gomes ◽  
Paulo Santos ◽  
Paulo Correia ◽  
Pedro Pezarat-Correia ◽  
Goncalo V. Mendonca
Keyword(s):  
Sex Differences ◽  
Muscle Fatigue ◽  
Human Performance ◽  
Knee Extension ◽  
Muscle Contractions ◽  
Limiting Factor ◽  
Maximal Voluntary Isometric Contraction ◽  
Isokinetic Exercise ◽  
Isokinetic Contractions ◽  
The Impact

Abstract Muscle fatigue is a limiting factor of human performance. It is unclear whether sex-based differences in fatigability exist during dynamic exercise of varying velocities of contraction. We aimed at exploring sex differences in muscle fatigue elicited by maximal isokinetic muscle contractions performed at different angular velocities. Twenty-six healthy participants (13 men: 23.2 ± 1.5; 13 women: 21.9 ± 3.0 years) were tested for knee-extension at slow, moderate and fast angular velocity (60, 180 and 300º.s-1, respectively). The impact of sex on fatigue resistance and consecutive recovery for each isokinetic condition was explored by calculating the percent change in maximal voluntary isometric contraction (MVIC) and in rate of torque development (RTD), from pre- to post-isokinetic exercise. The isokinetic fatigue index was also determined. No sex differences were obtained in response to isokinetic contractions completed at 60º.s-1. After performing muscle contractions at 300º.s-1, women had a significantly greater loss in MVIC than men (-18.4 ± 5.5 vs. -12.9 ± 3.8%; p = 0.009) and larger decreases in work output during isokinetic exercise (-34.2 ± 8.9 vs -27.5 ± 10.6 %; p = 0.017). Recovery of initial MVIC strength was greater for women post-exercise at 180º.s-1 (6.7 ± 9.5 vs. 15.6 ± 4.1%; p = 0.003). No differences were found between sexes in any condition for RTD from pre- to post- fatigue. These results suggest the presence of a sexually dimorphic fatigability in response to dynamic (isokinetic) contractions favouring men at higher velocities of contraction.

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