Abstract

Sex differences in motor performance may arise depending on the mode of contraction being performed. In particular, contractions that are held for long durations, rather than contractions that are interspersed with rest periods, may induce greater levels of fatigue in men compared to women. The purpose of this study was to examine fatigue responses in a cohort of healthy men (n = 7, age [mean] = 21.6 ± [SD] 1.1 year) and women (n = 7, age: 22.0 ± 2.0 year) during sustained isometric and intermittent isometric contractions. Two contraction protocols were matched for intensity (20% MVC) and total contraction time (600‐s). Biceps brachii EMG and elbow flexion torque steadiness were examined throughout each protocol, and motor nerve stimulation was used to quantify central and peripheral fatigue. Overall, there were few sex‐related differences in the fatigue responses during intermittent contractions. However, men exhibited progressively lower maximal torque generation (39% versus 27% decrease), progressively greater muscle activity (220% versus 144% increase), progressively greater declines in elbow flexion steadiness (354% versus 285% decrease), and progressively greater self‐perception of fatigue (Borg scale: 8.8 ± 1.2 versus 6.3 ± 1.1) throughout the sustained contractions. The mechanism underlying fatigue responses had a muscle component, as voluntary activation of the biceps brachii did not differ between sexes, but the amplitude of resting twitches decreased throughout the sustained contractions (m: 32%, w: 10% decrease). As generating large sustained forces causes a progressive increase in intramuscular pressure and mechanical occlusion—which has the effect of enhancing metabolite accumulation and peripheral fatigue—it is likely that the greater maximal strength of men contributed to their exacerbated levels of fatigue.

Highlights

  • A common observation made in experiments that assess sex-related fatigue characteristics is that men are more fatigable than women

  • While declines in force and neural activation of the muscle are similar for each sex performing repeated submaximal concentric knee extensions, a 60 s maximal isometric contraction of the same muscle group will induce greater levels of central fatigue in men compared to women (Senefeld, Pereira, Pereira, Elliott, Yoon, & Hunter, 2018)

  • Voluntary activation is often associated with perceptions of effort (Smith, Martin, Martin, Gandevia, & Taylor, 2007; Søgaard, Gandevia, Gandevia, Todd, Petersen, & Taylor, 2006), our results indicate that the relationship between perception of fatigue and voluntary activation may differ with sex and mode of contraction

Read more

Summary

Introduction

A common observation made in experiments that assess sex-related fatigue characteristics is that men are more fatigable than women. It is curious that men performing low-force (20% MVC) isometric elbow flexions have consistently shorter times to task failure than females (Yoon et al, 2007, 2015)—a finding that is evident for contractions of the adductor pollicis (Fulco et al, 1999, 2001). Overall, these findings suggest that measuring voluntary drive to upper limb muscles at absolute time intervals (rather than relative to task failure) during low-force contractions may provide insight to sex-related mechanisms of fatigue

Objectives
Findings
Discussion
Conclusion
Full Text
Published version (Free)

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call