Menzies Health Institute Queensland, Griffith University, Gold Coast, Australia.
Griffith Sports Physiology and Performance, School of Allied Health Sciences, Griffith University, Gold Coast, Australia.
Physiol Rep. 2020 Apr;8(7):e14398. doi: 10.14814/phy2.14398.
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.
性别差异可能会出现在运动表现上，这取决于正在进行的收缩模式。特别是，与间歇收缩相比，持续时间较长的收缩可能会导致男性比女性更容易疲劳。本研究的目的是在一组健康男性（n=7，年龄[均值]±[标准差]1.1 岁）和女性（n=7，年龄：22.0±2.0 岁）中检查持续等长和间歇等长收缩时的疲劳反应。两种收缩方案的强度（20% MVC）和总收缩时间（600 秒）相匹配。在整个方案中，检查肱二头肌肌电图和肘部弯曲扭矩稳定性，并且使用运动神经刺激来量化中枢和周围疲劳。总体而言，在间歇收缩期间，性别相关的疲劳反应差异很小。然而，男性表现出逐渐降低的最大扭矩产生（39%比 27%降低），逐渐增加的肌肉活动（220%比 144%增加），肘部弯曲稳定性逐渐降低（354%比 285%降低），并且自我疲劳感逐渐增强（Borg 量表：8.8±1.2 比 6.3±1.1）在持续收缩过程中。疲劳反应的机制具有肌肉成分，因为肱二头肌的自愿激活在性别之间没有差异，但静息抽搐的幅度在持续收缩过程中逐渐降低（男性：32%，女性：10%降低）。由于产生大的持续力会导致肌肉内压力逐渐增加和机械闭塞，从而增强代谢物积累和外周疲劳，因此男性的最大力量较大可能导致他们的疲劳程度加剧。
