Electromyographic Kinesiology Laboratory, Department of Kinesiology, Brock University, St. Catharines, ON L2S 3A1, Canada.
Appl Physiol Nutr Metab. 2021 Sep;46(9):1065-1072. doi: 10.1139/apnm-2020-0953. Epub 2021 Mar 5.
The purpose of this study was to evaluate the relationship between the variability in the motor unit inter-pulse interval and force steadiness at submaximal and maximal force outputs between the sexes. Twenty-four male and 24 female participants were recruited to perform isometric dorsiflexion contractions at 20, 40, 60, 80, and 100% maximum voluntary contraction. Tibialis anterior myoelectric signal was recorded by an intramuscular electrode. Females had lower force steadiness (coefficient of variation of force (CoV-Force), 27.3%, < 0.01) and a greater coefficient of variation of motor unit action potential inter-pulse interval (CoV-IPI), compared with males (9.6%, < 0.01). There was no significant correlation between the normalized CoV-IPI and CoV-Force ( = 0.19, > 0.01), but there was a significant repeated measures correlation between the raw scores for root-mean-square force error and the standard deviation of motor unit discharge rate ( = 0.65, < 0.01). Females also had a greater incidence of doublet discharges on average across force levels ( < 0.01). The sex differences may result from motor unit behaviours (i.e., doublet and rapid discharges, synchronization, rate coding or recruitment), leading to lower force steadiness and greater CoV-IPI in females. Sex differences in force steadiness may be due to neural strategies. Females have lower force steadiness compared with males. Greater incidence of doublet discharges in females may result in lesser force steadiness.
本研究旨在评估男女在亚最大和最大力量输出下运动单位间脉冲间隔变化与力量稳定性之间的关系。招募了 24 名男性和 24 名女性参与者进行等长背屈收缩，力量输出为 20%、40%、60%、80%和 100%最大自主收缩。通过肌内电极记录胫骨前肌肌电信号。与男性相比，女性的力量稳定性较低（力变异系数（CoV-Force），27.3%，<0.01），运动单位动作电位间脉冲间隔变异系数（CoV-IPI）较大（9.6%，<0.01）。归一化 CoV-IPI 与 CoV-Force 之间无显著相关性（=0.19，>0.01），但均方根力误差的原始分数与运动单位放电率标准差之间存在显著重复测量相关性（=0.65，<0.01）。女性在平均力量水平上的双重放电发生率也较高（<0.01）。性别差异可能源于运动单位行为（即双重和快速放电、同步、率编码或募集），导致女性力量稳定性较低和 CoV-IPI 较大。力量稳定性的性别差异可能源于神经策略。与男性相比，女性的力量稳定性较低。女性双重放电发生率较高可能导致力量稳定性降低。
