PDF(Pubmed)
Abstract：
Improving muscle strength and preventing muscle weakness are important for older adults. The change in strength can be effectively explained by skeletal muscle mass and neural factors. Neural factors are important for older adults because the variation of neural components is greater in older than in young adults, and any decline in strength cannot solely be explained by a decrease in skeletal muscle mass. The purpose of the present study was to investigate whether skeletal muscle mass or motor unit firing properties could explain the change in muscle strength after 1 year. Thirty-eight older adults (75.0 ± 4.7 years, 156.6 ± 7.7 cm, 55.5 ± 9.4 kg, 26 women) performed maximum voluntary knee extension and their skeletal muscle mass was measured using a bioimpedance device. During a submaximal contraction task, high-density surface electromyography was recorded and the signals were decomposed into individual motor unit firing. As an index of motor unit firing properties, the slope and y-intercept (MU intercept) were calculated from the regression line between recruitment thresholds and firing rates in each participant. After 1 year, their maximum knee extension torque was evaluated again. A stepwise multiple regression linear model with sex and age as covariates indicated that MU intercept was a significant explanation with a negative association for the 1-year change in muscle strength (β = - 0.493, p = 0.004), but not skeletal muscle mass (p = 0.364). The results suggest that neural components might be predictors of increasing and decreasing muscle strength rather than skeletal muscle mass.
摘要：
提高肌肉力量和防止肌肉无力对老年人很重要。强度的变化可以通过骨骼肌质量和神经因素有效地解释。神经因素对老年人很重要，因为老年人的神经成分变化大于年轻人，任何力量的下降都不能完全用骨骼肌质量的减少来解释。本研究的目的是研究骨骼肌质量或运动单位放电特性是否可以解释1年后肌肉力量的变化。38名老年人（75.0±4.7岁，156.6±7.7cm,55.5±9.4kg,26名妇女）进行了最大程度的自愿膝关节伸展，并使用生物阻抗装置测量了其骨骼肌质量。在次最大收缩任务中，记录高密度表面肌电图，并将信号分解为单个运动单位放电。作为电机单元点火性能的指标，斜率和y截距(MU截距)由每个参与者的招募阈值和射击率之间的回归线计算.一年后，他们的最大膝盖伸展扭矩再次评估。以性别和年龄为协变量的逐步多元回归线性模型表明，MU截距是肌肉力量1年变化的显着解释（β=-0.493，p=0.004），但不是骨骼肌质量（p=0.364）。结果表明，神经成分可能是增加和减少肌肉力量而不是骨骼肌质量的预测因子。
