Age-related changes in motor unit firing pattern of vastus lateralis muscle during low-moderate contraction
Age-related changes in motor unit firing pattern of vastus lateralis muscle during low-moderate contraction
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DOI：
10.1007/s11357-016-9915-0
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发表时间：
2016-06-01
期刊：
影响因子：
--
通讯作者：
Moritani, Toshio
中科院分区：
文献类型：
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作者：
Watanabe, Kohei;Holobar, Ales;Moritani, Toshio
运动肌肉(如股四头肌)的运动单位激活特性随年龄的变化尚不清楚，尽管这些肌肉随着年龄的增长而优先萎缩，并在日常生活运动中发挥重要作用。本研究调查和比较了老年人和年轻人股外侧肌在低到中等力量水平下等长收缩时的详细运动单位放电特征。14名健康老年男性和15名健康青年男性在伸膝时进行等长递增收缩至最大自主收缩(MVC)的70%。采用电极二维网格记录股外侧肌多道表面肌电信号，并用卷积核补偿技术分解提取单个运动单位。年轻人的运动单位放电率(接近+29.7%)显著高于老年人(p<；0.05)。不同招募阈值的运动单位在不同部队水平下的射击率在年轻人中有显著差异(p<；0.05)，而在老年人中没有显著差异(p>；0.05)。在老年人中，在MVC水平的60%和20%时，运动单位的射击率与MVC力量显著相关(r=0.885，p<；0.0001)，而在年轻人中则不显著(r=0.127，p>；0.05)。这些结果表明，老年人股外侧肌的运动单位放电频率受年龄和肌肉力量的影响，和/或年龄相关性的力量丧失与运动单位的放电/招募特性有关。
Age-related changes in motor unit activation properties remain unclear for locomotor muscles such as quadriceps muscles, although these muscles are preferentially atrophied with aging and play important roles in daily living movements. The present study investigated and compared detailed motor unit firing characteristics for the vastus lateralis muscle during isometric contraction at low to moderate force levels in the elderly and young. Fourteen healthy elderly men and 15 healthy young men performed isometric ramp-up contraction to 70 % of the maximal voluntary contractions (MVC) during knee extension. Multichannel surface electromyograms were recorded from the vastus lateralis muscle using a two-dimensional grid of 64 electrodes and decomposed with the convolution kernel compensation technique to extract individual motor units. Motor unit firing rates in the young were significantly higher (similar to+29.7 %) than in the elderly (p < 0.05). There were significant differences in firing rates among motor units with different recruitment thresholds at each force level in the young (p < 0.05) but not in the elderly (p > 0.05). Firing rates at 60 % of the MVC force level for the motor units recruited at < 20 % of MVC were significantly correlated with MVC force in the elderly (r = 0.885, p < 0.0001) but not in the young (r = 0.127, p > 0.05). These results suggest that the motor unit firing rate in the vastus lateralis muscle is affected by aging and muscle strength in the elderly and/or age-related strength loss is related to motor unit firing/recruitment properties.