Practice reduces motor unit discharge variability in a hand muscle and improves manual dexterity in old adults
Practice reduces motor unit discharge variability in a hand muscle and improves manual dexterity in old adults
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DOI：
10.1152/japplphysiol.01149.2004
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发表时间：
2005-06-01
影响因子：
3.3
通讯作者：
Enoka, RM
中科院分区：
文献类型：
--
作者：
Kornatz, KW;Christou, EA;Enoka, RM
采用稳定性改善干预措施来确定运动单位放电率的变异性对老年人食指加速度和手动灵活性波动的影响。十名健康且久坐的老年人（年龄 72.9 +/- 5.8 岁；5 名男性）参与了涉及左食指外展的研究。在轻负荷训练前、2周后（10%最大负荷）和4周重负荷训练后（70%最大负荷）记录第一背侧骨间肌的单运动单位活动。正如预期的那样，轻负荷训练可有效减少缓慢缩短（0.25 +/- 0.12 至 0.13 +/- 0.08 m/s(2)）和延长收缩（0.29 +/- 0.10 至 0.14 +/- 0.06 m/s(2)）期间食指加速度的波动。随着波动幅度的下降，两种收缩类型期间放电率的变异系数也平行下降（33.8 +/- 6.8 至 25.0 +/- 5.9%）。大负荷训练并没有进一步改善加速度波动或放电率变异性。此外，左手的手动灵活性通过训练显着提高（普渡钉板测试：11 +/- 3 至 14 +/- 1 钉）。双变量相关性表明，缩短（r（2）= 0.24）和延长（r（2）= 0.14）收缩期间运动输出波动的减少以及手动灵活性（r（2）= 0.26）的改善与运动单位放电率变异性的下降直接相关。运动输出的波动和手动灵巧度之间存在很强的相关性（r(2) = 0.56）。这些结果表明，简单的手指任务的练习伴随着运动单位的放电率变异性的减少、手部肌肉的运动输出的波动的减少以及老年人的手动灵活性的提高。
A steadiness-improving intervention was used to determine the contribution of variability in motor unit discharge rate to the fluctuations in index finger acceleration and manual dexterity in older adults. Ten healthy and sedentary old adults ( age 72.9 +/- 5.8 yr; 5 men) participated in the study involving abduction of the left index finger. Single motor unit activity was recorded in the first dorsal interosseus muscle before, after 2 wk of light-load training (10% maximal load), and after 4 wk of heavy-load training (70% maximal load). As expected, the light-load training was effective in reducing the fluctuations in index finger acceleration during slow shortening (0.25 +/- 0.12 to 0.13 +/- 0.08 m/s(2)) and lengthening contractions (0.29 +/- 0.10 to 0.14 +/- 0.06 m/s(2)). Along with the decline in the magnitude of the fluctuations, there was a parallel decrease in the coefficient of variation for discharge rate during both contraction types (33.8 +/- 6.8 to 25.0 +/- 5.9%). The heavy-load training did not further improve either the fluctuations in acceleration or discharge rate variability. Furthermore, the manual dexterity of the left hand improved significantly with training (Purdue pegboard test: 11 +/- 3 to 14 +/- 1 pegs). Bivariate correlations indicated that the reduction in fluctuations in motor output during shortening (r(2) = 0.24) and lengthening (r(2) = 0.14) contractions and improvement in manual dexterity (r(2) = 0.26) was directly associated with a decline in motor unit discharge rate variability. There was a strong association between the fluctuations in motor output and manual dexterity (r(2) = 0.56). These results indicate that practice of a simple finger task was accompanied by a reduction in the discharge rate variability of motor units, a decrease in the fluctuations in motor output of a hand muscle, and an improvement in the manual dexterity of older adults.