REDUCED CONTROL OF MOTOR OUTPUT IN A HUMAN HAND MUSCLE OF ELDERLY SUBJECTS DURING SUBMAXIMAL CONTRACTIONS
REDUCED CONTROL OF MOTOR OUTPUT IN A HUMAN HAND MUSCLE OF ELDERLY SUBJECTS DURING SUBMAXIMAL CONTRACTIONS
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DOI：
10.1152/jn.1993.69.6.2108
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发表时间：
1993-06-01
影响因子：
2.5
通讯作者：
ENOKA, RM
中科院分区：
文献类型：
--
作者：
GALGANSKI, ME;FUGLEVAND, AJ;ENOKA, RM
1. 本文研究了年龄对22例（女性6例，男性16例）第一背骨间肌运动输出的影响。这项研究的目的是确定年龄对肌肉力量控制的影响，以及与之相关的单个运动单元放电行为和机械性能的变化。每位受试者执行三个需要左手食指等距外展的任务：最大自愿收缩（MVC）、恒力任务和阈值任务。在恒力任务中，通过量化四个次最大目标力（5、20、35和50% MVC）的等距力变化来评估控制力的能力。阈值任务包括维持孤立运动单元以低、稳定的速率放电约3分钟。在阈值任务中，通过测量脉冲间隔和峰值触发平均力的峰值幅度和峰值时间来确定单个运动单元的放电行为和力学性能。结果表明，年龄对亚最大目标力（范围：5-50% MVC）的力变化有影响，且相对于目标力计算，在较低的力水平下，老年被试的力变化更大。根据平均脉冲间隔和脉冲间隔的变异性，159名（年轻受试者：n = 83；老年受试者：n = 76）的放电行为在低、稳定的放电速率下识别出单个运动单元，在青年和老年受试者之间没有差异。在老年受试者中，单个运动单元以低、稳定的速率放电时，平均峰值触发的平均力（MVC百分比）更大。然而，在两个年龄组中，到达峰值的平均时间是相似的。7. 在阈值任务期间施加的力进行了频谱分析。在功率谱峰值的频率上，年轻组和老年组没有发现差异。然而，老年受试者的峰值幅度明显更大。这些结果表明，在阈值任务中，老年人在运动单元中与未融合放电率相关的频率上的力波动更大。我们的结论是，老年受试者维持恒定的次极大力的能力下降至少部分是由于低阈值运动单元施加的更大的力。这种关联可能是由于伴随衰老的运动单元的外围重组，尽管不能排除运动单元放电同步增加的作用。
1. The effect of age on the motor output of the first dorsal interosseous muscle of 22 (6 female, 16 male) human subjects was investigated. The purpose of the study was to determine the effect of age on the control of muscle force and the associated changes in the discharge behavior and mechanical properties of single motor units.2. Each subject performed three tasks requiring isometric abduction of the left index finger: a maximum voluntary contraction (MVC), a constant-force task, and a threshold task. The ability to control force was assessed during the constant-force task by quantifying the variation in isometric force about four submaximal target forces (5, 20, 35, and 50% MVC). The threshold task involved sustaining the discharge of the isolated motor unit at a low, steady rate for approximately 3 min.3. The discharge behavior and the mechanical properties of single motor units were determined during the threshold task by measuring the interimpulse intervals and the peak amplitude and time to peak of the spike-triggered average force.4. The data indicated that age had an effect on the variation of force about submaximal target forces (range: 5-50% MVC), and that these force variations, when calculated relative to the target force, were greater at lower force levels in the elderly subjects.5. On the basis of the mean interimpulse interval and the variability in the interimpulse interval, no differences were identified between the young and elderly subjects in the discharge behavior of 159 (young subjects: n = 83; elderly subjects: n = 76) identified single motor units when discharging at low, steady rates.6. The mean spike-triggered average force (percentage of MVC) exerted by individual motor units discharging at low, steady rates was larger in elderly subjects. However, the mean time to peak of the spike-triggered average force was similar for the two age groups. 7. The force exerted during the threshold task was subjected to a spectral analysis. No difference was found in the frequency of the peak in the power spectrum between the young and elderly groups. The amplitude of the peak, however, was significantly greater for the elderly subjects. These results suggest that the fluctuation of force at frequencies associated with unfused discharge rates in motor units was larger in elderly individuals during the threshold task.8. We conclude that the reduced ability of elderly subjects to maintain a constant submaximal force is at least partially due to the larger forces exerted by low-threshold motor units. This association is probably due to the peripheral reorganization of motor units that accompanies aging, although a role for an increase in the synchronization of motor unit discharge cannot be excluded.