Discharge rate variability influences the variation in force fluctuations across the working range of a hand muscle
Discharge rate variability influences the variation in force fluctuations across the working range of a hand muscle
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DOI：
10.1152/jn.01122.2004
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发表时间：
2005-05-01
影响因子：
2.5
通讯作者：
Enoka, RM
中科院分区：
文献类型：
--
作者：
Moritz, CT;Barry, BK;Enoka, RM
本研究的目的是提高运动单元模型的能力，以预测实验测得的力的变化范围很广的力量。从第一骨间背侧肌的38个运动单位获得运动单位放电特征。运动单位放电记录在单独的等长收缩，范围从4%至85%的最大随意收缩（MVC）的力量以上的招聘阈值。高阈运动单位的最小和最大放电率均高于低阈单位（P < 0.01）。随着募集阈值的增加，最小放电率从7增加到23 pps，峰值放电率从14增加到38 pps。相对放电率变异性（CV）指数下降为每个运动单位的平均值为30至13%，食指的力量增加以上的招聘阈值。在单独的实验中，在2至95%MVC的8个力水平下评估力的可变性。随着力从2% MVC增加到15% MVC，力的CV从4.9%降低到1.4%（P < 0.01），并在更高的力下保持恒定（1.2-1.9%; P = 0.14）。当使用这些实验结果修正运动单元模型时，放电率变异性是导致在所有力水平下模拟力变异性与实验力变异性之间无显著差异（P = 0.22）的关键因素。这些结果支持这一假设，即放电率的变异性是一个主要的决定因素，在整个工作范围的肌肉等长力量的变化趋势。
The goal of this study was to improve the ability of a motor unit model to predict experimentally measured force variability across a wide range of forces. Motor unit discharge characteristics were obtained from 38 motor units of the first dorsal interosseus muscle. Motor unit discharges were recorded in separate isometric contractions that ranged from 4 to 85% of the maximal voluntary contraction (MVC) force above recruitment threshold. High-threshold motor units exhibited both greater minimal and peak discharge rates compared with low-threshold units (P < 0.01). Minimal discharge rate increased from 7 to 23 pps, and peak discharge rate increased from 14 to 38 pps with an increase in recruitment threshold. Relative discharge rate variability ( CV) decreased exponentially for each motor unit from an average of 30 to 13% as index finger force increased above recruitment threshold. In separate experiments, force variability was assessed at eight force levels from 2 to 95% MVC. The CV for force decreased from 4.9 to 1.4% as force increased from 2 to 15% MVC (P < 0.01) and remained constant at higher forces (1.2-1.9%; P = 0.14). When the motor unit model was revised using these experimental findings, discharge rate variability was the critical factor that resulted in no significant difference between simulated and experimental force variability (P = 0.22) at all force levels. These results support the hypothesis that discharge rate variability is a major determinant of the trends in isometric force variability across the working range of a muscle.