Motor unit control and force fluctuation during fatigue
Motor unit control and force fluctuation during fatigue
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DOI：
10.1152/japplphysiol.00035.2009
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发表时间：
2009-07-01
影响因子：
3.3
通讯作者：
De Luca, Carlo J.
中科院分区：
文献类型：
--
作者：
Contessa, Paola;Adam, Alexander;De Luca, Carlo J.
Contessa P，Adam A，De Luca CJ.疲劳时的运动单位控制和力波动。J Appl Physiol 107：235-243，2009.首次发表于2009年4月23日; doi：10.1152/japplphysiol.00035.2009。在等长收缩期间，肌肉的力输出的波动随着肌肉疲劳而增加，并且收缩持续到耗尽。我们分析了股外侧肌的运动单元放电数据，以研究哪些运动单元控制参数与增加的力波动相关。受试者进行了一系列的等长恒定力收缩持续在20%的最大力量，每个间隔6秒的休息期。进行收缩，直到力输出的平均值不能维持在期望水平。肌内肌电信号的检测与四股细线传感器。通过使用基于人工智能的一组算法对肌电信号进行分解以识别几个运动单元的所有放电。随着耐力时间的推移，我们能够跟踪相同运动单位的行为。过滤肌肉的力输出以去除跟踪任务的贡献。力的变异系数随时间延长而增加（P < 0.001，R-2 = 0.51）。我们计算了放电率的变异系数、成对运动单位放电的同步性、成对运动单位放电率的互相关值、运动单位放电率与力的互相关性以及收缩过程中招募的运动单位数量。在这些参数中，只有放电率（P < 0.01，R-2 = 0.10）和募集的运动单位数量（P = 0.042，R-2 = 0.22）的交叉相关性随受试者的耐力时间显著增加。还观察到击发频率和力的交叉相关性显著增加（P < 0.001，R-2 = 0.16）。有人建议，在发射率的互相关的增加可能是由于从纺锤体的本体感受反馈的灵敏度降低。
Contessa P, Adam A, De Luca CJ. Motor unit control and force fluctuation during fatigue. J Appl Physiol 107: 235-243, 2009. First published April 23, 2009; doi:10.1152/japplphysiol.00035.2009.-During isometric contractions, the fluctuation of the force output of muscles increases as the muscle fatigues, and the contraction is sustained to exhaustion. We analyzed motor unit firing data from the vastus lateralis muscle to investigate which motor unit control parameters were associated with the increased force fluctuation. Subjects performed a sequence of isometric constant-force contractions sustained at 20% maximal force, each spaced by a 6-s rest period. The contractions were performed until the mean value of the force output could not be maintained at the desired level. Intramuscular EMG signals were detected with a quadrifilar fine-wire sensor. The EMG signals were decomposed to identify all of the firings of several motor units by using an artificial intelligence-based set of algorithms. We were able to follow the behavior of the same motor units as the endurance time progressed. The force output of the muscle was filtered to remove contributions from the tracking task. The coefficient of variation of the force was found to increase with endurance time (P < 0.001, R-2 = 0.51). We calculated the coefficient of variation of the firing rates, the synchronization of pairs of motor unit firings, the cross-correlation value of the firing rates of pairs of motor units, the cross-correlation of the firing rates of motor units and the force, and the number of motor units recruited during the contractions. Of these parameters, only the cross-correlation of the firing rates (P < 0.01, R-2 = 0.10) and the number of recruited motor units (P = 0.042, R-2 = 0.22) increased significantly with endurance time for grouped subjects. A significant increase (P < 0.001, R-2 = 0.16) in the cross-correlation of the firing rates and force was also observed. It is suggested that the increase in the cross-correlation of the firing rates is likely due to a decrease in the sensitivity of the proprioceptive feedback from the spindles.