Motor-unit synchronization increases EMG amplitude and decreases force steadiness of simulated contractions
Motor-unit synchronization increases EMG amplitude and decreases force steadiness of simulated contractions
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DOI：
10.1152/jn.2000.83.1.441
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发表时间：
2000-01-01
影响因子：
2.5
通讯作者：
Enoka, RM
中科院分区：
文献类型：
--
作者：
Yao, WX;Fuglevand, AJ;Enoka, RM
本研究的目的是使用肌肉收缩的计算机模型来确定运动单元同步化对表面肌电图（EMG）和等长力的影响。通过产生肌纤维动作电位、定义运动单元机械特性和领域、估计运动单元动作电位、指定运动单元放电时间以及施加各种水平的运动单元同步来模拟EMG和力。在11个激励水平下模拟输出（EMG和力），范围为最大值的5 - 100%。为了同步运动单元活动，调整了选定的运动单元放电时间;然而，对于给定的兴奋水平，在整个同步条件下，招募的运动单元数量和每个单元的平均放电率是恒定的。两个级别的同步施加的放电时间：一个中等和高水平，这近似于实验观察到的范围内的电机单元同步。中等水平的同步性导致平均EMG增加类似于65%，而高水平导致EMG相对于非同步性条件增加130%。两种同步条件都不影响平均力的大小。然而，电机单元同步增加了模拟力的波动幅度，特别是在中等水平的激励下。总之，运动单元同步增加了平均整流EMG的幅度，并降低了模拟收缩中肌肉施加的力的稳定性。
The purpose of the study was to determine the effect of motor-unit synchronization on the surface electromyogram (EMG) and isometric force using a computer model of muscle contraction. The EMG and force were simulated by generating muscle fiber action potentials, defining motor-unit mechanical characteristics and territories, estimating motor-unit action potentials, specifying motor-unit discharge times, and imposing various levels of motor-unit synchronization. The output (EMG and force) was simulated at 11 levels of excitation, ranging from 5 to 100% of maximum. To synchronize motor-unit activity, selected motor-unit discharge times were adjusted; however, the number of motor units recruited and the average discharge rate of each unit was constant across synchronization conditions for a given level of excitation. Two levels of synchronization were imposed on the discharge times: a moderate and a high level, which approximated the experimentally observed range of motor-unit synchronization. The moderate level of synchrony caused the average EMG to increase by similar to 65%, whereas the high level caused a 130% increase in the EMG with respect to the no-synchrony condition. Neither synchrony condition influenced the magnitude of the average force. However, motor-unit synchronization did increase the amplitude of the fluctuations in the simulated force, especially at intermediate levels of excitation. In conclusion, motor-unit synchronization increased the amplitude of the average rectified EMG and decreased the steadiness of the force exerted by the muscle in simulated contractions.