Influence of amplitude cancellation on the simulated surface electromyogram
Influence of amplitude cancellation on the simulated surface electromyogram
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DOI：
10.1152/japplphysiol.00894.2004
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发表时间：
2005-01-01
影响因子：
3.3
通讯作者：
Enoka, RM
中科院分区：
文献类型：
--
作者：
Keenan, KG;Farina, D;Enoka, RM
本研究的目的是量化的影响，选定的运动单位的属性和模式的活动幅度取消在模拟表面肌电图（EMG）。该研究涉及对运动单位群体的计算机模拟，这些运动单位群体具有生理学定义的招募和速率编码特征，这些特征激活了肌肉纤维，这些肌纤维的电位记录在肌肉上的皮肤上。幅度抵消量化为整流前后运动单位电位相加时信号幅度的百分比差异。这些模拟涉及改变运动单位群体的激活水平、记录配置、运动单位募集的上限、峰值放电率、运动单位同步的量、肌纤维长度、皮下组织的厚度以及随年龄增长而变化的运动单位特性。结果证实了先前的实验报告（Day SJ和Hulliger M，J Neurophysiol 86：2144 - 2158，2001），即表面EMG中的振幅抵消在最大激活时可以达到62%。运动单位电位的幅度范围的减小，如在疲劳收缩期间可能发生的，增加幅度抵消高达类似于85%。在所有模拟条件下观察到幅度抵消量的差异，并导致EMG信号的绝对幅度发生实质性变化。影响振幅抵消的最重要因素是活动运动单位的数量和动作电位的持续时间。当EMG振幅归一化为最大值时，振幅抵消的影响最小（< 5%），但峰值放电率和募集范围的变化除外，这导致不同条件下归一化EMG信号的差异高达17%。这些结果表明振幅抵消的量，可以发生在各种实验条件下，其对绝对和相对措施的肌电振幅的影响。
The purpose of the study was to quantify the influence of selected motor unit properties and patterns of activity on amplitude cancellation in the simulated surface electromyogram (EMG). The study involved computer simulations of a motor unit population with physiologically defined recruitment and rate coding characteristics that activated muscle fibers whose potentials were recorded on the skin over the muscle. Amplitude cancellation was quantified as the percent difference in signal amplitude when motor unit potentials were summed before and after rectification. The simulations involved varying the level of activation for the motor unit population, the recording configuration, the upper limit of motor unit recruitment, peak discharge rates, the amount of motor unit synchronization, muscle fiber length, the thickness of the subcutaneous tissue, and the motor unit properties that change with advancing age. The results confirmed a previous experimental report ( Day SJ and Hulliger M, J Neurophysiol 86: 2144 - 2158, 2001) that amplitude cancellation in the surface EMG can reach 62% at maximal activation. A decrease in the range of amplitudes of the motor unit potentials, as can occur during fatiguing contractions, increased amplitude cancellation up to similar to 85%. Differences in the amount of amplitude cancellation were observed across all simulated conditions, and resulted in substantial changes in the absolute magnitude of the EMG signal. The most profound factors influencing amplitude cancellation were the number of active motor units and the duration of the action potentials. The effects of amplitude cancellation were minimal ( < 5%) when the EMG amplitude was normalized to maximal values, with the exception of variations in peak discharge rate and recruitment range, which resulted in differences up to 17% in the normalized EMG signal across conditions. These results indicate the amount of amplitude cancellation that can occur in various experimental conditions and its influence on absolute and relative measures of EMG amplitude.