Solomonow M, Baratta R, Shoji H, D'Ambrosia R
Department of Orthopaedic Surgery, Louisiana State University Medical Center, New Orleans 70112.
Electromyogr Clin Neurophysiol. 1990 Apr-May;30(3):141-52.
The dependence of the EMG vs force relationships on skeletal muscles contraction rate, and its motor units recruitment control strategy were studied. An electrical nerve stimulation technique capable of orderly excitation of motor units according to their size with simultaneous increase in their discharge rate was applied to isometric preparations of the M. gastrocnemius muscle of the cat. Muscle force and intramuscularly recorded EMG were normalized and plotted against each other. The method of least squares (p less than .05) was used to yield the best fit linear regression polynominials to the pooled data from several preparations. Strong dependency on the motor unit recruitment strategy was exhibited by the results. Linear EMG vs force relationships was evident when all the motor units were recruited to generate the initial 50% of the maximal force while discharge rate continued to increase up to the maximal force. Progressive increase in non-linearity was evident as recruitment of motor units generated 60% and up to 100% of the initial force concurrently with firing rate increase. Contraction rate (force generation rate) increase from 36% sec up to 360% sec resulted in nearly identical normalized EMG vs force relationships, although the maximal force increased by up to 22.5% as the contraction rate increased to 360% sec. The results of this study issue a clear warning against the direct use of EMG to predict muscle force in biomechanical and kinesiological research without correcting for the variables discussed in this paper.
研究了肌电图（EMG）与力的关系对骨骼肌收缩速率的依赖性及其运动单位募集控制策略。将一种能够根据运动单位大小有序激发并同时增加其放电速率的电神经刺激技术应用于猫腓肠肌的等长制备物。对肌肉力量和肌肉内记录的EMG进行归一化处理，并相互绘制。使用最小二乘法（p小于0.05）对来自多个制备物的汇总数据得出最佳拟合线性回归多项式。结果显示出对运动单位募集策略的强烈依赖性。当所有运动单位被募集以产生最大力量的初始50%，而放电速率持续增加直至最大力量时，EMG与力的线性关系明显。随着运动单位的募集在放电速率增加的同时产生初始力量的60%至100%，非线性逐渐增加。收缩速率（力产生速率）从36%秒增加到360%秒，导致归一化的EMG与力的关系几乎相同，尽管随着收缩速率增加到360%秒，最大力量增加了高达22.5%。本研究结果明确警告，在生物力学和运动学研究中，若不校正本文所讨论的变量，直接使用EMG来预测肌肉力量是不可行的。
