Feasby T E, Brown W F
J Neurol Neurosurg Psychiatry. 1974 Aug;37(8):916-26. doi: 10.1136/jnnp.37.8.916.
One physiological method for estimating the motor unit number in a muscle depends on dividing into the maximum compound muscle action potential, the potential average of the first few motor unit potentials excited by a motor nerve stimulus above motor threshold. To be valid, such an average unit potential size must be representative of the whole motor unit population. This assumption may not be justified. The present study has shown that there are single motor units in healthy and abnormal, thenar, and EDB motor unit populations, many times larger than any motor unit excited close to the motor threshold. This finding suggests that previously reported motor unit estimates may not only be an overestimate of the true motor unit population number, but have excluded much larger motor units with higher thresholds. Low motor unit estimates in neuropathies may result from a change in the order of activation of motor units with the appearance of larger motor units, normally of higher threshold among the first few just above the motor threshold.
一种估算肌肉中运动单位数量的生理学方法是，将运动神经刺激超过运动阈值时最初激发的几个运动单位电位的平均电位，除以最大复合肌肉动作电位。要使这种方法有效，这样的平均单位电位大小必须代表整个运动单位群体。这个假设可能并不合理。本研究表明，在健康和异常的鱼际肌及指短伸肌运动单位群体中，存在单个运动单位，其大小比接近运动阈值时激发的任何运动单位大许多倍。这一发现表明，先前报道的运动单位估算值可能不仅高估了真实的运动单位群体数量，还排除了阈值更高的大得多的运动单位。神经病变中运动单位估算值较低，可能是由于运动单位激活顺序发生了变化，出现了较大的运动单位，通常在略高于运动阈值的最初几个运动单位中，阈值较高。
