McIlwain J S, Hayes K C
Am J Phys Med. 1977 Jun;56(3):122-35.
The dynamic properties of motor units involved in unrestrained H-reflexes and M responses have been studied in seven normal adult males. A linear relationship was observed between the peak to peak EMG of the M response and its twitch tension. Linear relationships were also noted between the EMG and peak displacement, velocity, and acceleration of the evoked muscle twitch for both the H-reflex and the M response. Contraction times for motor units recruited in the H-reflex were longer than those for the M response at low levels of motor unit recruitment. For both responses, however, the contraction times (time to peak force) were markedly shorter than those reported for isometric conditions. Differences were also noted between the H-reflex and M response in the absolute values of the tension to EMG ratio. These differences, together with the longer contraction times for the H-reflex, are quite consistent with the view that different motor unit subpopulations are recruited in the early stages of the two responses. The results and their interpretation, in terms of differential motor unit recruitment, generally confirm the conclusions of studies in which isometric twitch contractions have been investigated.
对7名正常成年男性参与无约束H反射和M反应的运动单位的动态特性进行了研究。观察到M反应的肌电图峰峰值与其抽搐张力之间存在线性关系。H反射和M反应的肌电图与诱发肌肉抽搐的峰值位移、速度和加速度之间也存在线性关系。在低水平运动单位募集时，H反射中募集的运动单位的收缩时间比M反应的收缩时间长。然而，对于这两种反应，收缩时间（达到峰值力的时间）明显短于等长收缩条件下报告的时间。H反射和M反应在张力与肌电图比值的绝对值上也存在差异。这些差异，加上H反射较长的收缩时间，与两种反应早期募集不同运动单位亚群的观点相当一致。就不同运动单位募集而言，这些结果及其解释总体上证实了对等长抽搐收缩进行研究的结论。
