Thomas C K, Ross B H, Calancie B
J Neurophysiol. 1987 Jan;57(1):311-24. doi: 10.1152/jn.1987.57.1.311.
Spike-triggered averaging was used to determine the twitch tensions and contraction times of motor units in the abductor pollicis brevis muscle of two human subjects for two directions of isometric contraction: abduction and opposition of the thumb. During isometric contractions in each direction, the threshold force for motor-unit recruitment and the twitch amplitude were correlated linearly. These data suggested that an orderly pattern of recruitment, according to increasing twitch size, describes the function of the human abductor pollicis brevis muscle for each contraction direction. Rank order of motor-unit recruitment in each isometric contraction direction was correlated, but not identical. All units contributed tension in each direction of contraction, so no clear evidence was found for task-dependent motor units. In two subjects, motor-unit recruitment order during isometric contraction of the first dorsal interosseous and abductor pollicis brevis muscles was then compared with that of motor-unit pairs in both muscles during repetitive dynamic movements. Recruitment according to increasing twitch size was largely preserved during the repetitive opening and closing of scissors. The recruitment reversals that were observed were usually between pairs of units with similar thresholds.
采用触发脉冲平均技术，在两名受试者的拇短展肌中，针对等长收缩的两个方向（拇指外展和对掌），测定运动单位的抽搐张力和收缩时间。在每个方向的等长收缩过程中，运动单位募集的阈力与抽搐幅度呈线性相关。这些数据表明，按照抽搐大小增加的顺序进行有序募集，描述了人类拇短展肌在每个收缩方向上的功能。每个等长收缩方向上运动单位募集的排序是相关的，但并不完全相同。所有单位在每个收缩方向上都产生张力，因此未发现明确的任务依赖性运动单位的证据。然后，在两名受试者中，将第一背侧骨间肌和拇短展肌等长收缩期间的运动单位募集顺序，与这两块肌肉在重复动态运动期间运动单位对的募集顺序进行比较。在剪刀的重复开合过程中，按照抽搐大小增加的顺序进行募集在很大程度上得以保留。观察到的募集反转通常发生在阈值相似的单位对之间。
