Kawakami Y, Amemiya K, Kanehisa H, Ikegawa S, Fukunaga T
Department of Life Sciences, University of Tokyo, Japan.
J Appl Physiol (1985). 2000 Jun;88(6):1969-75. doi: 10.1152/jappl.2000.88.6.1969.
Nine healthy men (22-45 yr) completed 100 repetitive maximal isometric contractions of the ankle plantar flexor muscles in two knee positions of full extension (K0) and flexion at 90 degrees (K90), positions that varied the contribution of the gastrocnemii. Electromyographic activity was recorded from the medial and lateral gastrocnemii and soleus muscles by using surface electrodes. Plantar flexion torque in K0 was greater and decreased more rapidly than in K90. The electromyographic amplitude decreased over time, and there were no significant differences between muscles and knee joint positions. The level of voluntary effort, assessed by a supramaximal electrical stimulation during every 10th contraction, decreased from 96 to 70% (P < 0.05) with no difference between K0 and K90. It was suggested that a decrease in plantar flexion torque was attributable to both central and peripheral fatigue and that greater fatigability in K0 than in K90 would result from a greater contribution and hence more pronounced fatigue of the gastrocnemius muscle. Further support for this possibility was provided from changes in twitch torque.
九名健康男性（22 - 45岁）在两个膝关节位置完成了100次踝关节跖屈肌的重复性最大等长收缩，这两个位置分别是完全伸展（K0）和90度屈曲（K90），这两个位置改变了腓肠肌的作用。使用表面电极记录了腓肠肌内侧头、外侧头和比目鱼肌的肌电活动。K0位置的跖屈扭矩比K90位置更大且下降得更快。肌电幅度随时间下降，肌肉和膝关节位置之间无显著差异。通过在每第10次收缩期间进行超强电刺激评估的自主努力水平从96%降至70%（P < 0.05），K0和K90之间无差异。研究表明，跖屈扭矩的下降归因于中枢和外周疲劳，并且K0位置比K90位置更容易疲劳是由于腓肠肌的作用更大，因此疲劳更明显。抽搐扭矩的变化进一步支持了这种可能性。
