Kawahats K, Miyashita M
Exp Neurol. 1983 Nov;82(2):287-302. doi: 10.1016/0014-4886(83)90402-8.
The EMG silent period has been observed frequently just before rapid movement from a slightly sustained contraction of the muscle. Our experiments were designed to show the relation between the tension developed in an intact human muscle and the occurrence of this silent period. Tension in the knee extensor was obtained from the floor reaction force of a living subject in a squatting position on the basis of a lever ratio-joint angle diagram obtained directly from measurements on an isolated knee extensor muscle of a human cadaver. The muscle tension was calculated under the condition that the floor reaction force in the squatting position passed through the anklebone, and decreased from 8.7 to 0.8 kN with an increase in the knee joint angle from 1.13 to 2.74 rad. When the center of pressure was not assumed, the increased knee extensor muscle torque with a decrease in the knee angle was estimated biomechanically from the free body diagram. Consistently, the EMG recordings confirmed an increased muscle activity with a reduction in the joint angle. The premotion silent period for the knee extensors and their antagonist with movement from the squatting position appeared to be limited to a knee joint angle of 2.44 to 3.07 rad, where the requirement for tension in those muscles was low. This silent period could be interpreted as an electromyographic transitional phase attributable to a switching mechanism in central nervous activity. The premotion silent period was most likely to appear prior to a swift, well coordinated movement.
在肌肉从轻微持续收缩快速运动之前，经常会观察到肌电图静息期。我们的实验旨在揭示完整人体肌肉中产生的张力与该静息期出现之间的关系。通过基于直接从人体尸体的离体膝伸肌测量获得的杠杆比 - 关节角度图，从处于蹲姿的活体受试者的地面反作用力中获取膝伸肌的张力。在蹲姿时地面反作用力通过踝骨的条件下计算肌肉张力，随着膝关节角度从1.13弧度增加到2.74弧度，肌肉张力从8.7千牛降至0.8千牛。当不假定压力中心时，根据自由体图从生物力学角度估计随着膝关节角度减小膝伸肌扭矩增加。一致地，肌电图记录证实随着关节角度减小肌肉活动增加。从蹲姿开始运动时，膝伸肌及其拮抗肌的运动前静息期似乎局限于膝关节角度为2.44至3.07弧度的范围，在该范围内这些肌肉对张力的需求较低。这个静息期可以解释为归因于中枢神经活动切换机制的肌电图过渡阶段。运动前静息期最有可能在快速、协调良好的运动之前出现。
