Department of Physiology and Pharmacology, University of Western Ontario, Medical Sciences Building, London, ON N6A 5C1, Canada.
Exp Brain Res. 2011 May;211(1):63-72. doi: 10.1007/s00221-011-2646-7. Epub 2011 Apr 6.
We tested the hypothesis that in fast arm movements the CNS deliberately utilizes interaction torques to decelerate (brake) joint rotations. Twelve subjects performed fast 2-D overarm throws in which large elbow extension velocities occurred. Joint motions were computed from recordings made with search coils; joint torques were calculated using inverse dynamics. After ball release, a large follow-through shoulder extension acceleration occurred that was initiated by shoulder extensor muscle torque. This shoulder acceleration produced a flexor interaction torque at the elbow that initiated elbow deceleration (braking). An instantaneous mechanical interaction of passive torques then occurred between elbow and shoulder, i.e., elbow extension deceleration produced a large shoulder extensor interaction torque that contributed to the shoulder extension acceleration which, simultaneously, produced a large elbow flexor interaction torque that contributed to elbow extension deceleration, and so on. Late elbow flexor muscle torque also contributed to elbow deceleration. The interaction of passive torques between shoulder and elbow was braked by shoulder flexor muscle torque. In this mechanism, shoulder musculature contributed to braking elbow extension in two ways: shoulder extensors initiated the mechanical interaction of passive torques between shoulder and elbow and shoulder flexors dissipated kinetic energy from elbow braking. It is concluded that, in fast 2-D throws, the CNS deliberately utilizes powerful interaction torques between shoulder and elbow to brake motion at the elbow.
我们验证了这样一个假说，即在快速手臂运动中，中枢神经系统故意利用交互扭矩来减速（制动）关节旋转。12 名受试者进行了快速的 2-D 过顶投掷，其中肘部伸展速度很大。关节运动是通过搜索线圈的记录计算出来的；关节扭矩是使用逆动力学计算的。在球释放后，会发生一个很大的肩部伸展加速度的跟进，这是由肩部伸肌扭矩引起的。这个肩部加速度在肘部产生了一个屈肌交互扭矩，从而开始了肘部减速（制动）。然后，肘部和肩部之间会立即发生被动扭矩的机械相互作用，即肘部伸展减速会产生一个很大的肩部伸肌交互扭矩，这有助于肩部伸展加速度，同时，它会产生一个很大的肘部屈肌交互扭矩，有助于肘部伸展减速，以此类推。肘部屈肌后期的肌肉扭矩也有助于肘部减速。肩部和肘部之间的被动扭矩相互作用被肩部屈肌扭矩制动。在这种机制中，肩部肌肉通过两种方式有助于制动肘部伸展：肩部伸肌启动了肩部和肘部之间的被动扭矩的机械相互作用，肩部屈肌从肘部制动中耗散了动能。因此，可以得出结论，在快速的 2-D 投掷中，中枢神经系统故意利用肩部和肘部之间的强大交互扭矩来制动肘部的运动。
