Department of Physiology and Pharmacology, The University of Western Ontario, Medical Science Bldg, London, ON, N6A 5C1, Canada.
Exp Brain Res. 2010 Jun;203(3):601-13. doi: 10.1007/s00221-010-2270-y. Epub 2010 May 8.
The speed of arm movements is normally increased by increasing agonist muscle activity, but in overarm throwing, an additional effect on speed may come from exploitation of interaction torques (a passive torque associated with motion at adjacent joints). We investigated how the central nervous system (CNS) controls interaction torques at the shoulder and elbow to increase speed in 2-D overarm throwing. Twelve experienced throwers made slow, medium, and fast 2-D throws in a parasagittal plane. Joint motions were computed from recordings made with search coils; joint torques were calculated using inverse dynamics. For slow and medium-speed throws, elbow extension was primarily produced by elbow muscle torque. For fast throws, there was an additional late-occurring elbow extensor interaction torque. Parceling out this elbow extension interaction torque revealed that it primarily arose from shoulder extension deceleration. Surprisingly, shoulder deceleration before ball release was not caused by shoulder flexor (antagonist) muscle torque. Rather, shoulder deceleration was produced by passive elbow-to-shoulder interaction torques that were primarily associated with elbow extension acceleration and velocity. It is concluded that when generating fast 2-D throws, the CNS utilized the arm's biomechanical properties to increase ball speed. It did this by coordinating shoulder and elbow motions such that an instantaneous mechanical positive feedback occurred of interaction torques between shoulder and elbow before ball release. To what extent this mechanism is utilized in other fast multijoint arm movements remains to be determined.
手臂动作的速度通常通过增加原动肌的活动来提高，但在过顶投掷中，速度的额外提高可能来自于对交互扭矩的利用（与相邻关节运动相关的被动扭矩）。我们研究了中枢神经系统（CNS）如何控制肩部和肘部的交互扭矩，以提高二维过顶投掷的速度。12 名经验丰富的投掷者在矢状面内进行缓慢、中速和快速的二维投掷。关节运动通过搜索线圈的记录进行计算；关节扭矩使用逆动力学计算。对于缓慢和中速投掷，肘部伸展主要由肘部肌肉扭矩产生。对于快速投掷，会出现额外的、后期出现的肘部伸展交互扭矩。细分这个肘部伸展交互扭矩表明，它主要来自肩部伸展减速。令人惊讶的是，球释放前的肩部减速不是由肩部屈肌（拮抗肌）的肌肉扭矩引起的。相反，肩部减速是由被动的肘部到肩部的交互扭矩产生的，这些扭矩主要与肘部伸展的加速和速度有关。结论是，在产生快速二维投掷时，中枢神经系统利用手臂的生物力学特性来提高球速。它通过协调肩部和肘部的运动来实现，即在球释放前，肩部和肘部之间会产生交互扭矩的瞬时机械正反馈。在多大程度上，这种机制被用于其他快速多关节手臂运动，还有待确定。
