Hore Jon, Watts Sherry
Dept. of Physiology and Pharmacology, University of Western Ontario, London, Ontario N6A 5C1, Canada.
J Neurophysiol. 2005 Jun;93(6):3189-99. doi: 10.1152/jn.01268.2004.
Previous studies on overarm throwing have suggested that throwing accuracy depends on a precise central timing mechanism. In the present study, we investigated an alternative hypothesis: that central control of finger opening is based on an internal positional representation of handpath. Angular positions of each segment of the middle finger, thumb, and arm were recorded with the search-coil technique as subjects made slow, medium, and fast throws at a target 3.1 m away. Onset of ball release from the hand was strongly correlated with extension at the proximal interphalangeal joint (PIJ). The velocity of this finger joint opening varied with the speed of the throw. In agreement with the hypothesis, at a fixed hand angular position in space, there was no difference across subjects in the amplitude of extension at the PIJ for throws of different speeds. That is, for these two parameters, a fast throw was the same as a slow throw that was sped-up. This occurred irrespective of whether the trunk was constrained (sitting throws) or unconstrained (standing throws). No equivalent relation was found between extension at the PIJ and elbow extension. These findings support the idea that precisely timed finger opening in overarm throwing depends, not on a central timing controller that triggers a step-like (ballistic) finger opening at the right moment in throws of different speeds, but on a central spatial controller that matches angular positions of finger opening to the intended handpath.
先前关于过肩投掷的研究表明，投掷准确性取决于精确的中央计时机制。在本研究中，我们调查了另一种假设：手指张开的中央控制基于手部路径的内部位置表征。当受试者以慢、中、快三种速度向3.1米外的目标进行投掷时，使用搜索线圈技术记录了中指、拇指和手臂各节段的角位置。球从手中释放的起始时间与近端指间关节（PIJ）的伸展密切相关。该手指关节张开的速度随投掷速度而变化。与该假设一致的是，在空间中固定的手部角位置处，不同速度投掷时PIJ伸展幅度在受试者之间没有差异。也就是说，对于这两个参数，快速投掷与加速的慢速投掷相同。无论躯干是受限的（坐姿投掷）还是不受限的（站姿投掷），都是如此。在PIJ伸展与肘部伸展之间未发现等效关系。这些发现支持了这样一种观点，即过肩投掷中精确计时的手指张开并非取决于在不同速度投掷的合适时刻触发阶梯状（弹道式）手指张开的中央计时控制器，而是取决于将手指张开的角位置与预期手部路径相匹配的中央空间控制器。
