Hore J, Watts S, Martin J, Miller B
Physiology Department, University of Western Ontario, London, Canada.
Exp Brain Res. 1995;103(2):277-86. doi: 10.1007/BF00231714.
How precisely does the CNS control the timing of finger muscle contractions in skilled movements? For overarm throwing, it has been calculated that a ball release window of less than 1 ms is needed for accuracy in long throws. The objective was to investigate the timing precision of ball release and finge opening for 100 overarm throws made using only the arm. Subjects sat with a fixed trunk and threw balls fast and accurately at a 6-cm-square target when it was 1.5, 3.0 and 4.5 m away. Three-dimensional angular positions in space of the clavicle, upper arm, forearm, hand and distal phalanx of the middle finger were simultaneously recorded at 1000 Hz using the magnetic-field search-coil technique. Ball release was determined by pressure-sensitive microswitches on the proximal and distal phalanges of the middle finger (proximal and distal triggers). Variability of ball release, defined in terms of the standard deviation (SD) of the means of release times, was different when synchronized to different hand kinematic parameters. It was highest to the start of movement (when the hand started rotating vertically forward and up around a space-fixed horizontal axis) and was lowest when synchronized to the moment near ball release when the hand was vertical. These values did not depend on target distance. When throws were synchronized to vertical hand position, and SDs were averaged across the 10 subjects, the average interval for 95% of the throws (4xSD) was 9.6 ms for ball release and 10.0 ms for onset of finger opening. Thus, two independent measures of timing precision gave similar results. It is concluded that for 100 fast and accurate throws made by male recreational ball players, timing of finger opening and ball release was controlled precisely but not to fractions of a millisecond.
中枢神经系统（CNS）在熟练运动中如何精确控制手指肌肉收缩的时间？对于过肩投掷，据计算，长距离投掷时要达到准确投掷，球的释放窗口需小于1毫秒。目的是研究仅使用手臂进行100次过肩投掷时球释放和手指张开的时间精度。受试者躯干固定就座，当目标距离为1.5米、3.0米和4.5米时，快速且准确地向一个6平方厘米的目标投掷球。使用磁场搜索线圈技术，以1000赫兹的频率同时记录锁骨、上臂、前臂、手和中指远节指骨在空间中的三维角位置。球的释放由中指近节和远节指骨上的压敏微动开关（近端和远端触发器）确定。根据释放时间平均值的标准差（SD）定义的球释放变异性，在与不同的手部运动学参数同步时有所不同。在运动开始时（当手开始围绕空间固定的水平轴垂直向前和向上旋转时）最高，而在与手垂直且接近球释放的时刻同步时最低。这些值不取决于目标距离。当投掷与手的垂直位置同步，并且对10名受试者的标准差进行平均时，95%的投掷（4倍标准差）的平均间隔对于球释放为9.6毫秒，对于手指张开开始为10.0毫秒。因此，两种独立的时间精度测量方法得出了相似的结果。得出的结论是，对于男性业余球类运动员进行的100次快速且准确的投掷，手指张开和球释放的时间控制精确，但并非精确到几分之一毫秒。
