Hirashima Masaya, Ohgane Kunishige, Kudo Kazutoshi, Hase Kazunori, Ohtsuki Tatsuyuki
Department of Life Sciences (Sports Sciences), Graduate School of Arts and Sciences, The University of Tokyo, Tokyo 153-8902, Japan.
J Neurophysiol. 2003 Sep;90(3):1449-63. doi: 10.1152/jn.00220.2003.
Many investigators have demonstrated that in swing motions such as ball-throwing, the motion of the proximal joint (shoulder) produced assistive interaction torque for the distal joint (elbow). In line with these studies, the shoulder and elbow motions would be expected to produce the assistive interaction torque for the wrist joint as well. However, we recently showed that the interaction torque at the wrist was always counteractive to the wrist muscle torque during ball-throwing. The purpose of this study is to clarify, by means of computer simulation, whether the counteractive relationship at the wrist during ball-throwing is caused by the neural contribution or the musculoskeletal mechanical properties of the human arm. First, we simulated the throwing motions of the normal forearm-hand model by systematically changing the proximal-to-distal delay of muscle activities and could line up two candidates for the determinant of the counteractive relationship: the rest angle (neutral angle) of the wrist and the length and mass of the hand. Second, we simulated the throwing motions of the virtual forearm-hand models, showing that only nonrealistic elongation of these two parameters produced the assistive relationship between the interaction torque and muscle torque. These results suggested that the mechanical properties of the human wrist are the main determinant of the counteractive relationship, which is advantageous for keeping the state of the wrist joint stable in multi-joint upper-limb movements and would lead to avoidance of excessive wrist extension or flexion and simplification of extrinsic finger control.
许多研究者已经证明，在诸如投球等摆动动作中，近端关节（肩部）的运动会为远端关节（肘部）产生辅助相互作用扭矩。与这些研究一致，预计肩部和肘部的运动也会为腕关节产生辅助相互作用扭矩。然而，我们最近发现，在投球过程中，腕关节处的相互作用扭矩总是与腕部肌肉扭矩相反。本研究的目的是通过计算机模拟来阐明，投球时腕关节处的这种反向关系是由神经因素还是人类手臂的肌肉骨骼力学特性引起的。首先，我们通过系统地改变肌肉活动的近端到远端延迟，模拟了正常前臂 - 手部模型的投掷动作，并确定了反向关系的两个可能决定因素：腕关节的静止角度（中立角度）以及手部的长度和质量。其次，我们模拟了虚拟前臂 - 手部模型的投掷动作，结果表明只有这两个参数的非现实性延长才会产生相互作用扭矩与肌肉扭矩之间的辅助关系。这些结果表明，人类腕关节的力学特性是反向关系的主要决定因素，这有利于在多关节上肢运动中保持腕关节的稳定状态，并有助于避免腕关节过度伸展或屈曲，简化外在手指控制。
