Hirashima Masaya, Yamane Katsu, Nakamura Yoshihiko, Ohtsuki Tatsuyuki
Department of Physical and Health Education, Graduate School of Education, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
J Biomech. 2008 Sep 18;41(13):2874-83. doi: 10.1016/j.jbiomech.2008.06.014. Epub 2008 Aug 3.
This study investigated how baseball players generate large angular velocity at each joint by coordinating the joint torque and velocity-dependent torque during overarm throwing. Using a four-segment model (i.e., trunk, upper arm, forearm, and hand) that has 13 degrees of freedom, we conducted the induced acceleration analysis to determine the accelerations induced by these torques by multiplying the inverse of the system inertia matrix to the torque vectors. We found that the proximal joint motions (i.e., trunk forward motion, trunk leftward rotation, and shoulder internal rotation) were mainly accelerated by the joint torques at their own joints, whereas the distal joint motions (i.e., elbow extension and wrist flexion) were mainly accelerated by the velocity-dependent torques. We further examined which segment motion is the source of the velocity-dependent torque acting on the elbow and wrist accelerations. The results showed that the angular velocities of the trunk and upper arm produced the velocity-dependent torque for initial elbow extension acceleration. As a result, the elbow joint angular velocity increased, and concurrently, the forearm angular velocity relative to the ground also increased. The forearm angular velocity subsequently accelerated the elbow extension and wrist flexion. It also accelerated the shoulder internal rotation during the short period around the ball-release time. These results indicate that baseball players accelerate the distal elbow and wrist joint rotations by utilizing the velocity-dependent torque that is originally produced by the proximal trunk and shoulder joint torques in the early phase.
本研究调查了棒球运动员在过肩投球过程中如何通过协调关节扭矩和速度依赖性扭矩来在每个关节产生大的角速度。使用具有13个自由度的四段模型（即躯干、上臂、前臂和手），我们进行了诱导加速度分析，通过将系统惯性矩阵的逆与扭矩向量相乘来确定这些扭矩所诱导的加速度。我们发现近端关节运动（即躯干向前运动、躯干向左旋转和肩部内旋）主要由其自身关节处的关节扭矩加速，而远端关节运动（即肘部伸展和手腕屈曲）主要由速度依赖性扭矩加速。我们进一步研究了哪个节段运动是作用于肘部和手腕加速度的速度依赖性扭矩的来源。结果表明，躯干和上臂的角速度产生了用于初始肘部伸展加速的速度依赖性扭矩。结果，肘关节角速度增加，同时，前臂相对于地面的角速度也增加。前臂角速度随后加速了肘部伸展和手腕屈曲。它还在球释放时间附近的短时间内加速了肩部内旋。这些结果表明，棒球运动员在早期通过利用最初由近端躯干和肩关节扭矩产生的速度依赖性扭矩来加速远端肘部和腕关节的旋转。
