Torso dynamics during follow through in baseball batting

The purpose of this study was to clarify the relationship between the bat swing speed immediately after the ball impact and the dynamics of the torso during the follow through in baseball batting. The batting motion and ground reaction forces acting on each foot for 29 collegiate baseball players were recorded using a motion capture system and two force plates. The biomechanical variables of the torso joint (i.e., the virtual joint that divides the torso between upper and lower) were calculated. For right-handed batters, the torque power of the right rotation in the torso joint was negative. Additionally, the bat head speed immediately after the ball impact was significantly correlated with the negative (i.e., right) peak rotation torque of the torso joint (r = > -.591, p < 0.001) and the negative peak power in the right rotation torque of the torso joint (r = > -.577, p = 0.001). These results suggest that the left external abdominal oblique muscle is in eccentric contraction during the follow through in baseball batting. Moreover, the results imply that the higher the bat head speed immediately after the ball impact, the higher the possibility to strain the abdominal oblique muscle.

本研究的目的是阐明棒球击球时球棒在击球瞬间后的挥动速度与随挥过程中躯干动力学之间的关系。使用运动捕捉系统和两个测力板记录了29名大学棒球运动员的击球动作以及作用在每只脚上的地面反作用力。计算了躯干关节（即划分上下躯干的虚拟关节）的生物力学变量。对于右撇子击球手，躯干关节的右旋扭矩功率为负。此外，球棒在击球瞬间后的头部速度与躯干关节的负（即右旋）峰值旋转扭矩（r => -0.591，p < 0.001）以及躯干关节右旋扭矩的负峰值功率（r => -0.577，p = 0.001）显著相关。这些结果表明，在棒球击球的随挥过程中，左侧腹外斜肌处于离心收缩状态。而且，结果意味着球棒在击球瞬间后的头部速度越高，腹外斜肌拉伤的可能性就越大。