野球打撃におけるインパクト時のバットのヘッドスピードと方位を決定する力学的要因

抄録

The purpose of this investigation was to describe how the bat-head speed and the orientation of the bat at ball impact were generated in baseball hitting. Seventeen male collegiate baseball players performed tee-batting aiming at hitting the ball toward the center field. A motion capture system (500Hz) was used to record three-dimensional coordinate of the bat during the performance. The resultant force and the resultant moment exerted on the bat by the batter’s hands were determined with the inverse dynamics approach and their contributions to the bat-head speed and the orientation of the bat were computed with the forward dynamics approach. The resultant force exerted on the bat along the long axis produced approximately 70% of the bat-head speed at ball impact, and the couple moment and the moment of resultant force produced 25% and 7%, respectively. The bat-head speed due to the gravity and the gyroscopic effect was negligible small. For the orientation of the bat at ball impact, the horizontal angle was produced by the positive contributions of the couple moment that exceeds the negative contributions of the moment of resultant force. The vertical angle was produced by the positive contributions of the moment of resultant force that exceeds the negative contributions of the couple moment and the gyroscopic effect.