A19 野球におけるバットの質量・重心位置が打撃に及ぼす影響(野球1)

Abstract

The purpose of this study was to investigate the effect of the mass and the position of center of gravity of a baseball bat on its hitting performance. Twelve skilled baseball players were used in the study. A bat was developed for which the mass and position of center of gravity could be adjusted. In this experiment nine different settings for the position of the center of gravity and the mass were used. The motion of the bat during swings was analyzed by the DLT method using two cameras, and three-dimensional kinematic data were calculated for the impact with the ball and during the hitting process. The main results are summarized as follows: 1) For all the baseball players, the head velocity of the bat at impact was large, so that the position of the bat's center of gravity was near to the grip. 2) For all the baseball players, the bat mass did not affect the head velocity of the bat at impact. 3) For all the baseball players, a significant negative correlation was found between the moment of inertia about the grip circumference of the bat and the head velocity at impact. 4) In one case, the mass of the bat had a significant influence on the angular velocity on impact for a player that had a translational swing. In this case, the characteristic of the swing type was shown to result in different hitting performances. When choosing a suitable bat for each player, the critical factor is the swing style of the player, which could be gauged from the mass and the position of the center of gravity of the bat. This finding suggests that the moment of inertia of the bat's circumference could be used as an index.