Abstract
The aim of this study was to investigate the kinematic characteristics of batting motions for the different speed balls. Twenty nine university baseball players volunteered as the subjects. The ball speeds were set for three conditions; slow (75-80km/h), medium (100-105km/h), and fast (125-130km/h). Three dimensional kinematic data of swing motions were collected using Vicon 612 system. Impact parameters and kinematic parameters of swing motion were analyzed. Impact angle, which was defined as the angle between the vector of bat velocity and the vector of hit ball velocity, was calculated for evaluating the hitting accuracy in both the temporal and the spatial viewpoints.
The results were summarized as follows. As the ball speed was increased, The impact angle was increased. The subjects decreased the displacement of center of gravity forward to pitcher so that the time from the ball release to the ball impact would be as long as possible, and the subjects decreased the range of rotational motions of the bat and upper torso from the instant of maximum twist of the torso to the ball impact. On the other hand, the maximum twist angle of the torso joint was consistent for the various ball speeds so that the bat speed should not be decreased as the ball speed was increased.
