The present research aimed to characterize the baseball bat swings of high-school baseball players. Despite the difficulties associated with establishing a classification standard for the quantitative evaluation of bat swings, the acceleration applied to the bat was measured during high-school baseball players' swings. Subjects were 53 high-school baseball players who swung an experimental bat. The knob of the experimental bat was equipped with accelerometers, which measured the three components of linear acceleration and the three components of angular acceleration applied to the bat. Classification of players' swings based on the acceleration applied to the bat revealed the following results.
(1) Evaluation of players' swings based on the acceleration applied to the bat was possible. This evaluation clarified methods for applying force and torque to the bat during a swing. (2) Based on changes in acceleration and the angular acceleration applied to the bat just before impact, the swings of these players were classified into nine categories. (3) These nine categories were further consolidated into three types based on changes in angular acceleration. In one type, angular acceleration of the bat decreases before impact. However, all subjects were divided into the remaining two types, in which angular acceleration of the bat increases before impact or angular acceleration of the bat does not increase before impact. These results suggest that classification of bat swings is possible.
