Abstract
In baseball pitching, breaking balls are often evaluated using the word Kire, which means the sharpness of the ball or how well-pitched the ball is. However, it is not obvious if the players have a common perception regarding the Kire of the breaking balls, and if the breaking balls can be expressed by their kinematic characteristics, such as speed and trajectory displacement. Therefore, we investigate the degree of agreement among the evaluators on the evaluations of breaking balls using Kire, and demonstrate the relationship between the Kire and the kinematic characteristics of those balls in this study. For this purpose, 12 high school and 20 collegiate pitchers threw balls of every pitch type as they would normally throw in a game. The pitched-ball velocities and trajectory displacements were calculated. Six high school and six collegiate catchers of the same team as the pitchers evaluated each breaking ball (curveball, slider, changeup, and cutter). The evaluation system corresponded to a five-point grade system. From the results, we found that the players had common perceptions of the Kire of some pitch types but not of the others. In addition, we were able to quantify Kire using the kinematic characteristics for the curveballs and cutters, but not for the sliders and changeups.
