Discussion on skillful baseball pitch using three-dimensional cinematographic analysis. Comparison of baseball pitch between skilled and unskilled pitchers

The purpose of this study was to compare baseball pitches between skilled and unskilled pitchers using a three-dimensional cinematographic analysis. Nine baseball pitchers were used as subjects. These subjects were rated by the coach as skilled and unskilled pitchers. The pitching motions were filmed by two high-speed cameras. The time series of three-dimensional landmark coordinates of the subject and the ball during the baseball pitch were calculated using the DLT method. First, the index called SFD which expresses quantitatively the dispersion of the shoulder joint on the opposite side of the throwing arm was proposed to compare the SFD between skilled and unskilled pitchers. Next, the kinematic parameters such as abduction/adduction angle at the shoulder joint of the throwing arm were calculated to investigate whether the pitching motion for the skilled pitchers were less different between types of pitches (fastball and curveball pitches) as compared with that for the unskilled pitchers. The results indicated that the SFD of skilled pitchers was smaller than that of the unskilled pitchers. It was also found that the kinematic variables for the skilled pitchers did not vary between types of pitches.