Document Type



The purpose of this study was to examine the release positions of the throwing arm and of the trunk in four delivery styles (overarm, three-quarter arm, sidearm and underarm) of the baseball pitching motion, and to identify criteria to define the four delivery styles based upon the positions of both the trunk and throwing arm (upper arm) segments. Thirty-four pitching motions were videotaped using the 3D DLT method. These motions were qualitatively classified by coaches’ observation into 15 overarm, 7 three-quarter arm, 7 sidearm and 5 underarm deliveries. The angles for the trunk lateral tilt and upper arm elevation in the global coordinate system were quantified, and regression analysis revealed a linear relationship between the two angles. Criteria based on these angles were developed that matched the coaches’ observations well, demonstrating that the baseball pitching motion could be quantitatively classified into the four delivery styles.