Influence of the Step Direction of Lead Leg on Baseball Pitching

Abstract

The purpose of this study was to investigate the influence of the difference of step directions on the pitching motion. Eight collegiate baseball players performed pitching under five kinds of conditions including the normal step, two kinds of closed steps and two kinds of open steps. The angular velocities of rotation of trunk, hip and upper limb were measured with accelerometers and gyroscope sensors, and the state of ball-release on the nails of index finger and middle finger were recorded with strain gauges during pitching under above conditions. As the results, there were no significant differences in the strains of nails of index finger and middle finger among the pitching trials under the five conditions of step direction. There were also no significant differences in the angular velocities of rotation of the trunk, the hip and the upper limb. However, there were tendency that the angular velocities of the upper-arm swing and the counterclockwise rotation of hip of closed step pitching were larger than those of other cnoditions. On the other hand, the peak time of the angular velocity of trunk counterclockwise rotation of open step pitching was significantly nearer to the ball-release than that of other conditions. The peak time of trunk and hip movements varied among step directions, but the peak time of upper-arm swing and forearm swing were constant in spite of step direction.