Relationship between velocity of center of gravity and kicking motion of pivoting foot in the windmill pitching of high school girl softball pitchers

Abstract

    The purpose of this study was to clarify the characteristic of kicking motion of pivoting leg of softball pitchers who have great velocity of center of gravity during pitching. The study was subject to 19 high school girl softball pitchers who specialize in the windmill pitching and we calculated the kinematic variables concerning the maximum velocity of center of gravity and kicking motion to the pitching direction by two-dimensional motion analysis of their pitching motion. After that, we conducted a correlation analysis between the maximum velocity of center of gravity and the kinematic variables. Our findings through this study concerning the characteristic of pitchers who have a great velocity of center of gravity are as follows.
1) The height of center of gravity was kept to be low during pitching. In addition, forward lean angle of upper body and hip flexion angle were large at the beginning of kicking.
2) The average angular velocity of overall leg and the average angular velocity of hip joints were large. Especially, the average angular velocity of hip joints in the latter kicking was large.
3) The range of motion of thigh was large and the inclination of overall foot and thigh to the pitching direction at the end of kicking were large.
    Including above, this study suggested a potential that it is effective for the instruction of the windmill pitching that we have them do a kicking motion by keeping their height of center of gravity to be lower during kicking and focusing on the extension motion of hip joints in order to enhance velocity of center of gravity.