PRONATE GLOBALLY BUT SUPINATE LOCALLY: EVIDENCE OF RADIO-ULNAR SUPINATION AT BALL RELEASE

Abstract

The purpose of this study was to investigate the radio-ulnar longitudinal rotation during baseball pitching. We captured movements of nine skilled pitchers during pitching by using a system with 16 high-speed cameras (Vicon MX, 1000 Hz). Ten fastest trials which hit a target were averaged to obtain representative data for each participant. We found that the radio-ulnar joint supinated at around the moment of ball release (BRL), although the wrist continued rotating in the direction of pronation at around BRL in the global coordinate. The supination occurred due to the influence of the combination of elbow extension and shoulder internal rotation.