1997 Volume 1 Issue 1 Pages 7-14
The purpose of this study was to compare two methods for determination of the three-dimensional (3 D) segment angular velocity. One is Tang's method (1995), which was calculated by using the relationship of cross products for angular velocity vector and displacement vector with global coordinate system. The other method, reported by small researchers, which calculated the angular velocity by differentiation of unit vectors in three-orthogonal moving coordinate system fixed at the segment. Twenty-four male university baseball players were used as subjects. 3 D coordinates of 15 body segments during the baseball throwing motion were obtained by using the 3 D DLT method. The angular velocities where the upper torso, the upper arm and thigh of throwing arm side were calculated with above two methods. Large differences were found in all segment angular velocities. These results indicated that Tang's method did not consider the angular velocity about the longitudinal axis of segment. Tang's method, however, may be useful for the 3 D motion analysis of the sport activities, except for the motion which observed the rotation about the longitudinal axis of body segment.
