Abstract
The objective of the present research is to provide basic materials for tennis training by analyzing kinematic factors in making topspin motions of forehand strokes when playing tennis. These factors include the contribution of the anatomical rotation of each joint on the ann to the speed of racket heads, the trace of racket head centers, the rotation of upper body and stance width before and after impacts, and the level of hitting points. The results of this research are as follows. 1. The internal rotation of shoulder joints appears to contribute most highly to the speed of racket heads, and is followed by wrist joints. In addition, the movement of elbow joints appeared to contribute least to the speed. Accordingly the movement of shoulder joints plays the most significant role in raising the ball speed in forehand top spin strokes. 2 The analysis on movement trace of racket head centers viewed fruur z-axis showed different results according to players. 3. The effects caused by factors other than the hitting arm at the point of hitting, were shown in linear velocity of the shoulder joints of arms holding rackets. Their contribution appeared higher than the effects caused by an elbow joint. 4. The angles of right and left knees forced for adjusting hitting points before and after impacts appeared to differ from each other. Front legs made a joint movement of a large angle compared to rear legs. It is considered that rear legs make adjusting motions using the angle joints rather than the knee joints. 5. While the steed of racket heads toward the front dropped immediately after the impacts, the up-and-down speed quickened. This suggests that players wind around the ball with the racket to give spins to the maximum.