Control of the Spin in a Tennis Serve Focusing on the Motion of the Upper Limb and Trunk*
2022 Volume 20 Pages 152-169
Details
2022 Volume 20 Pages 152-169
The purpose of this study was to investigate the relationship between motion and ball spin in tennis serves. Ten male university tennis players participated. The three-dimensional coordinates of the players performing flat, kick and slice serves were collected using a motion capture system with 8 cameras (250 Hz). Similarly, the three-dimensional coordinates of reflective markers on the ball were also collected (500 Hz). The primary variables computed were: racket face velocity and direction at impact, velocity and angular velocity of the ball after impact, hitting point, angles of the upper limb joints, and segment angles of the upper trunk. The differences in racket face velocity among flat, kick, and slice serves were divided into the following terms: 1) ΔVposture: A difference in velocity resulting from a change in upper trunk posture, 2) ΔVswing: A difference in velocity resulting from a change in arm swing (kinematics of the upper limb), 3) ΔVutrk: A difference in velocity resulting from a change in upper trunk translational and rotational motion. Repeated measures ANOVA ( p<.05) with Bonferroni multiple comparison was used to evaluate the effects of changes in form (with differences in ball spin) on each parameter. The findings are summarized as follows.
1) The impact point and swing direction were mainly controlled not by a change in arm swing motion, but by a change in upper body posture.
2) To generate ball spin, it is necessary to avoid a head-on collision between the ball and the racket (a normal vector of the racket face is parallel to the racket face velocity vector). Therefore, players decreased the amount of upper trunk leftward rotation in kick and slice serves at the point of impact so as to swing the racket more laterally.
3) It is necessary to swing the racket more vertically in order to lean the rotation axis of the ball. Therefore, players controlled the upper trunk leftward-rightward and forward-backward leaning in a kick serve at the point of impact.
4) Changes in upper body posture cause changes in the direction the racket faces. Therefore, players mainly controlled their elbow pronation-supination angle in order to maintain a racket face direction that satisfies a legal serve.
