Biomechanical Analysis for Control of Ball Spin in a Tennis Serve, Focusing on the Lower Limbs and Trunk

Abstract

In general, it is most effective to use a combination of various speeds and spin characteristics in order to maintain the service game in tennis. Thus, the authors investigated the relationship between the spin characteristic of the ball and the kinematics of the upper body in a previous study. The swing direction was found to be not mainly controlled by arm-swing motion but the change in upper-body posture. It is assumed that the kinematics of the upper body are mainly controlled by lower-limb and trunk kinetics. The purpose of this current study is to investigate the relationship between trunk posture and the kinetics of the lower limbs and trunk. Our findings (for a right-hand player) are as follows. The mechanical energy of the body is mainly generated by the extension torque of both knee joints. The energy flows mainly from the left leg into the lower trunk by joint force power. The right hip joint torque acts to resist the moment that acts on the trunk with mechanical energy flow. Thus, the main role of the left leg is to generate mechanical energy to obtain head speed. Conversely, the role of the right leg is not only to generate mechanical energy but also to control the trunk posture to change the spin characteristics of the ball.