The effect of racquet swing weight on serve kinematics in elite adolescent female tennis players

Objectives: Collision models for hitting implements denote how ball speed and swing weight increase proportionally when swing speed and impact location are held constant. The biomechanical effects of swing weight interventions are less understood. This study examined the effects of swing weight on serving arm mechanics, racquet kinematics, impact location and ball speed in the tennis serve.

Design: Repeated measures design, where racquet swing weight parameters distinguished between serve conditions.

Methods: Eleven elite adolescent female tennis players performed serves in three conditions: (1) regular, unperturbed racquet; (2) 5% increase in swing weight; and (3) 10% increase in swing weight. A 500 Hz Vicon motion analysis system captured three-dimensional serving arm, racquet and ball kinematics.

Results: When racquet swing weight was increased, the peak shoulder internal rotation and wrist flexion velocities during the forwardswing both decreased. The peak accelerations of shoulder internal rotation, elbow extension and wrist flexion also appeared to share an inverse relationship with swing weight. As swing weight increased, the impact location shifted significantly closer to the racquet tip and resultant racquet at impact decreased. Ball speed remained similar in all conditions.

Conclusions: The assumptions underlying the collision model appear to be violated by the biomechanical effects of a swing weight intervention in a sample of elite adolescent female players. Consequently, added swing weight fails to effect faster serves. From a dynamical systems perspective, the inherent response of the movement system deserves consideration prior to, and during, the administration of swing weight interventions.