Forces and duration of impact, and grip tightness during the tennis stroke.

The present study is concerned with the problem of the most desirable grip tightness during and after the impact phaseeof the tennis stroke. Moreover, impact forces and durations for different ball velocities are also investigated. Three series of experiments were conducted in order to obtain information on impact forces and durations, responses of the racket to impacts for loose and tight grips, and the magnitudes of the vibrations of the racket transferred to the hand in actual strokes. The experimental results were found to be in accordance with the predictions of a mathematical model of the system racket-hand. A simpler model, which neglects bending and possible translations of the racket, turns out to be inadequate for the present purpose. It is found that a tight grip increases both the impulse imparted on the ball and hence the power of the stroke, and the vibrational shocks which must be absorbed by the hand. The contrary holds true for a loose grip. An investigation on a top-class player revealed that he uses a tight grip in all his strokes. The possibility of a connection between grip tightness during and after the impact phase and the occurrence of the well-known "tennis elbow" is also discussed. Avoidance of the impact recoil was found to be impossible.