Prediction of Impact Shock Vibrations at Tennis Player's Wrist Joint (Comparison between Conventional Weight Racket and Light Weight Racket with Super Large Head Size)

Abstract

The lightweight racket with handle-light configuration and large head size is recent tendency of high-tech tennis rackets, increasing power or post-impact ball velocity with an increasing racket swing speed. This paper investigated the performance of lightweight balanced racket with super-large head size with 120 square inches in terms of feel or comfort. It predicted the effect of the mass and mass distribution of super-large head sized rackets on the impact shock vibrations of the racket handle and the player's wrist joint when a player hits a flat forehand drive. The prediction is based on the identification of the racket characteristics, the damping of the racket-arm system, equivalent mass of the player's arm system and the approximate nonlinear impact analysis in tennis. A lightweight balanced racket (mass: 292 g, the center of gravity LG: 363 mm from the butt end) and a conventional weight and weight balanced racket (349 g, LG: 323 mm) are selected as representatives. These two super-large head sized rackets made of carbon graphite have the same head size and same geometry. The result showed that the shock vibration of the lightweight balanced racket with super-large sized head is much larger than that of the conventional weight balanced type racket. It also showed that the sweet area of the former in terms of the shock vibration shifts from the center to the topside on the racket face compared to the latter. This is because the location of the grip on the racket handle is further from the location of the node on the handle of the first mode of lightweight balanced racket than that of the conventional weight balanced racket.