Tennis Top Spin Comparison between New, Used and Lubricated Used Strings by High Speed Video Analysis with Impact Simulation

Abstract

This paper made clear the mechanism of actual top spin and its improvement by lubrication of used and notched strings at the intersections using 10,000 frames/sec high-speed video analysis. Contrary to the hypothetical conventional spin theory, as the main (longitudinal) strings stretch and slide side ways more and they spring back by lubrication of notched strings, the ball is given more spin when the ball is released from the strings. The notches at string intersections reduce the spin rate of the ball. More spin produce longer contact time between ball and strings, resulting in the reduction of shock vibrations of the wrist joint during impact according to the impact simulation based on the experimental identification of racket-arm system. Furthermore, it showed that the spin rate of a newly strung racket without notch is much larger than that of a racket with lubricated used strings. The lubricant materials are most effective to the notched used strings.