Kinematics Analysis on Different Positions’ Serve Skills in World Elite Male Tennis Players

Objective: There are two serving positions in tennis matches, i.e., FU/foot-up and FB/foot-back, but which one is better has no certain conclusion. This study analyzed the kinematics parameters of the world's elite male tennis players in different positions combined with the VR technology, and hope to get some meaningful conclusions. Methods: The 3D high-speed video was used to record the finals at the Chengdu Open Tennis Tournament, 7 technical actions of the champion Tomic(FU position) and runner-up Fognini(FB position) were obtained to make comparative analysis. Results: Tomic used the FU position to serve and started to move on the right foot. His body gains kinetic energy and converts it into elastic energy of the lower limb muscles through the braking of the lower limbs. Then he took off and released energy to obtain a larger vertical reaction force on the ground and increase the vertical displacement of the center of gravity of the body, the tossing speed was faster(5.02 m/s). Tomic took a shorter time in the backward introduction phase, and the speed of right hip angle was faster, which was beneficial to increase the rotation speed and take-off speed of the lower limbs in the direction of impact. This position not only obtained a more reasonable hitting height, but also the joints were faster than Fognini when the racket touches the ball, making the whip hitting the ball more consistent.At the same time, the vertical distance between the highest point of the ball and the hitting point was shorter, so that the stability of the hitting height was higher. At the moment the racket touches the ball, Fognini's hitting point was mostly forward, and the racket hitting point was on the upper edge of the sweet spot. Tomic's batting point was in the sweet zone, better than Fergnini's position.Tomic's average serve speed was 169 km/h, which was 162 km/h of Fognini's. Tomic served 49% of the inside corners and 36% of the outside corners of the game, 85% of the total, while Fognini made 79% of the inside and outside corners. The results showed that Tomic's serving speed and landing point were both better than Fergnini, that is, Tomic's serve was more aggressive. As a result, the first serve success rate and first serve scoring rate of Tomic were higher than Fognini. Conclusion: By using 3D kinematics parameters combined with VR technology, it is showed that Tomic(FU position)is superior in offensive and stability than Fergnini(FB position).