Ankle and Knee Joint Kinematics Differ between Flat, Slice and Topspin Serves in Young Tennis Players

Abstract

The present study aimed to examine the differences in ankle and knee joint kinematics between the flat, slice, and topspin tennis serves. Twelve young tennis players (six boys, and six girls) aged 12-16 years old, performed flat, slice and topspin serve whilst three-dimensional body kinematics were recorded using an optoelectronic camera system. Ankle plantarflexion/dorsiflexion and knee extension/flexion angular positions were recorded at two-time instants: first, at the time of maximum knee flexion and, second, at time of ball to racket contact. Analysis of variance designs showed that the knee flexion angle of the back leg differed significantly between the three service types (P < 0.001). Further, the rear leg ankle angle at maximum flexion also significantly differed between the three serves (P < 0.004). It was observed that tennis players perform topspin and slice serves with smaller joint angles than flat serves, probably, because the former is being used as a second serve in the game. Τhe ankle, which is the closest point of the kinetic chain at the start of power generation, plays an important and different role in the performance of the three serve types. Therefore, the synergy of the ankle joint is very important in the initial phase of serve for the transfer of forces. Coaches should review the technical issues of serve movement based on the flexibility of the ankle joint because the limited ankle range of motion does not help to transfer forces from the ground.