Do serve distance and net height modify serve biomechanics in young tennis players?

The aim of this study was to determine whether decreasing serving distance and net height would immediately influence serve biomechanics and performance in young intermediate tennis players. Ten young tennis players (9 to 12 years) performed maximal effort flat serves from three court conditions ("red", "orange" and "green": serving distance at 6.40, 9.00 and 11.89 m from the net and net height at 0.80 m, 0.80 m and 0.91m, respectively). A radar measured ball speed while serve kinetics and kinematics were calculated with a 20-camera optical motion capture system. Repeated measures ANOVAs were used to analyze the effect of the three conditions on ball speed, serve kinematics and kinetics. No significant differences in shoulder and elbow kinetics were observed between the three conditions. Ball speed, maximal flexion angle of the back knee and maximal angular velocities of back knee extension and trunk flexion significantly improved when players served from the red conditions in comparison with green ones. This study shows that reducing serve distance and net height may be an effective coaching strategy to immediately increase ball speed, leg drive and trunk flexion in young tennis players.