Tennis Serve Constraints Delimit but Do Not Prohibit Individual Movement Strategies among Professional Players

In sport, copying the motion technique of top-level athletes, which is regarded as perfect and optimal, is a goal often targeted by coaches for their athletes. However, inter-individual variability has been shown to remain in sport motions even at the elite level, and its analysis is important to identify the different motor strategies used to respond to the same motor task. This study aimed to assess inter-individual variability of Center of Mass (CoM) vertical kinematics during the serve among a homogeneous population of twenty-two professional tennis players and to investigate its links with serve performance indicators. Vertical CoM trajectories, impact height and racket head velocity were analyzed using a marker-based motion capture system. Inter-individual variability was assessed using the coefficient of variation. The phase duration, the vertical CoM displacement and its maximal velocity showed greater variability during the loading phase compared to the acceleration phase. Strong correlations were found between vertical CoM parameters during the acceleration phase and ball impact height, but not during the loading phase. The serving task constraints seem to offer limited scope for inter-individual variability and tend to delimit CoM movement strategy during the acceleration phase. Conversely, individual strategies of CoM kinematics differ among professional players during the loading phase, which could be the result of the expression of organismic constraints. This inter-individual variability observed during the loading phase points towards a non-unique way of serving and the need for individualized coaching exercises.