Interpersonal dynamics in baseline rallies in tennis

In tennis, the relative positioning of players on court constrains their opportunities to perform successful actions. In this study we proposed and validated an empirical function that captures the spatial-temporal relationship between tennis players during competitive performance. This parameter, termed goal-directed displacement index (GDD Index), is defined over time by the product of both players' distances to the central line of the court and to the centre of the net. Results showed that the GDD index successfully described tennis players' patterns of interaction, as well as identified breaks in patterns of play during competitive performance, due to changes in relative positioning on court. Our analysis revealed two different patterns of interpersonal interactions, cross and down-the-line rallies, and two ways for a break to emerge in game dynamics, parallel variation (transition from a cross court rally to a down-the-line rally) and angle opening (lateral displacement). Data suggest that the elaboration of specific individual profiles of performance for different players, using the GDD index, could improve performance analysis in tennis