Method for calculating a parameter representing a tennis players endurance during a game period including a series of game sessions, includes: a) measuring the linear acceleration and angular speed of the racket during each stroke hit by the player, b) calculating the power developed by the player during each stroke using linear accelerations and angular speeds measured in step a) c) calculating the players average power defined as the average of power levels developed during each stroke calculated in step b) d) calculating the energy expended by the player during the last game session, the energy expended being equal to the number of strokes executed during the session multiplied by the average power calculated in step c) raised to a predetermined power, e) calculating the parameter, defined by the product of the number of game sessions per week during the game period, multiplied by the energy calculated in step d).
