ABSTRACT
The centre of gravity (COG), as a representative point (origin) for the gravitational force, is one of the key concepts of biomechanics. In racket sports it is important to take into account the distance from the COG to the handle, as this influences the movements made with the racket hand before, during and after the shot. This, along with the speed of the ball at the instant of impact and the speed with which the ball is intended to be sent will be important when playing shots, and may increase the risk of injury in the racket arm. Cross (1998) established a connection between these variables with regard to both the effect produced on the joints and the trajectory of a tennis ball. His model used the relation between the COG and the impact point of the tennis ball. When the impact point goes through the COG the racket will translate; if they do not coincide, a moment of force will be generated, and the racket will both translate and rotate.
