The forces and moments in the wrist and the elbow which are induced by striking a tennis ball were theoretically investigated. A dynamic model of a ball, racket and arm was simulated by two masses, a beam and two rigid bodies connected by springs. The modes of vibration and impulse response were calculated. The forces can be decreased by setting the striking point such that the translational and rotational movements at the grip cancel each other. The component of force with high frequency can be reduced by coinciding the striking point with the nodal point of the racket and by matching the natural frequency of the ball with that of the racket.