The role of upper limb segment rotations in the development of spin in the tennis forehand.

Increased topspin in the tennis forehand is produced by maintaining a perpendicular racket-face to the court surface at impact and increasing the trajectory and vertical velocity of the racket-head. These modifications to stroke technique from those previously identified in the flat forehand drive are the result of changes to the movement patterns of the segments of the upper limb. The contributions that the upper limb segment's anatomical rotations make to racket-head velocity at impact depend on both their angular velocity and the instantaneous position of the racket with respect to these movements. Six high performance tennis players were filmed at a nominal rate of 200 Hz by three Photosonics cameras while hitting flat (no spin) and topspin groundstrokes and a forehand topspin lob. The three-dimensional (3-D) displacement histories of 16 selected landmarks were then calculated using the direct linear transformation approach and 3-D individual segment rotations for the upper limb were calculated using vector equations. Significant differences were recorded in the effect that the various segment rotations made to the x-direction (forward) and y-direction (upward) impact velocities of the racket-head. These differences were not reflected in the contributions to racket-head velocity when the absolute velocities were expressed relative to the impact velocity. Trunk rotation, upper arm flexion/abduction, upper arm internal rotation, hand palmar and ulnar flexion all played integral roles in producing impact racket speed.