CONTRIBUTIONS OF UPPER-LIMB SEGMENT ROTATIONS DURING THE POWER SERVE IN TENNIS

In the high-velocity tennis serve, the contributions that the upper li mb segments' anatomical rotations make to racket head speed at impact depend on both their angular velocity and the instantaneous position o f the racket with respect to the segments' axes of rotation. Eleven hi gh-performance tennis players were filmed at a nominal rate of 200 Hz by three Photosonics cameras while hitting a high-velocity serve. The three-dimensional (3-D) displacement histories of 11 selected landmark s were then calculated using the direct linear transformation approach , and 3-D individual segment rotations for the upper limb were calcula ted using vector equations (Sprigings, Marshall, Elliot, & Jennings, 1 994). The major contributors to the mean linear velocity of the center of the racket head of 31.0 m . s(-1) at impact were internal rotation of the upper arm (54.2%), flexion of the hand (31.0%), horizontal fle xion and abduction of the upper arm (12.9%), and racket shoulder linea r velocity (9.7%). Forearm extension at the elbow joint played a negat ive role (-14.4%) and reduced the forward velocity of the center of th e racket at impact.