The role of upper limb segment rotations in the development of racket-head speed in the squash forehand.

In the squash forehand drive, the contribution that each of the upper limb segment's anatomical rotations make to racket-head velocity towards the front wall (x-direction) during the forward swing and at impact were calculated. Eight squash players (3 females, 5 males) capable of hitting a high-performance squash forehand drive were filmed at a nominal rate of 300 Hz by two phase-locked Photosonics cameras. The three-dimensional displacement histories of 12 selected landmarks were then calculated using the direct linear transformation approach and three-dimensional individual segment rotations were calculated using vector equations. Internal rotation of the upper arm at the shoulder joint (46.1%), hand flexion at the wrist joint (18.2%) and forearm pronation at the radio-ulnar joint (12.0%) were the major contributors to the mean 30.8 m s-1 x-direction velocity of the centre of the racket-head at impact. Pronation of the forearm at the radio-ulnar joint and extension at the elbow joint both played a significant role in generating racket velocity in the period prior to impact.