Three-dimensional cinematographical analysis of the badminton forehand smash : movent of the forearm and hand

Abstract

This study was designed to analyze the jumping forehand smash of elite players based on three-dimensional kinematic data, and to get insight into the basic badminton smash technique. Jumping smashes of four male elite players were filmed with two high speed camears operating at 250 frames per sec with exposure time of 1/1500 and 1/1250 sec. The nine jumping smashes were selected for the analysis, and were digitized from the take-off of the jump to the end of the swing in the air. Thirty three-dimensional coordinates for the segment endpoints and racket were computed by a Direct Linear Transformation Method. Small reference poles were fixed on the forearm of the swing arm of the subjects to detect their movements of the radio-ulnar joint and wrist joint. Following six joint angle changes were obtained throughout the smash motion. (a) pronation/supination angle at the radio-ulnar joint. (b) radial flexion/ulnar flexion angle at the wrist joint. (c) palmar flexion/dorsi flexion angle at the wrist joint. The resultd showed that pronation of the radio-ulnar joint seemed to contribute to produce great velocities of the racket head, because the rotation occurred the greatest range in the shortest time in the three rotations immediately before contact with the shuttle. Preliminary to the motions were motions in the opposite direction; e. g., supination of the forearm was detected. These motions in the opposite direction would be useful to extend the range of the motion in each joiot angle. The order of time of the last joint rotation starting immediately before contact was ulnar flexion, palmar flexion and pronation. Respective times required for the rotation until contact became shorter in turn of late occurring. The faster the rotation was, the later the rotation occurred and the shorter the rotation time was. This kind of chain and continuous movements of different joints, and different freedom in the same joint may accelerate the racket head efficiently. The averages of the racket angle (the angle between the forearm and racket shaft) was 147.0゜at the contact.