- vol.12, pp.73-84, 1994
This study was designed to analyze the jumping forehand smash of elite players based on three-dimensional kinematic data, and to gain insight into the basic badminton smash technique. Jumping smashes of four male elite players were filmed with two high-speed cameras operating at 250Hz with exposure times of 1/1500 and 1/1250 s. 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 to the forearms of the swing arms of the subjects to detect the movements of the radio-ulnar joint and wrist joint. The following six joint angle changes were obtained throughout the smash motion. (a) abduction/adduction angle at the shoulder joint; (b) internal rotation/external rotation angle at the shoulder joint; (c) flexion/extension angle at the elbow joint; (d) pronation/supination angle at the radio-ulnar joint; (e) radial flexion/ulnar flexion angle at the wrist joint; (f) palmar flexion/dorsiflexion angle at the wrist joint. The results showed that internal rotation of the shoulder joint, extension of the elbow joint, and pronation of the radio-ulnar joint seemed to contribute to produce great velocities of the racket head, because the three rotations occurred over the greatest range in the shortest time in the six rotations immediately before contact with the shuttle. Preliminary to the three motions were motions in the opposite direction: external rotation of the shoulder, flexion of the elbow, and supination of the forearm were detected. These motions in the opposite direction would be useful to extend the range of the motion in each joint angle. The results also appeared to be related to intrinsic muscle properties, that greater power can be exerted by the stretching-shortening cycle of the muscles. The time of the last joint rotation starting immediately before contact was in the order of decreasing inertia. Times required for the rotation until contact became shorter in order of occurrence. The faster the rotation was, the later it occurred, and the shorter was the rotation time. This kind of chain and continuous movement of different joints, and different freedom with the same joint, may accelerate the racket head efficiently. The averages of elbow angle and racket angle (the angle between the forearm and racket shaft) were 160.0°and 147.0°at contact, respectively the values may be the suitable choices between the contact height and contact speed in practical play.