• L. H. Wang
  • H. W. Wu
  • K. C. Lo
  • F. C. Su
Keywords: kinematics, upper limb, tennis, backhand stroke, velocity, trunk


INTRODUCTION: Tennis injuries caused by improper drives or overuse of the upper limb are very common in tennis. They may be prevented by using correct movement patterns. The purpose of this study was to analyze the threedimensional kinematics of the upper limb and trunk associated with performances of the single-handed backhand tennis stroke. METHODS: Six male national representatives performed tennis single-handed backhand drives in the laboratory. Sixteen reflective markers were placed on the subjects to represent the movements of the upper limb and trunk. They included one each on processus xiphoideus, incisura jugularis, 7th cervical vertebra, acromion, medialis and lateralis epicondylus, ulnar and radial styloid process, 2nd and 4th metacarpal heads, two anterior superior illiac spine and posterior superior illiac spine, and a triad markers on the upper limb. The markers’ positions were collected with the ExpertVision motion analysis system (Motion Analysis Corp., Santa Rosa, CA, USA) in order to estimate the joint movements of the shoulder, elbow, and wrist joints and the trunk. Ten trials were sampled for each subject. Eulerian angles were used to represent joint kinematics. RESULTS: The joint movements of the upper limbs were consistent while performing the tennis single-handed backhand stroke. The angular velocities of the clockwise rotation of the trunk and ulnar deviation of the wrist reached the maximum values at the middle acceleration phase and then decreased. In addition, the angular velocities of the shoulder external rotation, elbow flexion and wrist extension reached maximum values in the instant subsequent to impact. The results showed that the major movements of the shoulder joint were abduction/adduction (73.6±11.5°), flexion/extension (45.7±20.2°), and internal/external rotation (46.3±13.7°). The major movements of the elbow joint were pronation/supination (71.2±20.8°), and flexion/extension (35.3±14.4°). The results provide basic guidelines for tennis training and tennis evaluation. It is also helpful for the physician and therapist to assist in the diagnosis of sports injuries and to plan clinical treatment. CONCLUSIONS: In the acceleration phase, the trunk moves with the racket to increase angular momentum for the preparation of the impact. During this period, the movement of the shoulder is small. When the maximum angular velocities of the shoulder external rotation, elbow flexion and wrist extension occur in the instant prior to impact, they then immediately decrease. In this way, the hyperextension of the wrist joint, the cause of tennis elbow, may be prevented. The stability of the elbow joint and forearm is maintained by the contraction of the biceps and triceps.