Ball Velocity Variation on Tennis Forehand Stroke the Arm Joint Coordination Characteristics

Abstract Objective: To explore the influence of different ball speeds on the coordination characteristics of forehand arm. Methods: Two 3D high-speed cameras and video analysis system of Beijing Sport University were used to obtain 3D kinematic data of forehand stroke arms of 16 professional tennis players facing three ball speeds (80km·h⁻¹/100km·h⁻¹/120km·h⁻¹). Vector coding technique was used to calculate the ratio of shoulder-elbow and elbow-wrist coupling angles in three-dimensional plane. Results: The shoulder horizontal flexion and elbow flexion were different phase and elbow dominance, elbow flexion and wrist rotation were in phase and wrist dominance, shoulder adduction and abduction - elbow flexion and elbow extension-elbow flexion and elbow extension-wrist flexion and elbow extension pattern were dominant. Elbow extension-wrist extension-in-phase and elbow-led, elbow-extension-in-wrist rotation out-wrist dominant modes 80km·h⁻¹<100km·h⁻¹<120km·h⁻¹(P<0.05). Shoulder adduction, abduction and elbow extension in the swing phase and shoulder flexion and elbow extension in the swing phase were 80km·h⁻¹>100km·h⁻¹>120km·h⁻¹(P<0.05). The horizontal speed component, the angle of the racket face and the length of the hitting area increase with the increase of the ball speed, while the longitudinal speed component and the trajectory Angle of the racket head decrease with the increase of the ball speed. Conclusion: Under the three ball speed conditions, the coordination characteristics of the hitting arm showed a gradual "zero" effect from the near end to the far end. The degree of "freezing" of shoulder joint freedom increases with the increase of ball speed. Under the condition of high ball speed, the loss of shoulder joint strength may be compensated mainly by trunk torsion. The dominant pattern of elbow joint and wrist joint increased with the increase of ball speed. The index variability of batting time mainly shows that the batting mode increases with the speed of the ball, and gradually changes from topspin batting to flat batting.