| Research Purpose: At present,3D motion capture technology has been widely used in various sports.By measuring the technical movements of athletes with precise instruments,quantitative data can be obtained,which could help them optimize special movements and improve their sports performance.This paper mainly compared the kinematics and dynamics differences of forehand strokes of tennis players with different skill levels,so as to find out the problems existing in the details of the strokes of low level tennis players,and provide some theoretical basis for the tennis coaches to correct and train their technical movements.Research methods: In this study,8 second-level tennis players and 10 tennis majors were divided into the high-level group and the general group.VICON infrared motion capture system and 3D force measuring platform were used to record the kinematic data of forehand stroke and the ground reaction force of the participants.C3 D files were generated in VICON NEXUS software,and then imported into VISUAL3 D software to build the human body skeleton model,to calculate the corresponding kinematic and dynamic variables.The forehand stroke was divided into preparation stage,accelerated swing stage and following swing stage.The statistical method was independent-samples T test,and the significance level was set asα=0.05.Results:(1)The maximum swing speed of the high level group was 19.57±2.72m/s,and that of the general group was 14.72±2.70m/s,which was significantly higher than that of the general group(P < 0.001).The score of batting accuracy was 13.20±0.84 in the high level group and 9.64±0.98 in the general group.The score of the high level group was higher than that of the general group(P =0.012).The time of the stroke action(right foot landing-swing forward)of the players in the high-level group was0.85±0.07 s,while that of the players in the general group was 0.92±0.10s(P=0.009).(2)The right knee extension angular velocity,right hip extension angular velocity,pelvis internal rotation angular velocity peak,trunk internal rotation angular velocity peak and right shoulder,elbow,wrist center horizontal velocity peak were significantly higher in the high level group than those in the general group(P <0.01).However,about the peak speed-time series,the two groups were almost the same,there was no statistical difference.(3)There were significant differences in right knee angle and right hip angle between the high level group and the general group at the preparation stage.The flexion of the high level group was larger,and the right knee angle and right hip angle at the maximum buffer time were smaller than those of the general group(right knee Angle 120.3±7.10°vs 127.3±6.90°,P =0.032;Right hip angle 101.9±10.8°vs113.9±2.7°,P =0.029).The maximum shoulder-hip angle in the high level group was also higher than that in the general group(21.42±4.50°vs 11.03±4.27°,P <0.001).(4)There was a significant difference in the center of gravity displacement between the high level group and the general group(center of gravity forward,7.61±3.12 cm vs 4.24±2.75 cm,P =0.050;The center of gravity outward right12.04±5.10 cm vs 7.13±5.82 cm,P=0.124;center of gravity upward: 9.05±2.65 cm vs11.32±2.10 cm,P=0.082).(5)There were no significant differences between the high level group and the general group in the indexes of push impulse forward and push impulse upward,but the buffer impulse of the high level group was significantly greater than that of the general group(314.98 ±94.16N·S vs 200.94±59.55 N·S,P =0.006).In terms of work done by three joints of lower limbs,the contribution of work done by hip joint and ankle joint in the high level group was significantly greater than that in the general group(hip joint: 68.49%±9.81 vs 90.23%±5.47,P =0.001;ankle joint: 25.73%±7.80 vs 3.77%±3.80,P < 0.001),and no significant difference was found in the work proportion of knee joint(P =0.917).Conclusion:(1)The forehand stroke speed of the players in the high-level group was higher than that of the general group,the ability to control the landing point of the stroke was more stable,and the accuracy of the stroke was higher.(2)In preparation for the forehand,the high level group’s knee and hip flexion range was bigger,the related muscle stretching effect better,to accelerate the swing phase high level group of players has more stretch right knee angle and right hip angle range,more body center of gravity forward,to the more obvious role in promoting the direction of the ball to the body,was conducive to the transfer of momentum to the racket.(3)At the moment of hitting,the high level players holding the racket arm outreach angle was smaller,which was conducive to the control of the swing trajectory,while the wrist ulnar deviation angle was larger,which leads the racket to move forward and upward more.The control of the ball could be increased by increasing the rotation of the ball.(4)In the process of accelerated swing,the work of the right leg,hip,knee and ankle joint of the players in the high level group was significantly higher than that of the general group,and the lower limb stretching effect was more obvious. |
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