Study on the Kinematic characteristics of different level jumpers squatting and jumping under different ground

Abstract Objective: The purpose of this study is to compare the kinematic differences of different level jumping athletes in the process of squatting on different ground, and to reveal the biomechanical mechanism of the effect of squatting on different ground on training effect.Methods: The subjects were 11 first-class and above jumping athletes (excellent group) and 11 second-class athletes (ordinary group). The kinematic data were photographed by SONYDCRHC52E high-speed camera with a sampling frequency of 50 frames per second, and the data were analyzed by SIMI-Motion three-dimensional motion analysis system. The subjects squatted and jumped on four kinds of ground (force platform, balance pad, gymnastics pad and sand) with their hands on their hips.Results: In the intra-group analysis, it was found that the athletes of different levels squatted and jumped on four different kinds of ground, but there was no significant difference only on the balance pad and gymnastics mat (excellent group p=0.344, ordinary group p=1). In the inter-group analysis, it was found that there were significant differences between different levels of athletes in balance pad (p=0.043) and sand (p=0.02). In the buffering stage of squatting jump, there was no significant difference in the buffering angle displacement of lower limb joints of different athletes on different ground. In the stage of pedal and extension, the angular displacement of ankle on the middle platform of the excellent group was significantly different from that of the balance pad (p=0.014), gymnastics pad (p=0.017) and sand (p=0.013), but in the ordinary group, the ankle angular displacement of the middle platform was only significantly different from that of the gymnastics pad (p= 0.048) and sand (p=0.017), but not significantly different from that of the balance pad (p=0.166). The maximum angular velocity of hip joint of athletes of different levels was significantly different among different ground groups. The maximum angular velocity of ankle joint of common group was significantly different in force platform and sand (p=0.032), gymnastics mat and sand (p=0.008), but there was no significant difference in balance pad.Conclusion: Different places have great influence on the ordinary group, and on the ground with lower elastic coefficient, the maximum angular velocity of the ankle joint in the ordinary group is much smaller than that in the excellent group, which indicates that the rapid contractile ability of ankle muscles in the ordinary group is poor on the ground with low elastic coefficient. When squatting and jumping on the ground with lower elastic coefficient, the excellent group has better body control and coordination and lower joint energy loss, which makes the jumping effect better, while the ordinary group squats and jumps on the ground with low elastic coefficient and unstable ground. the jumping effect is poor.