A Kinematic Analysis Of The Last Two-step Approach And Take-off Technique Of Outstanding Female Long Jumpers In My Country

Research purpose: The combination of running and taking-off in long jump is the difficulty of the whole technique,and the last two steps of running are the key links for athletes to transition from running to taking-off.In order to find out the gap between China's female long jumpers and excellent athletes,to further improve sports performance,at the same time provide a certain theoretical basis and data reference for the training of Chinese female long jump athletes.Research methods: documentation method,3D video analysis method and mathematical statistics methodResults of the study: The last two steps of the run-up phase:(1)Lu Minjia,Xu Xiaoling,Zhong Jiawei and Zou Chang had the smallest step length differences,respectively 0.11 m,0.06 m,0.09 m and 0.06 m.(2)The last two steps of Lu Minjia,Wang Qingling,Zheng Yan,and Epic have a pace of 4.55 steps/s and 5.00 steps/s,and the last two steps of Chen Shuiqing's pace are 4.17 steps/s and 5.00 steps/s,Xu Xiaoling,Zhong Jiawei and Zou Chang's three athletes all had a pace of 4.17 steps/s and 4.55steps/s.(3)At T3,Lu Minjia's center of gravity horizontal velocity is 8.62m/s,while the world's best athletes are 9.59m/s.Takeoff stage:(1)Lu Minjia and Wang Qingling take off time is 0.10 s,Zou Chang is 0.14 s,the remaining five athletes are 0.12 s.The shortest buffer time is Lu Minjia and Wang Qingling,both are 0.02 s,the longest is Zou Chang's0.06 s.(2)Lu Minjia's largest angle of landing is 60.8°,and Zheng Yan,Chen Shuiqing and Zou Chang are not within a reasonable range.The only reasonable fan angle is Lu Minjia's 42.6°and Xu Xiaoling's 42.8°.(3)At T3,the angle of the knee joint of the jumping leg is Lu Minjia's 170.6°,and Zou Chang's 156.5°is the smallest.At T4,Zhong Jiawei's knee angle was 137.8°.At T5,the largest knee angle was Xu Xiaoling's165.6°,and the smallest was Zou Chang's 158.6°.(4)Lu Minjia's initial speed is8.22m/s,the smallest is Zou Chang's 7.53m/s,and the outstanding athlete's initial speed is 8.94m/s.The rising angles are all between 18°-24 °,the largest is Zheng Yan's21.4°.(5)The highest height of the center of gravity at T5 is Xu Xiaoling,which is1.23 m.The average height of the eight athletes during the cushioning process is 0.05±0.02 m.The average height of the eight athletes during the stretching process is 0.16±0.03 m.(6)Lu Minjia's swinging speed of the swinging leg is the fastest at 679.62°/s,and the smallest is Zou Chang's 588.4°/s.The average angular velocity of the swinging arm of the eight athletes on the takeoff leg was 671.85±23.73°/s,and the average angular velocity of the swinging arm on the swinging leg was 869.64±21.77°/s.Lu Minjia 's angle between the two thighs at T5 was the largest at 99.8°.Research conclusion: The last two steps of the run-up phase:(1)The difference instep length between Lu Minjia,Xu Xiaoling,Zhong Jiawei and Zou Chang is within a reasonable range,which is conducive to the play and maintenance of the final speed.The change in pace of the eight athletes is consistent with the development of long jump techniques.The last step has the fastest pace,but it is not ideal in controlling the stability of the step size.(2)The lower horizontal speed of the center of gravity of the upper board is a common problem of the eight athletes,and the absolute speed of the eight athletes is relatively large compared with the excellent athletes.The length and frequency of the last two run-ups have no obvious correlation with athletic performance,and are related to the athlete's own body shape and technical style.Take-off stage:(1)Except for Zou Chang,the other seven athletes have no difference in take-off time compared with the excellent athletes at home and abroad.Lu Minjia and Wang Qingling have the shortest buffer time,which can effectively reduce the loss of speed.There are certain differences.(2)The landing angles of the eight athletes are all too small,which causes the body's center of gravity to fall back when landing,which increases the horizontal resistance,which is not conducive to the completion of the rapid take-off.The three athletes,Zheng Yan,Chen Shuiqing and Zou Chang,all had small pedaling angles and left the ground late.Except for Lu Minjia and Xu Xiaoling,the other six athletes had a large take-off fan angle,and the working distance of the body's center of gravity increased,which reduced the take-off efficiency.(3)All the eight athletes controlled the rising angle better,but the absolute speed was too small to increase the gap between the initial speed and the excellent athletes,which is also the main factor affecting the final performance.During the take-off phase,the height of the center of gravity of the eight athletes all showed a gradual upward trend,which was extremely beneficial for the athletes to obtain vertical speed during the process of cushioning and stretching.(4)Eight athletes had weak legs and weak legs and poor resistance to impact,resulting in unsatisfactory cushioning.Lu Minjia's arms and swing legs swing at the fastest speed during the take-off phase,and can better use the reaction force of the ground to improve the take-off effect.