| At present,the highest level and the overall level of men's long jump in China have been significantly improved,and a group of athletes with a level of more than 8m have emerged.However,at the same time,the women's long jump in China has been stagnant,the highest level and the overall level are relatively low,and it has lost the greater advantage in Asia.Xu Xiaoling is one of the best female long jump athletes in China in the past ten years,but there is still a big gap between his sports performance and the world's top athletes.This study uses the methods of literature,expert interview,mathematical statistics,comparative analysis and video analysis to compare the take-off technical characteristics of Xu Xiaoling and the world's excellent female long jumpers.By analyzing the technical parameters of take-off link,the problems and technical advantages and disadvantages of take-off technology are found out,so as to promote the technical improvement of Xu Xiaoling and realize precise training Practice.At the same time,Xu Xiaoling is also an athlete with a long training period,who is in the stage of competitive maintenance.He hopes to optimize his technology through technical analysis and diagnosis,help him to stabilize his performance in the final stage of his sports career,and seek a breakthrough.The results are as follows:(1)the last two steps of Xu Xiaoling are 2.2±0.12 m and 2.08 ± 0.05 m respectively,showing a trend of "big small" rhythm change;however,the difference of steps is small,0.12±0.13 m,which is not conducive to fast convergence and jump.The data shows that the larger the difference of the last two steps,the more favorable for Xu Xiaoling to achieve good results.Xu Xiaoling's last two strides are 9.08±0.05m/s and 8.77±0.21m/s,respectively,in a state of deceleration,while the best foreign players are accelerating the board.In the last two steps,Xu Xiaoling's center of mass height decreased by 0.1±0.01 m,and his body's center of mass decreased more than that of foreign elite athletes.Before taking off,Xu Xiaoling tried to make up for the lack of taking off ability by improving the vertical speed through the center of mass reduction.(2)Xu Xiaoling's horizontal speed,loss of horizontal speed,vertical speed,initial speed and angle of takeoff are 7.8±0.12m/s,0.75±0.46m/s,2.89±0.24m/s and 8.37±0.1m/s18.5±1.29 ° respectively.In the process of taking off,Xu Xiaoling has a small loss of horizontal speed,resulting in a small conversion of vertical speed,which will affect the angle of take-off,and then affect the overall take-off effect.The greater the horizontal speed of Xu Xiaoling's take-off moment,the greater the loss of horizontal speed in the take-off process,the greater the vertical speed of take-off,and the greater the initial speed of take-off,the more conducive to his good performance.(3)At the moment of maximum buffer,the maximum buffer angle of the knee joint of Xu Xiaoling is 137.25±3.3 °,which is lower than the appropriate range of 138 °-145 °.It shows that Xu Xiaoling has a large buffer range of the lower limbs,which reflects the shortcomings of the support ability of the lower limbs from the side.(4)Xu Xiaoling's trunk angle was 91.5±5.51 ° at the moment of taking off from the ground.(5)Xu Xiaoling's landing angle,take-off angle and take-off time are 69.25±2.99 °,62±0.82 ° and 0.11±0.01 s,respectively.The take-off angle is too small and the take-off pedal extension is not sufficient.(6)Xu Xiaoling's leg angles were 40.25±5.74 ° and 86.5±4.51 ° at the moment of landing and leaving the board,respectively.The average angular velocity of the swinging leg is 712±54.98 ° / s,which is lower than the average level of the world's elite athletes,which is not conducive to obtain a better take-off effect.Conclusion:(1)The last two steps of Xu Xiaoling were 2.2±0.12 m and 2.08±0.05 m respectively,which were in line with the "big small" last two step rhythm change mode.However,the "big small" step difference of the last two steps of approach was small,with an average of 0.12±0.13 M,and the step rhythm change was not obvious;In addition,the height of the center of mass in the last two steps decreases greatly and decelerates in the last two steps.The lack of stability of the whole run-up rhythm and the poor connection technology of the last two steps may be the main reasons for the inconspicuous change of the last two steps.The rationality of running technique and the fluency of running jumping connection technique may be the main reason for the final two steps of deceleration.(2)In the process of taking off,Xu Xiaoling's horizontal speed loss is small,with an average of 0.75±0.46m/s,which is beneficial to reduce the horizontal speed loss and save the horizontal speed that was not dominant originally,and also to obtain a certain initial speed of take-off(8.37±0.10 m / s);at the same time,Xu Xiaoling also has the characteristics of short take-off time(0.11±0.01s).In traditional theory,Xu Xiaoling has the advantages of reducing the horizontal speed loss,the average landing angle of Xu Xiaoling is 69.25±2.99 °,which is good for reducing the horizontal braking force at the moment of landing and maintaining the horizontal speed.(3)Xu Xiaoling's small loss of horizontal speed increases the difficulty of obtaining vertical speed,which leads to the problem of insufficient take-off,which is manifested in the problems of low vertical speed(2.89±0.24 m/s)and low angle of take-off(18.5±1.29 °);in addition,his take-off leg support ability is insufficient(the minimum knee joint angle is small,137.25 ± 3.3 °;the take-off angle is small,62±0.82 °,and the take-off ability Insufficient)and take-off time is too short,so that it can not effectively complete the take-off action in a short time.The reason of the above phenomenon may be the insufficient take-off ability and unreasonable take-off support technology.(4)Xu Xiaoling's trunk is more upright(91.5±5.51 °)after taking off from the ground,and his forward motion is insufficient,and he shows a more obvious "head up" action;and his enthusiasm for swing leg is insufficient at the moment of landing and leaving the board,which is manifested in the big angle between the two thighs(40.25±5.74 °)at the moment of landing and leaving the board,the small angle between the two thighs(86.5±4.51 °)at the moment of leaving the board,and the speed of swing leg angle is slow(712±5 °)during the whole take-off process 4.98°/s)? The reason of the above phenomenon may be the insufficient take-off ability and the unreasonable technical cooperation of take-off pedaling.(5)According to Xu Xiaoling's shortcomings in the last two steps of run-up and take-off techniques,combined with his own actual situation,the corresponding special techniques and special ability training methods are put forward.Suggestions:(1)In the training,Xu Xiaoling should pay attention to maintaining the speed,strengthen the technical training in preparation for the take-off stage,improve the connection technology of running and jumping through the run-up training of different run-up steps,form a "big small" step rhythm,and speed up the boarding speed.Strengthen the connection speed of the last two steps,and pay attention to the "pick back" speed at the moment of the last step landing.(2)Xu Xiaoling should also strengthen the take-off consciousness,improve the take-off technology,develop the take-off leg strength and the swing ability of the swinging leg,strengthen the coordination consciousness of "kick swing",complete the buffering action earlier,increase the proportion of the centripetal contraction force stage,and improve the take-off effect.(3)According to the specific problems existing in Xu Xiaoling's special technology,a targeted improvement strategy is designed to promote the effect of technical improvement. |
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