| Long jump is an explosive far-degree jump event which integrates speed and strength into one.Take-off is the core technology of long jump,and the combination of run-up and take-off is the key link of it.There are around 16 to 22 steps throughout the run-up,and the stationarity and technology preparation of the last four steps are the crucial transition from run-up to take-off.The top eight athletes,who participated in the Men's long jump of the 2007 national athletics championships held in Shijiazhnang,were selected as the research object in this paper.Run-up and take-off technologies were investigated with the methods of literature material and film shooting analysis and statistics and comparison,and the results were compared with that of the world elite athletes.Furthermore,the relevant kinematical characteristics in run-up of the last four-steps and take-off are researched on the best men Long Jumpers in China,using the kinematical indexes such as the absolute utilization rate of run-up speed and the horizontal velocity loss rate.Conclusions were drawn as follows.1.Such run-up style,in which the last but three step length was greater than the antepenult step length which was less than the penultimate step length and the penultimate step length was greater than the last step length,was adopted by most eight objects in the last four steps of run-up.The last four step length and the step length difference were significantly different from excellent athletes abroad.There was a great significant positive correlation between the last four step length and the grade(P＜0.01).The walking speeds of the last step and the antepenult step and the last but three steps,assumed the significance with the grade to be connected(P＜0.05).The walking speed of the penultimate step assumed the great significance with the grade to be connected(P＜0.01).2.The absolute utilization rate of run-up speed of Gao Hongwei who won the first was the biggest which is 98%,and that of Wang Minsheng who was the eighth was the smallest which is 91%.Thus,the improvement of the absolute utilization rate of run-up speed was conducive to improve the grade.3.When landing board,increase of the ankle angles and knee joint angle and hip joint angle,and decrease two legs angle will help to improve the grade.When unstuck,increase of the ankle angles and knee joint angle and hip joint angle and two legs angle will also contribute to raise the grade.4.Landing angle(60.89±2.92) when taking offwas smaller,and sector angle(47.85±3.02) was bigger,which affect the coherence of run and jump combination,and go against vertical velocity.The mean of leg drive angle(71°±1.05°) was a litter different from excellent athletes abroad.5.The average horizontal velocity of the objects when instant boarding and taking off were about 10.169±0.19m/s and 9.192±0.43m/s respectively,and the vertical velocity when taking off was about 2.9637±0.11 m/s,which were lower than that of excellent athletes abroad.Therefore,athletes in China should raise the horizontal velocity when instant boarding.What is more important is that the loss of horizontal velocity is minimal when vertical speed is obtained when taking off.6.The biggest loss rate of horizontal velocity among the objects was Gao Hongwei, which is 17.78%,and the smallest was Wang Minsheng with 2.44%.Therefore,the smallest loss rate of horizontal velocity had adverse effect on the grade.7.The gravity center of the last four steps of the eight objects changed greatly,which has adverse effect on loss rate of horizontal velocity and horizontal velocity of landing board and vertical speed of taking off and take-off angle for the last step,so has adverse effect on the grade.
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