Kinematic And Kinetic Characteristics Analysis Of Take-off Technique Of Male Second-level Long Jumper

The long jump has high requirements on the speed,strength,flexibility,agility and coordination ability of the athletes,among which the jump is the key link between the top and the bottom.How well the technical movement of the jump is done is directly related to the quality of the vacating and landing movements,and is related to whether the horizontal speed can be used reasonably and effectively during the running phase,which can directly affect the final result of the competition.Kinematics can reflect the spatial position transformation of the human body,and dynamics can reflect the interaction force between the ground and the human body.The human movement data derived from the corresponding test means can record the performance of the athletes in the whole movement process in a more comprehensive manner.In this paper,we used literature method,expert interview method,testing method and mathematical statistics method,etc.,and used the infrared lens of Oqus700+ model made in Sweden and the Kistler 3D force measuring table of 9287 C model made in Switzerland to conduct simultaneous testing.8 male long jump athletes of Tianjin Sports Institute with second level were selected as test subjects,and the most complete and best data collection in the complete technique of test subjects was used.The kinematic and kinetic characteristics of the jumping technique in the jump with the most complete data and the best results were taken as the object of study.Data analysis and research were conducted on many aspects such as the angle of each joint,speed and force characteristics of the test subjects,revealing the technical movements and technical characteristics of male long jumpers at Level 2level,which can be used as reference for teaching and training.The results showed that:1.At the moment of takeoff and landing,from the perspective of kinematics,the overall performance of the 8 long jumpers is that the Angle of the hip and knee of the takeoff leg is too small,and the Angle between the two thighs is too large.From the perspective of dynamics,the horizontal component of most athletes is large,which is not conducive to the acquisition of vertical speed.Fx(COP)shows that the dynamic balance ability of Liu ** and Wang * is poor,which may be caused by the lack of ankle joint strength.From the perspective of synchronization,the Angle and speed of hip,knee and ankle of jumping leg and swinging leg have more influence on the value of Fx,the value of Fy is mainly affected by the upper limb movement,and the value of Fz is mainly affected by the vertical speed of the body’s center of gravity.2.In terms of kinematics,the fan Angle of 8 long jumpers is too large in the maximum buffering moment.In terms of dynamics,the average Fz force per unit body weight of the eight athletes had a great difference,and the transition time was relatively long,showing insufficient ankle joint support of the jumping leg.Generally speaking,the smaller the ankle Angle of the takeoff leg is,the smaller the Fx generated by the takeoff leg will be,and the easier it will be to obtain a good takeoff effect.Fy will be greatly influenced by the upper limb movements on the side of the takeoff leg.3.At the moment of take-off from the ground,in terms of kinematics,the hip,knee and ankle angles of the eight long jumppers’ take-off legs were much lower than those of the domestic and foreign elite athletes.Most of the athletes’ heave angles were within a reasonable range.4.In the landing buffering stage,in terms of kinematics,most Angle changes of the 8 long jumpers showed a decreasing trend,and the buffering time was long.In terms of dynamics,all the 8 athletes showed the problems of low stability of the jumping leg after landing,long buffering time,and insufficient strength of active and fast pushing.In general,the first wave of Fz is positively correlated with the Angle and velocity of the knee joint of the jumping leg,so athletes should increase the speed and Angle of the knee joint as much as possible during this stage.5.In terms of kinematics,the Angle between the legs,joint Angle and speed of the eight long jumpers all showed an increasing trend in the take-off stage,and the average time of the take-off stage was 0.081 s.In terms of dynamics,the force waveform of the 8 male long jumpers did not change significantly,but the force curve after the second wave peak of Fz was wavy,showing the phenomenon of secondary force when jumping,indicating that the stability and strength of the jumping legs were poor.In general,before Fx = 0,the athlete has already cushioned the knee and begun to push.