Three-dimensional Kinematics Research On Slip And Gllding Technique Of Chinese Excellent Female Shot-putters

In this paper,the slipping and sliding technique of shot from the back of the elite female shot putters in China are studied as the research target.By applying the methods including documentary,expert interview,close shot machine three-dimensional camera measurement method,mathematical statistics,comparative analysis and so on,we conduct the research of slipping and sliding technique for the six players,who participated in the2016 national track and field championships.This study is aimed to provide the more scientific data reference for athletes and coaches by analysing characteristics and laws of the slipping and sliding technique embodied from the excellent athletes,finding out the problems and the insufficiency and proposing the targeted solutions.The main conclusions are as follows:1.In order to conduct further research about back sliding shot technology sliding technique,the original sliding technique is divided into two stages: start sliding stage and sliding stage.The skidding stage is defined as the moment when the center of gravity is shifted from the body to the right foot.The slide stage is defined as the moment when the right foot is take off the ground to touch the ground.2.Only Liu Xiangrong adopts high boots up slide ready posture among the six outstanding female athletes in our country,while the remaining athletes adopt low profile slide posture.At the beginning of the start of slipping,Gong Lijiao,Geng Shuang,Rong Jun's body center of gravity and shot puter's center of mass are relatively low,while the group and the energy accumulation are sufficient.The body's center of gravity and the height of the shot's center of mass increased rapidly in the starting of slipping stages,and the magnitude is larger.The phase body center-of-mass speed curve shows a clear crest,and the depression rapidly causes the body's center of gravity speed to rise rapidly,but the speed synchronization of the man-ball system is poor.The initial heights of Bian Ka,Liu Xiangrong,and Dong Yangzi's center of gravity and the center of shot are higher,and the group's body is not full.After the completion of the group,the energy storage is less.Then,the energy release rate during the start-slip process is slower,while the body center of gravity and the shot center height increase relatively slowly.The amplitude is relatively small,and the body's center of gravity speed curve is relatively flat.The accelerating effect of the depression is not obvious enough,and the human-ball system is better speed synchronization.3.Compared with the world-class female athletes,the six Chinese female shot putters have a significantly shorter sliding distance,and the vertical impulses of speed aretoo large forstart sliding stage and sliding stage.The horizontal direction has a smaller impulse,but the body's center of gravity fluctuates greatly.It is not conducive to the rapid increase of the speed of the "human-ball" system to the throwing direction,which prolongs the time of starting the slippery and sliding steps,destroys the acceleration rhythm,and affects the effect of the glide technique.4.The maximum speed of the left leg swing of China's elite women shot athletes appear before the right leg,indicating that the squat stance is more reasonable.However,the time interval is longer,indicating that the transition from the smashing force to the active recovery is slower,and the slicker and slippery.Steps are not tight enough.5.The performance characteristics of Gong Lijiao and Bian Ka during the starting and sliding stages are typical and representative.Gong Lijiao's upper body is more forward lean.The transverse axis of the shoulder is basically parallel to the ground.The forward rake of the trunk is relatively small.The center of gravity of the body and the height of the center of the shot are low,and the left and right shaking amplitude is small,which keeps the sliding stability better.At the beginning,the upper body is fully flexed,but the longest time is in the slipping and sliding stages.The body center of gravity and the center of mass of the shot have obtained a good combined speed before the final force,but the increase in the combined speed is mainly due to the vertical speed ascension.The concrete manifestation of the body center of gravity and shot height changes,the upper body anteversion and shoulder and hip twist angle significantly increased,indicating that during the sliding process the upper body excessively lifting,the horizontal axis of the shoulder opens prematurely,affecting good final preparation for posture formation.