Experimental Study And Mechanical Analysis Of Knee Joint Angle During Trampoline Landing

By studying the kinematic parameters and dynamic response of the lower limb knee joint of trampoline athletes when taking off from the net,this paper explores the optimal method and time of exerting force of the knee joint of trampoline athletes when taking off,so as to improve the quality of technical movements of trampoline athletes when taking off,improve the training efficiency,and further improve the sports performance.In addition,the change of biomechanical environment of knee joint is an important factor leading to the injury of knee joint.Therefore,the other purpose of this study is to establish a finite element model of knee joint,and to simulate the force and deformation of knee joint based on the kinematic and dynamic data of trampoline athletes when they fall into the net,The biomechanical effects of impact force and joint angle on articular cartilage and meniscus were studied in order to improve the safety factor of training and prevent injury accidents.The idea of this study is as follows: first,we use high-speed cameras to collect the take-off movements of five Trampoline Athletes of Shanxi trampoline team,and then import them into the video three-dimensional analysis software to obtain the kinematic data of the athletes’ knee joint;Then,two college students from Taiyuan University of technology were experimented with VICON three-dimensional motion capture system to simulate the range of motion of knee joint when athletes jump vertically on the Internet;Finally,the lower limb knee joint of one member of Shanxi trampoline team was scanned by CT.According to the scanning data,3D modeling was carried out in mimics 19.0,and then the model was imported into ANSYS 18.0finite element analysis software to simulate the stress and strain distribution of articular cartilage and meniscus of athletes under different loads(4,5,6 times of their own gravity),Their biomechanical responses were analyzed.Through the above experiments,a series of results are obtained: from the video3 D motion analysis software,the kinematics data of five athletes,such as angle and displacement,are analyzed.The results show that there are some differences in the technical movements of Wang Lin *(A),Zhang *(B),Yao Jin *(C)and the other two excellent athletes,which are mainly reflected in the grasp of the net entry angle and net departure angle and the control of horizontal displacement,This is closely related to the change of their knee joint angle,that is,the grasp of the timing of pedaling and stretching.Through the VICON three-dimensional motion capture system,we can get the knee joint’s internal,external rotation and turn direction when the human body takes off and falls on the net.Through 3D finite element analysis of athletes’ knee joint,it is found that when the load of 4,5 and 6 times of human gravity is applied to the tibial plateau,the peak stress of tibial plateau increases from 2.32 MPa of 4 times of human weight to 2.73 MPa of 5 times of human weight,and finally to 3.31 MPa of 6 times of human weight.The lateral part of tibial plateau is the most stressed part,This is more obvious.Finally,through the research of 3D video analysis system,it is found that Wang Lin *(A),Zhang *(B),Yao Jin *(C)need to improve the net pressing depth,net entry angle selection and the timing of knee joint extension.It is found that Zhang Xin*(D)has the most stretch and the most sufficient extension.All athletes have insufficient take-off,and the knee angle needs to be increased,especially Wang Lin *(A)needs to improve the knee’s push and extension,so as to make the force more sufficient and complete the push and extension at the lowest point.It is suggested that the athletes should strengthen the training of the core parts to make the force more coordinated,increase the net deformation,and obtain higher flying height;In addition,athletes should grasp the angle of the net,reduce the horizontal movement speed and horizontal displacement.Through the 3D finite element analysis of the knee joint,it is found that the stress level in the joint generally increases with the increase of the height of the athletes,and the stress level in the lateral and front side is higher than that in the medial and rear side,which is easy to cause the injury of the lateral tibial cartilage and anterior crucial ligament.