Computer Simulation of Kinetics Relationship between Gymnast and Landing Mat in Vault Based on LifeMod

Lower extremities of gymnasts suffer larger impact forces during landing of vaults which often induce injuries of lower limbs.In order to provide scientific reference for prevention of the injury,this paper investigated the effects of mechanical characteristics of landing mat on landing impact.A subject-specific model with 19 segments of a gymnast was firstly developed using simulation software of human movement LifeMod/ADAMS.After that,the model was tested and proved to be valid and feasible using our experiment data of motion-capture system,high-speed cameras and force-plate.A vault performed by the gymnast was then simulated.Using the model computer simulation was performed to investigate how modifications to the mat stiffness and damping affect the impact forces.The results indicated that the landing maneuver included two phases,impact phase and balance phase.The joint reaction forces of ankle,knee and hip reached their respective peaks in the impact phase with delays of about 15ms,17ms and 19ms due to the attenuation of the musculo-skeletal system.The torque of knee extensors played an important role in the dissipation of forces in sagittal plane during landing,and that of hip abductors did in frontal plane.The simulation results also indicated that the reaction forces in sagittal plane of ankle increased obviously when mat damping increased,while mat stiffness affect little on the impact loads.All the reaction forces in frontal plane of the joints increased greatly when landing mat damping and stiffness increased,which meant increment of injury risk.