Computer Simulation Of Kinetic Relationship Between Human And Apparatus In Gymnastics Vaulting Based On LifeMod

Purpose:In gymnastics vaulting, techniques of springboard take-off, table push-off and landingare all essential for successful performance. However, the kinetic relationshipbetween human and apparatus in these techniques are still unclear. Based on ahigh-difficulty vault routine performed by an elite gymnast, a subject-specificmulti-body model with19segments and gymnastic apparatus were developed inLifeMod software to quantify internal and external loads in upper and lower limbsduring springboard take-off, table push-off and landing. Computer simulations werealso performed to research the effects of mechanical parameters of the apparatus onhuman joint loads, and further to investigate the key roles that induce joint injuries inthe interaction between human and apparatus, as well as the influence onperformance.Methods:A female champion vault routine in the2011Chinese Gymnastics Championship,Tsukahara Stretched with2/1Turn (720°) off, was captured by two high-speedvideo cameras (CASIO EX-F1) with300Hz frequency and1/320s shutter speed.Kinematic data were gotten over through digitization and calibration using SIMIMotion3D analysis software and a PEAK frame with25markers. The3D kinematicdata were introduced into LifeMod with Python script language to construct asubject-specific model of gymnast based on GeBOD databases, which included theanthropometric parameters of the gymnast, such as gender, height, weight, age etc.With the help of MSC ADAMS software, models of the springboard, vaulting tableand landing mat were all established, and their contacts with the human model weredefined respectively. After optimizing the mechanical parameters of the apparatus, thesystem models were evaluated to be valid. Then, computer simulations wereperformed to analyze the effects of mechanical characteristics of apparatus on loadsupon the gymnast.Results:Comparison of kinematic and kinetic data between actual performance and thesimulation verified the good repeatability and reliability of the human-apparatus system model based on LifeMod software.The peak board reaction force (BRF) and joint reaction force (JRF) increased with theincrement of both spring and board stiffness. But both BRF and JRF decreased withincrease of the board damping. Thus, it was suggested that take-off velocity in verticaldirection can be effectively increased by modifying the stiffness of spring. However,effects of the damping of the spring and the board in the springboard were notobvious. Although the peak BRF and JRF were reduced when the board dampingincreased, the loading rate augmented significantly. The gymnast would be up againstbigger impact load when the punch contact was in the rear zone of the board, whilethe contact force was well maintained and in favor of enhancing take-off velocity inthe vertical direction.During the table contact phase, the peak table reaction force (TRF), JRF and jointtorque (JT) in the left upper limbs as well as take-off velocity from the table in thevertical direction were all increased with the increase of table (horse) stiffness, butthose in the right upper limbs were decreased. Meanwhile, the loading rates in bothleft and right were increased when the table stiffness was increased. Moreover, thepeak TRF in both upper limbs were lowered by increasing the table damping, but itresulted in obvious increase of JRF and loading rate in the left, while the peak JRF,peak JT and loading rate in the right were all decreased.The landing included two periods: impact phase and balance phase. The impact phasewas short with11.40BW of a peak ground reaction force in vertical direction (GRFV),but the balance phase was much longer and the peak GRFVwas about0.91BW.Comparing to peak GRFV, the ankle, knee and hip joint delayed15ms,17ms and19ms reaching their peak JRF respectively. When the stiffness or damping of mat wasincreased, peak GRFv, all the peak JRFs in the lower limbs were all increased;meanwhile, all peak JTs in lower limbs in frontal plane and the peak JT of ankle insagittal plane were increased. Nevertheless, the peak JT of hip in sagittal plane wasdecreased with the increase of mat stiffness, and the peak JT of knee in sagittal planewas decreased with the increase of mat damping.Conclusion:It is feasible to incorporate3D kinematic data digitized manually from high-speedvideos of high-difficulty vault routine performed by an elite gymnast into computersimulation. The analysis of internal and external impact loads upon the gymnastduring springboard take-off, table push-off and landing will be helpful to understandthe roles played by the apparatus in the prevention of sports injuries and improvement the sports performance.The take-off velocity from the springboard in the vertical direction can be promotedby increasing spring stiffness or punching in the rear zone of the springboard.Therefore, in the condition that the mechanical properties of springboard meetphysiological requirement of human musculoskeletal system, appropriately increasingthe springboard stiffness or punching in the rear zone will be helpful to perform moredifficult routines.During the table contact phase, the time to reach the peak JRF in the left elbow wasthe shortest and the loading rate was always the greatest regardless of any tablestiffness. Meanwhile, increasing table damping will reduce external load, but it willcause obvious increment of internal load in the left arm.In the landing, extension torque of knee joint in sagittal plane and abduction torque ofhip joint in frontal plane plays the dominant role in sustaining the impact load.Greater damping of the mat results in higher load of ankle. The JTs of the lowerextremities in frontal plane increase obviously with more stiffed and damped mat.