Abstract: Objective: Taking off skill for aerial movements is key to high-difficulty routines in gymnastics balance beam event. The purpose of the present studyis to investigate the kinetics characteristics of taking off skill of the movement of salto forward piked with 1/2 twist (F180)in balance beam event. Methods:First,a F180 performed by a world champion (SUI Lu) was analyzed through 3D motion analysis method. Then a model of 19 segments of human body and balance beam model were developed through LifeMod software, and the take-off movement of F180 was simulated. Themodel was evaluated by a comparison between the actual performance and simulation results.Finally, the simulated loads in lower limb were analyzed in connectionwith the taking off skill. Results: During take-off of F180, the peaks of joint reaction force(JRF) among leg hip, knee and ankle were increasedorderly. Balance beam reaction forces (BRF), JRFs and torques on the right side of the lower limbs were greater than those in the left. In the both sagittal and frontal plane, torques in hips were greater than that in knees, and thenin ankles.The horizontal BRFs on the two feet were in closed magnitudes and in the directions to the median sagittal plane.Conclusion:In order to increase the stability of movement,the gymnast should land feet on the beam simultaneously and contract the feet towards the median plane in much closed forces during F180 take-off stage. Hip plays a major role in take-off of F180, and the right lower limb produces a greater pushing force.The effective coordination of forces and torques in lower limbs provides vertical momentum and angular momentum for the taking off action of F180.

Key words: Balance Beam, Take-off, Kinetics, Computer Simulation