An insight into the reversal of rotation in the Hecht vault

In a Hecht vault the direction of somersault rotation is reversed during horse contact. Gymnasts contribute actively to this reversal using muscle-generated shoulder torques during this contact phase. There is also the possibility that the way in which the gymnast contacts the horse may contribute to the reversal of somersault rotation by creating naturally occurring total body rotations at horse impact. To investigate this, a two-segment model was used to simulate an instantaneous inelastic impact during which internally generated shoulder torque was constrained to zero. The simplicity of the model used in the simulation provided valuable insight into the role that the preflight trajectory plays in the reversal of total body rotation at horse impact. It was found using realistic takeoff conditions from the board, that over half of the reversal of rotation could be produced by a suitable preflight trajectory.