Development of a method to quantify the contributions of horizontal and vertical forces to angular momentum generation in trampolining somersaults, and application to forward rotating somersaults.

Abstract

The angular momentum generated by horizontal and vertical forces during contact with a trampoline were calculated for one elite male trampolinist performing a range of forward-rotating somersaults. To calculate torque due to vertical forces, a method of predicting the centre of vertical force from the bed was developed and tested for its accuracy in the calculation of torques. The accuracy for individual trials was considered to be adequate, and very good where groups of trials were averaged, when compared to observed angular momentum during contact. It was found that torque due to vertical forces contributed to angular momentum generation, but this contribution was most significant during the second half of the contact period as the centre of mass moved further in front of the centre of vertical force. During the early stages of contact, horizontal forces accelerated the centre of mass forwards and effected torque in opposition to forward rotation, limiting angular displacement. During the latter stages, horizontal forces reversed, decelerating the forwards movement of the centre of mass and effecting torque which assisted the development of angular momentum for the somersaults. The forward movement of the centre of mass was greater for more demanding somersaults; in the most demanding somersaults, the reversal of the horizontal forces was later, and insufficient in magnitude to fully remove horizontal velocity.