The biomechanics of twisting somersaults. Part I: Rigid body motions.

This series of four papers comprises a theoretical investigation into twisting somersaults. Both simple and complex mathematical models are used to provide an understanding of the mechanics of the production and removal of twist in somersaults. Various twisting techniques are evaluated and a method is developed for the partitioning of an actual performance into contributions from these twisting techniques. In Part I, analytical solutions for the torque-free rotational motion of a rigid body are derived. It is shown that there are two distinct modes of motion which may be characterized as a twisting somersault and a wobbling somersault. The phenomenon of unstable rotations about the intermediate principal axis is explained in terms of these two modes.