YEADON, M.R., 1993. The biomechanics of twisting somersaults. Part I: rigid body motions. Journal of Sports Sciences, 11 (3), pp. 187 - 198
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
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.