Joint forces and moments involved in giant swings on the high bar

Aims- Assess the forces and moments of the joints responsible for producing the segmental motions involved in a series of large circling movements culminating in a tkatchev release-regrasp skill. Methods- A planar eight- link kinematic chain was considered. The Newton-Euler formalism was used to determine the forces and moments involved in the moving kinematic chain. The dynamic model was formulated using a recursive formulation of joint velocities and accelerations from the distal segment to the proximal one. Results- During the standard and accelerated giant swings, the tensile forces increased as the gymnast turn from 60 degree to 240 degree and reached a maximum of two bodyweight (BW) for the upper limb joints at the lower vertical (180 degree ). This maximal value was 3 BW at 160 degree during the swing in preparation to the tkatchev. The magnitude of the components of the bar reaction reached largest values (4.5, 6 and 4 BW) when the gymnast turn at 60 degree , 160 degree and 250 degree during the preparatory swing. Conclusion- Compared to the other ones, this last swing required at the hip and shoulder joints, larger values of moment ranging from-200 to 300 Nm when the body turn from 125 degree to 160 degree .Original Abstract: Objectifs- Determiner l'evolution des efforts actionneurs articulaires developpes au cours d'une serie d'elans circulaires realises a la barre fixe pour executer une figure acrobatique complexe appelee tkatchev . Materiels et methodes- La modelisation considere Le corps du gymnaste comme une chaine cinematique ouverte composee de huit segments rigides articulee a un support deformable representant la barre fixe. La determination des forces et des moments articulaires s'appuie sur la mise en [oe ligature]uvre du formalisme de Newton-Euler selon une procedure iterative appliquee du segment distal au segment proximal. Resultats- Les efforts De traction aux articulations Du membre superieur augmentent lors des elans standard et accelere lorsque Le gymnaste evolue De 60 degree a 240 degree et atteignent un maximum De deux fois Le poids Du corps (BW) a 180 degree . Ces efforts s'intensifient (3 BW) a 160 degree , lors De l'elan preparatoire au tkatchev . Au cours De cet elan, l'intensite De la force De reaction De la barre est particulierement elevee lorsque Le gymnaste franchit 60 degree , 160 degree et 250 degree (4,5, 6 et 4 BW). Conclusion- La reussite De cette acrobatie necessite De produire a la hanche et a l'epaule, des mome