The biomechanics of an overarm throwing task: A simulation model examination of optimal timing of muscle activations

A series of overarm throws, constrained to the parasagittal plane, were sim ulated using a muscle model actuated two-segment model representing the for earm and hand plus projectile. The parameters defining the modeled muscles and the anthropometry of the two-segment models were specific to the two yo ung male subjects. All simulations commenced from a position of full elbow flexion and full wrist extension. The study was designed to elucidate the o ptimal inter-muscular coordination strategies for throwing projectiles to a chieve maximum range, as well as maximum projectile kinetic energy for a va riety of projectile masses. A proximal to distal (PD) sequence of muscle ac tivations was seen in many of the simulated throws but not all. Under certa in conditions moment reversal produced a longer throw and greater projectil e energy, and deactivation of the muscles resulted in increased projectile energy. Therefore, simple timing of muscle activation does not fury describ e the patterns of muscle recruitment which can produce optimal throws. The models of the two subjects required different timings of muscle activations , and for some of the tasks used different coordination patterns. Optimal s trategies were found to vary with the mass of the projectile, the anthropom etry and the muscle characteristics of the subjects modeled. The tasks exam ined were relatively simple, but basic rules for coordinating these tasks w ere not evident. (C) 2001 Academic Press.