MINIMUM MUSCLE TENSION CHANGE TRAJECTORIES PREDICTED BY USING A 17-MUSCLE MODEL OF THE MONKEYS ARM

Four computational problems to be solved for visually guided reaching movements, hand path, and trajectory formations, coordinate transforma tion, and calculations of muscle tensions are ill-posed in redundant b iological control systems. These problems are ill-posed in the sense t hat there exist an infinite number of possible solutions. In this arti cle, it is shown that the nervous system can solve those problems simu ltaneously by imposing a single global constraint: finding the smoothe st muscle- tension trajectory that satisfies the desired final hand po sition, velocity, and acceleration. Horizontal trajectories were simul ated by using a 17-muscle model of the monkey's arm as the controlled object. The simulations predicted gently curved hand paths for lateral hand movements and for movements from the side of the body to the fro nt, and a roughly straight hand path for anterioposterior movements. T he tangential hand velocities were roughly bell shaped. The simulated results were in agreement with the actual biological movements.