A MINIMUM ENERGY-COST HYPOTHESIS FOR HUMAN ARM TRAJECTORIES

Many tasks require the arm to move from its initial position to a spec ified target position, but leave us free to choose the trajectory betw een them. This paper presents and tests the hypothesis that trajectori es are chosen to minimize metabolic energy costs. Costs are calculated for the range of possible trajectories, for movements between the end points used in previously published experiments. Calculated energy mi nimizing trajectories for a model with biarticular elbow muscles agree well with observed trajectories for fast movements. Good agreement is also obtained for slow movements if they are assumed to be performed by slower muscles. A model in which all muscles are uniarticular is le ss successful in predicting observed trajectories. The effects of load s and of reversing the direction of movement are investigated.