Dynamics of the Upper Limb with a Detailed Model for the Shoulder

Abstract

The human muscle-skeletal system has a large number of redundant muscles, implying that the same motion may be obtained by different combination of muscle forces. As a consequence, the modeling of the kinematics of biomechanical models used for human motion task simulations has important implication on the distribution of the muscle forces and joint reaction forces. This work compares the performance and applicability of three biomechanical models, with different levels of complexity, in face of specific kinematic modeling assumptions for the anatomical joints and muscle geometry. The muscle contraction dynamics is simulated by the Hill-type muscle model, being the activation of each muscle a unknown in the redundant force sharing problem. An optimization technique is applied to minimize of an objective function related with muscle metabolic energy consumption. The input for the model analysis comprises the data for an abduction motion, kinematically consistent with the biomechanical models developed, acquired using video imaging at the Laboratory of Biomechanics of Lisbon.