A key to high‐amplitude movement synthesis: the muscle lever arm

Abstract

AbstractPulling actuators play an important role in biomechanical simulations. In most animals, muscles are the actuators exerting torques onto the joints. These torques highly depend on the muscle line of action or, in other words, muscle lever arms. Common methods focus either on single‐joint movements, on two‐dimensional problems, or on imitating physiological lever arms only in a small working range. However, especially in complex multibody simulations, where reduced descriptions of muscles as massless, visco‐elastic, active bands are used, a correct representation of lever arms is mandatory for a large range of joint angles for all degrees of freedom. To address these issues, we developed a new design and computational algorithm for modeling the path of linear pulling actuators. The method is based on finding the shortest muscle path while the actuator is lead through a small number of two‐dimensional shapes. It allows for multiple degree of freedom and high‐amplitude movements as well as combinations of both, ensuring reasonable lever arms at all possible joint configurations even for muscles spanning more than one joint. We applied this method to a multibody model of the human musculoskeletal system. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)