Modular Control of Human Walking: A Modeling and Simulation Study

Recent evidence suggests that performance of complex locomotor tasks such as walking may be accomplished using a simple underlying organization of co-active muscles, or “modules”, which have been assumed to be structured to perform task-specific biomechanical functions (e.g., to provide body support and forward propulsion). Modular organization has been shown to explain muscle activity across a wide range of walking speeds, levels of body weight support and other combined movement tasks (e.g., [1]). However, no study has explicitly tested whether the modules would actually produce the biomechanical functions associated with them or even produce a well-coordinated movement. The purpose of this study was to generate muscle-actuated forward dynamics simulations of normal healthy walking using muscle activation modules identified using nonnegative matrix factorization as the muscle control inputs to a) assess whether the modules are sufficient to produce well-coordinated walking, and b) identify the contributions of each module to the necessary biomechanical walking sub-tasks of body support, forward propulsion and leg swing. This analysis will critically assess the functional output of the previously identified modular organization of muscle activity in walking and investigate whether it provides a foundation for the neuromotor control of human locomotion.