Modeling and Analysis of Sensorimotor Dynamics in Inter-leg Coupling Leads to a Novel Model-based Approach to Human Gait Rehabilitation

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The main research goal of this project is to create a dynamic model of coordination between legs during gait, and to apply that model to rehabilitation of individuals suffering from hemiparesis, that is, weakness on one side of their body. Such weakness -- due to injury, or to a neurological disorder such as stroke -- and the associated difficulty in walking, has become a pressing public health problem. One of the main reasons gait rehabilitation has not been very successful so far is the lack of basic understanding of the dynamics of gait in both intact and impaired walkers. A major scientific challenge for the field is the creation of a comprehensive sensorimotor model, which can be used to understand inter-leg coordination, a fundamental mechanisms of walking. Experiments enabled by a novel robotic variable stiffness treadmill will be used to model walking gaits of individuals with hemiparesis, and to inform model-based robotic interventions for rehabilitation. The benefits of this approach will be also realized in other fields, including orthotics and prosthetics, as well as in robotic walkers. The project will address important research questions related to inter-leg coordination mechanisms during gait that will provide the foundation for transformative gait retraining methods. More specifically, the unique investigation of the effect of sensory feedback on neuromuscular mechanisms of inter-leg coordination, made possible by the Variable Stiffness Treadmill, will be used as a window into the sensorimotor control mechanisms of gait. A system dynamics and control approach to robotic intervention for retraining gait will enhance our understanding of the role of the sensori-motor processes involved in gait. Understanding and modeling the dynamics that govern the sensori-motor mechanisms of inter-leg coordination in gait naturally results in the introduction of model-based interventions for gait therapy using inter-leg coupling, which has never been attempted before. Specifically, the project leverages existing central mechanisms of leg coordination and introduces the concept of evoking activity on the paretic leg through model-based interventions on the unimpaired leg. Inter-leg coordination, a fundamental process of walking, is going to be investigated and modeled as a multivariable dynamical system in intact walkers using the unique sensori-motor capabilities of the Variable Stiffness Treadmill. Then, the same experimental protocol will be applied to hemiparetic walkers. The goal is to understand the altered dynamics and specific gait mechanisms and pathways that are disrupted in hemiparesis. Finally, the developed models will result in targeted model-based interventions towards gait therapy of stroke survivors.