Forward Simulations of Walking on Surfaces with Asymmetric Mechanical Impedance: Insights for Gait Rehabilitation.

Gait asymmetry, prevalent in stroke survivors and various other neurological and musculoskeletal conditions, leads to abnormal joint loading, increased fall risk, and reduced walking efficiency. Traditional rehabilitation methods often fail to consistently reduce weight-bearing gait asymmetry, necessitating innovative approaches. This study explores the potential of an adjustable mechanical impedance treadmill to amplify weight-bearing asymmetries, leveraging the "error amplification" technique akin to split-belt treadmill training. We developed a 2D optimal control gait model in OpenSim to simulate walking on a rigid platform with one leg and a compliant platform, with adjustable stiffness and damping, with the other. We simulated 112 unique mechanical impedance conditions of the compliant platform and analyzed the effects of these conditions on stance time, ground reaction forces (GRFs), and muscle activations. Our results identified specific impedance parameters that can be utilized to amplify propulsion asymmetries, providing a potential new approach for gait rehabilitation post-stroke. Future work should validate these results in experimental settings and further explore optimal impedance parameters for effective gait therapy of various gait impairments.