ReAble: a Wearable Robotic Locomotor Trainer for Post-Stroke Individuals

Background. Post-stroke individuals usually show walking impairments, including reduced walking speed and gait asymmetry. One possible reason for these impairments may be due to the reduced propulsion forces and muscle activity on the paretic leg. Different robotic systems have been developed but current rehabilitation approaches are not often effective in improving paretic leg propulsion. Objective. To develop and validate a novel wearable robotic system that is able to improve paretic propulsion in individuals post-stroke and that can be used during overground walking. Methods. This work proposes ReAble: a cable-driven soft wearable robotic system that forces the paretic leg usage by resisting to the non-paretic leg swing. The resistive force was real-time controlled by ankles kinematic wearable sensors and a load cell measurement. In addition, ReAble exploits the constraint induced movement therapy principle on the lower limb training in an innovative way allowing overgound walking training. The feasibility of the robotic locomotor training device has been tested on three healthy control subjects and one post-stroke patient. EMG signals from 8 leg muscles of the non-directly perturbed leg (the paretic leg for the patient post-stroke) and ground reaction forces of both legs were recorded to evaluate the effect on the non- perturbed/paretic leg activity. Two different walking speeds and two different timings of the resistive force were also tested to examine the characteristics of Re- Able. Results. The preliminary results show significant increases in the non-perturbed/paretic leg integrated EMG of gluteus maximus, rectus femoris, vastus medialis, biceps femoris, hip adductor and soleus when the resistive force was applied. The resistive force also induced an increase in the braking force on the non-perturbed/paretic leg, and improved propulsion force from the perturbed/non-paretic leg. In addition, the walking speed had no significant impact on muscle activity induced by the perturbation force, suggesting that it may be used on individuals post-stroke with different function levels. Conclusion. This novel soft cable-driven portable robotic system is feasible to be used to increase the paretic leg muscle activity during overground walking in individuals with poststroke hemiparesis.