Assessment of gait symmetry, torque interaction and muscular response due to the unilateral assistance provided by an active knee orthosis in healthy subjects

摘要

Stroke survivors usually present asymmetric gait and mobility impairments as consequence of hemiparesis. In order to alleviate this unilateral loss of mobility and correct this asymmetry, we developed an active knee-orthosis to assist the movement of the impaired leg. The control strategies of the orthosis that we have implemented are based on the kinematics of the healthy leg, by replicating the movement of the healthy one, or by using this movement to synchronize the application of a normalized healthy pattern over the impaired leg. Our main aim is to understand how stroke patient’s gait evolve to adapt to the assistance provided, as a preliminary study, in this paper we describe the effects of the assistance provided in twelve (12) healthy subjects who wore the robotic exoskeleton while they performed overground walking trials. Results indicated that the robot improved the gait symmetry of the users, reducing the spatial and temporal differences between the movements of both legs, without significantly disturbing the stance/swing ratio of the users. In addition, results showed that users tended to respond to this assistance by generating torque in the same direction of the robot action instead of taking advantage of the assistance provided by the exoskeleton. Muscular response of the assisted leg also shows variations according to this torque response, increasing the muscular activity in the 22.7% of cases against the 4% of cases where it was decreased. Finally, we detected changes not only in the assisted leg, but also in the unassisted one, whose muscular activity increased in the 28% of cases against the 1% of cases where it was decreased, showing the effect that the assistance on one leg have over the whole gait dynamics.