Changes in Muscle Activity with Assistance Level During Exoskeletal Gait in Acute Stroke

Abstract BackgroundThe level of assistance provided to the user is an important decision in rehabilitation training using robotic devices. Both fully assistive and assist-as-needed paradigms have shown benefits in functional outcomes in healthy individuals and users with chronic stroke and spinal cord injury. The effect of assistance level on muscle activity and kinematic gait parameters has not yet been directly examined during overground exoskeletal gait in a stroke population. Furthermore, it is not clear whether an assist-as-needed approach could elicit increased voluntary activity in individuals in the acute stages of stroke. The aim of this study was to examine the effect of assistance level on muscle activity and kinematic parameters during exoskeleton gait in individuals in the acute stage of stroke care.MethodsNine individuals in the acute stage of post-stroke care performed walking tasks in the EKSO GTTM exoskeleton using both maximal assistance and adaptive assistance control paradigms. Temporal gait parameters and muscle activity were recorded using accelerometers and surface EMG on the lower limb muscles.ResultsShorter swing times and longer double support times were observed on the non-paretic side during adaptive assist mode than with maximum assist mode (p<0.0065). No significant effect of exoskeleton mode was observed on the remaining temporal gait parameters. On the paretic side, proximal lower limb muscles (RF and ST) and plantar-flexors (SO) (p<0.00125) exhibited greater activation in adaptive assist mode than in maximum assist mode. On the non-paretic side however, the lower limb distal muscles (TA and SO) displayed greater activity during maximum assist mode than adaptive assist mode (p<0.00125). ConclusionsThe level of assistance provided by an exoskeleton in the acute stages of stroke care is an important clinical decision. The results indicate that an adaptive or assist-as-needed approach elicits higher levels of activation in muscles acting around the knee joint and plantar-flexors on the paretic side than a maximal, fixed assistance paradigm, in the acute stage post-stroke. Increased activity around the ankle joint during maximum assistance mode was also noted. Improved understanding of the effect of assistance level can help inform future control paradigms for exoskeleton gait in acute stroke.