Walking after partial paralysis assisted with EMG-triggered or switch-triggered functional electrical stimulation — Two case studies

Functional Electrical Stimulation (FES) facilitates walking after paralysis by activating the muscles of the lower extremities. The FES-assisted stepping triggered either by a manual switch (switch-trigger), or by an electromyogram-based gait event detector (EMG-trigger) were presented in random order to two subjects with incomplete spinal cord injuries (iSCI) during ten trials over two alternate days. Subject iSCI-1 (C6 ASIA C) was non-ambulatory without the assistance of FES and could stand but not initiate a step volitionally. Subject iSCI-2 (T1 ASIA D) could walk only short distances with great difficulty without FES. Gait kinematics and kinetics were captured during FES-assisted over-ground walking with a rolling walker under laboratory conditions. Gait parameters including speed, left and right step length, left and right double support duration, left and right swing phase durations were extracted from the kinematic data. Mean, standard deviation, coefficient of variation, and 95% confidence interval were computed for each gait parameter under each triggering condition. The ground reaction forces were recorded for both the subjects while upper body support provided by the instrumented walker was recorded for iSCI-2. One way analysis of variance (ANOVA) was performed to determine whether significant differences existed in gait parameters between command sources. The left and right double support duration were significantly lower (p<;0.05) during EMG-triggered gait than switch-triggered for iSCI-1. The average normal ground reaction force was significantly (p<;0.05) higher during EMG-triggered gait than switch-triggered for iSCI-1 and iSCI-2. The average body weight support on the walker was significantly lower for EMG-triggered gait than switch-triggered one for iSCI-2. The results suggest that less user effort was needed when walking with EMG-triggered stepping than with manual switch trigger.