Paralysis can be caused by an injury to the spinal cord that may partially or completely interrupt communication between the brain and the muscles. If the paralyzed muscles below the level of injury remain innervated then they can be activated by applying small electrical currents in a process known as Functional Electrical Stimulation (FES). The electromyogram (EMG) is the time history of the electrical activity of a muscle that can be used to find its level of activation. This dissertation investigated the use of EMG as a command source for FES-assisted ambulation after incomplete spinal cord injury (iSCI). The synergistic modulation of the volitional EMG was used to identify the intent to transition from step to step even when partially paralyzed muscles were too weak to produce enough moment at the joint to produce effective push-off.
This work has shown that:
1. The controllability of the surface EMG from a partially paralyzed muscle from individuals with iSCI during a visual pursuit task was similar to able-bodied subjects.
2. Surface EMG from the ipsilateral erector spinae and medial gastrconemius consistently performed well to identify the intent to step in able-bodied and iSCI subjects.
3. Spatio-temporal gait parameters with EMG-triggering were at least as good as with standard switch-triggered FES for iSCI subjects in spite of the differences in their injury levels, degree of preserved volitional control, and muscle set chosen for stimulation.
4. EMG-triggering improved the coordination of the FES-assisted iSCI gait during stand-to-walk transitions to levels similar to able-bodied gait.
5. Command sources can be selected objectively prior to implementing a fully implantable EMG-triggered FES system for walking.
6. The optimal number of command sources, features, and signal processing techniques can be determined to further improve the accuracy of EMG-triggering.
More research is needed to optimize the implantation site for EMG recording electrodes and define the technical requirements for a clinically practical EMG-triggered system to facilitate ambulation after iSCI.