Ultrasound for Quantifying Muscle Activation Elicited by Spinal Cord Stimulation and Functional Electrical Stimulation

Transcutaneous (non-invasive) spinal cord stimulation (tSCS) has been shown to facilitate volitional motor activity in patients with spinal cord injury. tSCS is known to activate the same neural structures as invasive SCS, meaning it may have the potential for functional restoration without an expensive surgical implant. Functional electrical stimulation (FES) is also used in therapy for patients with spinal cord injury to locally activate paralyzed or weakened muscles. There is evidence that combining FES and tSCS may elicit greater muscle activation than either modality alone. The objective of this study is to quantify the torque at the ankle joint generated by tSCS, by FES, and by tSCS + FES. Additionally, ultrasound images will be collected during stimulation to provide a metric of muscle activity. The correlation between ultrasound and torque will be assessed to determine if ultrasound is a useful modality for quantifying tSCS-elicited muscle activity.