Acute Effects of Transcutaneous Spinal Cord Stimulation (tSCS) on Gait Symmetry in People with Chronic Stroke

Objectives To determine whether transcutaneous spinal cord stimulation (tSCS) modulates gait symmetry after a single bout of 25 minutes of treadmill gait training and to establish whether a particular combination of tSCS frequency and intensity elicits greater gait symmetry changes. Materials and Methods In each of six sessions, 20 chronic stroke participants received 25 minutes of treadmill gait training while they received either SHAM stimulation or one of four unique STIM (tSCS) parameter combinations: 30 or 50Hz frequency, and intensity at participant tolerance (TOL) or 30% of minimum resting motor threshold (RMT min ). In each session, our primary outcomes were step length (m) and swing duration (sec) symmetry during the 10-meter Walk Test (10MWT) PRE and POST treadmill training. We also computed an "overall" symmetry measure, the Combined Gait Asymmetry Metric (CGAM), and 10MWT gait speed. PRE to POST-intervention changes and how they differ among stimulation parameters were assessed via the Timepoint x Intervention interaction effect of a two-way repeated measures ANOVA. A complementary exploratory analysis was performed to determine individualized "best" vs "worst" stimulation parameters compared to SHAM. Results Among the five interventions tested, we found no statistically significant difference in the PRE to POST change in the primary outcome variables – step length symmetry ( Timepoint x Intervention effect, p=0.0564) and swing duration symmetry (p=0.6215) – or in CGAM (p=0.5350) or 10MWT gait speed (p=0.4828). Conclusions We found that 25 minutes of tSCS plus treadmill training did not significantly change gait symmetry or speed compared to treadmill training alone. These findings also suggest that in a single session setting there may not be a best frequency or intensity that is optimal for everyone. Future work should investigate whether person-specific stimulation parameters may yield single-day gait symmetry changes, as well as potential longitudinal effects of tSCS plus gait training.