Body movement induced by electrical stimulation of toe muscles during standing

The purpose of this study was to investigate whether artificially induced muscle contractions of toe muscles using functional electrical stimulation (FES) would cause center of pressure (COP) displacement and corresponding body acceleration. Ten able-bodied subjects were asked to stand still on force plates. The flexor digitorum brevis and the flexor hallucis brevis in both legs were simultaneously stimulated using a transcutaneous FES device. The muscles were stimulated 20 times at random intervals with four different stimulation intensities. We demonstrated that the toe muscle activity induced by electrical stimulation evoked COP displacement, which generated body acceleration. As expected, a larger stimulation induced a larger COP movement and acceleration. Therefore, we propose the use of FES-induced contractions of the toe muscles as a means to control balance during FES-assisted quiet standing. Spinal cord-injured and severe-stroke patients could benefit from this electrical stimulation technique for improving FES-assisted standing.