The combined effects of transcutaneous spinal direct current stimulation and neuromuscular electrical stimulation on corticospinal excitability and gait performance in humans.

Abstract

Transcutaneous spinal direct current stimulation (tsDCS) and neuromuscular electrical stimulation (NMES) are beneficial rehabilitative techniques to increase neuronal excitability and improve motor function. However, the combined effects of tsDCS and NMES remain uncertain. The present study aimed to investigate the effects of tsDCS and NMES on corticospinal excitability and gait performance in two experiments. In experiment 1, 12 healthy participants received tsDCS + NMES, tsDCS + sham NMES, or NMES + sham tsDCS for 20 minutes on different days. We evaluated motor evoked potentials (MEPs) of the tibialis anterior muscle with transcranial magnetic stimulation before and after the intervention. In experiment 2, two hemiparetic stroke patients participated in a single-case design (ABABAB). They received NMES alone (A) or tsDCS + NMES condition (B) for 3 days each over 18 days. In experiment 1, tsDCS + NMES significantly increased MEPs at 15 minutes and 60 minutes after stimulation compared to the before stimulation levels (p＜0.05), whereas no changes were observed in the other conditions. In experiment 2, no changes in the maximum gait velocity and number of steps were observed after tsDCS + NMES condition compared to NMES alone. These findings suggest that tsDCS combined with NMES can increase corticospinal excitability in healthy individuals; however, the effects on gait performance were unclear. Further studies with a large sample size are needed to investigate the combined effects of these techniques on gait performance in stroke patients.