A comparative study of changes in Hmax/Mmax under spinning permanent magnet stimulation, repetitive peripheral magnetic stimulation, and transcutaneous electrical nerve stimulation in healthy individuals.

Abstract

We have developed a compact device using a spinning permanent magnet (SPM) that induces an electrical field by changing the magnetic flux. We hypothesized that SPM stimulation also reduced spasticity, comparable with repetitive peripheral magnetic stimulation (rPMS) and transcutaneous electrical nerve stimulation (TENS). This study evaluated the effect of a single session of SPM stimulation and compared it with those of rPMS and TENS in healthy individuals. Eleven healthy adult men participated in this study. The active electrode was placed on the soleus muscle, and the reference electrode was placed at 5 cm distal from the active electrode on the medial side of the Achilles tendon. The stimulating electrodes were fixed on the popliteal fossa to stimulate the tibial nerve. The maximum H-reflex (Hmax) and the maximum motor response (Mmax) were measured, and Hmax/Mmax was calculated under the following conditions: a) 15 min SPM stimulation, b) 30 min SPM stimulation, c) 10,000 pulses rPMS, d) 15 min TENS, and e) 15 min rest (control). The devices for SPM, rPMS, and TENS were applied to the belly of the soleus muscle in the prone position. Compared with the control, Hmax/Mmax significantly decreased under SPM stimulation for 15 and 30 min, as well as under rPMS and TENS (p < 0.005). The changes in Hmax/Mmax under 15 min SPM stimulation were significantly smaller than those under 30 min SPM stimulation and rPMS (p < 0.005). SPM stimulation reduced Hmax/Mmax in healthy individuals and is a potential new treatment for spasticity.