Repetitive Peripheral Magnetic Stimulation (15 Hz RPMS) of the Human Soleus Muscle did not Affect Spinal Excitability.

The electric field induced by repetitive peripheral magnetic stimulation (RPMS) is able to activate muscles artificially due to the stimulation of deep intramuscular motor axons. RPMS applied to the muscle induces proprioceptive input to the central nervous system in different ways. Firstly, the indirect activation of mechanoreceptors and secondly, direct activation of afferent nerve fibers. The purpose of the study was to examine the effects of RPMS applied to the soleus. Thirteen male subjects received RPMS once and were investigated before and after the treatment regarding the parameters maximal M wave (Mmax), maximal H-reflex (Hmax), Hmax/Mmax-ratio, Hmax and Mmax onset latencies and plantar flexor peak twitch torque associated with Hmax (PTH). Eleven male subjects served as controls. No significant changes were observed for Hmax and PTH of the treatment group but the Hmax/Mmax-ratio increased significantly (p = 0.015) on account of a significantly decreased Mmax (p = 0.027). Hmax onset latencies were increased for the treatment group (p = 0.003) as well as for the control group (p = 0.011) while Mmax onset latencies did not change. It is concluded that the RPMS protocol did not affect spinal excitability but acted on the muscle fibres which are part of fast twitch units and mainly responsible for the generation of the maximal M wave. RPMS probably modified the integrity of neuromuscular propagation. Key pointsRPMS probably did not affect spinal excitability.Data suggested that RPMS likely acted on the muscle fibres which are part of fast twitch units and mainly responsible for the generation of the maximal M wave.RPMS probably modified the integrity of neuromuscular propagation.