Sympathetic responses to repetitive trans-spinal magnetic stimulation.

PURPOSE: Electromagnetic fields have been administered, with mixed success, in order to treat a variety of ailments. Transcranial magnetic stimulation (TMS) elicits brief changes in peripheral sympathetic nervous system (SNS) activity. The purpose of this study was to explore the utility of repetitive trans-spinal magnetic stimulation (rTSMS) for acute and prolonged modulation of SNS in adult humans. METHODS: 23 healthy men and women were randomly assigned to receive either rTSMS (figure-eight coil aligned with the sixth and seventh cervical vertebrae; 10 Hz; n = 14, at 100% intensity of stimulator output) or sham stimulation (n = 13). RESULTS: Compared with sham, rTSMS did not affect skeletal muscle SNS activity (via microneurography) during the 60-s or 10-min period following stimulation. rTSMS also had no effect on R-to-R interval (RR(int)) and standard deviation of RR(int) (a marker of heart rate variability), blood pressure or plasma concentrations of norepinephrine, epinephrine, insulin and glucose (condition/time interaction, all P > 0.10). CONCLUSION: These data suggest that rTSMS does not influence SNS in adults. While rTSMS represents a novel application of TMS technology, further study and perhaps modification of the technique is required before use in clinical studies of peripheral SNS function.