# Temporal Modulation of Corticospinal Excitability by Repetitive Peripheral Magnetic Stimulation in Healthy Young Adults

## TL;DR

This study explores how repetitive peripheral magnetic stimulation affects corticospinal excitability in the tibialis anterior muscle of healthy young adults.

## Contribution

The study investigates the short-term effects of rPMS on lower-limb corticospinal excitability, which has been less studied than upper-limb effects.

## Key findings

- rPMS produced a modest, side-specific increase in corticospinal excitability lasting up to 60 minutes.
- The largest increase in motor evoked potential amplitude occurred 30 minutes post-stimulation.
- No significant changes were observed in MEP latency or duration.

## Abstract

Background: Repetitive peripheral magnetic stimulation (rPMS) delivers magnetic pulses to peripheral nerves and muscles, producing afferent input that can modulate corticospinal excitability (CSE). While the effects of rPMS on upper-limb muscles have been explored, its short-term effects on lower-limb CSE remain less understood. This study aimed to investigate the short-term effects of rPMS on CSE in the tibialis anterior (TA) muscle among healthy individuals. Methods: Twenty participants completed a repeated- measure, pre-post study. rPMS was applied to the non-dominant TA muscle at 10% above motor threshold for 15 min. CSE was assessed using transcranial magnetic stimulation (TMS), with measurements of motor evoked potential (MEP) amplitude, latency, and duration recorded at baseline, immediately after, 30 min, and 60 min post-stimulation. All analyses were conducted on clean datasets following removal of artifact-related outliers. Results: MEP amplitude showed a significant main effect of Side (p = 0.005), with greater values on the stimulated compared to the non-stimulated side. No significant main effects were found for Time (p = 0.351) or for the Side × Time interaction (p = 0.900). Descriptively, the largest increase in amplitude on the stimulated side was observed at 30 min post-stimulation (12% above baseline). MEP latency and duration showed no significant main or interaction effects. Conclusions: In conclusion, a single rPMS session applied to the TA produced a modest, side-specific increase in CSE lasting up to 60 min, as reflected in MEP amplitude. However, the absence of a significant time effect and perhaps non-optimized stimulation parameters limit the interpretation of sustained neuromodulatory effects. Future studies should examine optimal stimulation parameters and explore underlying mechanisms using measures such as the cortical silent period and interhemispheric inhibition.