Effect of physical activity on paired-pulse suppression in the somatosensory cortex after tibial nerve stimulation

Paired-pulse somatosensory evoked potentials (ppSEPs) offer a robust, non-invasive measure of inhibitory interactions in the human somatosensory cortex. The impact of long-term habitual physical activity on gating mechanisms remains poorly understood. This study quantified whether regular physical activity over extended periods modulates paired-pulse suppression (PPS) after tibial nerve (TN) stimulation and whether PPS relates to weekly training volume. Fifty-nine healthy participants (29 female; 22.4 ± 3.9 years) were analyzed. Physical activity over the previous two years was assessed by questionnaire and participants were classified as physically active (PA, n = 38) if they reported more than 1.25 h/week of regular training during this period. All others were classified as non-active (NA, n = 21) participants. Single-pulse (spSEP) and ppSEPs were recorded bilaterally after suprathreshold TN stimulation using a Cz'-Fz montage. Across all participants tested, significant PPS was observed for N30/P40, P40/N50 and N50/P60 ppSEP amplitudes after both left and right TN stimulation. However, PPS and spSEP did not differ between PA and NA. PPS in right N30/P40 correlated negatively with weekly training hours in PA. No such associations were found for P40/N50 or N50/P60, nor for left-sided PPS measures. Long-term physical activity does not seem to modulate SEP components or PPS after TN stimulation. However, training volume within PA was associated with PPS of the N30/P40 amplitude after right TN stimulation, indicating a potential selective dose-dependent modulation. Longitudinal studies are needed to establish causality, explain side-specific effects, and determine the behavioral relevance for sensorimotor performance.