Effect of focal muscle vibration on sEMG activity during repeated elbow movements in healthy adults

Focal muscle vibration (FMV) is a non-invasive intervention that can modulate neuromuscular excitability, traditionally assessed with electrostimulation-evoked responses like F-waves or H-reflexes, which can be uncomfortable and impractical for many populations. Although the effects of FMV on targeted muscles have been well characterized, its impact on antagonist muscles, particularly during recovery after stimulation, remains poorly understood. Surface electromyography (sEMG) offers a non-invasive and clinically accessible method to assess these short-term changes and guide FMV-based interventions.

30 healthy adults participated in a within-subjects crossover design with two sessions (control and FMV) separated by at least 24 h. Both sessions began with a baseline recording of triceps sEMG during repeated elbow flexion-extension movements to assess initial muscle activation. In the FMV session, focal vibration (120 Hz, 1.2 mm amplitude) was applied to the biceps brachii (agonist) for 5 min immediately after baseline, whereas in the control session, participants rested quietly for the same duration. In both sessions, triceps brachii (antagonist) activity was recorded using sEMG every 5 min over a 30-minute follow-up period, resulting in 7 trials. Root mean square (RMS) values were computed for each trial and expressed as post-baseline ratios. Intragroup effects were analyzed using linear mixed-effects models to account for repeated measures. Intergroup differences (FMV vs. control) were evaluated using paired t-tests or Wilcoxon signed-rank tests when normality was violated. All resulting p-values were adjusted using the Benjamini-Hochberg procedure to control the false discovery rate.

FMV induced a significant and sustained reduction in triceps RMS ratios, lasting up to 20 min post-intervention (p < 0.05). The control session showed no significant changes. Intergroup comparisons revealed lower RMS ratios in the FMV session at several follow-up time points (p < 0.05), which remained significant after the p-value adjustment.

The findings support the hypothesis that FMV applied to the agonist muscle can transiently attenuate antagonist (triceps) muscle activity. sEMG proved to be a suitable and accessible method for detecting vibration-induced changes in muscle activation. This neuromodulatory effect may represent a promising tool for future rehabilitation or motor training strategies aimed at enhancing neuromuscular control and functional recovery.