Acute effects of whole-body vibration training with additional loading on lower limb muscle synergies during running

The aim of this study is to investigate the acute effects of loaded whole-body vibration (WBV) training on both the spatial (muscle weightings) and temporal (activation patterns) characteristics of lower-limb muscle synergies during running.

Thirty-nine healthy male recreational runners completed running biomechanics assessments before and after a single loaded WBV training session. The intervention comprised dynamic squats on a vibration platform (20 Hz, 6 mm) while wearing a weighted vest. Surface electromyography signals from lower-limb muscles were recorded and decomposed into muscle synergies using nonnegative matrix factorization. Pre- and post-intervention comparisons were conducted using paired-sample t-tests or Wilcoxon signed-rank tests.

Muscle synergy analysis consistently identified five synergies before and after the intervention. Compared with pre-intervention, muscle weights increased for medial gastrocnemius in SYN1 (p = 0.036), peroneus longus in SYN3 (p = 0.045), rectus femoris (p = 0.007), and vastus lateralis (p = 0.049) in SYN5, while those for the vastus medialis in SYN2 (p = 0.013) and vastus lateralis in SYN4 (p = 0.031) decreased. After the intervention, temporal parameters demonstrated a longer activation duration in SYN1 (p = 0.028), as well as earlier onset (p = 0.047), earlier offset (p = 0.033), and earlier peak activation (p = 0.041) in SYN3.

A single-loaded WBV session acutely reorganized muscle synergy, indicating rapid neural adaptations that may enhance propulsion efficiency and landing stability. Overall, these enhancements support the use of single-loaded WBV session as an effective warm-up strategy for running.