Author(s): PAIZIS, C., CUKOVÁ, J., TIMBERT, T., COMETTI, C., HITIER, M., BABAULT, N., Institution: UNIVERSITY OF BURGUNDY - LABORATOIRE INSERM, Country: FRANCE, Abstract-ID: 2501

INTRODUCTION:
When applied to a muscle, local vibration (LV) can decrease its maximum force output. Previous studies indicate that the magnitude of force reduction increases with longer durations of vibration exposure. Beyond force modulation, LV has also been shown to increase range of motion (ROM) and decrease passive torque. Whether LV modulates maximal force production and ROM when applied to the tendons remains unclear due to inconsistent LV parameters and its frequent application following exercise sessions or in combination with stretching interventions. To the best of our knowledge, no study has investigated the acute effects of prolonged LV applied to the hamstring tendons during rest. Therefore, the objective of this study was to investigate the effects of a 30-min tendon LV on maximal voluntary isometric contraction, ROM, and passive torque at rest.
METHODS:
17 recreationally active adults participated in a randomized cross-over study. Each participant completed two experimental sessions separated by at least 48 hours, one with local vibration (LV), and one control condition (CC). LV (100 Hz, 2-3 mm) was applied for 30 minutes to the distal tendons of the biceps femoris and semitendinosus while participants remained in a passive seated position. Surface electromyographic (sEMG) activity was recorded to verify muscle relaxation during both conditions. Maximal voluntary isometric contraction (MVIC), ROM, and passive torque during a passive knee extension test were assessed 1 min before and immediately after each condition. A repeated-measures ANOVA was used to examine the effects of Time and Condition.
RESULTS:
The ANOVA revealed a significant main effect of Time for ROM (p = 0.045), indicating an increase from pre- to post-measurement independently of the condition. No significant main effect of Condition (p = 0.227) nor Time × Condition interaction (p = 0.995) was observed. Passive torque showed no significant effects of Time (p = 0.536), Condition (p = 0.803), nor interaction (p = 0.646). For MVIC, a significant main effect of Time was detected (p = 0.001), reflecting a decrease in maximal voluntary strength from pre- to post-measurement independently of the experimental condition. No significant main effect of Condition (p = 0.548) nor Time × Condition interaction (p = 0.815) was found.
CONCLUSION:
The results suggest that prolonged tendon-targeted LV alone does not induce acute changes in hamstring flexibility or passive mechanical properties compared to the control condition, whereas strength performance declines over time regardless of intervention. Further research should examine whether LV applied to tendons or muscles yields similar neuromuscular adaptations under different vibration frequencies and application parameters.