Localised application of vibration improves passive knee extension in women with apparent reduced hamstring extensibility: a randomised trial

QuestionDoes the localised application of vibration over the hamstrings improve hamstring extensibility?DesignRandomised controlled trial with concealed allocation, intention-to-treat analysis, and assessor blinding.Participants30 non-athletic females (aged 18–22 yrs) with limited hamstring extensibility bilaterally.InterventionThe experimental group received 3 sessions of localised application of vibration per week for 8 weeks. At each session, 3 sets of vibration were applied over the left and right hamstring muscles. The control group continued their usual daily activities. Both groups were asked to perform no specific exercises during the 8-week intervention period.Outcome measuresHamstring muscle extensibility was measured bilaterally at baseline and at the end of the 8-week intervention period by measuring passive knee extension in supine with 90 deg of hip flexion.ResultsAt baseline, the mean lack of knee extension was 27 deg (SD 9) in the experimental group and 24 deg (SD 8) in the control group. At 8 weeks, this had changed to 13 deg (SD 5) in the experimental group and 23 deg (SD 9) in the control group. This was a significant treatment effect: mean between-group difference of 13 deg (95% CI 11 to 16).ConclusionAn 8-week regimen of localised application of vibration over the hamstring muscles significantly reduces knee extension lack in women with reduced range on the passive knee extension test.Trial registrationIRCT201011031254N6.