Effects of vibration training on hamstring muscle shortness

Hamstring shortening may cause postural defect and gait abnormality. Recently, it has been shown that application of whole body vibration may increase muscle flexibility in normal subject. This study has been designed to find out the effect of local hamstring vibration on the hamstring shortening. 30 non-athletic females (aged 18-22 yrs) who suffered from hamstring shortness were participated in the study. They have been assigned in one of the two experimental groups: vibration group (3 times a week for 8 weeks) and control group (no intervention). The subjects in both groups were not allowed to perform any sport activity during 8 weeks of study. Before and after the intervention, the rate of hamstring muscle shortness was evaluated by passive knee extension (PKE) test. The findings showed that hamstring muscle length was increased significantly in the vibration group (p=0. 000), in term of decrease of knee joint angle during PKE test. While no significant change was found from the control group (p=0.181). Also vibration raised muscle flexibility on average 15 units while in control group it was only 0.73. This difference was statistically significant. Local hamstring vibration is a suitable method to improve hamstring shortening. It is recommended to combine this method with other muscle elongation methods to find the most beneficial method for muscle shortening.