The Effects of Static Stretch Duration on the Flexibility of Hamstring Muscles

The effects of duration of a static stretching protocol (Intervention) on hamstrings tightness were evaluated. Sixty purposively sampled subjects with unilateral hamstring tightness that had no history of low back and lower extremity dysfunctions that necessitated medical intervention participated in the study. They were randomly assigned into one of 5 intervention and one control groups. Groups a, b, c, d, e subjects had their hamstrings passively stretched for 120, 90, 60, 30, and 15 seconds respectively, while group f served as control. This intervention was carried out on alternate days for 6 consecutive weeks. Knee extension deficit (KED) was measured for all groups at baseline, weekly and 7 days post cessation of the intervention (carry-over). Data were analysed using one-way ANOVA and paired t-test at 0.05 alpha. Asignificant reduction (P<0.05) was observed in the KED of subjects in all the intervention groups across the 6 intervention weeks. There was no significant difference between the immediate post intervention and carry-over KED values (p>0.05). The study shows that statically stretching tight hamstrings for any duration between 15 and 120 seconds on alternate days for 6 weeks would significantly increase its flexibility. The effect was also sustained for up to 7 days post intervention.