Acute effects of static stretch on the static and dynamic balance indices in the young healthy non-athletic females

Applying static stretch before sport activities has been emphasized to improve range of motion، flexibility and muscle performance and also to reduce pain and muscle stiffness. Regarding to the controversies about the effect of static stretch and the importance of the balance control to prevent injuries during sport activities، this study was designed to investigate the effect of short and long duration static stretch on the static and dynamic balance indices. 45 young healthy non-athletic females were assigned to one of the three; a) 15 seconds static stretch، b) 45 seconds static stretch and c) control groups. Three set of 15 or 45 seconds static stretch exercise were applied over the Hamstring، Quadriceps and Gastrocnemius muscles of both lower limbs of the experimental groups، while no static stretch was applied for the control group. Before and after the intervention، static and dynamic balance indices including; overall، anterior-posterior and medial-lateral balance indices، were measured in all groups by Biodex SD machine. Our findings showed decreased overall، anterior-posterior and medial-lateral dynamic balance indices in the 45 second stretch group compared to the 15 seconds stretch group (P<0. 0001) and also the control group (P=0. 003)، while no significant differences in balance indices were seen between 15 seconds and control groups. The results may indicate that long duration static stretch exercises may disturb the function of the dynamic balance and so may cause sport injuries in athletics. Further studies are needed to investigate the specific effect of static stretch in the different type of sport activities