The relationship between hamstring muscle shortness and dynamic and static balances in young healthy individuals

Impaired postural control affects the safety and quality of movements during daily life activities and physical exercises. One of the effective factors on postural control is the muscle flexibility. Despite the relative high incidence of hamstring shortness, no study has yet evaluated the relationship between hamstring shortness and dynamic and static balances. The aim of this study was to investigate the relationship between hamstring shortness and dynamic and static balances in young healthy individuals. This cross sectional study was carried on 40 healthy young subjects (20 cases with and 20 cases without the shortness of hamstring as control). The 90-90 test was used to measure the hamstring length. To evaluate the quality of balance control, subjects stood on a force plate and Biodex system on one foot and level of displacement of centre of pressure was used as an index of static and dynamic balances, with and without external perturbation. The comparison of mean and standard deviation of the center of pressure displacement with and without external perturbation, showed no significant difference between the two experimental and control groups. The results of present study showed that the hamstring shortness does not significantly affect the static and dynamic postural balance control.