THE EFFECT OF STATIC STRETCH AND DYNAMIC-RANGE OF MOTION TRAINING ON THE FLEXIBILITY OF THE HAMSTRING MUSCLES

To date, limited information exists describing a relatively new stretc hing technique, dynamic range of motion (DROM). The purpose of this st udy was to compare the effects of DROM with static stretch on hamstrin g flexibility. Fifty-eight subjects, ranging in age from 21 to 41 year s and with limited hamstring flexibility (defined as 30 degrees loss o f knee extension measured with the femur held at 90 degrees of hip fle xion), were randomly assigned to one of three groups. One group perfor med DROM 5 days a week by lying supine with the hip held in 90 degrees of flexion. The subject then actively moved the leg into knee extensi on (5 seconds), held the leg in end range knee extension for 5 seconds , and then slowly lowered the leg to the initial position (5 seconds). These movements were performed six times per session (30 seconds of t otal actual stretching time). The second group performed one 30-second static stretch, 5 days per week. The third group served as a control group and did not stretch. Before and after 6 weeks of training, flexi bility of the hamstring muscles was determined in all three groups by measuring knee extension range of motion (ROM) with the femur maintain ed in 90 degrees of hip flexion. Data were analyzed with a 2 x 3 (test x group) two-way analysis of variance (ANOVA) with repeated measures on one variable (test) and appropriate post hoc analyses. The results of the two-way ANOVA revealed a significant interaction. Further stati stical post hoc analysis of data to interpret the interaction revealed significant differences between the control group (gain = 0.70 degree s) and both stretching groups, as well as a significant difference bet ween the static stretch group (gain = 11.42 degrees) and the DROM grou p (gain = 4.26 degrees). The results of this study suggest that, altho ugh both static stretch and DROM will increase hamstring flexibility, a 30-second static stretch was more effective than the newer technique , DROM, for enhancing flexibility Given the fact that a 30-second stat ic stretch increased ROM more than two times that of DROM, the use of DROM to increase flexibility of muscle must be questioned.