Comparison of cyclic and sustained passive stretching using a mechanical device to increase resting length of hamstring muscles

The purpose of this study was to compare the effects of cyclic versus sustained passive stretching with a mechanical device on resting hamstring muscles' length. Group 1 subjects (5 men, 17 women) underwent cyclic stretching of their right hamstring musculature, and Group 2 subjects (5 men, 16 women) underwent sustained stretching of their right hamstring musculature. The stretching procedures were performed for 15 minutes on 5 consecutive days. A follow-up examination of the subjects' relative knee flexion range of motion was made one week posttreatment. The Group 1 subjects had a mean ROM increase of 15.4 +/- 5.0 degrees after the five stretching treatments and maintained a mean ROM increase of 10.4 +/- 5.5 degrees on the follow-up examination (p less than .001). In Group 2, the five stretching treatments resulted in a mean ROM increase of 13.4 +/- 4.4 degrees, and a mean increase of 7.9 +/- 4.0 degrees was maintained on the follow-up examination (p less than .001). Linear regression analysis revealed that initial ROM, sex, and treatment method significantly contributed to increases in ROM from Day 1 of treatment to the follow-up examination (F = 6.04; df = 4,36; p less than .0008). The cyclic stretching method resulted in a greater gain in ROM when the other variables were considered. Predicted values of ROM increases were also examined and discussed.