In 2004 a study conducted by Russell T. Nelson and William D. Bandy, et. al., the effectiveness of eccentric training and static stretching in enhancing hamstring flexibility among high school males was thoroughly examined. The objective was to ascertain whether a 6-week eccentric exercise regimen could bring about notable improvements in flexibility. Additionally, the study aimed to compare these changes with those resulting from a similar duration of static stretching and a control group that received no stretching intervention.

Employing a test-retest control group design within a laboratory setting, a total of 69 male subjects, with an average age of 16.45 years and exhibiting limited hamstring flexibility, were recruited. Limited flexibility was defined as a loss of 20 degrees in knee extension with the thigh maintained at 90 degrees of hip flexion.

The measurement of hamstring flexibility was conducted using the passive 90/90 test both before and after the 6-week intervention period. Results revealed significant differences in the test outcomes and the test-by-group interactions.

Further analysis indicated that both the eccentric training and static stretching groups exhibited substantial gains in hamstring flexibility compared to the control group, which experienced a minimal increase of 1.67 degrees. Notably, there was no statistically significant difference between the improvements observed in the eccentric training group (12.79 degrees) and the static stretching group (12.05 degrees).

These findings suggest that the gains achieved in knee extension range of motion, indicative of enhanced hamstring flexibility, were comparable between eccentric training and static stretching regimens. Consequently, high school male athletes seeking to improve hamstring flexibility may benefit equally from either of these interventions.

This study sheds light on the efficacy of different training modalities in improving flexibility among young athletes, providing valuable insights for coaches, trainers, and practitioners involved in sports performance enhancement and injury prevention programs.

Reference: Nelson, R. T., & Bandy, W. D. (2004). Eccentric training and static stretching improve hamstring flexibility of high school males. Journal of athletic training, 39(3), 254.