Comparison Between Different Eccentric Exercises and Static Stretching Exercise on Hamstring Flexibility: A Randomized Controlled Trial

Abstract

Background and Objective: Hamstring strain is one of the most common sports injuries contributed by lack of hamstring flexibility as one of the injury risks factors. Eccentric training could serve to reduce the risk of hamstring strain by improving hamstring flexibility. However, the effectiveness of different eccentric hamstring exercise in improving hamstring flexibility is still understudied. The aim of this study is to compare the effectiveness of eccentric exercises and static stretching exercise on hamstring flexibility of recreational athletes. Methods: A randomized controlled trial was carried out to examine the effects of Nordic Hamstring Exercise (NHE) and Sliding Leg Curls (SLC) on hamstring flexibility of recreational athlete for four weeks. Participants with hamstring tightness were classified as sit and reach test score for less than 30cm for males and 33cm for females. Participants were randomly assigned using sequentially numbered, opaque, and sealed envelopes to three equal groups (n = 15 for each group): NHE, SLC and Static Stretching (SS). Assessor was blinded from participants’ group assignment. Results: A total of 45 recreational athletes (28 male and 17 female), mean age 20.36 ± 1.25 years participated in the study. There was no difference between eccentric hamstring (NHE and SLC) and static stretching exercise in improving hamstring flexibility (p = 0.82). NHE and SLC exercises are equally effective in increasing hamstring flexibility [NHE: p < 0.0001, ES = 0.90, 95% CI (4.36, 6.77); SLC: p < 0.0001, ES = 0.70, 95% CI (4.26, 6.09)], as to static stretching [SS: p < 0.0001, ES = 0.62, 95% CI (3.18, 4.71)]. Conclusion: Eccentric hamstring exercises are equally effective as static stretching in improving hamstring muscle flexibility.