Differential effects of two different Nordic hamstring exercise protocols on physical performance in male athletes: a randomized clinical trial

Abstract Purpose To compare the effects of two NHE protocols, applied once or twice a week for 10 weeks, on the physical performance of male intermittent sports athletes. Methods This randomized clinical trial has parallel arms and a balanced distribution. Thirty-five amateur male intermittent sports athletes were randomized and allocated to two experimental conditions: practicing NHE once a week (G1, n = 18) or twice a week (G2, n = 17), for 10 weeks. Due to dropouts during the intervention period, the final analysis included 17 athletes (G1, n = 7; G2, n = 10). Participants were evaluated before and after the interventions, by measuring hamstring muscle capacity levels (primary outcome), flexibility, jump height, velocity, and change-of-direction (secondary outcomes). The primary and secondary outcomes were compared between the groups using repeated-measures two-way ANOVA, and Bonferroni’s post hoc test. Results G1 and G2 significantly changed the hamstring muscle capacity after the NHE intervention protocol ( p = 0.047; η 2 p = 0.238). Although both groups improved after the intervention, no significant interaction effect between group and time was observed, indicating similar responses to the interventions ( p = 0.142; η 2 p = 0.138). The same trend remained for the other variables, in which no significant differences were revealed between the groups. Conclusion NHE resulted in similar hamstring muscle capacity in the group that performed it once or twice a week. Relative to other physical performance outcomes, applying it once or twice a week has induced similar results. Trial registration Brazilian Registry of Clinical Trials (ReBEC): RBR-8mdbmcp (03/17/2021).