Sex Differences In Hamstring Strength Following 6 Weeks Of Eccentric Training

The Nordic hamstring exercise (NHE) and Romanian deadlift (RDL) are hamstring-focused exercises, with the NHE mainly used for injury prevention and RDL for strength training. While general resistance training shows minimal sex-based differences in lower-body strength changes, research on sex-specific adaptations to hamstring-targeted eccentric training in adults is limited. Understanding these differences could refine injury prevention and training strategies across sexes. PURPOSE: To investigate sex-specific differences in hamstring strength following a 6-week eccentric hamstring training intervention. METHODS: Participants completed three-repetition maximum (3RM) testing for RDL with a standard 20 kg Olympic barbell and NHE using the Nordbord (Vald Performance, Queensland, Australia). They were then randomly assigned to either RDL or NHE groups for 6 weeks of supervised training. Post-intervention 3RM RDL and NHE strength were reassessed. Separate linear mixed-effects models were run to assess differences in 3RM RDL and NHE peak force percent strength change by sex and between groups. Data are summarized as mean (standard deviation) and model estimate percent change [95% confidence interval]. RESULTS: A total of 27 participants were included across the RDL (n = 13, females = 7, age = 20.5 (1.1) years, body mass = 69.7 (4.8) kg, height = 172 (9.1) cm) and NHE groups (n = 14, females = 8, age = 21.1 (1.2) years, body mass = 70.1 (1.8) kg, height = 170.3 (10.9) cm). No differences in strength changes were observed between sexes in 3RM RDL (females: 15.7% [9.8, 21.7], males: 20.2% [13.9, 26.5], p = 0.51) or NHE peak force (females: 13.5% [7.53, 19.4], males: 18.0% [11.71, 24.2], p = 0.23). CONCLUSIONS: The 6-week intervention produced comparable strength gains increases across sexes, suggesting that the NHE and RDL are both effective exercises for increasing eccentric knee flexor strength. These data suggest strength training regimens can interchangeably use these exercises. It is unclear if sex-specific differences exist in modifying hamstring injury risk factors (e.g., fascicle length). Future research should examine longer intervention durations and additional sex-specific factors influencing strength adaptations to further refine injury prevention and eccentric training strategies across sexes.