Comparison of the effects of modified razor curl and nordic hamstring exercises on hamstring muscle strength and posterior-chain endurance in male football players

The aim of this study is to compare the effects of 6-week modified razor curl and nordic hamstring exercise (NHE) protocols on eccentric peak torque, relative muscle strength, bilateral strength difference, and trunk-hip extensor endurance in active male football players. A total of 45 licensed male football players aged 18–23 years participated in the study. The mean age, height, and baseline body weight were 19.17 ± 1.28 years, 177.11 ± 5.05 cm, and 67.68 ± 6.39 kg, respectively. Participants were randomly assigned to a control group (CG) that performed football training only, a Nordic Hamstring Exercise Group (NHEG) that performed NHE in addition to football training, or a Modified Razor Curl Exercise Group (MRCEG) that performed MRCE in addition to football training. The exercise groups completed their respective protocols three days per week for six weeks. Hamstring strength was assessed using the H-Bord device, while static endurance of the lower-back, hip, and core muscles was evaluated using the Superman test before and after the intervention. A two-way repeated-measures ANOVA was used to examine pre–post changes and the group×time interaction. Significant group×time interactions were observed for dominant-leg peak torque (F = 21.61, p < 0.001, ηp²= 0.50), non-dominant-leg peak torque (F = 20.96, p < 0.001, ηp²=0.49), dominant-leg relative strength (F = 25.75, p < 0.001, ηp²= 0.54), non-dominant-leg relative strength (F = 24.04, p < 0.001, ηp² = 0.52), and Superman test performance (F = 12.95, p < 0.001, ηp²= 0.37). No significant group×time interaction was found for bilateral strength difference (F = 1.11, p = 0.338 η p 2 = 0.049). Both the modified razor curl and nordic hamstring exercise protocols improved eccentric hamstring strength and trunk-hip extensor endurance in male football players. The MRCE may represent a practical alternative to the NHE and allow a greater training volume.