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Abstract
Background
Hamstring strain injuries are among the most common non-contact injuries in football and frequently result in prolonged absence from sport, high recurrence rates, and reduced athletic performance. Eccentric hamstring strengthening interventions, particularly Nordic Hamstring Exercise (NHE) and Leg Curl Exercise (LCE), have been widely implemented to reduce injury risk while enhancing physical performance. However, uncertainty remains regarding their comparative effectiveness across multiple performance and injury-related outcomes.
Objective
To systematically evaluate and quantitatively synthesize the effects of Nordic Hamstring Exercise and Leg Curl Exercise on performance enhancement and hamstring injury prevention in football players.
Methods
A systematic review and meta-analysis were conducted in accordance with the PRISMA 2020 guidelines. Six electronic databases (PubMed/MEDLINE, Scopus, Web of Science, Embase, SPORTDiscus, and Cochrane CENTRAL) were searched from database inception to March 31, 2026. Randomized controlled trials, quasi-experimental studies, and controlled clinical trials evaluating Nordic Hamstring Exercise and/or Leg Curl Exercise in football players were included. Random-effects meta-analyses were performed to calculate pooled Risk Ratios (RR), Standardized Mean Differences (SMD), or Mean Differences (MD) with corresponding 95% confidence intervals (CI). Methodological quality was assessed using the Cochrane RoB 2 and ROBINS-I tools, and the certainty of evidence was evaluated using the GRADE approach.
Results
Twenty-six studies involving 1,684 football players met the inclusion criteria, of which 22 studies were included in the quantitative meta-analysis. Eccentric hamstring strengthening interventions significantly reduced hamstring injury incidence (RR = 0.56; 95% CI: 0.43–0.72; p < 0.001; I² = 18%), corresponding to an approximate 44% reduction in injury risk. Significant improvements were also observed in sprint performance (SMD = −0.48; 95% CI: −0.71 to −0.25; p < 0.001), vertical jump performance (SMD = 0.39; 95% CI: 0.18–0.60; p < 0.001), change-of-direction ability (SMD = −0.36; 95% CI: −0.59 to −0.13; p = 0.002), eccentric hamstring strength (SMD = 0.92; 95% CI: 0.71–1.14; p < 0.001), and biceps femoris fascicle length (MD = 1.84 cm; 95% CI: 1.28–2.40 cm; p < 0.001). Subgroup analyses indicated that combined NHE and LCE interventions yielded the greatest improvements in sprint and jump performance, whereas NHE alone produced the largest reduction in hamstring injury incidence.
Conclusion
Nordic Hamstring Exercise and Leg Curl Exercise are effective eccentric strengthening interventions for reducing hamstring injury risk and enhancing football-specific performance. Nordic Hamstring Exercise demonstrated superior effectiveness for injury prevention and eccentric strength development, while combined intervention programs produced the greatest improvements in sprint and jump performance. Integrating structured eccentric hamstring training into football conditioning and rehabilitation programs may improve player performance while reducing injury burden.