Impact of Nordic hamstring breaking point angle on football player performance

Abstract

Background: Football demands both aerobic and anaerobic capacities due to its dynamic movements, which include jumps, directional changes, ball control, and sprints. The Nordic hamstring exercise (NHE) enhances eccentric strength, which is crucial for high-intensity movements. However, the relationship between Nordic breaking point angle (NHEbpa), which is associated with eccentric hamstring peak torque during Nordic hamstring exercise, and sprint, countermovement jump (CMJ), and change of direction (COD) speed in soccer players has not been sufficiently investigated.

Objective: This analysis examines the relationship between the Nordic breaking point angle and critical performance indicators-sprint speed, COD ability, and vertical jump-in football players.

Methods: Fifty-eight male soccer players volunteered for the study. Assessments included anthropometric measurements, CMJ tests, 10-20-30 m sprint tests, and COD (zig-zag) tests. NHEbpa was measured using motion analysis software. Correlation analysis was used to determine the relationship between variables. A multiple linear regression analysis was conducted to evaluate the individual effects of the sprint, CMJ, and COD performances on NHEbpa, with data analyzed using JASP 0.18.

Results: Correlation analysis showed strong positive correlations between NHEbpa and sprint performances (r = 0.633 to 0.666), moderate negative correlation between NHEbpa and CMJ (r = -0.406), and moderate positive correlation between NHEbpa and COD (r = 0.580). Regression analysis results were used to analyze the independent coefficients of multiple variables more comprehensively, revealing significant predictors for performance: 20-m sprint (β = 24.166, p = 0.030), 10-m sprint (β = 22.564, p = 0.047), 30-m sprint (β = 10.677, p = 0.027), and CMJ (β = 4.974, p = 0.034). Conversely, COD performance (β = -0.154, p = 0.470) did not demonstrate a significant effect.

Conclusions: The study identified significant relationships between NHEbpa and sprint/CMJ performances (p < 0.05), while no meaningful effect was observed for COD speed (p > 0.05). These findings highlight the importance of eccentric strength in sprint performance, suggesting that other factors may play a more prominent role in COD. Incorporating eccentric-focused training, particularly through Nordic exercises, is recommended to enhance sprint performance and hamstring strength, which are essential for football players.

Keywords: Change of direction; Hamstring muscle strength; Nordic Hamstring breaking point angle; Performance in football players.

Figure 1. Research design.

Figure 2. Residual plot showing the relationship between residuals of the NHEbpa and residuals of 10-m, 20-m, 30-m sprint, COD, and CMJ performance.

The red line represents the linear trend of the residuals, and the dashed blue lines represent confidence intervals or limits of variability.

Figure 3. Residual graph showing the relationship between 10 m, 20 m, 30 m sprint, COD, and CMJ performance residuals and the NHEbpa.

The red line represents the linear trend of the residuals, and the dashed blue lines represent confidence intervals or limits of variability.