Eccentric Hamstring Strength Asymmetry among Football and Soccer Athletes

Case StudiesSep 13, 2024Last Updated: Oct 23, 2024

Study Information

Benson, E. M., Elphingstone, J. W., Paul, K. D., Schick, S., Shihab, Y. A., Barlow, D., Ponce, B. A., Brabston, E. W., & Momaya, A. M. (2024). Eccentric Hamstring Strength Imbalance among Football and Soccer Athletes. Southern Medical Journal, 117(4), 214-219.

https://doi.org/10.14423/smj.0000000000001674

Purpose of the Study

The study investigates hamstring strength asymmetries in soccer and American football athletes, focusing on how these asymmetries vary with age, sex, sport and skill level. Hamstring strain injuries (HSI) are common in these sports and eccentric strength asymmetry is a contributing factor for HSI. The research aims to determine whether high school athletes show greater asymmetry compared to collegiate and professional athletes and if soccer athletes exhibit greater hamstring asymmetry than American football athletes.

Methods and Key Findings

Participants included 632 athletes, encompassing high school, collegiate and professional soccer, and American football players. The Nordic test was conducted on the NordBord to measure peak force (N), torque (N·m) and impulse/work (N·s). Data on age, sex, weight, sport specialization and sport level were recorded. Hamstring asymmetry (%) was calculated as the absolute value of the difference in leg forces divided by their sum. One-way Analysis of Variance (ANOVA) and independent sample t-tests were used for comparisons.

Key findings include:

High school soccer players exhibited significantly greater hamstring asymmetry for torque (P = 0.030) and work (P < 0.01) compared to American football athletes (Figure 1).
Male high school soccer players showed higher hamstring asymmetry for maximum force (P = 0.035), torque (P = 0.018) and work (P = 0.033) compared to collegiate and professional soccer players.
Female high school soccer players had significantly higher hamstring asymmetry for torque (P = 0.045) and work (P = 0.001) than collegiate soccer players.
Football athletes did not show significant changes in force asymmetry across different skill levels.

Boxplots showing the percentage of asymmetry in maximum force, torque and work across different sports groups. Panel A displays the data for high school athletes, while Panel B presents the data for college athletes. Statistically significant differences (p < 0.05) are indicated by asterisks, with more asterisks representing higher levels of significance.

VALD’s Solution

The NordBord allows for fast and accurate testing of hamstring strength in the field. Data can be quickly visualized in the app for real-time player monitoring to identify changes in strength asymmetry over time. Additionally, group data can be examined in detail on VALD Hub. This enables coaches and practitioners to identify athletes with significant asymmetries relative to the group, facilitating targeted interventions to reduce injury risks and improve performance.