Normalized Eccentric Hamstring Strength in Collegiate American Football: Position-Based Norms and Longitudinal Patterns

ABSTRACT: Wilwand, M, VanderAkker, J, Guymon, I, Mortensen, BB, and Johnson, AW. Normalized eccentric hamstring strength in collegiate American football: Position-based norms and longitudinal patterns. J Strength Cond Res XX(X): 000-000, 2026-The purpose of this study was to (1) establish normative values for eccentric hamstring strength in collegiate American football players; (2) evaluate how normalized strength differs by player position, age, and team affiliation; and (3) assess longitudinal changes across competitive seasons. Eccentric hamstring strength was measured in 332 National Collegiate Athletic Association Division I athletes from 4 teams using the NordBord device and normalized to body mass (N·kg-1). A multiple linear regression identified significant predictors of normalized strength, and longitudinal data from 2 teams (n = 50; 15% of the full sample) were analyzed across 3 seasons using repeated measures analysis of variance. Results showed that skill, power, and special teams athletes had significantly greater normalized strength than linemen (p < 0.001), and that age (p = 0.04) and team affiliation, specifically Teams B (p < 0.001) and D (p < 0.001) compared with Team A, were also significant predictors. Effect sizes indicated small-to-large magnitudes of difference between position groups. Post hoc analyses revealed that the skill group had significantly greater strength than the power group (p = 0.008), while the special teams group did not differ significantly from the skill group (p = 0.18). Athletes from 2 teams exhibited lower normalized strength than their peers. Longitudinal analysis showed no significant changes in normalized strength over time (p = 0.89), and trivial effect sizes were observed, suggesting that substantial changes are unlikely within this experienced athlete population. These findings support the use of normalized-rather than absolute-eccentric strength values and highlight meaningful differences by position and program. Practical applications include using position-specific benchmarks to guide individualized training, rehabilitation, and return-to-play strategies aimed at optimizing performance and reducing injury risk in American football athletes.