American Football Position Does Not Influence Symmetry in Joint Power During High-Speed Running

Introduction: The distinct physical and tactical roles of American football positions may influence interlimb symmetry of ankle, knee, and hip power distribution during high-speed running. This study examined differences in joint power distribution symmetry between position groups and joints using inverse dynamics. Methods: Sixty-eight draft-eligible American football players (Big n=18; Big-skill n=24; Skill n=26) completed a single high-speed running trial (6.4 m/s) on an instrumented treadmill synchronized with a motion capture system. Joint powers were computed via inverse dynamics and expressed as positive (generation) and negative (absorption) percent contributions to total limb power. Interlimb differences were quantified using the Asymmetry Index (AI = |left−right|/[(left+right)/2] ×100%). Group differences were analyzed using Kruskal-Wallis tests with Bonferroni-adjusted post hoc comparisons (α = .017). Results: No significant differences in AI were found among position groups for positive ankle (p = .868), knee (p = .082), or hip power (p = .846), nor for negative ankle (p = .222), knee (p = .181), or hip power (p = .496). AI differed significantly among joints for both positive (F(2,134)=33.4, p