Résumé
Relative age effects (RAE), usually reflected in overrepresentations of athletes born early in the selection year, have been documented in physically demanding sports. While theoretical models suggest RAE depend on interactions between individual, task, and environmental constraints, evidence in lacrosse remains limited.
We analyzed birth distributions of 6,545 youth lacrosse players (2,476 men, 4,069 women) from the USA Lacrosse National Team Development Program (NTDP) (2019-2024 U15/U17 in 2019, 2021–2024 U16/U18). The NTDP is an annual cycle consisting of three stages: regional ID clinics, combine, and Youth National Team selection. Bayesian hierarchical logistic regression models examined binary outcomes (made the combine, made the Youth National Team) predicted by relative age (days from cutoff date), gender, and their interaction. Models included year-specific intercepts and RAE effects to account for temporal variation
Quartile 1 (September-November) players were overrepresented in regional ID clinics (1.20x expected). However, relative age provided no advancement advantage for either gender. Gender-specific analyses revealed minimal effects for both women (ID to combine: β = -0.017, 95% HDI: [-0.309, 0.280]; combine to team: β = 0.014, 95% HDI: [-0.400, 0.406]) and men (ID to combine: β = 0.138, 95% HDI: [-0.183, 0.460];combine to national team: β = 0.060, 95% HDI: [-0.310, 0.434]) with all intervals including zero.
RAE within the USA Lacrosse NTDP appears limited to players attending regional ID clinics . Once players enter the system, selection shows no bias toward relatively older athletes . Therefore, relatively younger players should be encouraged to attend ID clinics.
