Relative Age-Related Performance Differences in Elite Orienteering: An Athlete-Level Analysis

Relative Age Effect (RAE) research has shown that individuals born early in the annual selection year may experience developmental and performance advantages, producing disparities in competitive opportunities and outcomes. However, whether birth quartile is associated with performance at the senior elite level remains unclear, particularly in individual endurance sports. This cross-sectional, retrospective study analysed 423 distinct competitors (160 women and 263 men) from the Spanish Foot Orienteering League between 2005 and 2023. Each athlete contributed one aggregated Performance Indicator (PI), calculated as the arithmetic mean of all eligible seasonal PI values; the source dataset comprised 1402 athlete-season records. Athlete-level PI differed across birth quartiles in men, H(3) = 12.513, p = 0.006, η2 = 0.037, with Q1 athletes outperforming Q2 (p = 0.002) and Q3 (p = 0.006), but not Q4 (p = 0.128). No significant quartile differences were detected in women, H(3) = 2.201, p = 0.532; however, the female sample had limited power to detect small effects (minimum detectable f = 0.264). A complementary linear mixed-effects analysis of 1396 complete athlete-season records, with athlete as a random intercept and adjustment for age, calendar season, and number of races, preserved the male quartile ordering, although the adjusted male global test was borderline (p = 0.058); the female global test was non-significant (p = 0.126). The athlete-level permutation interaction (p = 0.054) and adjusted mixed-model interaction (p = 0.042) lay on opposite sides of the conventional threshold. Accordingly, the findings support a small male-stratum association, but evidence that the association differs by sex is model-sensitive rather than definitive, and no within-athlete developmental continuity can be inferred.