# Born to Win? The Hidden Bias of Birthdates in Spanish Orienteering Talent Selection
###### Abstract  
The Relative Age Effect (RAE) refers to the advantage that relatively older athletes within the same age group may have in sports. While this phenomenon has been widely documented in numerous disciplines, its presence in orienteering remains largely unexplored. This study aimed to analyse the existence of RAE among Spanish orienteers selected for international competitions organised by the International Orienteering Federation (IOF) between 1987 and 2023. A total of 384 participations (225 male, 159 female) were examined across the European Youth Orienteering Championships (EYOC), Junior World Orienteering Championships (JWOC), and the European and World Orienteering Championships (EOC + WOC). The distribution of birth dates by quartiles and semesters was compared using chi-square tests, Cramer's V, Z-tests, and odds ratios with 95% confidence intervals. The results revealed a significant RAE in male athletes, particularly in JWOC, where those born in the first quartile were up to 3.77 times more likely to be selected than those in the third quartile. In contrast, no significant associations were found in female athletes, which may reflect structural or developmental differences related to sex. These gender-based disparities highlight the importance of integrating sex-specific considerations into selection policies. Overall, the findings suggest a selection bias favouring relatively older males, which may hinder the development of late-born talent. Therefore, it is recommended that selection criteria be reassessed to ensure fairer and more inclusive talent identification and development in youth and elite orienteering. relative age effect; sports performance analysis; orienteering talent selection; Spanish orienteers; gender differences; international orienteering competitions 20252025157993  
20 June 20  
evaluated for their physical resistance and navigational skills [3]. Furthermore, coaches play a key role in managing training opportunities for their athletes, frequently giving priority to those who show outstanding performance from the earliest phases of their development [1]. Each season, the competitive season includes a range of regional and national events, offering athletes opportunities to score points and improve their skills through deliberate practice [4]. The results obtained in these competitions are frequently decisive for accessing higher competitive levels, as strong performance paves the way toward greater opportunities [5], such as representing Spain in international orienteering events. In many sports, including international orienteering competitions for youth, athletes are grouped by their chronological age in order to guarantee fairness [6]. Theoretically, this system allows the most talented within each age group to emerge and access further developmental opportunities under equal conditions. However, numerous studies have demonstrated a phenomenon known as the Relative Age Effect (RAE), which involves an overrepresentation of athletes born in the first months of the selection year [7]. This age-based inequality is often explained by the maturity-selection hypothesis, positing that chronologically older children within their cohorts tend to be more physically developed, possessing anthropometric and physiological traits that enhance their performance [7; 8]. In this context, grouping by year of birth introduces substantial differences in physical and psychological maturity, as an athlete born in January may be nearly twelve months more developed than another born in December of the same year. These differences are especially pronounced between the ages of 10 and 19, coinciding with the period of biological maturation. They tend to diminish or even disappear in adulthood [8]. This initial overrepresentation of relatively older athletes may contribute to the premature exclusion of potentially talented individuals born later in the year, thereby reducing the pool of talent at higher levels [9; 10].