The role of a relative age effect in the first winter Youth Olympic Games in 2012

Background Owing to the separation into age groups at the first winter Youth Olympic Games (YOG), athletes differed in age by up to two years, leading to a potential relative age effect (RAE). Objective The purpose of this study was to define the role of the RAE in the first winter YOG with regard to sex, type of sport and performance. Methods The birth dates and anthropometric data of all 1021 athletes (557 male, 464 female, 14-19 years old) participating in 15 sports were analysed. A chi(2) test was used to assess the difference between the observed and expected birth distributions. ANOVA (analysis of variance) and Kruskal-Wallis analyses were used to investigate differences in anthropometrics. Results The birth date distribution of the overall sample was significantly different from an equal distribution, with an over-representation of athletes born shortly after the cut-off date (chi(2)=284.7, p<0.001). A significant RAE was found in both male (chi(2)=245.1, p<0.001) and female competitors (chi(2)=74.6, p<0.001). An analysis based on the type of sport showed an RAE in all categories (strength-chi(2)=229.9, p<0.001, endurance-chi(2)=60.4, p<0.001 and technique-related sports chi(2)=25.2, p=0.001). Relatively older competitors were also over-represented among medal winners (chi(2)=47.9, p<0.001). Relatively older male competitors were significantly taller (p=0.005) and heavier (p<0.001) than younger competitors. No differences were found in female competitors. Conclusions The results suggest that relative age had a highly significant influence on participation in various sports regardless of sex. A possible strategy to reduce the RAE would be a fixed quota for each birth year within the two-year age group across events.