The relative age effect is more than just participation bias in badminton

Background: Annual age grouping is a widely used strategy to allocate players to age categories for more equal and fair opportunities considering the developmental differences. Although it is a well-intended strategy, certain (dis)advantages occur because of the subtle age-related differences within the same age groups. Objective: The purpose of the current study was to investigate the relative age effect among badminton players reaching the podium in the last three consecutive European U15, U17 and Junior (U19) Badminton Championships. Methods: A total of 288 medal owners from 20 countries were evaluated in the study. Chi-square (chi(2)) goodness-of-fit tests were used to compare the obtained birth month distributions across the quartiles (Q), and odds ratios and 95% confidence intervals were calculated in order to compare quartiles with each other. Results: Statistically significant relative age effects were determined favouring relatively older athletes in the total sample (chi(2) = 82.278, p < .001). Statistically significant distribution differences were noted in both singles and doubles categories in total be (chi(2 )= 18.778, p < .001; chi(2) = 63.815, p < .001, respectively). Striking findings were determined in Q1-Q4 and Q2-Q4 comparisons as players in Q1 and Q2 were more than five and four times as likely to reach the podium than players in Q4, respectively. Conclusions: Results of this study confirm the presence of relative age effect among award-winning badminton players which goes beyond the classical participation trends findings, and stress the importance of the issue for talent development, selection and success.