Transient relative age effects across annual age groups in national level Australian swimming

Objective: To determine the prevalence, magnitude and transient patterning of RAEs according to sex, stroke type and distance across all age-groups at the Australian National age swimming Championships. Design: Multiple years of repeated cross-sectional participation data were examined. Method: Participants were 9595 male and female swimmers (aged 12-18 years) who’d participated in a 50 or 400m Freestyle and/or 100 or 200m Breaststroke at the National age swimming Championships between 2000-2014 (inclusive). RAE prevalence, magnitude and transience were determined using Chi-square tests and Cramer’s V estimates for effect size. Odds Ratios (OR) and 95% Confidence Intervals (CI) examined relative age quartile discrepancies (e.g., Q1 v Q4). These steps were repeated across age-groups and according to sex, swimming stroke and distance. Results and discussion: Consistent RAEs with large-medium effect sizes were evident for males at 12-15 years of age and with large-medium effects for females at 12-14 across swimming strokes. RAE magnitude then consistently reduced with age-groups across strokes (Q1 v Q4 OR range - 14 year old male = 1.77-2.29; female = 1.10-1.39). While noting a few exceptions, at 15-16 years, RAEs had typically dissipated; and by 17-18 years, descriptive and significant inverse RAEs emerged, reflecting overrepresentation of relatively younger swimmers. Conclusion: Performance advantages associated with relative age (and therefore growth and maturation) are transient. Greater consideration of transient performance and participation in athlete development systems is necessary. This may include revising the emphasis of sport programmes according to developmental stages and delaying forms of athlete selection to improve validity.