Relative age effects in international rugby union: Consequences of changing the cutoff date and exploring youth to senior transitions

Relative age effects (RAEs) are independent of specific cutoff dates that can vary from country to country. However, the consequences of changing the selection cutoff dates within a national sport organization are unknown. Further, the transition from international youth to senior representation is yet to be explored in rugby union. Thus, the aims of this article were twofold: Study 1 compared the birth quarter (BQ) distributions of the England Rugby Football Union (RFU) under-18 representatives based on September to August and January to December selection cutoff dates. Study 2 explored the BQ distributions within the RFU international development pathway through analyzing the under-18, under-20, and senior representatives, as well as the BQ distributions of youth players who were subsequently capped at senior level. Chi-square analysis was used to compare BQ distributions in each sample against expected distributions. Results revealed a corresponding shift of a skewed birthdate distribution favoring chronologically older players that was mediated by specific cutoff dates (p < 0.05). Moreover, whilst RAEs were present within both youth cohorts (p < 0.05), it was not apparent at the senior level (p > 0.05). Furthermore, during the transition from international youth to senior representation, more chronologically older players were successfully capped.