Background: Recent research in a French context suggested that relative age effects (RAEs) in rugby union may be influenced by playing position; specifically, that RAEs may be more pronounced in back row players who do not have as extreme an anthropomorphic profile as other forward positions.
Methods: In the present study, dates of birth of 6 663 players from four nations (Australia, England, New Zealand, South Africa) were analysed for relative age effects.
Results: The hypothesis that RAEs would be more pronounced in back row players was not supported. South African rugby was an obvious outlier due to the finding that RAEs were present across all playing units. These results suggest that late maturing players have been disproportionately lost to the South African system across all positions.
Conclusion: Nation-specific youth sport culture appears to be more important than playing position for determining who is at risk of RAEs in rugby union.