Relative Age Effect and Biological Maturity in Swedish Elite Girls Football : A quantitative study of players selected for theF15/09 national team and national camp in 2024.

Women’s football is growing rapidly both in Sweden and internationally, between 2003 and 2022 the organized football participation among young girls and women in Sweden increased by 121%. In an increasingly globalized football world, structured talent development is crucial to maintain competitiveness at the elite level. It is therefore important to explore biological maturity and chronological age in young female players. Relative age effect (RAE) and variations in biological maturity can influence selection in youth football and previous research shows strong evidence of RAE among boys, while evidence among girls is more limited. The aim of this study was to analyze how biological maturity and chronological age were distributed among girls selected for the national training camp (riksläger) and national teams and whether there was an over- or underrepresentation of early maturing or early-born players. This study uses a quantitative design based on a web-based survey sent to 140 players born 2009. Biological maturity was estimated for each player using the Khamis-Roche method based on their date of birth, height, weight and parental information. A slight overrepresentation of players born in the first half of the year was identified but no association was found between biological maturity, chronological age and national team selection. Most players’ participation was classified as “on time” in terms of biological maturity. The results suggested that biological maturity was not a determining factor for initial national team selection among girls. However, biological maturity should be considered at younger ages to support sustainable and equitable development environments. Further research on girls’ development at younger ages is recommended.