Selection of the Extremes - Male Junior and Adult Ice Hockey Success in relation to Relative Age and its Interaction with Biological Maturation.

Objectives: This study aimed to investigate the relationship between the relative age effect (RAE) and success in ice hockey during adolescence and adulthood in male Swedish players, as well as potential interactions between relative age (RA) and biological maturation.

Methods: Anthropometric data were collected from high schools with a certified ice hockey programme over 20 years. Birth dates were extracted from public databases to calculate numerical relative age (n = 2211 players). Biological maturity timing was defined as the z-score of the percentage of adult height (z%AH) reached at term 1 (~ 16 years of age). Retrospective longitudinal data on selection to junior national teams (U16, U18, U20) and the National Hockey League (NHL) were retrieved from open databases. Junior and adult success probabilities were modelled using generalised logistic modelling (GLM). Spearman correlation analysis was used to assess the correlation between the anthropometric data, relative age, and biological maturation. In addition, the predictor z%AH was added to the GLMs to characterise interactions.

Results: Individuals with a higher relative age were overrepresented in Swedish ice hockey programmes. Players born between January and March (Q1) were about twice as likely to reach the U16 national team as players born between October and December (Q4). Consequently, in a GLM, relative age was identified as a significant predictor of junior success. The addition of z%AH improved model fit for U16 selection, and an interaction between z%AH and RA was observed (p < 0.05). In contrast, relative age was not a significant predictor of reaching the NHL (p = 0.21). There was no interaction between the RA and z%AH (p = 0.44) for adult success. When cross-tabulated, the players most likely to reach both the NHL and the U16 national team were either born early and matured late or born late and matured early.

Conclusion: Early-born and early-maturing players in certified Swedish high school programmes are more likely to be selected for the U16 national team. In terms of adult success, RA had no significant effect on the likelihood of playing in the NHL. However, in a combined model, regardless of relative age, players with late biological maturity timing were more likely to reach the NHL.