Factors influencing youth academy promotion in Japanese soccer: Mediation analysis of biological maturation, sprint ability, and match play ratio

Abstract

Promotion from under-15 (U-15) to U-18 categories is a decisive selection point in Japanese soccer academies; however, the structural process underlying this decision remains unclear, and evaluations conducted during the adolescent growth spurt may favor early-maturing players. In this study, the structural relationship between biological maturation, physical performance, and youth academy promotion was investigated among Japanese soccer players, with particular attention to match play ratio as a potential mediating variable. Participants included 60 male U-15 players from a J-League youth academy, and they were categorized into a promotion group (n = 32) and a nonpromotion group (n = 28). Measurements included skeletal muscle mass, maturity offset estimated by a Japanesespecific equation, sprint times (10 and 30 m), jump performance, and match play ratio (actual playing time divided by the total possible playing time). Group differences were examined using independent t-tests, and four logistic mediation models were tested. The promotion group showed significantly higher muscle mass and match play ratio and significantly faster sprint times than the nonpromotion group. No significant difference in biological maturation was observed, although effect sizes indicated a small-to-medium difference. Although biological maturation showed a limited indirect effect, logistic mediation analysis revealed that, a significant mediation path was identified from 30-m sprint time to promotion via match play ratio (indirect effect = −2.73, p < 0.01). These findings indicate that sprint ability is a primary determinant of coach selection for match participation, which subsequently influences promotion decisions. The results of this study emphasize the need for long-term development strategies that account for individual differences in physical maturation to ensure a fair and effective talent identification process.