Maturity-specific trajectories of physical fitness in talented youth athletes: a longitudinal study of Japanese local talent identification and development programme

Purpose Despite the global emphasis on talent identification and development (TID), longitudinal evidence on physical development in Asian youth remains scarce. Using Japan's local TID (L-TID) multi-sport matching model, this study examined longitudinal trajectories of physical fitness in talented Japanese youth athletes categorised by maturity status. Methods Data were analysed from 96 participants (43 males, 53 females) in a Fukuoka L-TID programme, followed from Grade 4 to Grade 9. Somatic maturity (Early, Average, or Late) was based on the timing of peak height velocity (PHV). Measurements included height, body mass, 25-m sprint, standing broad jump (SBJ), reaction time (RT), and 20-m shuttle run (SR). Results In males, improvements in SBJ and sprint speed synchronised with the PHV period ( p < 0.05), supported by medium-to-large interaction effects. Conversely, females demonstrated a significant post-PHV decline in SR ( p < 0.05), suggesting a transient physiological constraint. RT improved independently of maturation across both sexes ( p < 0.05), reaching a plateau between Grades 8 and 9. Correlation analysis revealed substantial performance ranking instability between programme entry and exit, particularly within the Average maturity group ( r = 0.09–0.22). Conclusion Biological maturation acts as an accelerator for males but a constraint for females. Observed ranking instability suggests proximity to PHV disrupts motor coordination, requiring neuromuscular re-integration. Therefore, these findings suggest that early-stage TID programmes could consider integrating neurocognitive development to establish a stable foundation before the onset of maturation-related physical fluctuations.