Seasonal changes in the force velocity sprint profile of Spanish youth football players across age categories.

The purpose of this study was to investigate the changes in the force-velocity (F-V) profile and 30-metres sprint times of youth football players over a competitive season and across different age groups. Sixty-four players were categorized into five age groups (Under-10 (U10), Under-12 (U12), Under-14 (U14), Under-16 (U16), Under-18 (U18)) and assessed at three time points during the season: the pre-season (P1), mid-season (P2), and end season (P3) using GNSS/GPS technology. Results showed that the theoretical maximum force (F0) increased by the end of the season compared to the baseline in U14, U16, and U18 (p < 0.05; ES: 1.92-5.19) and was also higher at the end compared to mid-season in U14 players (p < 0.05; ES: 3.01). The theoretical maximum velocity (V0) was significantly higher at the end of the season compared to the baseline in U12 (p < 0.05; ES: 2.61) and mid-season in U12 and U16 players (p < 0.05; ES: 1.70-2.37). U10 and U12 showed lower F0 and V0 values compared to older players across all periods. The study concludes that both the timing of the season and the age influence the F-V profile, with older age groups showing greater improvements. These findings provide valuable insights for optimizing training programs tailored to the seasonal changes and age of football.