Assessment of Tactical Actions in Under-15 Male Football Players Following a Tactical Periodization Training Period: An Observational Study.

This observational study aimed to assess the quality of tactical actions and the tactical performance of Under-15 football players before and after 25 training sessions conducted using Tactical Periodization methodology. Sixty-six U-15 players from five teams in Brazil, Portugal, and Canada participated, performing a total of 12,552 tactical actions. Tactical behavior was assessed using the FUT-SAT. Tactical Performance Index (TPI) and the percentage of successful actions were used as indicators of collective and individual quality of tactical actions. Pre- and post-training comparisons were made using a Linear Mixed Model (p < .05). Changes were observed for Team 2 and overall, in the quality of tactical actions across both offensive and defensive dimensions, with medium to large effect sizes (d = 0.60-1.18). Additionally, changes in Tactical Performance were identified for Teams 1 and 2, and overall, at the general game level, showing small to large effect sizes (d = 0.41-2.47). No statistically significant changes were detected in Teams 3, 4, or 5, and the pooled findings should be interpreted as exploratory. In conclusion, improvements in tactical performance and the quality of tactical actions were observed in specific teams following 25 training sessions. These findings may partly reflect the correspondence between training content and the tactical principles assessed by FUT-SAT and cannot be attributed specifically to Tactical Periodization.