Influence of Biological Maturation on Training Load and Physical Performance Adaptations After a Running-Based HIIT Program in Youth Football

The aim of this study was to examine the influence of biological maturation on young football players adaptations and monitor and analyse variations in external (EL) and internal load (IL) during a running-based HIIT programme, according to the players’ maturity status. A total of 41 players (13.9 ± 0.7 years) participated, divided into an experimental group (EG) (n = 19) and a control group (CG) (n = 22). Acceleration (5 m and 30 m) and intermittent endurance (vIFT via the 30-15 IFT test) were assessed before and after eight weeks of intervention. EL and IL load variables and the rating of perceived exertion (RPE) were recorded. The results showed better initial performance in advanced maturity status players (post-PHV). Players from the EG had significant improvements in the 5 m and 30 m sprints and in the vIFT, whereas the CG only showed significant improvements in the 30 m sprint. Post-PHV players perceived less intensity (RPE) and thus, less IL than players with a delayed maturity status (pre-PHV). The pre-PHV group also exhibited significant improvements in the 30 m sprint and vIFT. However, no significant interaction effect (time × maturational group) was detected for any variable. These findings underscore the importance of considering maturity status in performance evaluation, training load prescription, and adaptations.