Can Maturation Level Influence Long-Term Physiological and Physical Adaptations in Youth Female Soccer Players Exposed to Combined Sided Games and HIIT? A Comparison Across Maturation Statuses.

The aim of this study was to assess the effects of a 6-week high-intensity interval training combined with small-sided games (HIIT&SSG) program on maximal strength, sprint performance, and aerobic capacity in female athletes and to examine how these effects vary across different stages of maturity (pre-, mid-, and post-peak height velocity [PHV]). Specifically, we sought to determine whether the improvements in performance outcomes were consistent across maturity groups or if the training effects differed based on the athletes' maturity status. Fifty-four female soccer players (aged 9-16 years) were categorized into pre-PHV, mid-PHV, and post-PHV maturity groups. Participants were randomly assigned to either an HIIT&SSG group (n = 27) or a control group (n = 27). The HIIT&SSG group performed two additional training sessions per week, focusing on 2v2 small-sided games and individualized high-intensity runs at 85% of their final velocity during the 30-15 Intermittent Fitness Test (VIFT). Control continued their regular training routines. Pre- and post-intervention assessments included isometric mid-thigh pull (IMTP) for maximal strength, 30-meter sprint time, and VIFT for aerobic capacity. Pre- and post-intervention assessments included isometric mid-thigh pull (IMTP) for maximal strength, 30-meter sprint time, and VIFT for aerobic capacity. The HIIT&SSG group demonstrated large effect sizes for IMTP (ηp² = 0.996), 30-m sprint time (ηp² = 0.991), and VIFT (ηp² = 0.878), with substantial improvements in strength and aerobic capacity in mid- and post-PHV athletes. For IMTP, significant group differences were observed in mid-PHV (p = 0.021) and post-PHV athletes (p < 0.001). Post-PHV athletes also showed significantly faster 30-meter sprint times post-intervention (p < 0.001). VIFT improvements were significant across all maturity stages (Pre-PHV: p = 0.045; Mid-PHV: p < 0.001; Post-PHV: p < 0.001). Effect sizes for group differences ranged from moderate to large (ηp² = 0.540 to ηp² = 0.928). HIIT&SSG program is effective in enhancing maximal strength, sprint performance, and aerobic capacity, with particularly benefits for mid- and post-PHV athletes. However, the improvements in sprint performance were primarily observed in post-PHV athletes, which may limit the generalizability of these effects to all maturity stages.