Observation of Intermittent Running Performance During Different Training Periodizations in Youth Football Players

Background This study investigated whether incorporating high-intensity interval training (HIIT) into Verheijen's periodised small-sided game (SSG) training model improves the intermittent running performance of elite U16 and U17 footballers. Methods The U-16 team (n = 16) followed the SSG+HIIT protocol, while the U-17 team (n = 16) served as the control group, performing only SSG sessions on days designated for physical conditioning. The intervention group's HIIT sessions were prescribed using individualized thresholds based on the 30 − 15 Intermittent Fitness Test (30 − 15 IFT). Both training protocols were matched for total volume, with the SSG-only group completed 136 minutes of SSG, and SSG+HIIT group performed 106 minutes of SSG plus 30 minutes of HIIT. Pre- and post-30–15 IFT final velocity (V _IFT ) scores were compared within and between groups. Results In the SSG+HIIT group, a significant 8.1% improvement in V _IFT was observed after the intervention (p<.001, Cohen’s d = 1.54), which was significantly greater than the non-significant 1.3% increase in the SSG-only group (p = 0.087, d = 0.43). The group×time interaction showed a large effect size (η²=0.404), indicating the superior aerobic adaptations induced by the hybrid training model. Conclusion A combined SSG+HIIT training model enhances intermittent fitness more effectively than SSG-only training in elite youth football players, supporting its application in early-season conditioning programs.