Introduction and Purpose: The objective was to compare the effects of High-Intensity Interval Training (HIIT) versus Small-Sided Games (SSG) on the performance indicators of elite young football players.

Materials and Methods: In a quasi-experimental study, 34 elite young players (ages 16-18) were randomly assigned to three groups (HIIT, SSG, and control). The training period lasted for six weeks with three sessions per week. The HIIT protocol consisted of 4 sets of 4-minute runs at 80% heart rate, while the SSG group played 6v6 games on a 30x40 meter pitch.

Results: The results indicated that both experimental groups (HIIT and SSG) showed significant improvements in aerobic power, maximal oxygen consumption, and agility compared to the control group. However, within-group analysis revealed that the HIIT protocol had broader effects, being the only group to also significantly improve 36-meter speed (p = 0.016) and Yo-Yo test distance (p = 0.007). Neither of the two protocols had a significant impact on upper and lower body explosive power.

Discussion and Conclusion: Both HIIT and SSG are effective tools for improving aerobic power and agility. However, HIIT appears to be the superior option for simultaneously improving speed and aerobic endurance, while SSG is an efficient choice for enhancing agility in a specific and motivating environment. To develop explosive power, the addition of specific strength training to the programs is essential.