## 1 Introduction
In another study conducted on U17 players [34], significant variations in running performance were observed depending on position, with Side Midfielders covering the greatest distance at high intensity, performing the most sprints and accelerations, while Central Defenders displayed the lowest values. A decline in running performance towards the end of the match was also noted. In a recent study [35], which compared running load among young footballers in two different formations, differences were observed between playing positions in both formations (1-4-4-2 vs. 1-3-6-1), with midfielders covering greater distances and Central Defenders covering less distance and at lower speeds. Finally, in a study involving U19 footballers [36] in the 1-4-2-3-1 formation, Central Midfielders were found to cover the greatest distance at higher speed, while Central Defenders covered the least sprint distance. Moreover, Central Midfielders performed the highest number of accelerations and decelerations among all positions. Despite the growing interest in performance analysis in soccer, there remains a significant gap in the literature concerning the influence of playing position on the match running performance of youth soccer players. While several studies have explored positional differences in professional or elite adult players [12; 18], there is a notable lack of research focusing on younger age groups. Most existing studies have emphasized top-level competition, leaving youth and amateur categories underrepresented in the data [31; 32]. This limitation hinders the development of age-appropriate training protocols, as the physical and tactical demands placed on youth players may differ substantially from those experienced at the professional level. Moreover, the few studies that do focus on youth athletes often generalize findings across positions without accounting for formation-specific roles or the physiological development stage of the players. Addressing this gap is essential for creating evidence-based training strategies that facilitate both athletic development and a smoother transition between age categories in competitive football. The creation of a running profile helps coaches understand the actual loads players experience depending on the formation and position they play in. This way, coaches can quantify training based on the real demands of the position, using training time more effectively (e.g., more high-intensity running for Side Midfielders than Central Defenders) [37]. Additionally, youth fitness coaches can use these running profiles in specific formations to better prepare players for the next step in their careers (e.g., preparing an Under-17 player for a smoother transition to Under-19 in terms of physical conditioning). As mentioned earlier, the formation a team uses affects the running performance of the players. There is a wide variety of formations; however, the 1-4-3-3 formation is used particularly frequently by both professional teams and teams with young players. Nevertheless, the literature concerning the running profile of playing positions within the 1-4-3-3 formation is particularly limited. Based on the above, the purpose of this study was to create the running profile of high-level young players (Under-19) when playing in the 1-4-3-3 formation and to investigate the differences between playing positions in the formation and between halves. Based on previous studies on professional players, we hypothesize that side players will cover the greatest distance as well as the greatest distance at high intensity. We also hypothesize that the running performance of the players in the second half will decrease as a result of fatigue, according to the existing literature.