## 4 Discussion
Statistically significant differences were found only in the main variables of the study, Ac and Dec, and these differences were uneven depending on the possession of the ball. The players who had a higher number of Ac/Dec and higher maximum values in the attack phase were WAs. In defense, they also showed higher average Ac/Dec, but it was WDs who accelerated and decelerated more frequently. Similar research with football players of the same age group, but without differentiating by ball possession, obtained very similar results, also concluding that WAs and WDs perform a greater number of Ac/Dec with respect to CMs, STs, or CDs [37; 40; 46], and do not differ from the results obtained with senior football players [6; 9; 28; 43]. These differences between positions may be due to the requirements of the role and the needs of the game, since both profiles are continually moving from one field to another to cover spaces or teammates [5; 40], but also to tactical decisions regarding pace management, such as the one previously exposed of playing with a greater line width and less depth, in which WAs play in a more central position and generate spaces that are used by WDs to attack [28; 33]. These results suggest that, in young football players, both WA and WD positions support higher Ac/Dec and higher intensity, being exposed to greater physical demands and greater risk of injury [5; 37], which should be taken into account by strength and conditioning specialists in order to prepare them for the demands of competition by designing position-specific training exercises [49]. In terms of practical implications, our study highlights the importance of adapting training programs for players in positions that require high levels of acceleration and deceleration, such as wingers (WAs) and full-backs (WDs). These players could benefit from specialized training aimed at improving their explosiveness and agility. Furthermore, our research shows how tactical strategies and ball possession can affect the physical demands placed on players during matches. To optimize player performance and minimize fatigue, coaches should adjust team tactics, taking into account the spatial distribution of players on the field and the tactical approach employed. This knowledge can serve as a basis for the development of more effective training programs tailored to the needs of young footballers, ultimately improving performance and reducing the likelihood of injury. The primary advantage of this study is rooted in the sophisticated data collection methodology employed, centered around a local positioning system, uniquely equipped to provide real-time ball tracking. This innovative approach has yielded exceptional precision and reliability in documenting not only the players' positions but also their acceleration and deceleration patterns (Ac/Dec). However, this study is not without its limitations. The primary limitation lies in the small sample size and the number of games, resulting in unequal participation among players in terms of minutes. Although the results add to the available knowledge on Ac/Dec, extrapolation to other teams, playing standards, ages, and genders should be performed with caution. Future research should seek to replicate the current study with young players, using a greater number of matches, both training and official, a greater variety of teams, considering women's football, and possibly seeking to establish comparisons between different positions, formations, game strategies, or ball possession, as well as determining the sensitivity of Ac/Dec to accumulated game time.