## 4 Discussion
Regarding positional comparison, significant differences were found across all positions between the senior category and both the U20 and U17 categories. The players who covered the greatest HMLD in all categorieswere ST and FB, while CB covered the least distance, which is consistent with previous studies [22; 23]. Neuromuscular kinematic variables (accelerations and decelerations) showed a clear progression with age. Similar to our findings, acceleration and deceleration profiles in male soccer players from the U17, U19, and B team categories (mean age: 21 years) reported a progressive increase in neuromuscular demands as players matured and advanced to higher competitive levels [24]. Furthermore, the authors emphasized the importance of developing both acceleration and deceleration capacities from early stages, acknowledging that these abilities should not be trained with the same volume or under identical criteria. While accelerations occur more frequently within low to moderate intensity ranges, decelerations tend to increase at higher intensities, as they are typically executed after reaching elevated running speeds [24]. This asymmetry in the load profile supports the need for a differentiated training approach, considering not only the intensity and frequency of these actions but also their tactical relevance and positional specificity. In our study, senior players performed 33% and 39% more accelerations, and 23% and 28% more decelerations than U20 and U17 players, respectively, reflecting greater neuromuscular demands at elite levels [5; 25; 26]. It is worth noting that, unlike other studies [3] that report higher counts of these actions due to the use of broader thresholds, the present study only quantified high-intensity accelerations and decelerations (>3 m\(\cdot\)s\({}^{-2}\) and <-3 m\(\cdot\)s\({}^{-2}\), respectively). This decision followed the methodology established by the Performance Area of the Spanish Women's National Team, aiming to better capture the physiological load and injury risk associated with high-intensity actions. When comparing these actions by position, a trend was observed in which FB and ST registered the highest counts, while CB recorded the lowest. This is particularly relevant, as these neuromuscular variables can impose considerable mechanical stress on players, especially decelerations, which involve significant eccentric and quasi-isometric work and therefore result in greater muscle damage [27]. Football is recognized as a deceleration-dominant sport [6], and the mechanical stress, fatigue, and tissue damage accumulated from these actions may account for up to 65% more impact on physical load than any other kinematic variable, and up to 37% more than accelerations [28]. In this context, it is essential to implement targeted recovery strategies for players in FB and ST positions, particularly during periods of highly competitive density, when accumulated load may compromise performance and increase injury risk. Furthermore, it would be beneficial to systematically reinforce the musculature involved in deceleration actions through microdosed strength training aimed at inducing protective adaptations. Furthermore, female athletes tend to exhibit a more pronounced dynamic knee valgus and greater frontal-plane trunk motion during braking tasks, both biomechanical factors associated with an elevated injury risk, especially at the knee joint [29; 30]. Consequently, the development of neuromuscular strengthening programs targeting these structures, along with specific movement skill training, is essential for players in these positions given their higher exposure to high-intensity deceleration actions during match play. Although similar studies exist, this is the first to compare female national teams from the same country throughout the FIFA World Cup. It is important to note that data collected during World Cups represent a qualitatively distinct competitive context compared to friendly or qualification matches. Studies such as [PERSON] et al.