## 1 Introduction  
The paradigm of training in sports has changed; the control and quantification of the loads that the player supports during training or competitions [1] is an increasingly explicit reality. External load refers to the physical demands placed on athletes during training or competitions and is a crucial indicator for training planning and evaluation [2]. With the knowledge of the data from external and internal loads that the competition requires of players, it enables the coaches to optimize training processes [2, 3]. In this sense, the customization of the load should be based on the knowledge of the demands imposed by the competition [4]; however, without the individualization of the sample, serious consequences may affect the planning and results of the team during the competition [5]. As far as is known, there is little research that individualizes load thresholds according to youth population. Proposals have been made to individualize the demands of specific external loads in professional women [5] or professional men [6], but not in U14 men. Despite growing interest in individualized load monitoring, research focused on youth athletes--particularly under-14 (U14) male basketball players--remains limited. While individualized external load thresholds have been established for professional female [5] and male athletes [6], similar approaches are lacking in youth contexts. Individual factors such as age, competitive level, and playing position significantly influence athletes' responses to training loads and must be considered when analyzing external load [7]. Individualizing both external and internal load thresholds allows training to be tailored to each athlete's age and physiological profile, enhancing adaptation, optimizing performance, and adjusting training volume and intensity according to individual needs [3; 8; 9; 10]. Evidence from team sports supports this need for individualization, as external load data vary across contexts, including age, gender, sport, and competition level [2; 7; 8; 11; 12; 13]. However, the scarcity of reference data for youth athletes highlights the need for further research to support developmentally appropriate training strategies. Basketball performance is characterized by a predominance of aerobic activity, with decisive contributions from anaerobic efforts during high-intensity phases of play [14]. The sport involves intermittent, short-duration bursts of high intensity interspersed with periods of lower intensity [15], making the ability to sustain repeated high-intensity efforts a key determinant of success [3; 16]. Research shows that elite players often cover less total distance but reach higher peak speeds during competition [17], and players from stronger teams tend to cover shorter distances at lower speeds compared to those from weaker teams [18]. Although some studies have proposed generic movement intensity classifications (standing >6 km/h, walking 6-12 km/h, jogging 12-18 km/h, running 18-24 km/h, sprinting >24 km/h) [19], these thresholds are typically based on manufacturer defaults and may not accurately reflect basketball-specific demands [20]. Therefore, individualized intensity zones--based on variables such as speed, acceleration, and deceleration--are essential for accurate external load monitoring [2; 3; 5; 21; 22; 23]. Performance in basketball is closely linked to fundamental motor abilities, including strength, power, agility, speed, and coordination [24]. These capacities are reflected in mechanical and locomotor stress--collectively referred to as external load--which can be measured through kinematic variables such as speed, acceleration, deceleration, and distance covered [25]. Among these, acceleration and deceleration are particularly important, as they capture the frequency and intensity of explosive movement [8].