# Influence of Category and Sex in Game Structure Variables in Young Elite Tennis
## 1 Introduction  
The physiological analysis of sport games examines the set of systems that constitute the structure and dynamics of gameplay [1]. Alongside other performance indicators, it contributes to profiling the complexity of competitive performance in tennis [2, 3], which is conditioned by tactical, technical, and physical factors [4]. Several authors [5, 6, 7] highlight that performance analysis should be conducted through field studies in natural environments, reflecting the sport's inherent diversity and competitiveness by analyzing representative samples. Furthermore, such analysis must consider the influence of individual and interactive constraints on athletes' behavior [8, 9]. From a methodological standpoint, observational methodology [10, 11] is well-suited to scientifically describe and analyze the sociomotor dynamics involved in sport performance. Notational analysis based on video recordings is the most commonly used approach to obtain quantitative data in natural contexts. This method is direct and non-participatory, with the added benefit that athletes are unaware they are being analyzed, thus eliminating potential bias in data collection [12, 13]. In net and alternate participation sports--tennis being a prime example--temporal and structural variables are considered specific performance indicators derived from the game's framework. These have been studied at various units of analysis such as the match, set, game, and point [14]. Regarding tennis's intermittent dynamics, active time is characterized by repeated short-duration anaerobic efforts involving reactive acceleration-deceleration movements, multidirectional agility, and explosive jumps. Nevertheless, the high frequency of rest periods leads to prolonged match durations, underscoring the importance of the aerobic system for recovery [15]. Additionally, rest times are regulated by the International Tennis Federation (ITF), which stipulates a maximum of 20 s between points, 90 s during changeovers when the total number of games is odd, and 60 s between sets [16]. Currently, there is a growing interest in identifying and enhancing tactical variables that lead to match victories. As in other sports, tactical decisions in tennis are influenced by external game-derived parameters--such as ball type, court surface, match format (number of sets), and player ranking--as well as internal ones like sex-category, strategy employed, performance level, or physical attributes. Most research has focused on professional players, while studies involving youth athletes remain limited. When conducted, these studies often examine contexts removed from elite competition and do not comprehensively account for all surfaces and categories. Consequently, there is a knowledge gap concerning gameplay development during formative stages [15; 17; 18]. Concerning total match duration, similar values have been found across sex and category in U-18 players at both international and national competitive levels (77.2-85.0 min for males; 77.9-80.6 min for females) [18; 19; 20; 21; 22; 23; 24]. In contrast, national-level competitions report shorter durations for U-14 players (65.4 min for males; 59.8 min for females) and longer durations for U-16 (108.0 min for males; 99.7 min for females) [21; 22; 23]. Regarding average set and game duration--two underexplored parameters in the literature--studies have identified similarities between professional (41.2 min for males; 43.5 min for females) and U-18 players (34.6 min for males; 34.2 min for females) at the set level, and between 174.2-178.6 s for males and 183.8 s for females at the game level [18; 25; 26]. With respect to point duration, notable differences have been observed in U-12 players compared to other age categories (12.1 s in U-12 males; 7.3 s and 6.3 s in U-14; 9.1 s and 9.0 s in U-16; 7.2 s and 8.2 s in U-18) [20; 21; 22; 23; 27; 28; 29]. Sex-based analyses have found similarities in U-14 and U-16 [21; 22].