## 1 Introduction  
Practiced both professionally and recreationally, esports is a thriving field, and sports science is devoting more and more attention to it [1]. Currently, the viewership of major esports tournaments is comparable to that of many traditional sports. According to Newzoo, the number of esports viewers worldwide in 2021 exceeded 465 million people. This number is projected to grow to nearly 580 million by 2024 [2]. While the training of professional sports athletes and the factors determining sports success are based on well-established scientific research, esports training and markers of esports performance are not yet in the full scope of sports science. However, they are crucial for optimizing coaching, prescribing adequate training and predicting performance. Moreover, knowledge of the psychophysiological responses of the athlete's body to esports competition is the basis of rational training management. There are reports in the literature on the effects of playing video games and esports on behavior and brain function. Research findings indicate that action video games enhance a wide range of perceptual-cognitiveskills [3; 4]. The associations of electronic games with, among other things, aggression [5; 6], depression [7; 8] or addiction [9] have also been analyzed. However, only a few studies deal with e-sports. [PERSON] et al. [10] observed no significant relationship between e-sports and anxiety, whereas a positive relationship was found between e-sports and aggression, and a negative relationship was found between e-sports and psychological well-being. Moreover, to our knowledge, and according to the related scientific literature, significant gaps remain in the physiological and performance-related aspects of participation in esports. Esports games are complex and can be divided into specific genres, such as multi-player online battlefield arena (MOBA), first-person shooter (FPS) and real-time strategy (RTS) and sport simulations [11]. In every genre there are different digital games, with different competition rules and different mechanics that have to be mastered by the players. Furthermore, different games at different levels of competition place different demands on the player. Therefore, in order to understand and describe the physiological responses in players during a game as accurately as possible, the focus should be on one particular game. In our research, we have decided to focus on Counter-Strike: Global Offensive (CS:GO), one of the most popular e-sports games. CS:GO is a tactical FPS game based on a first-person shooter perspective. Players use their mouse to control the character's view, typically to aim toward and shoot enemies [12]. The CS:GO game demands high visuomotor coordination, fast reaction time, optimal perceptual skills, good planning behavior, high flexibility, and appropriate inhibition [13]. Esports competitions are accompanied by strong emotions that cause physiological responses. These include neuroendocrine responses (the release of stress hormones such as testosterone, cortisol, and ACTH), increased blood pressure, change in heart rate (HR) and heart rate variability (HRV), increased muscle tension and biochemical changes in the body [14; 15; 16]. A study by [PERSON] et al. [17] found that, compared to the game genre MOBAs, FPS games induce larger change in low-to-peak heart rate and systolic blood pressure [17]. Few studies exist in the literature on the changes in hormone concentrations during the playing of esports games. However, as the investigated populations and game genres differ, the results of these studies remain inconclusive. [PERSON] et al. [18] observed no changes in testosterone, cortisol, dehydropiandrosterone, and androstenedione levels in young gamers playing League of Legends. Different results were obtained by [PERSON] et al. [19], who reported a significant increase in cortisol levels immediately following competition.