## 1 Introduction  
In sports medicine diagnosis, it is essential to select the tests that point to certain motor and functional abilities, based on which we can indirectly, with high accuracy, establish or assess the current status and development level of these abilities. Using objective assessment methods, we draw certain conclusions that we use for the improvement of these abilities [1]. Firstly, to improve certain abilities, it is necessary to accurately and objectively determine the level of development in order to improve said ability. As sports science is rapidly developing, expanding and finally getting attention and visibility within scientific social networks and platforms, new methods for assessment of abilities and levels of training are being increasingly explored and established. Aerobic capacity is one of the most important determinants for team-sport success [2]. In order for an athlete's aerobic capacity to be at the optimal level, adequate programming and training processes are required. Training programming is crucial for optimization of training responses in order to achieve physical aims by dividing the training period into various phases, periods and cycles. Designing a proper training program for a particular team sport helps with unique challenges due to the variety of training goals, volume of concurrent training and practices, and extended season of competition [3]. As all of team sports are high-intensity, aerobic capacity is one of the most important variables for team-sport success [2]. Therefore, is necessary to determine the optimal test protocol that can be used in daily monitoring of these abilities [4]. Conducting different types of tests in team sports has proven to be valuable by being highly reproducible, standardized and precisely reliable in terms of evaluating players' physical abilities, determining their individual strengths and weaknesses and assessing the effect of various training processes in order to significantly improve athletic performance [5]. These tests provide both staff and players with useful information concerning how to improve team performance, as well as individual performance, by exploiting the results [6]. Putting to use these tests may provide improved insight into a player's strengths and weaknesses, suggest suitable training loads and help to monitor the effectiveness of training [7]. There are numerous studies that describe the importance of field tests and their effects on team-sport fitness [7; 8; 9; 10]. Although the Yo-Yo Intermittent Recovery Test Level 1 (Yo-YoIR1) is considered to be the most popular test for assessment of aerobic capacity and is one most frequently used tests, a new test has appeared as an alternative [11]. Intermittent Fitness Test 30-15 (IFT 30-15) is used as a field test to indirectly assess maximal oxygen uptake (VO\({}_{2}\)max), as well as to program training to develop aerobic endurance. However, the test also includes several additional factors [12]. It requires around 20-30 min to be completed and allows large groups of athletes to be tested simultaneously [13]. This type of test, made for specific sports in order to express the nature of different team sports, has begun to attract the attention of researchers and coaches. The test uses a progressive intermittent test protocol, which includes change of direction and a higher maximal speed compared to the customary protocols. Moreover, according to [PERSON] [11], the final speed reached at the end of the 30-15 test (Vift) is concurrently associated with aerobic capacity, anaerobic capacity, the neuromuscular system, as well as with inter-effort recovery. In recent years, there have been several studies published that examined the validity and reliability of the 30-15 IFT test in diverse participants groups [14; 15; 16; 17; 18; 19]. Current research has shown unclear results concerning the 30-15 IFT test. [PERSON] et al.