## 4 Discussion
### Reliability, Validity and Aerobic Capacity Assessment
In any case, due to a low number of sports covered by this overview study, it is necessary to examine the validity of the 30-15 IFT for other team sports, especially those with an intermittent activity structure, where the application potential of this test is high. On the other hand, a potential disadvantage of this validity assessment is the small number of respondents sampled in the reviewed papers (the highest number of participants was 63). The 30-15 IFT is a field test used in certain cases to assess cardiovascular capacity. The presented formula for calculating VO2 max has attracted the attention of several authors (Table 3). Considering that Vift obtained during the 30-15 IFT test is simultaneously related to aerobic capacity, anaerobic capacity (or at least the percentage of used AVR), the neuromuscular system and as inter-effort recovery, [PERSON] suggested that this test should be used to reproduce and evaluate physical capacity that occurs during high-intensity interval training involving change of direction. The 30-15 IFT is not highly-specific for particular sports but for the training sessions commonly performed in intermittent sports [35]. [PERSON] et al. [36] used the same test to assess the performance of 67 elite rugby players and to calculate MAS (maximal aerobic speed) and ASR (anaerobic speed reserve) using the obtained Vift 30-15 value and VO2 max. MAS represents the lowest running speed at which maximal oxygen uptake occurs, such as the velocity at the maximal oxygen uptake (VO2 max). The final speed obtained in the test can also be largely related to anaerobic capacity [32] or to the results of tests that evaluate anaerobic capacity, such as the 300 m shuttle-run test, repeated-sprint tests or the 5-0-5 COD (12,24). Research aimed at determining the effects of certain programs without using the 30-15 IFT as an indicator of aerobic capacity was conducted among handball players [23] and elite competitive handball players [37]. Research was also conducted to determine the difference in aerobic capacity depending on the position and role on a team of elite female basketball players, where the 30-15 IFT was used to assess VO2 peak. Among female basketball players, starters have better aerobic capacity than bench players, just as backscatter players have better aerobic capacity than front court players [19]. The primary variables of the 30-15 IFT are running speed (Vift) for the last completed stage of running, VO2 max and HRpeak [28,35]. There are several studies that use the 30-15 IFT for measuring VO2 max, which gives coaches an adequate perspective concerning their athletes' aerobic [12,16,19]. \"Corrective equations:\" are used for assessment of VO2 max, and they consist of the last completed stage, age and body weight [11]. A high correlation between VO2 max and 30-15 IFT was found in soccer [1,15,32], basketball [16], rugby [12,30], ice hockey [14], and handball [23] players. Furthermore, the correlation is present in both indoor and outdoor applications of the test [19]. Based on the abovementioned facts, the 30-15 IFT is indisputably correlated with VO2 max; therefore, it can be used for quality estimation of aerobic fitness in team sports.