## 4 Discussion  
The hypothesis of this study proposed that a 12-week training programme that included twice-a-week, 4v4, and maximal aerobic speed training would improve the VO2 max level and distance travelled of male football players. Our findings showed that the CT and MAS groups improved Vo2 max and distance was covered better than the normal training group as a further improved endurance indicator. Pre-season football training aims to prepare for the match period by increasing physical performance. In this training period, exercises that improve aerobic capacity are performed with technical and tactical skills [26; 55; 56]. Similarly, reducing the risk of injury during the match period is a process component [57]. Training small-sided games with maximal aerobic speed can lead to more fatigue during the season, depending on the intensity of the training. In this study, three different training programmes were applied to three different groups. The first group consisted of maximal aerobic speed and small-sided game combined (CT), the second group consisted of maximal aerobic speed (MAS), and the third group consisted of normal training (NT). The results showed that the CT and MAS groups developed more than the NT group. In addition, one of this study's important findings was that the distance covered in Yo-Yo IR1 progressed more in the CT and MAS groups than in the NT group (\(p<0.001\)). The results obtained in the study agree with previous studies that pre-season training significantly improves aerobic capacity. In this regard, the time spent at high intensity should be 7-8% of the total training time during pre-season [58]. In our study, players in all groups have similar aerobic capacities and are moderately trained at baseline like in related studies [59; 60; 61]. However, the improvement observed in CT and MAS groups may be associated with the effect of high-intensity training with or without the ball. This development may be due to the high intensity of the footballers' training within the time allocated during the training period [37]. Thus, progressively increasing the load of the combined training (SSG + MAS) and maximal aerobic speed training programs (for 12 weeks) was more effective for inducing large improvements in aerobic capacity. The results show that players in combined training are more motivated during SSG under game-specific conditions than maximal aerobic speed and normal football training. SSG game demands an intensity close to match performance in terms of game format. Compared to interval training, this is a better alternative for football players [36; 62]. Our findings are consistent with previous research investigating its effect on improving aerobic capacity. Maximal aerobic speed training provides valuable information about the effects on VO2 max and aerobic capacity in footballers [13]. In the context of aerobic capacity and high-intensity training, [PERSON] et al. [54] (2009) emphasised the importance of repeated maximal velocities in developing aerobic endurance capacities in football players. [PERSON] et al. [63] (2007) showed that high-intensity aerobic endurance training significantly improved VO2 max. This suggests that HIIT may be effective in improving aerobic and anaerobic endurance, which are crucial for football performance [64]. In a study by [PERSON] et al. [65] (2010), high-intensity interval training consisting of 15 s sprints was performed at 120% of the individual maximal aerobic rate with a 15 s rest. It has been shown that this training can be useful for improving aerobic endurance. In another study conducted, four-week HIIT and MICT results showed increased anaerobic threshold, VO2 peak, and anaerobic power values. HIIT results were found to be more significant than MICT [32]. Furthermore, a meta-analysis by [PERSON] et al. [49] (2021) suggested that the internal load demands imposed by running-based long-interval HIIT were similar to those of small-sided games (SSGs), demonstrating the potential of HIIT to improve aerobic endurance in football players.