## 1 Introduction
There are studies that have already investigated the effects of training with different types of small-sided games (in various forms and with the manipulation of the playing rules) on junior football players' physical capacity and they did not find significant differences compared to traditional non-specific endurance training [19; 20; 21]. In terms of the aspects of functional capacity, SSG forms suggest that low-player games (two vs. two; three vs. three) are more intense, favoring the development of anaerobic endurance [22]. [PERSON] et al. [11] rated U14 players after 20 training sessions where SSGs were used as a methodical strategy and found significant improvements in the reported tactical actions of defensive tactical principles, both in the number of actions and in tactical index performance. There are systematic reviews related to small-sided games. The authors investigated the applications of SSGs in the sports training context with physical, physiological and tactical goals [23; 24; 25; 26]. In the review conducted by [24], nine longitudinal research studies were found, that related to small-sided games, and in five of these, the subjects were junior football players. Most of the cross-sectional studies focused on describing differences between small-sided game protocols, while other studies focused on comparing exercise regimes in 'interval' and 'continuous' training and SSGs. Training programs based on small-sided games (two to four SSG sessions per week) show significant increases in player performance in terms of improved speed, repeated sprint ability and change in direction, along with muscular and physiological adaptation [24]. Training with small-sided games seems to be an effective strategy; variables controlled by the trainer through systematic programming adapted to training periods can influence the intensity of the exercise during a SSG [13; 27; 28]. Thus, small-sided game intensity can be changed according to the objectives of training, including changing several variables, such as player number, field size, game themes (number of passes, number of ball touches, etc.) or the use of a floater player [29]. In order to influence players' physical and physiological parameters during a SSG, the number of ball touches should be limited. A smaller number of touches of the ball leads to an increase in game intensity. This seems to be the essential condition for playing elite-level football [30]. [PERSON] et al. [19] analyzed two vs. two, three vs. three and four vs. four SSGs with four \"jolly\" players on the side-lines in professional football players; the theme was to maintain possession, and the number of ball touches was limited to one to two. The authors observed increased concentrations of blood lactate, a higher rating of perceived exertion (RPE) levels, a longer total distance covered, a higher total distance covered in high-speed running (HSR) and a higher total distance covered in very-high-speed running (VHSR), under conditions limited to one or two ball touches, compared to conditions in which there were no limits to the number of ball touches. Heart rate remained constant, except in the case of a 4 vs.4 small-sided game. In this case, the heart rate was higher when the number of touches was limited to one to two [19], and the number of technical errors increased. Compared to amateur players, the professional players covered greater distances at higher speeds and had fewer technical mistakes [19; 31]. [PERSON] et al. [26] performed a critical analysis regarding the way SSGs are applied, how they are monitored and how they influence the performance of football players in the short and medium term. As a conclusion, they found that the use of small-sided games mainly in the form of three vs. three (pitch size between 20 \(\times\) 25 m and 27 \(\times\) 36 m) and four vs. four (pitch size between 30 \(\times\) 35 m and 30 \(\times\) 40 m) with three and five workouts per week, for at least one month, seems to have beneficial effects in terms of physical performance in junior footballers.