Over the last years there has been a substantial growth in research related to specific training methods in soccer with a strong emphasis on the effects of small-sided games. The increase of research in this topic is coincident with the increase of popularity obtained by specific soccer conditioning, which involves training players to deal with soccer match situations. Given the limited time available for fitness training in soccer, the effectiveness of small-sided games as a conditioning stimulus needs to be optimized to allow players to compete at the highest level. Available studies indicate that physiological responses (e.g. heart rate, blood lactate concentration and rating of perceived exertion), tactical and technical skill requirements can be modified during small-sided games by altering factors such as the number of players, the size of the pitch, the rules of the game, and coach encouragement. However, because of the lack of consistency in small-sided games design, player fitness, age, ability, level of coach encouragement, and playing rules in each of these studies, it is difficult to make accurate conclusions on the influence of each of these factors separately.

The aim of this study was to compare footballers' movement behaviour during 2-, 3-, 4- and 5-a-side small-sided games. Ten young professional players (age = 18.0 ± 0.67 years) participated in 3 bouts of each small-sided games for 6 min with 1 min of active rest between bouts. Positional data were collected using GPS system units and used to calculate the following variables: team centroid, distance between each player and own and opponent team centroids and distance between centroids. Approximate entropy was used to identify the time series regularity for each variable. The distance to own team centroid increased with the number of players (effect sizes from moderate to perfect). The results from the distance to the opponent's centroid exhibited a similar trend. The distance between centroids decreased from 2- to the 4-a-side, but then increased in 5-a-side. A higher number of players were associated with lower approximate entropy values, suggesting higher positional organisation in small-sided games with more players. The highest movement regularity found in 4- and 5-a-side identified these formats as more adequate to promote team-related emergent and self-organised behaviours.

The aim of this study was to identify the acute physiological responses and activity profiles of football small-sided games (SSG) formats. Ten professional football players participated in 4 variations of SSG (2-, 3-, 4-, and 5-a-side) with an intermittent regime involving 3 × 6-minute bouts with 1 minute of passive planned rest in which the heart rate (HR), rating of perceived exertion (RPE), activity profile, and body load were recorded. The higher percentage of maximum HR values were found in 2- and 3-a-side formats (p ≤ 0.05). The lowest RPE value was found at the 5-a-side, and the highest was found at the 2-a-side (13.48 ± 2.67 and 17.01 ± 1.80, respectively, p ≤ 0.05). The distance covered in the 2-a-side format (598.97 ± 78.91 m) was smaller than in all other formats. The 2-a-side format presented the lowest number of sprints (0.71 ± 0.86) and the 3-a-side the highest (2.50 ± 1.65). Statistically significant differences were found across SSG in the total body load. The 4-a-side presented the highest and the 5-a-side the lowest values (95.18 ± 17.54 and 86.43 ± 14.47, respectively). The body load per minute declined each 2 minutes of play. Maintaining a constant area:player ratio, coaches can use lower number of players (2- and 3-a-side) to increase cardiovascular effects but use higher number of players (4- and 5-a-side) to increase variability and specificity according to the competition demands.