The dynamics of combined passes is thought to be one of the most striking features of modern soccer (Tenga et al., 2010). Barcelona FC, for example, typically has a game style (Chassy, 2013) characterized by fast, accurate, and locally built passes capable of breaking the stability of the opposing team (Paixao et al., 2015). This style of play was considered an evolutionary phenomenon in elite soccer (Barreira et al., 2015) and has attracted the attention of spectators, coaches, and sports scientists. For example, Paixao et al. (2015) showed that players using this style act more grouped, particularly in the half field sector, due to the defensive strategies and balance between the teams. This configuration caused higher density and congestion of players in the center of the field, thereby affecting the distances covered by the players, their passing style, and the overall ball speed (Kuhn, 2005). Thus, to perform a successful pass and take advantage of the action opportunities offered by the dynamic structure of the game, a player needs to perceive the location of a teammate and then pass the ball with a specific speed and direction. Indeed, in competitive team games, opportunities to make a pass arise and disappear according to the spatiotemporal relationships established between competing performers (Travassos et al., 2012a).
Recently, ecological dynamics has been proposed as a reliable theoretical framework to examine sport performance based on performer-environment relationships, i.e., at the ecological scale of analysis (Araujo et al., 2006). These studies revealed that players couple their actions in space and time to information emerging from key environmental and task constraints during performance (Travassos et al., 2012c). Thus, successfully using the opportunities for action (i.e., affordances) that emerge as individuals interact with their environment ultimately sustains adaptive performance behaviours and task achievement.
The ecological theoretical approach raises the hypothesis that experiencing unfavourable situations in the teaching-learning environment encourages players to explore the information from key environmental and task constraints and thereby create potential innovative gameplay solutions (Davids et al., 2013; Passos and Davids, 2015; Silva et al., 2016). A few studies examined how the manipulation of specific constraints in small-sided and conditioned games (SSCG's), such as the number of players (Silva et al., 2015; Travassos et al., 2012c) and the spatial dimension of the game (Silva et al., 2014; Vilar et al., 2014), can influence interpersonal interactions. Indeed, such manipulations affected the spatial relationship between the players because they imposed continuous and diversified co-adaptations between attackers and defenders. For example, decreasing relative space constrains the interactions between players, as they have less time and space to act. These spatiotemporal constraints produce new information for ball-passing opportunities, which in turn promotes certain patterns of behavior by teammates and opponents. Previous research addressing the effects of field dimensions on tactical behavior reported different co-adaptations among players, depending on the available space between them. Silva et al (2014) observed larger trajectories of the players' movements in smaller game spaces. In addition, Vilar et al. (2014) showed that in smaller spaces, the players reduce their ball possession time by encouraging the exchange of passes and by increasing the rhythm of the game. These results suggest that key manipulations force players to engage in different functional-tactical behaviors, such as dribbling, passing, kicking, and marking, to create potential game-play solutions.
A specific type of SSCG's used by soccer coaches to reinforce local problem-solving (e.g., controlling and exchanging passes under the pressure of marking) is known as "rondo". Rondo is the term popularly used in Europe, but it can also be known as "bobinho" in South America, or by the recreational term "piggy in the middle" in the USA. The rondo game is a traditional activity in soccer used in various countries and contexts of sport action, such as recreational, educational and professional (DiBernardo, 2014). In this game, the players engage in combined passes while being pressed by a marker, and they are typically in numerical inferiority and have short time windows and space of action. The marker(s) must try to intercept the exchange of passes or force the opponents to error under a delimited area. On the other hand, the passers must keep the marker(s) as far as possible and exchange passes between them to maintain possession of the ball. Almost everything that happens in a soccer match other than kicking to the goal can be simulated in the rondo in its many possible configurations. Moreover, many coaches believe that the dynamic interpersonal interactions involved in the exchange of marking passes promote the development of functional and adaptive skills for space exploration/occupation in a soccer match environment (DiBernardo, 2014).
Although rondo is widely used and popularized in soccer, few studies describe the characteristics of this game or the patterns of marking behaviour that emerge from this competitive context. This type of information is, however, important for soccer coaches aiming to organize their activities according to the intended behavior.
Travassos et al. (2012d) analyzed ball velocity and passing accuracy data in an exchange-of-passes training situation involving four passers, and found that the characteristics of these passes were similar to those from a formal game of futsal. These results suggest that this particular task (training situation) has the ideal configuration to reproduce the characteristics of passes in the game situation (see representative design, Pinder et al., 2011; Araujo and Davids, 2015).
We propose that the inclusion of a marker in the center of the exchange of passes may influence the players' pass options by limiting the formation of pass lines, similar to situations of triangulation of pass exchanges, as in the formal game context. Thus, we hypothesize that rondo expresses characteristics of team synergies (Araujo and Davids, 2016) such as: (1) dimensional compression, which can be analyzed by team behavior-composed variables such as geographical center; and (2) an inherent tendency for self-organization (i.e. interpersonal dynamics push the system into a state of order) as a function of the task constraints; (3) reciprocal compensation between players; and (4) degeneracy (i.e., flexibility in the ways to achieve the same goals).
In this study, we test this hypothesis by analyzing the effects of manipulating playing space and ball possession time on the coupling between marker and passers with an experimental protocol based on rondo. By using the configuration defined by Travassos et al. (2012d), we also assessed whether these interpersonal interactions between players differed between age groups.
Our specific objectives were: a) to analyze the characteristics of the passes, specifically, interpersonal distance between the passer and the marker, interpersonal distance between the passer and the receiver, interpersonal distance between the marker and the receiver, angle and speed of each of these passes; b) to analyze the players' correlations (coupling strength and the time lag) between the passers (represented by the passers group centroid) and the marker throughout a rally; and c) to determine the differences in the characteristics of the passes, and in the players' correlations, between age groups (U13, U15, U17 and U20).
Twenty (n = 20) Brazilian male soccer players participated in this study. The participants were selected in a distributed manner across four training categories: U13 (n = 5), U15 (n = 5), U17 (n = 5) and U20 (n = 5). The data for each group is shown in Table 1.
The inclusion criteria for this study were that the participants: (1) had trained for at least one year in the club analyzed; (2) played in a outfield position (defender, midfield or forward positions); and (3) had taken part in official competitions (regional, state and/or national).
All participants and their parents were informed verbally and in writing of the aims and requirements of the experiment. For the participants under 18 years old, the parents signed an informed consent. The research project was fully approved by the Ethics Research Committee of the Santa Cruz State University (Brazil) with protocol number CAAE: 28947714.7.0000.5526 according to the Declaration of Helsinki.
The task was carried out in a grass field of the training club. The experimental task was based on the rondo game with the configuration of four (n = 4) passer players and one (n = 1) marker player (Figure 1A). Four experimental conditions were presented: (1) expanded space and free pass (EF,2) expanded space and direct pass (ED,3) restricted space and free pass (RF), and (4) restricted space and direct pass (RD).
In the expanded and restricted space conditions, the participants were allowed to move inside a circular spatial dimension of 9 or 6 meters in diameter, respectively. In both conditions, the marker started the task in the center of the circle, and the passers could position themselves freely inside the circle (without moving beyond the border).
In the free-pass condition, the passers had no any restrictions on ball possession and could therefore easily keep the ball under control, statically or dynamically, whenever and wherever they wanted. In contrast, in the direct-pass condition, the passers could not touch the ball more than once, and therefore had to receive and pass the ball with one touch only.
The task manipulations aimed to change the intensity of the marking and the movement of the ball during game performance...