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This paper focuses on the paradoxical relationship between game unpredictability and the certainty of players' actions in team ball sports. Our research on this relationship leads us to suggest a method for training decision making, which we exemplify in the team sport of Rugby Union. The training methodology is based on application of theoretical insights from Ecological Psychology Complex Dynamical Systems and the Constraints-Led Approach. The paper starts with a critical overview of traditional approaches to studying decision making in sport. Next we describe the sport of Rugby Union to exemplify a complex dynamical system, and explain how that conceptualisation captures the interactions of players within that performance context. We conclude our analysis by describing how to manipulate task constraints to improve decision-making performance, as players search for an appropriate blend of stability and variability in their actions. In the final part of the paper, we suggest some methods to train decision making based on four stages: I) identifying the problem; ii) setting out a strategy to solve it; iii) creating an action model; and iv) building a decision-making exercise. The main conclusion from our work for coaches and sports scientists is that decision making should be improved through training methods that provide an accurate balance between stability of actions, which gives structure to the players' performance, and variability which allows them to cope with the uncertainty of situational constraints, such as the behaviour of specific opponents

Previous work on dynamics of interpersonal interactions in 1 vs. 1 sub-phases of basketball has identified changes in interpersonal distance between an attacker and defender as a potential control parameter for influencing organizational states of attacker-defender dyads. Other studies have reported the constraining effect of relative velocity between an attacker and defender in 1 vs. 1 dyads. To evaluate the relationship between these candidate control parameters, we compared the impact of both interpersonal distance and relative velocity on the pattern-forming dynamics of attacker-defender dyads in the sport of rugby union. Results revealed that when interpersonal distance achieved a critical value of less than 4 m, and relative velocity values increased or were maintained above 1 m x s(-1), a successful outcome (i.e. clean attempt) for an attacker was predicted. Alternatively, when values of relative velocity suddenly decreased below this threshold, at the same critical value of interpersonal distance, a successful outcome for the defender was predicted. Data demonstrated how the coupling of these two potential, nested control parameters moved the dyadic system to phase transitions, characterized as a try or a tackle. Observations suggested that relative velocity increased its influence on the organization of attacker-defender dyads in rugby union over time as spatial proximity to the try line increased.

Ecological dynamics characterizes adaptive behavior as an emergent, self-organizing property of interpersonal interactions in complex social systems. The authors conceptualize and investigate constraints on dynamics of decisions and actions in the multiagent system of team sports. They studied coadaptive interpersonal dynamics in rugby union to model potential control parameter and collective variable relations in attacker-defender dyads. A videogrammetry analysis revealed how some agents generated fluctuations by adapting displacement velocity to create phase transitions and destabilize dyadic subsystems near the try line. Agent interpersonal dynamics exhibited characteristics of chaotic attractors and informational constraints of rugby union boxed dyadic systems into a low dimensional attractor. Data suggests that decisions and actions of agents in sports teams may be characterized as emergent, self-organizing properties, governed by laws of dynamical systems at the ecological scale. Further research needs to generalize this conceptual model of adaptive behavior in performance to other multiagent populations.

This study examined the effects of the numbers of players involved in small-sided team games (underloading and overloading) on opportunities for maintaining ball possession, shooting at goal and passing to teammates during training. These practice constraint manipulations were assumed to alter values of key performance variables identified in previous research, such as interpersonal distances between players and time to intercept shots and passes. Fifteen male soccer players (age: 19.60±1.99 years) were grouped into three teams and played against each other in different versions of small-sided soccer games, in which the number of players was manipulated in three different conditions: 5 vs. 5, 5 vs. 4 and 5 vs. 3. Dependent variables were the values of interpersonal distance between an outfield attacker and nearest defender (ID), and the relative distance of a defender needed to intercept the trajectory of a shot (RDi shot ) or pass (RDi pass ). Statistical analyses revealed that mean ID values were significantly lower in 5 vs. 5 than in 5 vs. 4 and 5 vs. 3 conditions, and significantly lower in 5 vs. 4 than 5 vs. 3. They also revealed that mean values of RDi shot were significantly higher in 5 vs. 3 than in 5 vs. 5 conditions. Finally, results showed that the mean values of RDi pass were significantly higher in 5 vs. 3 than in 5 vs. 5. Findings revealed how task constraints in SSGs can be manipulated to vary values of key spatial and temporal performance variables (interpersonal distance and time to intercept) to influence the nature of interpersonal interactions between competing players during practice. We observed that these manipulations tended to decrease opportunities for maintaining ball possession during training when equal numbers of attackers and defenders existed in SSGs, and led to more shots and passes emerging when the number of defenders was decreased relative to attackers.Key words: Affordances, Association Football, Ball Possession, Constraints-Based Approach, Interpersonal Distance, Small-Sided Games, Soccer INTRODUCTIONSuccessful performance in team sports like soccer is influenced by the ability of players to identify opportunities for actions from their spatial-temporal relationships with other players (both teammates and opponents) and key task constraints (such as the location of the sidelines, goal and ball) 1 . For example, an ecological dynamics analysis of performance has demonstrated how defenders decrease the values of interpersonal distance to ball carriers to dispossess them and recover ball possession 2 . To prevent this from happening and maintain ball possession, teammates use information of this closing gap in distance between ball carriers and defenders to move towards the ball carrier and afford him more passing opportunities 3 . Additionally, ball carriers have also been observed to regulate their passing and shooting actions according to the time available for the opponents to reach the trajectory path of the ball to intercept a shot at goal or a pass 4, 5 . Importa...

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