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.

Background:This study was conceived to analyze how exercise and weight management psychosocial variables, derived from several health behavior change theories, predict weight change in a short-term intervention.

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.

Background: Changes in body image and subjective well-being variables (e.g. self-esteem) are often reported as outcomes of obesity treatment. However, they may, in turn, also influence behavioral adherence and success in weight loss. The present study examined associations among obesity treatment-related variables, i.e., change in weight, quality of life, body image, and subjective well-being, exploring their role as both mediators and outcomes, during a behavioral obesity treatment.

Team games conceptualized as dynamical systems engender a view of emergent decision-making behaviour under constraints, although specific effects of instructional and body-scaling constraints have yet to be verified empirically. For this purpose, we studied the effects of task and individual constraints on decision-making processes in basketball. Eleven experienced female players performed 350 trials in 1 vs. 1 sub-phases of basketball in which an attacker tried to perturb the stable state of a dyad formed with a defender (i.e. break the symmetry). In Experiment 1, specific instructions (neutral, risk taking or conservative) were manipulated to observe effects on emergent behaviour of the dyadic system. When attacking players were given conservative instructions, time to cross court mid-line and variability of the attacker's trajectory were significantly greater. In Experiment 2, body-scaling of participants was manipulated by creating dyads with different height relations. When attackers were considerably taller than defenders, there were fewer occurrences of symmetry-breaking. When attackers were considerably shorter than defenders, time to cross court mid-line was significantly shorter than when dyads were composed of athletes of similar height or when attackers were considerably taller than defenders. The data exemplify how interacting task and individual constraints can influence emergent decision-making processes in team ball games.

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Identifying the reasons for which some individuals and teams achieve success is one of the most common goals in the research literature on sport performance. The methodologies used to study sport performance have been established to compare the actions of successful and unsuccessful teams and athletes, and the outcomes include a range of statistical data of discrete actions performed by teams and players during competition (see Hughes & Franks, 2004). Despite the importance of these data, a significant criticism of the notational analysis of sport performance is that it does not identify the reasons for those discrete actions in order to explain the difference between successful and unsucessful teams. The data typically inform us of what happens, but not of how and why it happens.To understand the dynamical processes in sport performance, McGarry and Perl (2004) used a specific type of neural network: the Kohonen feature map. They argued that the neural networks approach must be used first to recognize situations and analyze processes, and only then to identify decision-making processes. However, with that approach, a 2-D information structure (e.g., a pair of coordinates) was implemented to represent a pattern, which decreases the ability of a neural network to analyze the complex processes that emerge in sports contests.Additional problems of network learning processes include their dependency on input patterns and the fact that those patterns change continuously as a result of a player's tactical behaviors. A theoretical rationale from the field of ecological psychology allows us to understand that tactical behaviors are dependent on the information available in specific contexts, and that that information is geared to each player's tactical behavior. Clearly, the use of Kohonen feature maps to study performance might incur problems in reliably recognizing patterns in sports contests. Another method proposed by McGarry and Perl (2004) is the dynamical controlled network (DyCoN), already tested successfully in different areas of sport (Perl, 2002). This method deals with the problem of dependency on input patterns. The DyCoN has the ability to learn continuously or in discrete phases, so input patterns need not be presented to the network in a single data set. McGarry and Perl (2004, p. 241) argued that the information acquired during the learning of the DyCoN could be used in "complementing our understanding of the processes that take place in the learning of cognitive and/or motor skills In previous attempts to identify dynamical systems properties in patterns of play in team sports, only 2-D analysis methods have been used, implying that the plane of motion must be preselected and that movements out of the chosen plane are ignored. In the present study, we examined the usefulness of 3-D methods of analysis for establishing the presence of dynamical systems properties, such as phase transitions and symmetry-breaking processes in the team sport of rugby. Artificial neural networks (ANNs) were employed to re...