The aim of this study was to adopt concepts and tools from nonlinear dynamics in examining effects of boxer-target distance and perceived punching efficiency on emergent decision-making during a typical practice task in boxing.

ABSTRACT

Previous research has shown how dynamical systems theory provides a relevant framework for investigating decision-making behavior in sport. The aim of this study was to adopt concepts and tools from nonlinear dynamics in examining effects of boxer-target distance and perceived punching efficiency on emergent decision-making during a typical practice task in boxing. Results revealed the existence of critical values of scaled distances between boxers and targets for first time appearance and disappearance of a diverse range of boxing actions including jabs, hooks and uppercuts. Reasons for the diversity of actions were twofold: i) abrupt (qualitative) changes in the number of the possible punches, i.e. motor solutions to the hitting task; and ii), fine modification of the probabilities of selecting specific striking patterns. Boxers were able to exploit the emerging perception of strikeability, leading to a changing diversity of selected actions and a cascade of abrupt changes in the perceptual-motor work space of the task. Perceived efficiency of a punching action by the participants also changed as a function of the scaled distance to a target and was correlated with the probability of occurrence of specific boxing actions. Accordingly, scaled distance-dependent perceived efficiency seems an important perceptual constraint in the training task of punching a heavy bag in boxers.

INTRODUCTION

How do boxers choose their actions? What are the perceptual information sources used for coordinating punches at opponents? In combat sports such as boxing, studying decision- making behavior could inform sport scientists and coaches how to structure practice sessions so that athletes learn to perceive information and select appropriate actions as performance contexts change. Studying decision-making processes in motor behavior permits insights into the coordination of actions with respect to the environment i.e. investigating how perceptual information from the environment (e.g., information on target location and movement) constrains actions. Research from the theoretical perspective of dynamical systems theory is revealing that sports are providing rich movement models for the study of the dynamics of adaptive human movement behaviour, characterized as performer-performer and performer-environment interactions (Davids et al., 2005; McGarry et al., 2002).

The main characteristic of nonlinear dynamical systems theory is that it emphasizes the study of biological movement systems under the constraints of their natural environments, focusing on the parametric control of such systems. In nonlinear dynamical systems modeling, control parameters are defined as informational variables that can guide a system between different states of organization and order parameters are defined as collective variables that describe the organization of such systems. Control parameters are mathematical representations of the constraints that act on biological movement systems. These can be nonspecific (i.e. constraints that have a distinct informational nature from movement characteristics) and specific (i.e. constraints which have the same informational nature as movement characteristics). For example, perceptual information is a nonspecific source of information which can be harnessed to regulate the directional or timing characteristics of a movement because it does not specifically inform the dynamical characteristics of movement systems. On the other hand, intentions are specific constraints that can impose particular (intended) directional or timing information on a desired movement pattern. An important example of specific constraints on a biological movement is task constraints.

In nonlinear dynamical systems, unlike anything in the linear characterization of the movement systems, a minute change in the value of a control parameter can bring about a drastic (qualitative) change in a movement system's dynamics. For example, such an apparently small change in a control parameter can lead to the emergence of a new type of system organization such as a new type of punch in boxing or a new phasing mode among the limbs during walking which was not present before (see Kelso, 1995). This event is called a bifurcation or a phase transition in the systems' dynamics and is related to the spontaneous (i.e. not prescribed by some agent or system controller) self-organization of the motor system degrees of freedom. This spontaneous change is a result of the loss of the stability of a previous state of organization (e.g. an original action) and is not a consequence of some specific agent prescribing the change. Therefore, it is of particular interest in the movement and sport sciences to uncover the influential constraints (i.e. the key control parameters of the movement system), especially those with high ecological validity, which play an essential role in bringing about such spontaneous changes and determining the context in which athletes assemble goal directed movements. Perceptual constraints (i.e. key perceptual control parameters of the movement system) with the highest ecological validity are the directly perceivable affordances (see Vicente, 2003). These variables refer to the objective properties of the environment in which an organism (for example a boxer) acts in relation to his or her personal capabilities. They directly (not inferentially) specify to the organism what the environment affords him or her to do. Due to their dispositional nature the affordances take such names as reachability, climbability, pass - through - ability etc. For these reasons, specific boxing strikeability of the target (i.e. the heavy bag or an opponent) is a possible affordance candidate).

So, control parameters are key variables which act as information sources to harness the movement system dynamics. Of equal importance is the discovery of so called 'order parameters' which are collective variables which capture the macroscopic order of a movement system manifested as a characteristic action pattern (e.g., the relative phasing of two limbs). Such a dynamical systems modeling of boxer-opponent interactions requires that control parameters and order parameters are identified.

In an analysis of boxing movements inspired by dynamical systems theory, punching movements can be taken to represent classes of short lived, interceptive action patterns formed amongst upper limb motor system degrees of freedom. These actions are assembled or annihilated depending on emerging performance constraints on individual boxers considered as nonlinear dynamic movement systems (Davids et al., 2002). In boxing, the temporarily stable (meta-stable) actions represent time-varying intra- and inter- limb coordination states in movement systems with respect to more or less dynamic targets such as opponents, speed bags, hand pads and heavy bags (Turvey, 1990).

Theoretical modeling from the perspective of nonlinear dynamics has already disclosed the emergent characteristic of decision-making in performer-performer interactions (i.e. 1 v 1 sub-phases) in a range of different sports including sailing, basketball and rugby (Araújo et al., 2004; 2005; Passos et al., 2006). The study described in this article extends such analyses to the task constraints of combat sports. In many sports, a rule- governed system formed by a performer-performer dyad may be conceptualized as a dynamical system exemplifying interpersonal coordination and linked by visual (and other) informational fields (e.g. , Araújo et al., 2004). Araújo et al. (2004) have argued that, as with any other dynamical system, the emergent behaviour of performer-performer dyads (e.g., attackers and defenders) can be characterized by control parameter and order parameter relations.

This conceptual model of human interpersonal activity implies that a boxer and opponent may form a temporarily stable interactive dynamic system, since any striking movement of the boxer may be counterbalanced by defensive movements of an opponent. Anecdotal evidence from observing performer- performer interactions in boxing matches reveals that boxers do not activate striking patterns in all situations with equal probability. As in the 1 v 1 sub-phases of team ball sports, it seems likely, therefore, that diverse striking patterns are emergent, being conceptualized as a dynamic 'perceptual-motor landscape' assembled by boxers as they attempt to satisfy a range of interacting constraints arising from a specific performer-target system. In the perceptual-motor landscape formed by each boxer, actions differ in probability of emergence and stability, depending on the constraints acting on each specific performer-target system (Davids et al., 2003). For example, in boxing, observations suggest that jabs usually emerge at specific locations and distances from targets which differ from uppercuts and hooks. More formal dynamical systems modeling is needed to verify this observation. Analysis of the coaching literature in boxing (e.g., Walker, 2003) reveals that a candidate control parameter for an attacker-target system could be the intrinsic metric of the interpersonal distance between the attacker and a target such as an opponent or punch bag. This system metric is 'action-scaled' (Konczak, 1990; Konczak et al., 1992), because the dimensions formed by each individual performer-target dyad will differ. The use of an intrinsic metric signifies that the value of the control parameter might change depending on the action- scaled features (e.g., limb sizes) of specific performer-target systems. Furthermore, because of the configuration of motor system degrees of freedom into different boxing actions during performance, it is tempting to assume that each punching action has its own reachability domain, dependent on unique physical constraints of each individual, e.g., effective arm length, and the objective distance to a target. Thus, by intentionally changing the relative distance to a target, performers can influence the emergence of certain types of punches and consequently the diversity of their action space. Hence, it might be useful to examine whether adaptive behaviour of boxers might emerge as a consequence of the context, potentially defined by a finite set of task, environmental and personal constraints, varying on different time scales.

Keywords : Martial arts, boxing, affordances, decision-making, action selection

Average user rating

   (0 vote)