An examination of the visual exploratory actions of association football players

Successful performance in association football (soccer) is determined by the interaction between the technical, tactical and physical components of match-play. While each of these factors have received extensive research attention, the actions that inform the technical, tactical and physical components of play have been relatively under-investigated. Football environments change on a moment-to-moment basis, therefore, to successfully guide their actions, players need to maintain a constant understanding of their surrounding environment. This is done with active movement of the eyes, head and body – termed visual exploratory action - which allows visual perception of affordances, that is, the possibilities for action in one’s surrounding environment. Performatory actions, such as passing, moving to space and tackling, are informed by the perception of affordances that exploratory actions provide. Whether these performatory actions are afforded, however, is constrained by the relations between each individual actor (and their action capabilities), the environment (such as the weather, the ball and social expectations), and the task (such as the laws of the game and the team’s strategy). Given the complexity of these interacting constraints, and the difficulty in quantifying these constraints at any given time, gaining an understanding of how an athlete visually perceives their environment (that is, their visual exploratory actions) is necessary before moving to more complex questions relating to what a player visually perceives. Taking the Ecological approach to visual perception, this thesis aimed to gain an understanding of the visual exploratory actions used by football players to perceive their environment in 360-degrees. To fulfil this aim, a series of four studies were completed. Study 1, a systematic review of literature investigating the technology assisted quantification of visual exploratory actions, showed that eye-movements of football players have been examined extensively, but that representative designs were rarely used to investigate these actions. As a result, there is not a clear understanding of the eye-movements of players during actual football match-play. Further, the reliance on eye-movement registration technology has resulted in experimental designs that primarily present information directly in front of participants or do not require realistic responses. This is problematic given that, during match-play, players are required to perceive their environment in 360-degrees and need to respond with footballing actions. The systematic review of literature showed that there is a need to investigate the visual exploratory head movements of football players, using alternative technologies, while they perform in representative environments. vi Studies 2, 3 and 4 utilised head-mounted microelectromechanical systems (MEMS) inertial measurement unit (IMU) technology to quantify the head movement of footballers while they participated in either a football passing task (Study 2) or 11v11 match-play (Study 3 and 4). Depending on the research question, IMU data were processed to obtain the number, frequency and/or excursion (i.e. size in degrees) of exploratory head movement events. Study 2 investigated the relationship between exploratory action prior to receiving the ball and subsequent performatory action using a novel experimental design. By presenting task relevant information 360-degrees around the participants and requiring a football passing response, this study was able to investigate the relationship between exploratory head movement and passing response speed. Findings revealed that, when players were given 2- seconds or 3-seconds to explore before receiving the ball, they would explore with a lower frequency of head movements with the ball and were able to complete the passing response more quickly, compared to when they were given only 1-second to explore. Importantly, categorical linear regression revealed that when players explored with a higher frequency of head movements before receiving the ball, they were able to respond with a passing action more quickly. Study 3 extended on Study 2 by investigating the relationships between exploratory action before receiving the ball and performance with the ball during 11v11 match-play. In addition, to understand when visual exploration is most important for performance, this study quantified the exploratory head movements of players in various time-periods before ball possession. When players explored with a higher frequency or with greater excursion than their individual average before ball possession, their performatory actions with the ball were more likely to be turns with the ball, a pass to an area that was opposite to where it was received, or a pass in an attacking direction. However, players were not more likely to play a successful pass following higher than average exploratory action. Additionally, the strength of these relationships changed according to the time-period before ball possession that was quantified. These findings showed that extensive visual exploratory action supports players’ performance with the ball, such that they are better able to make use of their surrounding environment. Study 4 represented the first study to investigate the constraining factors on players’ visual exploratory actions during 11v11 match-play. Results showed that playing role, pitch position and phase of play all constrained the visual exploratory actions of players. Players explored most extensively when they had possession of the ball, and least extensively during transition phases of play. In contrast, however, there were no differences between team vii possession and opposition phases of play. Wide players explored more extensively during defensive phases of play (i.e. opposition ball possession), while central players explored more extensively during attacking phases of play (i.e. team ball possession). This deeper understanding of constraining factors on visual exploration can be used to inform the development of representative training designs in football. Together, the findings supported the theoretical basis of the thesis, such that visual exploratory actions supported the discovery of afforded actions and prospective control of movement. Additionally, the findings provide some insight into the constraining factors on visual exploratory action in football. The findings have important implications for research methodology and applied practice. The novel use of wearable technology to quantify visual exploratory head movement throughout this thesis shows the value of these alternative methods for future investigations, particularly in the ability to quantify exploratory head movement in representative environments. Further, by developing the visual exploratory actions of players when they do not have the ball, coaches may see improvements in technical and tactical performance. While the novel methods used throughout this thesis have some limitations, the theoretical underpinnings, methodology and findings of this thesis provide a platform for future investigations of visual exploratory action in football and various other domains