Competition and training induced physical fatigue, as an outcome of involvement in sport, has been shown to affect the motor skill execution of athletes (Aune et al., 2008). Fatigue can be considered as a performance constraint that affects not only motor processing but also the perceptual processing that is linked to the execution of skills required in expert level ball game participation (McMorris and Graydon, 1997; Royal et al., 2006). The performance of perceptual skills involving tasks such as choice reaction time typically improve during the completion of exercise tasks of increasing intensities until maximal energy expenditure is reached (Brisswalter et al., 1997; Chmura et al., 2002; Tomporowski, 2003). Many sports require participants to complete physical activities that involve moderate and maximal exercise intensities and at the same time perform perceptual motor skills that must be completed as quickly and accurately as possible (Chmura et al., 2002; Rendi et al., 2007). Furthermore, variations in the balance of exercise intensity and psychomotor response requirements between ball game sports may lead to the athletes involved demonstrating different perceptual processing attributes to support their physical and motor performance.
Sport oriented studies investigating the influence of the perceptual-cognitive skills related to visual processing, such as anticipation and pattern recognition, are capable of contributing valuable evidence to better understand the psychophysiological attributes of elite level athletes (Jackson et al., 2006; Williams et al., 2006). One aspect of visual processing that requires further investigation in the sport domain is decision-making time and accuracy in relation to discrimination of the speed of a moving object. Previous research in the neuroscience field has provided a more specific descriptor for this process termed 'speed discrimination' (Clifford et al., 1999; Huang et al., 2008; Overney et al., 2008).
Williams and Ford (2008) provided a detailed overview of the adaptations that may occur to perceptual-cognitive skills as a result of on-going involvement in practice and training. They proposed that "improvements in anticipation and decision-making skill are caused by changes in perceptual-cognitive skills, knowledge, and mechanisms that mediate how the brain and nervous system process information and control performance" (p. 10). Overney et al. (2008) used a set of seven visual discrimination tasks that included a measure of speed discrimination to assess differences in perceptual processing between tennis players, triathletes, and non-athletes. They found that time-related skills, such as speed discrimination, were superior in tennis players. In relation to team ball games, Kioumourtzoglou et al. (1998) reported significant differences between samples of elite and novice level volleyball players in the mean estimation time of the speed and direction of a moving object using computer based stimuli. Differences between the groups were not found in relation to the number of correct responses associated with the identification of the speed and direction of the moving objects. As yet no researchers have found a clear pattern of differences in the perceptual-cognitive processing skills of athletes involved in different sports.
During involvement in the game situation an athlete's cognitive activity is influenced by the level of fatigue. Several theories have been proposed that provide predictions about the effect of physical exertion on cognitive and decision making performance. In particular, Easterbrook's (1959) cue utilisation theory was developed to explain how variations in physical exertion produce changes in attentional processes. At low levels of exertion, cognitive performance may be poor as the individual attends to both relevant and irrelevant cues. As exertion levels increase, attention narrows until it reaches the level when attention is directed toward only task-relevant information. If the physical requirements continue to rise beyond the individual's optimal level, the capacity to focus on task relevant stimuli may be restricted causing cognitive performance to deteriorate. Tomporowski (2003) presented a detailed overview of studies examining the effects of exercise on cognitive function. The major conclusion drawn was that submaximal exercise resulted in an improvement in cognitive tasks such as reaction time and memory, whereas, tasks that involved bouts of exercise leading to voluntary exhaustion did not result in any significant improvement in cognitive performance. Of specific interest was Tomporowski's suggestion that maximal exercise tasks that involved decision-making skills typically resulted in faster response times but no change in the participants' error rates. None of the studies referred to by Tomporowski specifically investigated the effect of fatigue on the performance of speed discrimination tasks.
A number of studies have been completed that focus on fatigue in relation to the cognitive processing of athletes involved in specific sports. McMorris and Graydon (1997) found that the cognitive performance of experienced soccer players while undertaking both moderate and maximal exercise was significantly better than their cognitive performance at rest. The results, however, with respect to the speed-accuracy trade off indicated that the players' improvement in performance was due to quicker decision-making rather than accuracy, which was not significantly affected by exercise. Chmura et al. (2002) reported that improvements occurred in the choice reaction skills of 22 soccer players involved in the Polish Third Division league at each 3 minute assessment point during a progressive workload cycling protocol except for the final assessment at or near the maximum individual exercise workload. Zwierko et al. (2008) used an anaerobic running task, involving 18 Polish Division 2 male handball players, as the physical protocol for the assessment of peripheral perception skills. Players improved in both...