Training methods for athletes have changed regularly over the years, as coaches, sport scientists and the athletes themselves continually experiment to try and find the best types and structure of practice to hasten the acquisition of expertise and to ensure maximal performance. With the performance gains possible through the refinement of physical conditioning progressively diminishing, there has been increasing interest in how performance improvements might be gained through changes in the design of practice for skill learning. It is within this context that there has been growing interest over the past decade or so in the potential of systematic visual training as a means of hastening skill development. The purpose of this paper is to explore the evidence base for, and relative merit of, of general visual training and sport-specific visual training. Fundamental Assumptions Underpinning the Efficacy of Visual Training If any visual training program is to be successful in enhancing skill learning and skill performance then three fundamental conditions must hold true. First, the aspect or aspects of vision being trained must be directly related to skilled performance in the sport of interest. Ideally there should be a monotonic relationship between the level of development of the visual attribute and skill performance, such that sub-normal development of the attribute limits performance and supra-normal development is beneficial to performance. Second, the attribute must be able to be trained and its level not simply determined by immutable genetic factors. Third, improvements in the visual attribute in response to training must translate directly into an improvement in sport skill performance. This latter condition is especially important given the possibility that a visual attribute/function might be improved with training without concomitant improvements in skilled performance (such as in the case where the trained attribute is not a limiting factor to skilled performance) or conversely the possibility that performance may be improved (e.g., in response to improved confidence, self-efficacy, technique) without a corresponding improvement in vision. Generalised Visual Training: The Evidence Generalised visual training programs are characterised by the use of training stimuli and exercises that are simple and non-sport-specific. Repetitive eye exercises (typically using generic alphanumeric stimuli) are used in an attempt to improve basic visual functions (such as acuity, eye tracking and peripheral awareness) with the consequential assumption that this will enhance sports performance. The majority of the existing generalised visual training programs have their origins in behavioural optometry with support for efficacy being based primarily on anecdotal evidence and clinical reports. There is reason for some scepticism as to the likely efficacy of generalised forms of visual training. First, there is far from a compelling evidence base to indicate that basic visual functions of the type targeted by generalised training programs are monotonically related to skill. There is a paucity of evidence to indicate that superior athletes are characterised by superior basic visual function - indeed there are a surprising number of reports that indicate, to the contrary, unexpectedly high levels of uncorrected basic visual defects in elite athletes (e.g., Garner, 1977). There is also evidence that fundamental visual attributes, like acuity, can be degraded quite dramatically without having a major impact on motor performance (e.g., Applegate & Applegate, 1992). As exceptional levels of function on general visual attributes do not appear to characterise expert performance (Starkes & Deakin, 1984), and as general visual attributes do not appear to be consistently the limiting factors to the attainment of expert sports performance, focusing effort on the training of general visual attributes may be ill-directed (Abernethy, 1996). A second concern is in relation to the trainability of basic visual functions. While there is good evidence that basic visual attributes such as foveal acuity, accommodation and visual field size can all be improved with training (e.g., McKee & Westheimer, 1978), in many cases the improvements are most marked in those with pre-existing defects (thus leaving open the question of transferability of these findings to athletes with normal vision). Moreover, much of the evidence for positive training effects is from studies where both the training and measurement device are identical, hence making the differentiation of genuine visual function improvement from instrument familiarity effects impossible. There are relatively few controlled trials of the efficacy of generalised visual training. West and Bressan (1996) reported favourable effects for generalised visual training programs but in the absence of suitable placebo groups to control for expectancy effects. Wood and Abernethy (1997), using exercises advocated by sports optometrists, and Abernethy and Wood (2001), using commercially available visual training programs, were unable to find any positive effects of visual training upon skill performance. The visual and sports performance of groups given visual training were indistinguishable from those of placebo and control groups. Sport-Specific Visual Training: The Evidence In contrast to generalised visual training, in sport-specific visual training the emphasis is upon training using visual stimuli, patterns and situations typical of those encountered in the actual sport task. Given this sport-specificity, it is possible to more closely match the type of training stimuli that are used to the limiting factors to performance. The existing studies on sport expertise are consistent in their findings that both the ability to recognise sport-specific patterns and the ability to anticipate the actions of an opponent on the basis of advance (movement pattern) information are characteristics that reliably discriminate expert performers from non-experts, even in situations where the basic visual function measures of the different skill groups are indistinguishable (e.g., Starkes, 1987). As performance on sport-specific pattern recognition and anticipation appear to be monotonically related to skill level, and potentially limiting factors to the performance of non-experts, it is logical to try to hasten the acquisition of expert performance by systematically training these attributes. A growing number of studies now exist to demonstrate that through the use of repeat exposures to video simulation of the displays normally encountered by athletes it is possible to bring about improvements in sport-specific pattern recognition and anticipation. Studies in racquet sports (e.g., Abernethy, Wood & Parks, 1999; Farrow et al., 1998) and in team sports such as basketball (Starkes & Lindley, 1994) demonstrate significant improvements in key perceptual skills after repeated videobased training. However, a persistent shortcoming among many of these studies is failure to demonstrate transfer of training effects beyond the laboratory and into the actual performance setting. A limiting factor in this respect has been difficult in finding a suitable in situ measure of anticipation or pattern recognition. In a recent study we (Farrow & Abernethy, 2002) attempted to address this concern by measuring the anticipatory movements of tennis players on court when their vision of the server's action and the subsequent ball flight was selectively occluded using liquid crystal goggles. Pre- to post-training improvements in anticipation were compared between groups given two different types of visual training (implicit and explicit learning conditions) and control and placebo groups. Some evidence was accrued to suggest that for perceptual learning, like learning in self-paced motor tasks such as golf putting (e.g., Masters 1992), superior learning of expert-like characteristics may be achieved in conditions in which verbal, conscious attention to task rules and procedures is minimised rather than maximised. More fully understanding implicit and explicit learning of those visual attributes known to be important to expert sports performance must be an important priority for future skill acquisition research..
© Copyright 2002 Expertise in Elite sport. 2nd International Days of Sport Sciences, 12.-15. November 2002, INSEP, Paris (France). Veröffentlicht von INSEP. Alle Rechte vorbehalten.