There is a growing body of research investigating improvement in sport performance as a result of the use of vision training interventions [1,2,3]. Perceptual information influences many motor tasks, subsequently enabling accurate control to be maintained in fluctuating or uncertain environments . Consequently, alterations to the environment will regularly produce task performance variations. As vision is typically our central source of sensory information, researchers have established different methods to explore visuo-perceptual mechanisms (see Williams and Jackson  for a review). For example, research has been conducted to explore the possible uses of audio-based interventions to promote significant improvement in sport performance . Alternatively, the use of synchronised metronome training and temporally occluded videos has been shown to be successful in improving elite performers timing ability and anticipation in female soccer players and male goalkeepers, respectively [7, 8].
A common experimental intervention has been to present participants with discontinuous visual feedback or information while they complete tasks demanding a high amount of temporal and spatial precision (visual occlusion) . This procedure involves using video editing to occlude body parts or movements to investigate how athletes use vision to anticipate actions successfully. Early studies indicated that visual pick up might not be essential for continuous motor control due to continuous interaction of motor processes with cognitive and perceptual processes [10,11,12].
However, in tasks that encompass interceptive action, research has reported that the comparative prominence of vision is magnified . Consequently, authors have suggested that the neural reaction of the visual system is united which effectively results in uninterrupted perception [14, 15]. Through practice and enhanced knowledge due to experience, accomplished performers have more efficient and optimal cognitive processes making fewer errors by means of advanced visual cues to predict the result [16, 17]. More recently, technological advances have led to stroboscopic spectacles being developed, which, have been shown to reduce this dependence and force the performer’s visual system to train in more difficult conditions, potentially leading to improved performance once the eyewear has been removed [1, 18].
The growth of liquid crystal occluding spectacles (stroboscopic) has delivered a potential technique of addressing some of the restrictions intrinsic to past research which include field accessibility, portability and ease of administering interventions . The underpinning theory of stroboscopic vision training (SVT) is that the reduction in visual samples received forces the participant to employ the remaining samples more resourcefully and make greater use of other senses, in particular, kinaesthetic awareness. By taking away partial vision, varying speeds and modes, another principle of stroboscopic vision is to assist in creating autonomous schemas to prepare an athlete for performance. This reduction in visual samples received has been assumed to improve the natural connection between visual perception and action mechanisms and improve skills in anticipation  and processing speed . For a comprehensive review, see Wilkins and Appelbaum .
Stroboscopic visual training has been shown to have an impact on selected visual variables (e.g. peripheral accuracy), and provides an opportunity to examine eye–hand coordination (EHC) in relation to performance evaluation due to a paucity of research in this area. Research using stroboscopic exposure has been conducted into the prevention of air travel sickness , space motion sickness , and has been shown to be an effective countermeasure in these particular ecologically valid environmental settings.
The question of whether visual-motor training under stroboscopic visual conditions produces and generalises learning to an untrained domain is currently under debate [1, 2]. The logical progression is to examine the integration of discontinuous visual samples in several perceptual-motor activities. In tasks that are less reliant on uninterrupted visual parameters (e.g. movement behaviour), there are often no effects of discontinuous vision manipulations, even with obscured vision intervals as long as 500 ms . When the binocular samples are disconnected by a non-visual interlude of less than 40–80 ms, performance is maintained at a practical level . This area of research has examined the integration of discontinuous visual samples in perceptual-motor tasks such as manual aiming and one-handed catching. For example, an analogous decrement in catching performance has been identified for increase in the no-vision interval between uninterrupted 20 ms visual samples (i.e. from 0 to 80 ms) .
Recent research has investigated the use of SVT to improve sporting performance [2, 18,19,20, 25,26,27,28,29,30,31,32]. Overall, these studies have utilised differing training period lengths and time points for measurements of performance. For example, Appelbaum et al.  conducted research on 157 university students and athletes exploring catching, frisbee throwing accuracy, and speed and agility drills. The participants attended between 2 and 10 sessions of varying lengths of time (15–28 min). Strobe Vision Training led to significantly improved detection of centrally presented motion coherence and improved divided attention, but not in multiple-object tracking. Applebaum et al.  followed a similar design and demonstrated that an SVT group showed greater improvement in memory, and was also retained 24-h post-training period. At present, few studies employ post-training tests to measure any residual learning. An exception to this is Smith and Mitroff’s research  that assessed anticipatory timing (AT) using a 5–7 min acute exposure to SVT and included immediate, 10-min and 10-day post-training period performance tests. These authors indicated that the experimental group had significantly better anticipation in post-test but not in retention.
Reichow et al.  also evaluated stroboscopic effects on AT using a Bassin Anticipation Timer. Stroboscopic vision training did not improve accuracy in this case and the authors speculated that this might be due in part to the relatively slow testing speeds used. An investigation by Schwab and Memmert  used impulse shutter glasses as part of a 6-week general vision training (GVT) intervention with youth male field hockey players. Although they found improvement in terms of performance for the experimental group, the strobes were one of a multitude of loading devices and therefore effects could not be attributed exclusively to the effects of the SVT.
An intervention study combining multiple weeks of prolonged exposure to SVT drills in conjunction with typical softball activities identified that effects of training may have led to improvement in sensorimotor skills  The collegiate athletes completing a SVT exhibited improvement in dynamic drills associated with sensory-motor performance that are important for sporting performance. Second, a 6-week pre-season period (followed by a maintenance programme during the season) including standard vision training exercises (including wearing strobes) was found to improve bating parameters by 10% or more in a group of university baseball players . Whilst it is impossible to know if the stroboscopic element was the primary cause for improvement, this seemed encouraging. There is also currently a pre-registered study combining SVT with other techniques whilst testing far transfer to baseball performances and using a placebo-controlled design which may add extra understanding of the techniques used in an applied setting .
Wilkins and Gray  investigated the acquisition of ball catching skills over a sustained 6-week period. No significant differences were found between catching or visual tests, however, catching performance changes were strongly correlated with scores in the visual tests. Another SVT intervention exposed male national hockey league players to either strobe or control conditions during their normal training camp activities . The strobe group wore glasses a minimum of 10 min a day for 16 days and were observed to show 18% improvement post-training on the ice hockey-specific performance tasks. Consequently, stroboscopic spectacle equipment offers a flexible and reasonably unobtrusive solution to investigating perception and action in its natural occurrence; however, less is understood with regard to more acute exposures.
Temporal and spatial paradigms only capture a specific aspect of the task and omit a real-world response. This type of research typically shows that experts are better able to envisage event outcomes using information offered early in the event structure . This phenomenon has been investigated in terms of the overall effect of perceptual cue usage and visual search behaviours on performance . Studies using this type of technology suggest the use of natural tasks may help discover expertise effects in a performance setting, away from traditional laboratory settings [33, 35, 36]. Research testing stroboscopic exposure to date has suggested potential influences on a variety of perceptual or cognitive abilities . One way to train vision and attention for sport is to practice and train in suboptimal environments to overload perceptual processes, making return to the performance setting seem easier . Other training regimes already apply this principle, for example, the use of resisted sprint training to improve speed and strength performance .
From a skill acquisition perspective, early research by Bennett, Button, Kingsbury and Davids  suggested that varying visual informational constrictions to encourage investigative rehearsal might signify an important instructional methodology to motor learning in a sporting environment. The present study employs some of the same logic and does so through the use of intermittent SVT. Under normal circumstances, we use continuous online information from vision, offering intermittent snapshots of the visual world forces performers to perform in these suboptimal conditions. In a more recent study, Wilkins, Nelson and Tweddle  conducted pilot study research with three elite youth football goalkeepers to determine if a longer prolonged exposure (10 h over a 7-week period) SVT protocol might have the potential to improve visual responses. Whilst findings suggested potential of improving visual response times, evidence for benefits for a range of other perceptual and visual skills including EHC was not found. It would therefore be useful investigate whether a shorter/acute SVT period has a similar effect on EHC.
Aims and hypothesis
The primary aim of the present study was to determine the effects of an acute training period of SVT on the practiced task (measured by three retention tests: immediately, 10 min, and 10 days later). We used a Sport Vision Trainer™ that measures reaction time and eye–hand coordination ability requiring the simultaneous use of hands and eyes as the main test and practice mechanism for the study . The secondary aim was to establish if these benefits transfer to a non-trained visual search (VS) task that relies on different (but similar) cognitive mechanisms measuring speed and accuracy.
Based on previous research, it was hypothesised that participants completing SVT would significantly improve performance in the retention tests, whilst the control participants would have some improvement (due to task familiarisation), however, not of the same magnitude.