Joseph Clark and his colleagues (including Hall of Fame catcher Johnny Bench) said "there are few sports that could not benefit from some form of vision training."
Thrice weekly 30-minute training sessions began six weeks prior to the 2011 season, becoming twice weekly during the season. There were eight different training exercises, which escalated in difficulty over time.
Here's a flavour of what was involved. With the "Brock string", balls were suspended on an 8-foot string extending from an athlete's nose, parallel to the ground. His task was to switch his focus from near balls to farther balls, thus training convergent movements of the eyes. Another exercise with strobe glasses had the effect of intermittently blinding the athlete as he tracked incoming balls ("the brain is forced to visualise where the pitch is going by processing the information it gets from the eye faster," the researchers said). The "rotary" task required that the athlete track letters and numbers that were spinning round at increasing speed (training smooth pursuit eye movements). The Dynavision exercise involved the athlete tapping targets as quickly as possible as they appeared on a large touch-screen.
Clark and his colleagues stressed that this was an observational study. They had no control group as such. To gauge the success of their training intervention they compared changes in their team's batting performance from the 2010 to 2011 season with changes recorded for other teams in the Big East league. The difference was striking. The batting average of the Cincinnati team showed a substantial improvement, whereas the average for all other teams actually deteriorated slightly, perhaps because of the introduction to the league of new aluminium bats designed to simulate wooden equipment.
The Cincinnati team's "slugging percentage" (a measure of batting power) also increased after the introduction of the vision training, whereas the slugging percentage of all other teams declined over the same period. "On-base percentage", another statistic related to batting performance, also improved in the Cincinnati team while falling in their rivals. The Cincinnati team's final league position was fourth for the 2011 season, up from seventh at the end of the prior season.
The researchers conceded that these batting improvements could in theory have had many causes, including maturation of existing players and the arrival of superior newcomers. However, they argued that there was no reason why these factors should improve performance for the Cincinnati team but not do so for any of their rivals.
"The muscles in the eyes can be trained and conditioned to perform better and faster in focusing and tracking objects such as baseballs," the researchers said - an idea they believe was corroborated by reports of eye muscle soreness among their players.
The time-frame for responding to a baseball pitch is so short, the researchers further explained, that the vision training likely provides batters with "a competitive edge ... a millisecond advantage." There was also some evidence of fielding improvements among the Cincinnati team and here the researchers speculated that "action on the field may appear slower and easier to follow for the vision trained athlete."
So, should other teams in baseball and related sports (the England cricket team, perhaps?) start their own vision training programmes, if they haven't already? Maybe not. These findings do imply that the vision training was beneficial, but there's no evidence here whatsoever that the benefits were mediated by improvements in visual function or enhanced eye movements. No data were presented for changes in the athletes' performance on the training tasks over time, and there was no analysis linking any such changes to the observed improvements in batting performances. For that reason, combined with the lack of a control group or control intervention, it's impossible to rule out the possibility that the observed benefits arose from anything other than a placebo effect.
Clark, J., Ellis, J., Bench, J., Khoury, J., and Graman, P. (2012). High-Performance Vision Training Improves Batting Statistics for University of Cincinnati Baseball Players. PLoS ONE, 7 (1) DOI: 10.1371/journal.pone.0029109
Further reading. According to a 2008 Guardian report, the British Olympics Team employ the services of a vision training coach.
Post written by Christian Jarrett for the BPS Research Digest.