MLB batting averages slump after concussions

"Although players who sustain a concussion may be symptom-free and cleared by MLB protocol to return to play, the residual effects of concussion on the complex motor skills required for batting may still be a problem," says Jeffrey J. Bazarian. (Credit: p caira/Flickr)

After a concussion, Major League Baseball players don’t perform as well at bat during their first two weeks back.

The concussed players’ batting performances were significantly worse than another group of players who were rusty because of being away for paternity or bereavement leave during the same period.

Brain injuries are most often associated with contact sports, but they are prevalent in baseball, too. During this year’s World Series, head injuries affected two San Francisco players, one of whom was not able to play due to his concussion.

At the high school and college levels, baseball concussions are rising at a rate of about 14 percent a year, researchers says.

Why batting suffers

In the MLB study, players returning after a concussion had lower batting averages (.234 versus .264); lower slugging percentages (.359 versus .420); and lower on-base plus slugging percentages (.654 versus .747) compared to players returning from bereavement or paternity leave.

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“Although players who sustain a concussion may be symptom-free and cleared by MLB protocol to return to play, the residual effects of concussion on the complex motor skills required for batting may still be a problem,” says principal investigator Jeffrey J. Bazarian, associate professor of emergency medicine at the University of Rochester School of Medicine and Dentistry.

When a batter is at the plate, the brain and its neural networks must be in top form to master hand-eye coordination, intense visual acuity, fast reaction time, postural stability and balance, and swing control in just 400 milliseconds—the estimated time it takes most balls to pass from pitcher to batter, Bazarian says.

After a concussion, brain function can be impaired for weeks or months resulting in symptoms such as slowed thinking or response speed, and poor concentration. Understanding the impact of concussions on batting performance can help to inform decisions about when to return to the lineup.

Gathering the data

Concussions account for about 2 percent of all injuries that result in loss of playing time, behind strains and contusions as the most common MLB injuries.

Bazarian and colleagues believe their study is unique; only one other scientific article has looked at the relationship between concussions and a sport-specific performance such as batting, and that sport was football. The data were culled from the MLB’s disabled list, a Baseball Prospectus database, and game logs of all at-bats from baseball-reference.com.

Researchers compared seven batting metrics among 59 players recovering from a concussion and 63 episodes of paternity/bereavement leave, controlling for the number of days missed and each player’s position. They analyzed the numbers again at the end of four-to-six weeks following the medical leave, and found that batting performance metrics still remained slightly lower for concussed players.

Erin Wasserman, an epidemiology doctoral student, presented the data recently at the annual meeting of the American Public Health Association in New Orleans.

Source: University of Rochester