Concussions are not as common in Major League Baseball as they are in professional football, but they happen often enough, with players getting hit by pitches, running into walls or catching a knee in the head sliding into a base. Catchers are particularly at risk — a foul tip off the mask will snap the neck back and give the brain a solid rattle. Collisions at the plate take a toll, too.
Now, a study published in the American Journal of Sports Medicine suggests that position players in the majors who sustain concussions do not hit as effectively in their first weeks back after their injury.
Under Major League Baseball rules, players can return after a concussion if they pass the concussion protocol — a series of interviews and tests of physical and mental functioning. But the new study found that even after passing the tests and having no apparent symptoms, hitters showed an initial decline when they returned to action.
The study identified 66 position players who had concussions between 2007 and 2013, including some who never went on the disabled list. The study then compared their performance in the weeks before and after the injury.
The gap was noticeable. In the two weeks before their injuries, the players hit .249 with a .315 on base percentage and a .393 slugging average. For the two weeks after the injury, their line was .227/.287/.347.
Baseball instituted a seven-day disabled list in 2011, specifically to let players recover from concussions while allowing the team to maintain a full roster. But there is no set time that a player must stay out after a concussion. If he passes the protocol, he is cleared to play.
“I would say that what they’re doing now is a good start,” the senior author of the study, Dr. Jeffrey Bazarian, a professor of emergency medicine at the University of Rochester, said of baseball’s protocol. “But if they integrated some kind of analysis about how the player is swinging the bat, then you could see if they’re really back to where they were.”
Recovering 90 percent may be enough for most ordinary activity, Bazarian said, but not enough for playing major league baseball. “You really need to be fully recovered to swing a bat at a 95-mile-an-hour fastball,” he said.
Dr. Gary Green, the medical director for Major League Baseball, defended the sport’s concussion policy. “Before people go back to play, not only do I review the data and the impact testing, but it’s also reviewed by a neurologist from the players association,” he said.
He added: “The player association and M.L.B. make the decision on return. If there’s any discrepancy, we have an independent neurologist give his opinion.”
Green was also unimpressed with the study, which he said had major methodological problems and lacked proper controls. “You really can’t draw many conclusions from it. If it shows anything, it shows that the batting parameters — strikeouts and walks — are actually fairly consistent before and after injury.”
Green said he felt that there was no way to distinguish the changes the study found from ordinary variations over the course of the season that happen with all players.
It may be that time off by itself, even without an injury, can throw a hitter off, so the researchers did look at that factor as well. They checked the before-and-after performance of players who took similar amounts of time off for bereavement or paternity leave.
Before their leave, those players hit .255; after, they averaged .271. Their on-base average was .331 before and .332 after, and the slugging percentage went from .724 before to .765 when they returned.
The researchers also checked to see what happened to concussed players four to six weeks after their return, and they found that players were still performing a little worse than before their accidents, but the difference was not statistically significant.
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