Soccer balls are a lot lighter than they used to be, but hitting one with your head too many times can still do bad things to your brain, a new study suggests. Researchers scanned the brains of 32 amateur players and found that those who headed the ball more than a thousand times a year—not an unrealistic number for somebody who practices frequently—had signs of mild brain damage similar to that found in patients with concussions, the BBC reports.
Players who headed the ball frequently performed worse on tests checking verbal memory and reaction times. "Heading a soccer ball is not an impact of a magnitude that will lacerate nerve fibers in the brain," the lead researcher explains. "But repetitive heading could set off a cascade of responses that can lead to degeneration of brain cells." Some researchers disagree with the findings, believing the brain damage is not being caused by heading the ball, but by players banging their heads together when competing for an airborne ball. (Read more soccer stories.)