Without such basic information, it’s hard to know for sure what is a risk and what isn’t. Is heading the ball bad for young soccer players? Is checking OK in youth hockey? If doctors and educators are going to take a stand on such issues and make it stick, they need solid evidence to back them up. “Right now we are backing it up largely with intuition,” says Washington.

It could be years before the necessary studies are done. In the meantime, the researchers from the University of Pittsburgh who authored the Pediatrics study recommend some immediate steps that could reduce injury risk in youth sports. One is for leagues to provide and require first-aid training for coaches, including recognition and immediate response to head, neck and spine injuries. Leagues should also have clear and enforceable return-to-play rules for concussions and other serious injuries. Losing should be the worst thing that happens in a kids’ game.