Youth participation in football is down, however, notes Dan Lebowitz, executive director of the Center for the Study of Sport in Society at Northeastern University in Boston. If professional football wants to have the kind of robust network of young players funneling up through the various levels that it has traditionally relied upon, he notes, “it will have to change.”

The center is in the midst of a year-long study devoted to answering the question of where the best middle ground lies, notes Mr. Lebowitz. “How do we reduce the risks of traumatic injury without losing the athleticism, the grace, and the character-building that go along with sports in our culture?” he asks.