When St. Louis Rams quarterback Case Keenum sustained a concussion in a game in Baltimore last month, commentators focused on how he wobbled as got up and why he was not taken out of the game. Few mentioned that he had slammed his head on the turf.
In the rush to reduce head trauma in sports, doctors, researchers, leagues and equipment makers have looked at everything from improving helmets to teaching safer tackling techniques.
But one little-explored cause of concussions is the fields beneath the feet of the millions of athletes who play football, lacrosse, soccer and other sports.