Chris Nowinski, a Harvard grad and former WWE wrestler (there’s a resume you don’t see too often), began investigating the subject of brain trauma in contact sports after a particularly bad shot to the head in June 2003 prompted him to retire from the ring. Three years later his book Head Games rocked the sports world with its argument that concussions can result in degeneration of brain tissue, which manifests itself in dementia and may have been responsible for the suicides of several professional athletes. Director Steve James (Hoop Dreams) centers this 2012 documentary on Nowinski, but there are affecting profiles of various NFL and NHL veterans who are living with the damage—or may have died from it. Typical of James’s dramatic instinct is the movie’s narrative frame, a grade school football game in which underprivileged kids hammer each other. One mother, who’d rather have her boy on the field after school than on the streets, remarks, “You just have to protect them as much as you can, and pray.”