Whether repeated concussive or subconcussive blows cause permanent or cumulative brain injury is a complex and controversial question. Press coverage highlighted the case of Jeff Astle, a former England international football player, where the coroner ruled the cause of his death as an “industrial disease”—suggesting that repeated heading of balls during his professional career was the cause of his subsequent neurological decline.1 This case was at odds with that of Billy MacPhail, a former Glasgow Celtic player, who in 1998 lost a legal battle to claim benefits for dementia that he said was due to heading the old style leather footballs. Concern has been raised over whether heading in soccer may be the basis for injury and cognitive impairment, and in the United States this has led to calls advocating the use of protective headgear for soccer …