Two 11-year-old Cuban boys face each other in the ring during a boxing training session at an Old Havana neighborhood boxing gym, in this Aug 12, 2003 photo. When it comes to boxing, health experts and scientists - and even some competitors - have been worried about brain injuries for decades. Irish former featherweight world champion Barry McGuigan said in 1988: "Boxing damages your brain; don't let anyone tell you any different." Claudia Daut / Reuters