morneau of the twins sat out almost the entire year. what is a concussion, what causes it? >> well concussion is either the head gets hit or maybe the head gets moved back and forth violently such as the brain moves inside the skull. and our brain floats in this bath of sir cerebral spinal fluid and most of the time it recovered. there's also maybe a genetic predisposition. it can lead to long-term problems in a minority of players. >> larry: could a problem be in the helmet. >> helmet design is important, but in my opinion, helmets aren't the whole answer. i think we need to take the head impact, the motion of the brain inside the skull out of the game. >> larry: the nfl is fearing it >> larry: could a problem be in the helmet. >> helmet design is important, but in my opinion, helmets aren't the whole answer. i think we need to take the head impact, the motion of the brain inside the skull out of the game. >> larry: the nfl is fearing it may shorten life, can it? >> we have autopsied quite a few athletes who have had a shortened life because of this syndrome. i support football, i think it's america's greatest sport. we want to make it safer, in