immediately but the brain doesn't. that moving back and forth, the reverberation is the villain here. >> you mentioned all the various propositions including the sideline exam. as advisers to the nfl, how do you enforce that? there is a culture of playing through it. it's a kpcompetitive sport. will there be penalties if players don't abide by this? how do you make sure it happens? >> i think players are attuned to the fact that something has to change. no one wants a long-term problem after they have suffered multiple concussions. i think you wille s see ale cule change among the players and fans. they will insist on it. i think there will be rule changes and that's up to levels above hunt and i with nfl competition committee and the