are the most high profile, most expensive spots to run. the nfl will use one of those spots to run an ad that talks about what the league is doing to promote safety. this past week on 60 minutes roger goodel said players need to share responsibility and also to be honest about their injuries. some of it s a warrior mentality. some of it s wanting to be out there to contribute, but that s part of our education is to make sure that the players understand the seriousness of the issue and that they have to report these injuries. so the question a lot of people ask, just how hard are those big hits? i recently spoke to a concussion expert kevin ust owi tz who said you can measure the force. we ll see what happens. it s recorded up here at 23.6 g s of acceleration. reporter: he recently won a macarthur genius grant for his work on concussions in football. he is going to with stand an impact of 157 g s. wow. that s similar to a car accident. right. 157 g s. it s