Some hits lead to dramatic concussions, like this one by Steeler James Harrison.
FILE – In this Oct. 17, 2010, file photo, Pittsburgh Steelers linebacker James Harrison (92) hits Cleveland Browns wide receiver Mohamed Massaquoi (11) during the second quarter of a an NFL football game in Pittsburgh. Harrison was fined $75,000, for his hit against Massaquoi. The NFL’s brain, neck and spine committee meets Wednesday, Dec. 8, 2010, to talk about possible changes to helmets and other equipment. (AP Photo/Don Wright, File)