NFL data shows that the number of reported concussions has increased more than 20 percent from 2009, and more than 30 percent from 2008.
Yet the players who grind out the tough yards — and some of those who tackle them — say knocking heads is inevitable.
Running backs like Steven Jackson, Michael Turner and Arian Foster tend to plow forward for the first-down marker — and that means helmet-to-helmet contact with a defender. Neither player is likely to be considered defenseless under NFL rules.
Earlier this season, Packers linebacker Nick Barnett complained he's faced too many backs with their heads straight down. Cowboys linebacker DeMarcus Ware says there's a double standard since running backs are not going to get called for a penalty if they lead with their heads.