NFL Helmets and little kids.

If you put a standard NFL football helmet on an 80 pound kid who can run 40 yards in 8 seconds, he is unlikely to be protected by his helmet pad.  The current NFL helmet systems are all designed (poorly) for a large adult moving at a 4.4 sec 40 yard dash.   The big guy gets his concussions at 10 to 15 ft/sec squared.  The little guy can't generate that speed or acceleration so he is more likely to have collisions in the 8-10 ft/sec squared range.  Most NFL pads are so stiff that they only start to absorb energy at peak accelerations of 15 ft/sec squared.   Putting NFL helmets on little kids is akin to strapping bricks on their heads.