[patdennis]

No helmet can stop concussions. If they could, the NFL would redesign football helmets and save themselves a lot of trouble. G-forces are G-forces, whether you're in a helmet or not.

EDIT: There are a lot of very smart people working on this problem. But it's a hard problem.

From the Associated Press:

In a series of interviews with The Associated Press, representatives of the NFL, its players' union and the four equipment companies that make every helmet worn in the league all agreed there's no football helmet -- in production or on drawing boards -- that can eliminate concussions. And there might never be one.

http://sports.espn.go.com/nfl/news/story?id=5797046

[SamReidHughes]

Helmets could spread the impulse over a longer period of time, reducing G-forces.

[pbhjpbhj]

Doesn't a [more] deforming helmet like that in the OP do just that?

[aryastark]

helmet braking. I like your style, SamReidHughes.