Full90 does not claim that its headgear prevents concussions.

"There is no evidence that headgear prevents concussions," Purcell tells WebMD.

Because of the fact that concussions cannot be seen on X-rays nor CT scans, attempts to prevent concussions have been difficult.

How should schools prevent and manage concussions among student athletes?

By the nature of its violent game, the N.H.L. also can't prevent concussions.

Schutt has been active in preventing concussions in American football, including having created a device in 2008 for Arena Football League players called the "Shockometer".

Next: preventing and treating concussions.

The league has also been criticized for its efforts in preventing concussions, in which eight former players have died, and have also had concussions throughout their careers.

The Westish cocoon, though it seems safe to the characters, can't prevent multiple concussions, depression, an eating disorder, addiction to prescription drugs, the complications of illicit relationships, and ultimately, death.

If the N.F.L. wants to go out of their way and prevent concussions, they can get rid of artificial turf.