Don Johnstone wrote:

I suppose if an impact in a glider is severe enough
to cause the whiplash then that injury may be the least
of your problems as you are much closer to the crash
in a glider that you are in a car.

There is less of a crumple zone than in a car, but
most well designed gliders will absorb
some energy in the nose and cockpit area during
impact that will protect you to a certain extent.
Whiplash injury is therefore indeed an issue.
Even a groundloop during an outlanding can give
a whiplash and a good headrest is an important
safety feature.

Nils