GMC 2010 Acadia Owner's Manual page 56

3-2 Seats and Restraints
Head Restraints
The vehicle's front seats have
adjustable head restraints in the
outboard seating positions.
WARNING
With head restraints that are
not installed and adjusted
properly, there is a greater
chance that occupants will suffer
a neck/spinal injury in a crash.
Do not drive until the head
restraints for all occupants are
installed and adjusted properly.
Adjust the head restraint so that the
top of the restraint is at the same
height as the top of the occupant's
head. This position reduces the
chance of a neck injury in a crash.
1. Pull the head restraint up to
raise it. To lower the head
restraint, press the release
button, located on the head
restraint post on the top of the
seatback, while you push the
head restraint down.
2. Push down on the head restraint
after the button is released to
make sure that it is locked in
place.