If the head rest were not there, your head would momentarily remain in place due to inertia as your body moved forward, then suddenly be pulled along with the body as the tissues of the neck became st...If the head rest were not there, your head would momentarily remain in place due to inertia as your body moved forward, then suddenly be pulled along with the body as the tissues of the neck became stressed (and strained). The headrest doesn’t necessarily reduce the acceleration felt by the head as much as provide the force needed to accelerate the head along with the body, thus reducing the forces between the head and neck.
