Rear-end collision tend to result in minor injuries and about a half of such cases are neck injuries. Whiplash is the most common neck injury, but it is said that most low cerebrospinal fluid syndrome cases caused by leaking cerebrospinal fluid are triggered by whiplash injury from rear-end accident.
Mazda uses a seat structure as one of its measures to reduce the severity of damage from rear-end collisions. It makes the occupant's torso to sink into the seat back to optimize the position of the head restraint and the occupant's head when there is a impact from the rear. The front seat supports the head and torso simultaneously to mitigate shock to the neck when the vehicle is hit from behind.
How Front Seat that mitigates shock to the neck works