Pathophysiology
While the time associated with a specific collision will vary, the following provides an example of the occupant and seat interaction sequence for a collision lasting approximately 300 milliseconds.
| 0 ms |
- Rear car structure is impacted and begins to move forward and/or crushes
- Occupant remains stationary
- No occupant forces
|
| 100 ms |
- Vehicle seat accelerates and pushes into occupant’s torso (i.e. central portion of the body in contact with seat)
- The torso loads the seat and is accelerated forward (seat will deflect rearward)
- Head remains stationary due to inertia
|
| 150 ms |
- Torso is accelerated by the vehicle seat and may start to ramp up the seat
- Lower neck is pulled forward by the accelerated torso/seat
- The head rotates and extends rapidly rearward hyper-extending the neck
|
| 175 ms |
- Head is still moving backwards
- Vehicle seat begins to spring forward
- The torso continues to be accelerated forward
- The head rotation rearward is increased and is fully extended
|
| 300 ms |
- Head and torso are accelerated forward
- Neck is “whipped” forward rotating and hyper-flexing the neck forward
- The head accelerates due to neck motion and moves ahead of the seat back
|