12) Front vs. rear seat position (6 studies).
13) Impact by vehicle of greater mass (i.e., 25% greater) (2 studies).
14) Crash speed under 10 mph (one study).

Real world occupants have the following risk factors for poor outcome or prognosis (chronic pain, symptoms):

1) Female gender (2 studies).
2) Body mass index in females only (one study).
3) Immediate/early onset of symptoms (i.e., within 12 hours) and/or severe initial symptoms (6 studies).
4) Ligamentous instability.
5) Initial back pain (one study).
6) Greater subjective cognitive impairment (2 studies).
7) Greater number of initial symptoms (one study).
8) Use of seat belt shoulder harness (2 studies). For neck (not back) pain (one study); non-use had a protective effect.
9) Initial physical findings of limited range of motion (one study).
10) Initial loss of ROM (one study and different from Number 9).
11) Initial neurological symptoms (one study).
12) Past history of neck pain (one study) or headache (one study).
13) Initial degenerative changes seen on radiographs (4 studies).
14) Loss or reversal of cervical lordosis (one study).
15) Increasing age (i.e., middle age and beyond) (4 studies).
16) Front seat position (one study).


Clearly, human crash tests have a major problem with external validity, as there are many risk factors NOT present in human crash tests. That is clearly A MAJOR FLAW in your example of one, and most likely in your "office" crash tests. The most important risk factor for initial severity of injury, in my opinion, is lack of awareness (preparedness, really, which is a different thing) of the impending impact. There is no human volunteer who is not fully aware of the impending impact, no matter how loud the music on the headphones may be (if your group even thought to do that).

So if we could put the full spectrum of humans into these crashes at low speeds, with heads turned, totally unaware and unprepared, with prior injuries, osteoarthritis, osteoporosis, etc., using thin (ectomorphic) females with a history of headaches, etc., then we would be approaching external validity.

Tell me your "office" did that, and I'll introduce you to some gentlemen who will talk to you about Helsinki.

This is supposed to be a forum for serious discussion. Better do your homework.

Sincerely,

Greg Wright

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