How Does Whiplash Occur?

A whiplash accident occurs when one motor vehicle strikes another from behind, causing certain forces to be transmitted from the striking vehicle to the struck vehicle. These forces are then transmitted to the occupant(s) of the struck vehicle, where they have the potential to cause whiplash injury.

Research Findings on Whiplash Accidents

Research both in the Biomechanics Laboratory at Yale University in New Haven and in live crash tests using human volunteers has shed relatively new light on the contortions the cervical spine (neck) undergoes as a result of impact culminating in whiplash.1, 2

Shortly after impact (about 150 milliseconds), the cervical spine undergoes what is called an S-shaped curve. In this configuration, the cervical spine, rather than simply being curved to the front in a normal C-shape, as it would normally be at rest, takes on an altered shape:

  • The lower part of the cervical spine moves into extension (bent backward)
  • The upper part of the cervical spine moves into flexion (bent forward).

When a whiplash accident occurs, the lower part of the cervical spine moves well beyond its normal range of motion, causing the potential for injury to the ligaments and discs in that area. The upper part of the cervical spine also moves beyond its normal range of motion, but to a lesser extent.

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Cervical Spine Reactions to a Whiplash Accident

There is an inherent stabilization response in the cervical spine that helps protect it from potential whiplash injury:

  • The nervous system detects the presence of the impact
  • The muscles of the cervical spine, under the direction of the nervous system, contract quickly to try to minimize the affects of the impact on the ligaments and discs.

If this stabilization response is working efficiently following the whiplash accident, there is a greater likelihood of protection and less potential for whiplash injury.

But if the response is inefficient, an injury is more likely, with various types of whiplash pain possibly resulting and whiplash treatment potentially necessary.


  1. Panjabi MM, Cholewicki J, Nibu K, Grauer JN, Babat LB, Dvorak J. "Mechanism of whiplash injury." Clin Biomech 1998;13:239-249.
  2. Kaneoka K, Ono K, Inami S, Hayashi K. "Motion analysis of cervical vertebrae during whiplash loading." Spine 1999; 24(8):763-769.