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The Quebec Task Force defined whiplash as “an acceleration–deceleration mechanism of energy transfer to the neck”. It is logical that the lower the velocity change following impact, the lower the risk of injury. The accepted velocity change (delta-v) for whiplash injuries following rear impact has been quoted as 5 mph. There is some debate as whether this is valid in the clinical setting. We aimed to investigate this further.

A series of low speed controlled crash simulations were undertaken. There were a total of 27 runs on 23 individuals. Accelerometers were placed on the head and chest of the volunteers. Video recordings were analysed to assess relative displacement of the head and chest. The presence of symptoms was documented over a period of 7 days. The volunteers consisted of 23 males and 1 female with an average age of 38 (range 20–56). The average delta-v achieved was 2.3 mph (range 1.8–3.1 mph). The average maximum accelerations recorded were 3.46g at the chest and 2.93g at the head. The average difference was 0.53g. There was no significant displacement between the head and body. No symptoms were reported beyond 1 hour.

Whiplash is triggered if the disparity between movements of the head and neck is of sufficient magnitude. It seems logical that there is a threshold below which whiplash will not occur. Our results have shown that below a delta-v of 3 mph there is little difference in the magnitude and timing of the movements of the head and chest.

Therefore the whiplash mechanism of injury does not occur at these changes of velocity.

Correspondence should be addressed to: EFORT Central Office, Technoparkstrasse 1, CH – 8005 Zürich, Switzerland. Email: office@efort.org