Vibration and spinal lengthening in simulated vehicle driving

There is active interest in the relationship between back pain and driving. The availability of a precision stadiometer enabled experiments to be done to explore the effects of simulated driving on the change in spinal length, the hypothesis being that the spinal load would cause a shrinking in the length of the spine. The experiments demonstrated that, when exposed to a combination of vertical and horizontal vibration at 4 Hz the spinal length increased for all eight subjects, whilst under no vibration conditions there was a decrease in the average length. At 6 and 8 Hz there was no statistically significant change in length. The results suggest that there is an unloading of the spine when subjects under simulated driving conditions are exposed to vibrations in two directions at a frequency close to the spine's natural frequency.