MONDAY, March 14 (HealthDay News) -- Vibration and shock loading cause enough mechanical injury to exacerbate pre-existing intervertebral disc herniations in an in vitro setting, according to a study published in the March 1 issue of Spine.

Justin P. Yates and Stuart M. McGill, Ph.D., of the University of Waterloo in Canada, investigated the effect of vibration and shock loading on partially herniated discs in flexed and neutral postures. They randomly assigned 64 porcine spinal motion segments with partially herniated discs to one of eight experimental conditions: four types of load (whole-body vibration, shock, static load, and vibration combined with shock), applied in either a flexed or neutral posture. The researchers measured the progression of disc herniation using computed tomography imaging and also measured specimen height and average stiffness changes.

The researchers found that the combination of vibration and shock loading produced the largest exacerbation of the disc herniation. The static flexed posture did not affect the disc herniation, although it did make the disc marginally stiffer.

"The relevance to real life appears to be that once disc damage is initiated, it can be made worse with vibration and that a flexed posture may add to this damage exacerbation," the authors write.

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