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The disc in sitting – much ado about nothing

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GLOBAL YEAR

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When I went through physio school, I remember feeling more and more aware of how I sat, as the course went on. We were clearly learning our stuff – we knew, that back pain was caused in no small part by discs bulging – HANG ON! Let me start at the beginning (for as Mary Poppins says, it is a very good place to start). We actually knew that the disc was this slippable thing that sat somewhat precariously between our vertebra and it really was a matter of time before it slipped out and squashed the bejeebers out of our spinal cord. Clearly then, we had to make sure that we didn’t do anything that would elevate the risk of this occurring. Clearly then, we needed to watch our intra-discal-pressure.  We learnt, almost off by heart, the intradiscal pressure in a range of postures (small confession here – I didn’t really learn it all off by heart but I sort of pretended that I did when in conversation with the discites). We learnt to ask our patients on those student placements – “When you hurt your back, were you bending over, or sitting?” Then, when we had talked them into it, we said “Did you cough?” and we willed them into admitting that, even if they think they weren’t, they probably were because THAT is how you blow a disc!  Sound familiar? Well, thanks to Andrew Claus at University of Queensland, we now know what all those experiments that we didn’t really read ACTUALLY found. You guessed it – sitting is not really all doom and gloom for your disc. In fact, it is probably no worse than standing – he concludes this: “If sitting is a greater threat for development of low back pain than standing is, the mechanism is unlikely to be intradiscal pressure”. Have a read…..

Sitting versus standing: does the intradiscal pressure cause disc degeneration or low back pain

Claus A, Hides J, Moseley GL, Hodges P.
Division of Physiotherapy, The University of Queensland, Brisbane, St. Lucia, Qld 4072, Australia.

Abstract

Studies of lumbar intradiscal pressure (IDP) in standing and upright sitting have mostly reported higher pressures in sitting. It was assumed clinically that flexion of the lumbar spine in sitting relative to standing, caused higher IDP, disc degeneration or rupture, and low back pain. IDP indicates axial compressive load upon a non-degenerate disc, but provides little or no indication of shear, axial rotation or bending. This review is presented in two main parts. First, in vivo IDP data in standing and upright sitting for non-degenerate discs are comprehensively reviewed. As methodology, results and interpretations varied between IDP studies, in vivo studies measuring spinal shrinkage and spinal internal-fixator loads to infer axial compressive load to the discs are also reviewed. When data are considered together, it is clear that IDP is often similar in standing and sitting. Secondly, clinical assumptions related to IDP in sitting are considered in light of basic and epidemiologic studies. Current studies indicate that IDP in sitting is unlikely to pose a threat to non-degenerate discs, and sitting is no worse than standing for disc degeneration or low back pain incidence. If sitting is a greater threat for development of low back pain than standing, the mechanism is unlikely to be raised IDP.

See full article at J Electromyograph Kinesiol 18,4 550-58
ResearchBlogging.org
Claus A, Hides J, Moseley GL, & Hodges P (2008). Sitting versus standing: does the intradiscal pressure cause disc degeneration or low back pain? Journal of electromyography and kinesiology, 18 (4), 550-8 PMID: 17346987

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