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More fragility in core stability

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The evidence for the role of exercise in chronic low back pain has been a bit of a theme on the blog here at BiM. We’ve discussed different perspectives regarding the evidence of its efficacy (see here, here and here), where it sits against other treatments in that regard and considered a recent review of its effects, or lack of, on parameters of spinal function.

A new paper by the same group, led by Anne Mannion, who performed that last review have had a closer look at the role of spinal stabilisation exercises in chronic low back pain, effectively asking the question – are the observed clinical improvements seen following a spinal stabilization exercise regime reflected in the sort of changes in abdominal muscle function that the core stability model would predict? Or simply – do patients get better after core stability exercises for the reasons we think they do?

Core stability is an interesting case. It divides opinion and yet stands as one of the preeminent models for treating back pain through rehabilitation. In the mid-nineties a rehabilitation movement was created, born from the experimental observation that deep abdominal and paraspinal muscles are altered in their activation patterns in patients with back pain. Those early experiments and subsequent ones gave the model plausibility but, for me, what was more fascinating than the phenomenon of altered trunk muscle function was the phenomenon of a clinical dogma thrusting its way relentlessly through the therapy world. From this fair but limited data, enthusiastic entrepreneurs and self-elected authorities duly sprinted with the ball, creatively developing detailed treatment approaches with strict and specific rules that far exceeded the actual data. “Contract this muscle but not that one, definitely not that one” or “move like this, not like that”, spreading the empirically unsubstantiated (but potentially harmful?) concept to therapists and patients alike of spinal segmental instability, wherein poorly controlled vertebral segments shear excessively resulting in pain. You too could have the answer to treating back pain as long as you attend these 5 sequential courses at $$$$ a pop. Colleagues were falling over each other to buy the equipment needed to apply this model that had been accepted as gospel, from not-too-pricey pressure biofeedback cushions to very-pricey-indeed real time ultrasound imaging devices and the rehabilitation philosophy of the long-late Joseph Pilates experienced a remarkable resurrection. As a case study into how new treatment approaches are adopted in our profession it is perhaps second to none. Maybe the model was correct – we couldn’t know at that time, but in my early clinical career core stability came to dominate thinking as an accepted truth way before we had a good answer about whether it worked.  Maybe a better approach to introducing new treatments might be that recently advocated in this great paper by and Kari Bø and Rob Herbert?

But I digress. This new study by Mannion and colleagues followed a single group of 37 chronic back pain patients through a 9 week programme of spinal stabilisation exercises. The measured a battery of clinical variables but also measured the aspects of trunk muscle function that the core stability approach would seek to change – anticipatory activation of the lateral abdominal muscles and voluntary activation of transversus abdominus during abdominal hollowing. They found that clinical improvements in disability were not related to changes in voluntary or anticipatory activation of the abdominal muscles. In fact the only variables that they measured that were associated with improvement were a reduction in catastrophising and the range of lumbar flexion.

So in this group it appears that where patients did improve it was unlikely to be as a result of improved core stability. By that interpretation it follows that those who improved did not uniquely respond because they were part of a subgroup whose back problem was the result of poor spinal stability. Since there is no comparison treatment group those improvements might simply reflect natural history, but they might also be due to the non-specific effects of care, the fear reducing effects of doing some (any) exercise or the belief that the spine was more stable.

This isn’t the biggest study and some might argue that the lack of attention to the function of paravertebral muscles such as multifidus is a problem. Nonetheless this study adds to the large body of evidence that has already suggested that, for chronic low back pain, exercise helps a little, but no specific exercise approach is clearly superior, and now in this group it appears that this very specific type of exercise does not seem to induce clinical improvements in the way that it is very specifically designed to. For the plausibility of core stability in the treatment of CLBP that is something of a blow.

About Neil

Neil OConnellAs well as writing for Body in Mind, Neil O’Connell is a researcher in the Centre for Research in Rehabilitation, Brunel University, West London, UK. He divides his time between research and training new physiotherapists and previously worked extensively as a musculoskeletal physiotherapist. He also tweets! @NeilOConnell

He is currently fighting his way through a PhD investigating chronic low back pain and cortically directed treatment approaches. He is particularly interested in low back pain, pain generally and the rigorous testing of treatments. Link to Neil’s published research here. Downloadable PDFs here.

Reference

ResearchBlogging.org

Mannion, A., Caporaso, F., Pulkovski, N., & Sprott, H. (2012). Spine stabilisation exercises in the treatment of chronic low back pain: a good clinical outcome is not associated with improved abdominal muscle function European Spine Journal DOI: 10.1007/s00586-012-2155-9

Bø, K., & Herbert, R. (2009). When and how should new therapies become routine clinical practice? Physiotherapy, 95 (1), 51-57 DOI: 10.1016/j.physio.2008.12.001

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