Back pain with sitting is commonplace if you are a back sufferer . . . and the search for a comfortable chair a seemingly endless mission. The reasons for pain with sitting are mainly to do with pressure against the back wall of the lumbar discs.
Of all the postures, the internal pressures are greatest in the lumbar discs with sitting. Intra-discal pressures are even higher with slumped sitting. When the spine loses its elegant elongated 'S' bend and assumes a 'C' bend the intradiscal pressure increases by over 50%. This has both short and long term ill-effects, both of which amount to escalating back pain in sitting.
In the following video Sarah explains and demonstrates exactly what is going on. The second video shows the types of chairs you should and should not use.
As you saw in the video, transient low back pain with sitting comes from stretching the back disc wall (the posterior annulus). The lumbar vertebrae pinching together at the front forces the liquid nucleus towards the back of the disc and this pressurises the highly sensitive outer ligamentous layers at the back. Over time, this causes PAIN. It's the sort of pain relieved by an irresistible desire to arch backwards and move about a bit, literally taking the pressure off the wall.
It's often misguided beliefs about how you should sit that causes a healthy disc (left) to deteriorate into a painful flattened washer (right). You will read below how bolt upright sitting, as in holding yourself rigidly erect and not relaxing back with sitting, can be equally as bad as long-term slumping .
Excessive pressure from within discs causes pain (the early astronauts returning to Earth were in agony from their vastly engorged discs). But pulling apart the backs of the discs vertically, as in extended periods of slumped Western sitting postures, also causes problems. Real problems.
The backs of the discs are very bendy-stretchy things (they have to be to allow for free functional activity, like tying up the shoelaces) and this is why they can lengthen by between 50% to 90%. However, any ligament subjected to unremitting stretch (as in day to day computer-or-long-distance-driving-postures) suffers cumulative tearing and snapping of its fibres, albeit on a microscopic scale. It's like forcibly bending a finger back and keeping it back.
With repeated breakage of tiny ligamentous filaments of the posterior disc wall, the beginnings of damage starts. In fact, with all the bending, twisting and lifting we do, this part of the disc suffers non-stop wear and tear that can amount to micro-injury through being traumatised in this way. That's why scientists speak of this part of the disc having a high maintenance load.
Those of you who've read other parts of this website will know that one of the chief causes of back pain is scarring of the disc's back wall.
And here's the clue . . . .
Sitting can both cause the scarring, through cumulative micro-trauma, and set you up for greater damage for when you really do do something to hurt your back. So it can be both cause and effect.
When you 'do something' to your back it is likely to have been by a chance, errant movement that managed to pierce the serried ranks of soft tissue structures protecting the disc from the outside in. This incidental (often minor) action is almost invariably totally un-noteworthy - almost pure bad luck - when it manages to damage a few fibres in the sensitive outer 'skin' of a disc in its posterior wall. You will read that we believe this to be the cause of most cases of 'non-specific' back pain. 90% of cases in fact.
There are also longer term ill-effects suffered by the lumbar discs caused by prolonged sitting. Being an upright stack, the bricks at the bottom of the spine suffer greater compression from the weight above. This causes greater fluid loss from the low lumbar discs, while at the same time is smothers the metabolic vigour of the discs and hampers the natural repair processes.
The lumbar discs naturally lose fluid through the course of a day. We all lose about 20% each day, and we all go to bed approximately 2cm shorter. For the most part, we regain the same amount of fresh disc fluid each night when we are relaxed and spread out during sleep. Our spine imperceptibly undulates across the mattress as it elongates while we dream, like a beautiful streamlined concertina pulling out.
Sitting squashes the discs, so that we lose 10% of our discal fluid in first 2 hours of sitting - nearly half the daily quota! This is no bad thing. In fact, it's quite a good thing as it evacuates all the disc's waste products more rapidly. Just as long as we get the full amount of fresh fluids back in! But with our universal penchant for sitting, and then more sitting, with insufficient stretching in between there tends to be an incremental fluid movement one-way, as our lumbar discs very slowly dehydrate.
Don't be tempted to use one of these chairs when your back is bad. It will make it worse. Ideal though, when you are in the clear ~ and it will stop relapse
The steady dehydration does not necessarily cause back pain with sitting but it does lead to a steady decline in the over-all health of the lumbar discs. The loss of fluid on a more permanent basis causes load to be transferred from the buoyant-bubble-of-fluid nucleus at the centre to the 3D mesh of the disc wall, causing it to bunch down and become less compliant. The lower back becomes generally 'stiffer' as the bottom end of the streamlined concertina can't pull apart again overnight.
Gradual loss of extensibility of the posterior annulus of a problem link causes it to become a sitting duck to further trauma. It is much more easy, with a chance incidental action or movement to injure a dehydrated disc. Trauma on stiffness on trauma. And so it goes.
Sitting rigidly upright causes MORE pain!
Just as bad at causing back pain with sitting is sitting perched upright. Sitting rigid with your spinal muscles working overtime causes almost screaming agony in a matter of minutes. The reasons for this are twofold: thousands of Newtons of compressive forces pinches the discs even more, plus the build-up of waste products in the long spinal muscles from the never ending contraction (normally these are sluiced away in the periods of inactivity when muscle fibres are relaxed and the muscle off duty).
You will see in the graphic photograph below how essential it is to pad out the lumbar hollow as you sit, particularly if you are someone who gets back pain with sitting. The trick is to not be-labour the spine too much while it's in recovery mode. It is important to keep the spine 'up' but it's also important to keep it relaxed.
Yes, you must keep an elongated 'S' bend of the spine, but you have to keep it with little or no effort as you slowly get yourself out of pain. When your back is healthy and painless again, you will be able to sit perched upright with your core and back muscles both working in a balanced way to hold you up - but not before you are ready. While you're in recovery mode you have to support your lumbar hollow to sit. In other words, you need a pillow in the small of the back.
At the same time, you must be doing the different spinal appeasing exercises to get yourself out of the pain caused by sitting. Quite quickly (within the same session) this should be followed by spinal decompression exercises once your pain has become more manageable.
You may also be interested to read about how to sit in a car, since this is where many people get back pain with sitting. You will see here that I suggest while driving long distances you tie a pillow to the small of your back.
Just about all of us need a pillow in the small of the back to be comfortable sitting
Despite all the gadgets on the market, often a simple bed pillow in the small of your back is the best way to keep a lumbar hollow. Remember though, it should be bulky enough that you can lean back and still keep your lumbar arch when sitting.
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