Lower back pain is now the leading cause of disability and work absence throughout much of the world, and is increasing. But our early ancestors must have evolved healthy backs simply to survive, so most of us have probably inherited healthy backs. This suggests that something about our modern lifestyle may be responsible for this epidemic. Some research shows that sitting with a bad posture may be largely to blame.
Most of us distort our spines when sitting 'upright'. If you do this regularly it weakens your spine. It is then easily injured when lifting, twisting etc. You may not feel any pain while sitting but it is still likely to be the underlying cause. This page explains why...
Why sitting often causes a strained spine and high disc pressure
Have you noticed that most people sit ‘upright’ like in Fig.1? The chair has tipped the pelvis backwards off balance. As the torso weight bears down on the spine and the seat pushes the base of the pelvis up, the pelvis becomes a lever bending the spine forwards and distorting it. (There are ligaments to limit this bending. They are strong for brief exertions like lifting, but under prolonged stress they stretch till they can't protect the discs.)
The results are strained ligaments and compressed intervertebral discs.
A healthy lumbar spine should be curved inwards like in Fig.2. Compared to this, notice how the pelvis has slumped back, squashing the fronts of the lowest discs so they bulge under pressure. (In the healthy spine the discs are not parallel, but are thicker at the front than the back.)
The angle, and or shape, of most seats tends to tip the pelvis backwards. If you look closely you will see that nearly everyone has a slumped pelvis when sitting upright. The more the pelvis slumps the more pressure it puts on the discs.
The damage this causes gets worse the longer you sit in this posture.
(Reclined sitting spreads the bending over the whole spine and is not as damaging as sitting upright but with a slumped pelvis.)
The best way to treat most back pain is to improve the way you sit, but if it doesn't improve within a few weeks you should see your doctor as the causel could be a medical one.
The three problems caused by a strained spine and high disc pressure
Dull chronic backache (lumbago) from overworked and tense muscles
"Mechanical back pain" Sudden acute pain usually brought on by bending, lifting, or twisting. Doctors often can't find a cause. John Gorman (see below) believes this has evolved as a warning to stop activity that is putting discs at risk.
Prolapsed or herniated (slipped) discs, and possibly sciatica, could happen at anytime when bending or lifting.
Lumbar Support can be harmful
If we introduce a lumbar support, like most 'ergonomic' chairs do, it will push the spine into an apparently healthy shape.
But it is too high up to support the pelvis, so this still tips backwards. Now only the spine below the lumbar support can bend, so all the distortion is concentrated here.
The lumbar support has increased the disc pressure even more, right at the point where most spinal injuries occur. (Pain from lower back injury can be transferred, and felt in different parts of your back or legs, but nearly always the damage originates in the lowest two discs.)
The theory of lumbar support is a simple but widespread mechanical error.
But I feel better with lumbar support!
When your back has been strained, muscles around the injury often tense to protect it.
They are lifting muscles, evolved for intermittent use, and will ache if under continuous tension. (This tension and dull ache can become chronic. Stress may trigger it regularly, sometimes long after the original disc or ligament injury has healed.)
We think lumbar support feels good because it gives relief to these overworked muscles, even though it is partly to blame for the original injury.
It is far better to stop causing the distortion, so the muscles can learn to relax.
Evidence that chairs can cause back-pain
Most of this information comes from John Gorman. He is possibly the first person to analyse the mechanics of the spine as a trained engineer, rather than from a medical perspective (although he is also a chiropractor). His very convincing conclusion is that much back pain is a result of mechanical damage to otherwise healthy backs, and is not a medical problem at all. The solution lies in changing the way we sit.
The medical profession is conservative and hasn't taken up these ideas yet, but it doesn't seem to have an alternative explanation. A near doubling of disc pressure from standing to sitting has been measured and is widely quoted. This is accepted without question, with little attempt to understand why the pressure should rise at all. John Gorman explains why - and how to avoid it.
We are grateful to John for permission to summarise his work, which you can read in full here
(John Gorman invented and advocates 'pelvic support' instead of lumbar support. This is the only solution for car seats - they are so low that they have to tip you backwards. He also has a useful set of stretching exercises.)
I (Andrew Webb) have been using John Gorman's ideas together with Alexander Technique since 1988, they do work and have cured my back pain. I am convinced he is right.
We evolved with healthy spines
Our backs are perfectly evolved for a hunter gatherer lifestyle, which was much more strenuous than ours (and did not include chairs!) Any early human crippled by back pain would be unlikely to survive (let alone feed children) long enough to have descendants, so evolution ruthlessly eliminated all but the healthiest.
This is supported by the fact that back pain is very rare among tribal people who still live more naturally. They also have less flexibility in the lower spine than people with sedentary lifestyles, suggesting that we have made our spines unnaturally flexible by distorting them.
(We are no longer as subject to natural selection since it is now possible to survive without being as healthy - but we have still inherited the superbly evolved hunter gatherer spine.)
It is always worth looking after your back. Whether completely healthy or with severe osteo arthritis, it is never too early or too late to protect yourself from further damage, and help your back heal as much as possible. There is nothing wrong with most backs except the way we misuse them when sitting