How sitting in normal chairs can injure your lower back

Our early ancestors had to have healthy backs simply to survive, so most of us must have inherited healthy backs. This means something about our modern lifestyle is probably responsible for the current epidemic of back pain. Research now suggests that sitting with a bad posture is most to blame.

Most people distort their spine when sitting ‘upright’. If you do this regularly the spine becomes weakened. Your weakened spine is then easily injured when lifting, twisting etc. You may not feel any pain while you are sitting but it is still likely to be the underlying cause.

This page explains why…

Distorted spine on normal chair

fig 1

Healthy spine on Wave Stool

fig 2

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 nearly as damaging as sitting upright but with a slumped pelvis.)

The three problems caused by a strained spine and high disc pressure

  • Dull chronic backache (lumbago) from 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.

Why Lumbar Support won’t help

If we introduce a lumbar support (most ‘ergonomic’ chairs do) it will force the spine back into an apparently healthy shape.

The pelvis will still tip backwards, but now only the spine below the lumbar support can bend, so all the bending 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 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 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.

Go to the Sitting Health page for a solution or continue reading about the spine:

Most of the information on this page comes from research by John Gorman

He is possibly the first trained engineer (he is also a chiropractor) to analyse the mechanics of the spine. He has come up with very convincing conclusions. The most surprising being that lumbar support is harmful.

The medical profession is conservative and hasn’t taken up these ideas yet, but it doesn’t seem to have an alternative explanation for back pain. 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 - so low 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 for 20 years, they do work and have cured my back pain. I am convinced he is right.

Human spine

How the human spine evolved

Our backs are perfectly evolved for a hunter gatherer lifestyle, which was much more strenuous than ours (and did not include chairs!) A bushman or aborigine crippled by back pain would be unlikely to survive long enough to have descendants, so evolution ruthlessly eliminated all but the fittest.

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.)

There is nothing wrong with most backs except the way we misuse them when sitting
Coccyx pain?

Do you suffer from a painful coccyx or tailbone? The coccyx didn’t evolve to support weight, but when we slump we sit on it (Fig. 1), and in some people it hurts. (It can also be damaged by a fall.)

As you can see the coccyx is not touching the seat in Fig. 2. Just changing to a Wave Stool will probably ease the pain, but we can make a cutout in the foam padding too - just ask us.

It is always worth looking after your back. It is never too early or too late to protect yourself from further damage, and help your back heal as much as it can.

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