Does sitting well really matter?
There are some people who seem to be able to disobey all ergonomic rules and get away with no pain for the whole of their lives. However, bearing in mind the prevalence of back pain, the rest of us may not be so lucky.
We know that once back pain has developed, then poor sitting posture makes the symptoms worse. So, if we abide by the premise that whatever makes the symptoms worse when you have the pain, is a predisposing factor to getting pain in the first place, then “yes”, the way that we sit does matter.
Spinal joints are weight bearing joints, but these are a little hard to visualize, so I will take the ankle, another weight bearing joint, to explain why it matters.
When we stand on our feet, we naturally put our weight through the ankle in the way in which it was designed. If I asked you to stand on the outside of your feet, with your ankles rolled in, then it would not take too long before you would complain that this was uncomfortable. If you did this all day and you ended up with swollen ankles, it would not be a surprise.
When we stand upright, our spinal joints are naturally aligned in their best position to take our weight, but when we sit slumped it is a bit like standing on our rolled in ankles.
There are a couple of reasons that we sit badly for many years before getting into trouble. (Skip this bit if you don’t want the nerdy explanation).
- The spinal joints are ridiculously strong. Have you ever made oxtail soup and tried to pull the bones apart, it’s really difficult. Oxtail bones are very similar in size to human spinal bones.
- The leverage is less in the slumped spine compared to the rolled in ankle. The ankle might roll up to 90° while the average lumbar spinal joint flexes 7°.
Studies measuring the internal pressure of our spinal discs show that when you sit slumped the pressure in the back of the disc increases to well over 100%, compared to the pressure when standing (1,2).
Almost all disc damage occurs in the back portion of the disc. This is the part of the disc that gets most force when we bend over forwards ‘badly’ i.e. when not bending our knees. This is why people with disc herniations hate both bending and sitting for long periods.
I sometimes call sitting ‘the silent evil’, as we cannot feel that it is doing anything bad. But it will be adding to the accumulation of adverse loads that can eventually result in low back pain.
I try and encourage people to cut down on unnecessary sitting. Do you really have to sit when you watch a screen, can you lie on the couch?
- Wilke et al. Spine 1999
- Nachemson; Elfström. Sweden. 1970