Do you ever have trouble straightening up or getting out of a chair, after you have been sitting for a prolonged period?
This stiffness is your body giving you a warning sign. Poor sitting posture has stressed the soft tissue in your back beyond its normal resting place. Once you take a few steps you will be able to correct, but if you continue to stress this same tissue it will become damaged. Slouched posture by itself is not a bad thing. The body is supposed to move and be in different positions. The problem is in the length of time that you are in that position.
The discs are the protective shock absorber between the bones in your back. The inside or nucleus is made up of mostly water. When we sit slouched for a long time, this constant pressure displaces the nucleus or jelly-like center posteriorly. You will not notice anything until you try to get out of that position. This displacement causes stiffness in the joint. Once you take a few steps you will feel better, because the walking motion places an opposite, anterior pressure on the displaced nucleus, pushing back to its central position. But over time, the nucleus may not be centered all the way and instead stays a bit posterior. It then only takes a little bit of pressure, like picking up a piece of paper to throw your back out!
Back pain is not the only detrimental effect of prolonged sitting. An analysis of 18 studies found that those who sat for the longest periods of time were twice as likely to have diabetes or heart disease, compared to those who sat the least. An earlier study, published in 2009, also highlighted evidence that linked sitting with biomarkers of poor metabolic health, correlates with an increased risk of type 2 diabetes, heart disease, and other prevalent chronic health problems—even if you exercise regularly.
Walking more, using a lumbar roll whenever you sit, and intermittent movements have been found to have the greatest benefit in counteracting the ill effects of prolonged sitting.