In his book on lower back disorders, Professor McGill recommends using an ergonomic chair, pointing out that such a chair must be used properl to facilitate ergonimic sitting. Changing posture as frequently as every ten minutes, allows the tissue loads to migrate, thereby minimising the risk of any single tissue`s accumulating micro-trauma. Even if you don’t get up from your chair, moving position or even just fidgeting can help.

Have a look at Active Ergonomics by Orange Box – here is  the Flo chair opposite.
As you can see Flo encourages moving and fidgeting. If you would like to find out more, here’s the link. So, even if you can’t easily get out of your chair, at least changing position on it will help protect your back, helping you to keep supple and healthy.