Sitting - yup bugs me too for a number of reasons. I have sore hips/SI Joint problems...so I tend to only sit for a hour at most at a time. If the chair back is high, like a few other people mentioned, and it hits my shoulder blade - instant pain! I think I just get stiff and with my bad posture (which gets worse as the day goes on) I just get sore.

I am off work now - I am hoping that helps. 8 hours a day at a desk was killing me....even with my frequent breaks to walk around. I had an ergo assessment done - got a new chair, adjusted it often, etc and I still had minimal to no relief.