Huh. So the last time I had shoulder/wrist/hand pain (which happens every so often when I overdo things and get into bad posture habits) and talked to someone who knew about ergonomics, he said that I should be leaning back in my chair and basically relaxing my shoulders/back-muscles-between-my-shoulder-blades against the chair. This was very weird to me because I had never ever seen that in any book (of which I have read a lot due to the shoulder/wrist issues) -- I had been under the impression I had to sit erect and without using the back of the chair at all. But it does seem to work reasonably. (I realize that this doesn't work for you -- it's not advice -- just that I had a mental connection with what you said and those muscles being a crucial piece of the puzzle, and Had To Share :) )