The trouble isn't the writing sessions - it's the job that requires me to spend nine hours a day in an un-ergonomic chair front of a computer plus the writing sessions. (I usually write longhand to avoid this: for NaNo I've been typing, and for far longer periods than I normally spend writing.) Time off work will help merely by dint of the fact that I use a sit-kneel stool at home :)

Thank you for the links - I've not seen that set of exercises before, and they look very useful!