Worst I've had was carpal tunnel syndrome – I completely lost the 'tingle' reflex where they tap the inside of your wrist. My right arm used to go totally cold and loose all feeling. It came on after several months intense DIY after moving in, I think it was forcing hammer drills through tough concrete and too much mnual screwdiving. The latter can bring it back.
Got so severe I was worried about MS but the next best thing to a cure has proven to be mouse mats witha silicon gel wrist-rest at hiome and work they stop the inside of my wrist rubbing on the edge of desk or table.
Mind you, I've had bad backache this week after doing a lot of lifting (too much rather than too heavy) – age is starting to catch up.
I find how I sit or perch to be really important – I sat down at the lathe (on a stool) for the first time this week because of the backache. I felt less 'in control' but could not have carried on otherwise.
Lumbar support when driving really helps too -new car hasn't got this, but stuffing a folded scarf into the small of my back was useful.
We have a straddle chair at work, as a few people have had issues, on and off – one chap has a computer stand made of plywood that looks like a child-size computer desk – it stands on his desk and he works standing up!
Neil.