I worked on a mattepainting for a upcoming TV series the last days. It was 5 days non stop photoshoping. Now my left wrist hurts a bit. I have to be careful not to get a typist's neuritis. ^^;
I was wondering 'Why my left hand?' when I paint with my right hand. Well it's the keyboard shortcuts I'm using with my left hand. I'm currently working with my laptop so the keyboard is placed in front of my graphic tablet (normally I place the keyboard to my left). Therefor I have to twist my hand in unnatural positions to press certain key combinations.
My wrist hurts most when I do the select->inverse command. (Ctrl+Shift+I). Put your keyboard right in front of you and try this combination with just your left hand. I think you'll understand why it hurts if you do it too often ^^; (I use pinky, ring finger and thumb for that combination btw)
So I tried painting without using my left hand... After 2 seconds my arm automatically moved towards the keyboard pressing Ctrl+z ^^
I should go back to pen and paper...then I won't need to use my left hand ;)