Way back when, it was typing that did me in. I never had trouble with mice. But now my mouse is messing me up. My fancypants chair-arm-mounted split keyboard has dual trackpads on it, but I hate trackpads. I've been trying to use them all day and they just drive me crazy.
I have a table-like mouse-pad clipped to the edge of my desk so that the mouse is lower than the desk surface, down near the keyboard, but I think I've been leaning on my elbow when using it. Which is, you know, bad.
I had one of those horizontally-gripped mice for a while (in the picture at that link), which sounded like a good idea, but after a couple of months, I found it even less comfortable than a flat mouse.
I wish this keyboard had a trackpoint. But even then, I'd really miss having a tilting scroll wheel.
Bah. And ow.