When I was riding a desk all day, I developed problems where my hand would hurt and sometimes spasm. I switched to my left hand, and soon developed the same problem there. Then I remember that way back in the day when mice were expensive (Window 3.1 on 386/486), I would use hot keys. So I went back to hot keys as much as possible, I also learned not to rest my palm on the desk. A track ball also helps. I would keep 2 different ones and switch them out every few weeks just to use different parts of my hand.