Many years ago, after developing intense pain in my wrists and shoulders I decided to look into it. I was spending 14 to 18 hours a day in front of the computer (which was part of the problem, of course).
After many experiments I finally arrived at a desk design that worked wonders. I welded the frame out of mild steel for rigidity --which I found was important-- and surfaced it with plywood and formica. It's a two level desk with the front dropped down to about 26 inches. The drop alone wasn't enough. The front edge of the keyboard shelf has a 1.5 x 1.5 inch piece of oak running the entire width. This piece has a generous radius and is highly polished and waxed.
During use your arms hang naturally on your sides. Your forearms are pretty much parallel to the floor and a point just behind your wrists rests on the oak support. Picture your hands lightly hanging into a cavity that contains the keyboard and trackball. No muscular tension to speak of.
This made ALL the pain go away and the carpal tunnel soreness evaporated. I went from being on a road to surgery to, well, feeling perfectly normal, even after extended sessions. And, BTW, ditching the mouse was a huge part of this. Mice introduce tension. A thumb operated trackball does not (after you get used to it).
I also like to work standing up but recognize that comes with it's own set of issues.