Want to throw some alernatives into the discussion. If you're talking about stress reduction and ergonomic input devices, you should take a look at (no particular order):
- Vertical mouse
I have a CST trackball which is nice when you don't have to be super precise. Old colleague of mine used a vertial mouse by Evoluent at the time, tried it once and felt very natural for the lower arm, but my hands were too small for the model in question. Maybe they have other sizes. The build quality was only mediocre though (go to Amazon and read some reviews about the coating and clicks).
What you take depends on your needs and what you feel comfortable with. Also if your work requires you to use the keyboard a lot, get a decent ergonomic one (like a Kinesis, ErgoDox, DataHand, there is a new one coming out from Matias).
You should maybe say a bit more about what your work implies. What do you do for work? Do you need precision, because you're controlling a rocket shooting drone? Some kind of CAD, modelling or maybe remote sensing? Or are you working for civil service and playing Minesweeper all day long?