My work is stiff.

I am a working stiff. Literally. I work at a desk, in front of a computer, sitting in a chair, and my body and my brain go stiff. Occasionally, there will be a brief respite from the doldrums of drudgery when I get thirsty and go to the water cooler and quench a thirst that I only think exists in order to give me an excuse to get out of my chair, off of my desk, and away from my computer.
I can try to convince you that I believe in what I am doing--because I do--but, that seems too cliche right now. Is that cynical, or just honest? Maybe it is not me that is stiff, but my work. I need to loosen it up a bit. How do I do that?