Have you seen this public service announcement about the dangers of sitting at work all day? This summer, while doing lab work, I've tried to stand for at least 4 hours of my workday. It turns out to have some unexpected benefits:
1) I work faster. I'm working in a lab with a wonderful comparative collection, but if I'm sitting down, then I constantly have to jump up and run to the correct drawer. I'm faster standing in the middle of the room, with my work on a box on top of a table, and just taking a step to one side or the other when I need a particular skeleton.
2) If I need a drink/walk/stretch in order to regain my concentration back, I don't have to fight inertia. I find that I can only do a few hours of lab work before my eyes start to cross. If I take a short break, walk outside, get a drink, then I am ready to start again, fresh. But, if I'm sitting with my work around me, I find it hard to get motivated to stand up and walk out of the room, even though I know it will make me feel better. When I'm already standing, I can do a little stretching, walk around the room, and find it easier to concentrate.
3) It's far easier to supervise students/volunteers if you're lurking over their shoulder - even while working - than when you're sitting at a different table in the same room.
4) I feel like I've earned my lunch. Desert? Sure, why not?