As an ASM in a theatre where the dressing rooms are down a flight of stairs from the deck, and the booth up above the balcony, I find that during show runs I feel like I'm getting enough exercise - especially on those two show days!
But I'm currently SMing a simple, 2-person show and we're in rehearsals. I've been walking to and from work (about a half mile), which definitely helps, but yesterday I was running late and drove, and found myself needing to run around on one of the 10 minute breaks to wake my body up.
I'd love to be doing some kind of movement. I really enjoy dancing, but my back is very temperamental and I generally find it's too much. I should do some yoga and stretching, though. I used to stretch before bed in high school and I found it very calming.