I don't work out on my days on. I work 12's, a mix of days and nights, 6:45 - 7:15 in NICU (unless it's Friday, when we ALWAYS get an emergency c-section at 6pm meaning baby isn't stabilised until ~8ish - I think "emergency" means "the OB may be called in off the golf course on Saturday morning if we don't do this now") - but I digress!
Like I said, I don't do formal exercise on the days that I work. BUT I work out every single day I don't (3-4 days per week) and I wear a pedometer at work. We've just moved into a brand new hospital - lovely, but a very long way to the storeroom, blood gas machine, etc. I usually do between 10,000 and 12,000 steps during a 12 hour shift. I think that's enough!
Carinna - what are these breaks of which you speak?

20 minutes a couple of times a shift is barely enough to chug down some food and water and go to the toilet. That's if the pager doesn't go off from birthing suite in the middle of it - I don't know how many cold cups of coffee I've come back to an hour later.