I've got two dogs. Even on my worst medicine months I still get out most evenings for 30-60 min. walk/run with them. It's a great way to clear my head, and the dogs love it. On days off I head to the hills and do a longer hike. It wears them out, gives me a harder workout and makes me feel like I've gotten away from work for a while. On easier months I try to make it to the gym in addition to the running/hiking at least 2-3 times for weights/elliptical/biking, etc. I also try to bike outside when I can (I'm in Colorado, so it's a given that biking is a big thing out here). I think I'd go crazy in intern year if I couldn't exercise, so I just try to fit it in any way I can.