Like others have said, I prefer to walk rather than "work out." First of all, I hate to sweat. I really do. Second, I hate to be in a room full of people. Third, I hate the concept of the treadmill--it's a psychological prison: you walk and walk and walk, yet go nowhere. That's not the kind of message I like to receive in life.
I absolutely adore to walk in forests, though. To get lost in them, especially. I like to walk for the art of it--like Nietzsche said, all truly great thoughts are conceived while walking. He was absolutely right--that's when I've had some of my best moments, in the quiet introspection of a morning or evening walk.
You can see how a room, painted with white walls, full of people all wearing similar outfits, and surrounded by grey artificial things would bother me.
It truly is a shame that we're so constricted on campus. There's nowhere to walk, since we're completely closed off, and the only option is to walk around campus, in a circle, feeling absolutely helpless, and surrounded by people you'd rather were not there. That's why, if I really get the urge, I walk at night, when everyone's gone.