I like walking too, although it's not a substitute for running. But I like getting out and stretching my legs and clearing my head now and again. I try to go for a little wander around the fields during lunch at work most days. And at home, I've got a nice little loop along a path around a little saltmarsh by the river. Probably not even a mile long, but enough to clear my head a bit when I've been studying for too long. I would love to get out for more strenous hikes more often, but unfortunately I live in the wrong part of the country for that. But maybe next year if all goes according to plan....