Perhaps it's getting a little chilly for slow, meandering hikes. Maybe just the thought of jumping in your favorite swimming hole makes your teeth chatter. Fall doesn't mean you have to stay off the trail, though: It just means you may have to pick up the pace. Enter trail running, one of the most invigorating, inspiring and just all-around awesome ways to get outside and stay fit in the fall. So grab a pair of trail shoes, read The American Trail Running Association's guide for getting started, and hit the road! Er, rather, the hit the trail!