I'm surprised there aren't more parkour practitioners here. I find it is one of the most physically demanding things a person can do, it is almost entirely free

I'm surprised there aren't more parkour practitioners here. I find it is one of the most physically demanding things a person can do, it is almost entirely free, and it requires both extreme focus and tons of creativity. Of course, the downsides are that you have to be in amazing shape (or work your way up to it) and that it does tend to result in small injuries, but I would say no more than a martial art. Definitely a great way to get out, move around, and stay focused.