Also, yoga. It's ubiquitous, you can start small, and although you may, you don't have to interact with people so it's a great stepping stone for a shy person.
Sure a high chance of meeting women (which is nice if you don't want to be Forever Alone), but other than the ability to strech a little more what is the gain?
I've gained strength, flexibility, and feel fantastic every time I leave a session. I also believe I'm less stressed and can focus better.
The classes I attend present the physical aspects as a gateway into meditation and relaxation.