I did Tai Chi for six months and it whipped me into the best shape ever. In just that short time I gained 20 pounds of muscle. I quit when a friend passed away, and I haven't gone back to it. I often think about it, because I really enjoyed it. It's expensive though.
Even if the open windows of science at first make us shiver after the cozy indoor warmth of traditional humanizing myths, in the end the fresh air brings vigor, and the great spaces have a splendor of their own - Bertrand Russell