A while ago I talked about Japanese kyudo archery and they way Rinzai Zen tradition combines Zen Buddhism and traditional art of Japanese archery (as well as other martial arts). In Japan and all martial arts traditions, the concept of "hara" is a very big thing (that big a thing that seppuku is occasionally called harakiri...).
On this link, a man who has studied Rinzai Zen and kyudo for 30 years shares his thoughts, ideas and practices associated with hara:
http://haradevelopment.org/ I have tried some of these things and they do work.
