It’s hard to buy the idea that tai chi is a martial art. This very leisurely exercise program seems less helpful in a combat situation than one where you are trying to relax, mediate while moving, refine your breathing techniques and, according to even Western medicine, help you with arthritis or a predilection to losing your balance and falling down. There are three main schools of Tai Chi –Yang, Chuan and Qigon- with dozens of subschools and classes all over the Bay Area, many free. Increasingly, the medical establishment is getting interested. For example, at the Mind-Body Research Program at Harvard Medical School.