tai chi?

Hi there! I just went to a Tai Chi class. It seems quite cool -- the gist of it that I understood was exercises built around the basics of traditional chinese medicine principles (qi manipulation / working with stimulating and relaxing different organs [i.e., stretches for the liver, breathing exercises for different areas of the lungs, and so on ... ]) I was at first pu toff by the instructors description of good posture as tucking your pelvis, but he himself seemed to have quite good posture, even when demonstrating this. I asked him about this after class, and he demonstrated that in some movements, people have a tendency to have an extreme curve in the lower back, around L5-S1, and so tucking was a way of controlling this. He said another way to say this was to use your abdominals to pull you through different movements, and I'm just wondering if he meant using the rib anchor muscles to keep the spine anchored ... I feel ok working with him for now as the postures he physically demonstrated while explaining and demonstrating this to me all looked quite fine (straight back, healthy lumbosacral curve ..) Anyhow, I was wondering what thoughts here were with regards to the general benefits of and health of Tai Chi / qigong exercises. :D