Dark Orpheus had expressed an interest in tai chi, and since this is one of my favorite subjects, I'm going to mention this site with information about a PBS special on qigong, which is such a large part of tai chi practice.
On my other blog I listed some sites with information about the medical studies done on tai chi and health, and I'll repeat them here. The Journal of the American Medical Association has listed a number of articles relating to the benefits of tai chi/ qigong. This site also lists some of the benefits of qigong on the heart.
The exercises are a form of standing meditation, and the following video is a good instructional introduction qigong and mentions the different kinds of breathing and its effects.
Here are links to Part 2, Part 3, Part 4.
This video shows another form of qigong in practice, but the crucial part is in the breathing, one long, slow breath for each movement.
The following video may seem a bit strange, but is from the PBS documentary and studies qigong as it is practiced in China.
Although the Chinese discovered and put to use the connection of physical movement, breath control, and emotional state before anyone else, there have been a number of scientific studies over the years that also make the link, with or without a connection to tai chi/ qi gong. Certain postures communicate emotion, but they also can determine your emotional state.
And here is a video of Vivian in Houston as she competes for the Grand Championship of that tournament. The video was uploaded to youtube by Tom Gohring.