I came to a page that discussing two pairs of chi routes that run along the front (yin channel) and back (yang channel) of the body. Apparently the symptoms I have–backache, headache, and joint swelling (arthritis)–can indicate that the yin channels are blocked, creating an excess of yang energy.

Huh. I have known for years that I had underlying back issues that should probably have been treated, but the problems only became acute after I spent last year doing hatha yoga nearly every day. Hatha yoga is pretty yang. Maybe the yoga I did strongly activated my yang energy, but wasn’t as effective in opening the yin channels on the front of the body. That would explain why I have been having so much success with yin yoga and qigong, both of which strive to gently open the chi routes and balance energy.