Yin Yoga is based on the Taoist concept of yin and yang, opposite and complementary principles in nature. Yin is the stable, unmoving, hidden aspect of things; yang is the changing, moving, revealing aspect. Other yin-yang polarities include cold-hot, down-up, calm-excited.
In the body, the relatively stiff connective tissues (tendons, ligaments, fascia) are yin, while the more mobile and pliable muscles and blood are yang.
A Yin yoga class usually consists of a series of long-held, passive floor poses that mainly work the lower part of the body—the hips, pelvis, inner thighs, lower spine. These areas are especially rich in connective tissues. The poses are held for up to five minutes, sometimes longer. Yoga postures are more passive postures, mainly on the floor and the majority of postures equal only about three dozen or so, much less than the more popular yang like practices. Yin Yoga is unique in that you are asked to relax in the posture, soften the muscle and move closer to the bone. While yang-like yoga practices are more superficial, Yin offers a much deeper access to the body. It is not uncommon to see postures held for three to five minutes, even 20 minutes at a time. The time spent in these postures is much like time spent in meditation, and I often talk students through the postures as if they were trying to meditate.