Yin practice is characterized by lack of strain or striving. It allows the yogini to metabolize difficult emotions and effectively can be targeted to benefit specific organ systems in the body.
Yin/yang practice stimulates chi flow in the meridians (electromagnetic routes) assisting each organ to function normally, removing energy and emotional blockages and awakening the yogini to an alert mind and balanced emotions.
Excessive and out of balance emotions result in illness as if the body were undernourished. Depleted energy (chi) leads to difficult emotions as well.
Out of balance kidneys are linked with fear and terror. The liver specifically feels anger and envy. The spleen takes on obsession and worry. The lungs are impacted by sadness and grief. The heart will lose balance with depression or hatred.
The organs in Chinese medicine are linked to health of the meridians flowing through them. Each yin designated organ and its meridian is complimented by a yang organ and meridian. What is done to one immediately effects the other. They combine in energetic, emotional and mental qualities.
12 of the 14 major meridians are considered regular and can be impacted by yoga practice. The 12 meridians are connected into 6 pair of yin/yang organs.
5 of the regular yin meridian/organ pairs (kidney, liver, spleen, lungs, heart) connect with the 5 emotions listed above. They influence the way in which our world is experienced. Each intense emotion throws our meridians and organs out of balance.
Each yin pose effects many meridians. Yin sequences can put stability back into and restore healthy life in each meridian/organ yin/yang pair. Repetition of certain yin poses impact deeper meridians as well.
Insight Yoga by Sarah Powers (2008) Shambala:Boston, gives a detailed explanation of yin sequences, meridian theory and detailed yin/yang practices to develop each meridian pair. She also devotes an instructive chapter to beginning the practice of yin or yang yoga. Information in the above article is referenced to this book.