Yin Yoga Intro
"There are two principles that differentiate yin practice from more yang approaches to yoga: holding poses for at least several minutes and stretching the connective tissue around a joint. To do the latter, the overlying muscles must be relaxed. If the muscles are tense, the connective tissue won't receive the proper stress. You can demonstrate this by gently pulling on your right middle finger, first with your right hand tensed and then with the hand relaxed. When the hand is relaxed, you will feel a stretch in the joint where the finger joins the palm; the connective tissue that knits the bones together is stretching. When the hand is tensed, there will be little or no movement across this joint, but you will feel the muscles straining against the pull."