YIN YOGA
 
Yin Yoga targets the connective tissues of the body.  The Yin Yoga postures are held several minutes because the connective tissues are tough and fibrous and don't respond to brief stretches the way muscles do in an active yoga practice.
 
Connective tissue is found in every bone, muscle and organ, and it's most concentrated at the joints.  If we never bend our knees or stretch our spines, then the connective tissue is going to slowly shorten to the minimum length needed to accommodate our activities.  After years of abuse or neglect, we try to flex our knees or arch our backs we won't be able to because our joints will have been "shrink-wrapped" by the shortened connective tissue.  To maintain our joint flexibilities, we must exercise them in a Yin fashion.  Many older people and athletes have joint problems and suffer with bad knees, bad backs and bad ankles.  Yin Yoga postures gently stretch and rehabilitate the connective tissues that form our joints.
 
Information from Paul Grilley's book - Yin Yoga Outline of A Quiet Practice.