Yin Yoga stretches the body in ways that other forms of yoga do not. Most other forms of yoga are focused on stretching the muscles of the body. Yin Yoga works to stretch the connective tissues of the body that are found in the joints and surrounding the muscles; particularly the joints of the spine. Just like muscles, if you do not use the joints of the body you will lose them; they will become fixated and immobile. What does this mean for you? It means that as you reach old age, you may find yourself unable to stand up straight; you may become hunched over because you have lost the ability to use the joints in the low back.
A great pose to start to counter this affect is with Caterpillar pose (seated forward bend). Just sit on the floor with your legs in front of you and fold the upper body forward keeping the muscles relaxed so the joints can take the stretch. If you find that folding forward is a challenge, you can also do this pose standing up by dangling the top half of the body forward, like you were trying to touch your toes. The key is to hold the pose for at least two minutes; more if you comfortably can.