In any given yoga session, it's easy to get caught up in the physical practice, and to totally forget that yoga's physical component is just part of the preparation for enlightenment. We go through the physical body as a doorway, but the effects on the physical body are secondary. We may be in class to work out that part of ourselves that wants to look great in tight jeans and baby tees, but the real point of yoga practice is to shape up that part of our being that allows our truest nature to be experienced and expressed in the external world.
One way an accomplished yogi directs the flow of prana, the universal life-force energy that animates and unites all of us, is through the engagement of Mula Bandha (Root Lock), an energy lock that is often practiced in conjunction with asana. Your teacher may explain Mula Bandha as a contraction of the anus, but it's much more than just a physical movement: It serves as a gateway into the mental, psychoemotional, and subtle energy planes.
To help his students find Mula Bandha, Richard Freeman, an Ashtanga Yoga teacher, offers this hint: "If you exhale very fully and smoothly, you'll notice that the end of exhalation creates a natural toning in the pelvic floor muscles that allows you to get the last of the breath out. This is the point where Mula Bandha is set. It's really complex but really simple.'"