Frank,
Ideally, as you begin your draw, the trapezius/rhomboid muscle group in your back come into action and as you set your drawing hand anchor point on your face, your draw wt is being held with that back muscle group. At this point you'd like your drawing elbow to be just outside of the line running from the tip of your arrow through your shoulders and through your drawing arm. You might say that you've set two anchors: 1) your drawing hand at your facial anchor, and 2) your back muscle group. Now you continue your back tension, moving your shoulder blades towards your spine. This causes your drawing elbow to rotate towards your spine so that at release, Your drawing elbow,has rotated from outside the line, and into a straight line from the tip of your arrow, through your shoulders, and through your elbow. Since the only tension upon release is in the muscle group in your back, your drawing hand cannot do anything other than fly straight back towards your shoulder. Hope this helps a bit. Have fun!