Properly engaging the external rotators takes some training. In fact, many students unknowingly let their shoulders slip into internal rotation in Downward Dog, leaving the external rotators lazy and inactive.
To get a feel for engaging the shoulder external rotators, stand facing a dining table or desk. Lean forward and place your hands on it, palms down and bearing a little weight. Now look at your elbows, noticing the crease on the inner sides and the point of the elbows on the outer sides. When you rotate your arms so that the elbow creases point forward, you will be externally rotating your shoulders. When you rotate in the opposite direction and the points of the elbows poke out to the sides, you will be internally rotating your shoulders. Play with this a bit by rotating in and out with this light amount of weight bearing, and you may even be able to feel the teres minor and infraspinatus contracting across the back of the shoulders as you turn the elbow creases forward.
Now go to your mat and do Down Dog. If you're a newer student or have tight shoulders, you may notice that they tend toward internal rotation, with the elbows sticking out to the sides and maybe even bent. Still in Dog, come forward a few inches toward Plank Pose and actively rotate the elbow creases relatively forward, so that they point toward your thumbs. Move back into Dog and try to keep some of this external rotation, though you'll have to give some of it up to fully open the shoulders. Maintaining some external rotation will keep the teres minor and infraspinatus contracting, and you'll probably notice more space opening up between your shoulder blades.
Once you've mastered keeping the external rotators engaged in Downward Dog, you can apply the action to more challenging poses such as Urdhva Mukha Svanasana (Upward-Facing Dog Pose) and Chaturanga Dandasana (Four-Limbed Staff Pose). From Downward Dog, come forward into Plank Pose. Rotate the creases of your elbows forward and hold your elbows against your sides as you let down to Chaturanga, then glide forward into Upward-Facing Dog. As you actively turn your elbow creases forward in this pose, the external rotators will be contracting strongly, and you should notice that this action broadens and lifts your chest.
Now notice how this shoulder rotation affects the weight placement in your hands. If the shoulders internally rotate, more weight tends to fall onto the inner side of the hand—that is, the thumb and index finger; in external rotation, the weight falls more onto the little-finger side. Ideally, your weight should be evenly balanced between your inner and outer hand, so that as you externally rotate at the shoulder, you'll need to focus on actively pressing down on the base of the index finger and thumb. This action of the forearm and hand is called pronation.
Typically, pronation of the forearm and hand occurs when the arms are internally rotated. For example, as I sit at my keyboard right now, palms down, my elbow points are sticking out to the side, which shows how pronation is linked with internal rotation. But Downward and Upward Dog require us to break our usual patterns by linking active shoulder external rotation with pronation of the hand. As you practice connecting these opposites, perhaps you'll appreciate anew how yoga helps you to break your old, unconscious habits in every aspect of life—and replace them with healthy, conscious, and considered ways of living.
Julie Gudmestad is a physical therapist and Iyengar Yoga teacher in Portland, Oregon.!--page-->