To help stretch and lengthen the shoulder flexors and external rotators, spend one minute twice a day with your forearms stacked behind your back and your hands reaching toward your elbows. Keep your chest lifted and open, and breathe into your upper chest and front shoulders. As the stacked-forearm position becomes more comfortable, start to work one hand up your back, gradually moving it up between the shoulder blades. Again, keep your chest lifted and your shoulders back and down. Once you can get your hand up between your blades, you have a shot at catching the fingers with the "up" arm.
To put the pieces together, stretch your right arm forward and up, maintaining external rotation as you flex your elbow, and bring the right hand down onto your upper back. Take your left arm out to the side and internally rotate it so your thumb points down and to the back. Then quickly swing your hand in and up between your shoulder blades to catch your hands. It's fine to use a belt between the hands until they meet naturally. Stand tall, with your chest lifted, shoulders broad, and both sides of the waist lengthening evenly. Practicing this pose a little bit two to three times a week goes a long way. The next time your teacher announces, "Gomukhasana," you'll be the one smiling while everyone else is looking apprehensive.
A physical therapist and Iyengar Yoga teacher, Julie Gudmestad runs a physical therapy practice and yoga studio in Portland, Oregon.