HOW: Get set-up with your hands behind your head in a seated position. To perform the stretch, pinch your shoulder blades back together and move your elbows out and back to open up your chest. As you do this also focus on lifting your chest up and looking up. You can make it dynamic and reverse the motion like you see in the video.
FEEL: You should feel a chest and anterior shoulder stretch with this exercise.
COMPENSATION: If you get anterior shoulder pain with this exercise try raising your elbows and not squeezing them back as much.