HOW: Get set up laying on your stomach with your hand resting behind your back in a comfortable position. Begin the exercise by squeezing your shoulder blade directly back. While maintaining this, lift your hand off your back for the time prescribed. Return your hand to starting position and repeat.
FEEL: This should feel like a shoulder and shoulder blade exercise working the muscles in and behind your shoulder. You also may feel a stretch in the front of your shoulder.
COMPENSATION: Try to limit motion to your shoulder and shoulder blade, try not to lean or bend too much with your trunk and upper body.