In simple terms, we think of the back as divided into three major areas: lower, middle back, and upper (at the base of the neck). Of those areas, the second is the least flexible and the hardest to stretch and release. But never fear—if you've been hunched over your work all day, you can use a modified version of a yoga posture called Garudasana (Eagle Pose) to stretch out the area between your shoulder blades.
Sit tall in your chair and soften your gaze. Take a deep breath, and reach your arms straight in front of you. As you exhale, wrap your arms around your torso, right arm under the left arm, hugging yourself. Inhale into the hug, then exhale and bring your hands up toward the ceiling so that the left elbow rests in the right elbow with the arms entwined and palms facing each other (if your wrists are very flexible, you may be able to twist them around each other to join your palms). Inhale and exhale three times, relaxing into the stretch. Then repeat with the left arm under the right.