The Arm Chair Stretch is one of the best stretches for the upper and middle back. It reaches muscle groups that generally can only be targeted by a good massage therapist. The muscles of the mid and upper back are chronically tight due to long office hours and poor posture. Stretching these muscles can help with any tension headaches, shoulder and neck pain. When performing the stretch, make sure you feel the muscles stretching and not the shoulder joints, especially if you are super flexible.