Exercises for posture for the upper back are mandatory if you have pain, particularly if you are a sedentary worker, use a computer a lot, or work at any task with your head down. 

The posture exercises for the upper back must be both stretching and strengthening. The stretching makes you straighter and the strengthening makes you stronger, so you can keep straight. It's then easier to hold you head up, keeping you more in line with the centre of gravity and lessening the strain across your shoulders. 

It may seem strange that upper body strength first requires lower body strength, even pelvic floor strength. It's as if being fortified from below makes it easier to hold your upper body up. Strong lower abdominals and pelvic floor make for a much more supportive intra-abdominal pressure that makes it easier to hold your head and shoulders back. 

The BackBlock for Stretching Out the Lower Back

Reverse Curl Ups for Strengthening Lower Abs and Pelvic Floor

The Prone Floor Stretch for Stretching Out Tight Shoulders

The BackBlock for Straightening the Upper Back

See here to purchase a Sarah Key BackBlock from Amazon

Handstands: Ultimate Strengthening for Arms and Shoulder Blades

Exercises for a Hunched Upper Back