Pain in this area can be from short tissue or long tissue. It may come from the lower trapezius, from the latissimus dorsi (lats), from some of the spinal erectors, from the pectoralis major (pects), from the abs (rectus abdominis), from the quads, or from all of them. The most likely culprits are the abs and the pects. These muscles pull on the shoulders and will have a tendency to roll them forward. Many people work out with weights and try to develop the abs and pects without paying sufficient attention to the corresponding back muscles. So the imbalance will cause pain in the mid-back. With some others there is a natural imbalance that comes from repetitious activity that has the same effect although the body may look differently. Additionally, spending time bent over at a desk is hardly healthy for your mid-back. This serves to compound the problem. If allowed to persist, i.e., the forward roll of the shoulders, the shoulder blades moved outward, the upper back rounded over, the tight abdomen; then there is a good possibility that a hunched back will set in place. The major effect of such a posture is the limiting effect on the lungs. The compressed front will make it difficult to take a deep breath as the diaphragm will be constricted.
Simple Remedy
Strengthen the back, especially the rhomboid muscles, i.e., those which pull the shoulder blades together; and open up the chest area. The simple act of strengthening the rhomboids will force the pectoralis muscles to open up; however, they must also be stretched on a regular basis. To strengthen the rhomboids raise your arms out to the sides so they are parallel to the floor, bend them at the elbow, and lean your back against a wall. From this position pull your scapulae together, hold for one second and repeat. To increase the resistance move your feet further from the wall. If you have access to free weights you can do the bent over row with a barbell or the bent over row with a dumbbell. To increase the effect you should also stretch the pectoralis muscles, but do so one side at a time. Do not try to stretch both sides at once by standing in a doorway as the effect will not be balanced and you will not be able to focus on the muscles appropriately. For the lower pect muscles move your arm to about forty-five degrees from the body and pull it back or hold on to the end of a table and lean forward. For the middle pect hold out your arm parallel to the floor and palm forward and pull it back or lean the arm against a wall or doorway and lean forward. For the upper pect, place the hand behind the head and hold the elbow at about forty-five degrees and lean against a wall. In all cases hold for about two seconds, relax, and then repeat. Do this several times during the day.
As far as the abs is concerned, interlace your fingers and place your hands behind your head. Slowly and gently pull back into a broad arc. Hold for two seconds and repeat. This may also be done while lying on carpeted floor or firm mat, although you will simply place your arms at your side while you extend your head back. If you have lower back issues, do not raise your legs as well as this can compromise your lower back and cause spasms or injury.
Further Support
If your have access to a swimming pool, swimming on your back with the back stroke will help to open up your front and strengthen your back. Additionally, pushing off from the side for the back stroke will stretch your abs. It will also be more enjoyable. Some reviews on good products is avalable on the page: Back Pain Relief Products
Long Term Remedy
The best solution for the long haul is to adjust your work environment. The best seat for computer or desk work is a firm adjustable stool. Most chair backs are contoured to conform to the curves of your back and are tilted back at an angle. The effect is that your weight winds up on the low back as opposed to the sitz bones in your pelvis. To sit in a balanced manner, locate your sitz bones, then slowly rock your torso forward and back slowly until you find the point of balance. Then do likewise sideways. When you find there is no effort in sitting, then you are balanced. Now feel your neck muscles. They should feel loose. The angle between your thighs and your torso should be ninety degrees or greater and your feet should be flat on the floor. When you achieve this posture, you should be able to maintain it for a considerable time without causing undue stress to your back. If you sit on bleachers for games, employ this method and you should be able to sit through the game without a problem. It does, however, take time to adjust. In addition to that you may consider strengthening your back by lifting free weights in a dead lift or bent over row. As before, all exercises should start off slowly so that your mind has a chance to understand and internalize the movements you are asking of your body.