Some back pain masks itself as shoulder pain or chest pain or even under your arm pain.
One muscle in particular bears the responsibility for causing these referred pains that have little or nothing to do with the shoulder, chest, or underarm: the subscapularis muscle.
The subscapularis muscle is a muscle that lies mostly under (sub) the shoulder blade (scapula).
The subscapularis is almost a vestigial muscle, meaning it was a muscle we used to use a lot but don't really employ much now.
It was a hunter/gatherer muscle used to stabilize the shoulder blades while harvesting grain or pulling up root vegetables or maybe even skinning animals.
These days we don't do much in the way of toting barges or lifting bales so the subscapularis is severely underused and it doesn't like it much.
If you find yourself sort of rotating your shoulder around because it just isn't comfortable, you probably have some subscapular issues.
Symptoms of subscapularis can include any of the following:

• Discomfort, sometimes pain, in the upper quadrant of your back usually on your strong side.
  
• A band of pain or discomfort around the upper part of your arm just under your shoulder.
  
• Pressure on your upper chest just under your collarbone.
  
• Achy pressure between your shoulder blade and your under arm.
  

Because of the attachment points for this muscle and the muscle groups it interacts with, it is very hard for the sufferer to identify where the discomfort is coming from.
If I had a dollar for every time someone complained to me of shoulder pain or just vague discomfort in an upper right or left quadrant of their back and it turned out to be their subscapularis muscle, I would have a fistful of dollars.
The problem stems from the fact that because we don't use the muscle, it becomes deconditioned and easily irritated if we move wrong or even just sleep in a bad position.
Usually a bit of acupressure is enough to stop the muscle spasm but what the muscle really needs is to be exercised and stretched.
Acupressure of the subscapularis You can self-apply acupressure but it is not easy and usually doesn't work as well as if someone does it for you.

1. Lie flat on your stomach on a comfortable surface.
   
2. Place the hand on the side of your body that has the discomfort on your back at your waist.
   Note that this causes the shoulder blade to lift up and move away from the center of your back.
   
3. Have the person who is going to apply the acupressure palpate the newly exposed are, meaning they should assess the texture of the muscle tissue under your shoulder blade.
   If the person giving the massage is at all sensitive, they may even be able to feel the muscle spasm under their fingers.
   That is what is causing the discomfort.
   
4. Have them find the center of the muscle, the lump that is easily discernible when it is irritated, and press firmly with their thumb for a count of 7.
   
5. Follow with a cold pack or ice massage.
   

Muscles do not have a mind of their own so stopping the spasm sometimes is enough.
The cold pack or ice massage removes the last bit of inflammation caused by the spasm and then the acupressure itself.
To self-apply acupressure, use a hand ball or racket ball.
They are firm without being so firm you could easily bruise yourself:

1. Sit on the floor.
   
2. Position the hand ball or racket ball on the floor behind you so that when you lie back, the scapula on your affected side would be on the hand ball or racket ball.
   You will probably need to be on a rug or use a towel to anchor the ball.
   A carpet may be too thick.
   Experiment a bit.
   
3. Cross the arm of your affected side across your body as if you were grabbing your opposite shoulder.
   
4. Lie back, trying to put the exposed muscle on top of the ball.
   You may need to squirm around a bit to position the ball correctly.
   
5. Allow the weight of your body to apply the pressure of the ball to your muscle for a count of seven.
   
6. Follow-up with ice pack or cold pack.
   

Exercising the subscapularis As I mentioned before, the reason we consistently have a problem with the subscapularis is because we don't really use it much anymore.
To exercise the muscle, we have to intend to focus on that muscle:

1. Kneel with your left knee on a padded bench and your right foot stabilizing your frame on the floor.
   
2. Place your left hand on the bench at a comfortable distance from your left knee.
   Make your body create as square a frame as possible.
   
3. Using the lightest weight possible, 2 lb for a woman or 5 lb for a man, hold the weight in your right hand so that the weight is just hanging freely from your shoulder.
   
4. With your arm and elbow staying firmly at your side, lift the weight up to your chest.
   
5. Keeping the weight in complete control, allow your arm to straighten back to the original position.
   
6. Relax completely.
   
7. Repeat 10 times and then switch sides.
   

You should use the lightest weight while you get comfortable with the exercise.
This is true of any new exercise with a free weight: learn the motion and then start adding weight gradually.
This is especially true when you are rehabilitating a muscle.
Stretching the subscapularis Stretches are always a good idea and can usually be done anytime, anywhere.
For the subscapularis, because it is a deep muscle and not very big, getting into the stretch can be a bit difficult.

1. Sitting or standing, cross your arm over your body and place your hand on your opposite shoulder.
   Don't grab your opposite shoulder because then you are using the muscles trying to stretch.
   That does not always work well.
   
2. Using the opposite hand, anchor your elbow in place.
   With your arm across your body, your elbow is usually right in front of your face.
   
3. Gently bow out your back.
   This pulls the shoulder blade up away from the muscles of your back and creates the stretch.
   
4. Hold the stretch for a count of 6 and then switch sides.
   

If you are not gentle enough, you will know it-later, unfortunately.
Fortunately, the cure for any soreness caused by not being gentle enough is the same as the cause: exercise, stretch, ice.
If you are like me, you will be amazed at the relief you get from exercising and stretching this muscle.
Who knew?