The latissimus dorsi muscle can contribute to pain in the shoulder, upper back, and arm going down into the hand. The muscle can also cause pain in the side of the ribcage and lower abdomen. It is the muscle that most often causes the ‘side stitch’.
Scalene muscles are a prime contributor to thoracic outlet syndrome as well as neck, shoulder, chest, upper back and arm pain. Muscle twitching, jerking and restlessness similar to restless leg syndrome felt in the neck and shoulder is a classic sign of scalene dysfunction
The pectoralis major contributes to pain in the chest, shoulder, breast and upper back. Pain can also travel down the inner arm, elbow and extend to the hand and last two fingers.
The serratus anterior muscle contributes to pain down the side of the ribs, around the shoulder blade, chest, arm, hand, and fingers.
The serratus posterior superior muscle is a muscle found in the upper back. It contributes to pain in the shoulder, shoulder blade region, arm, hand and little finger. It can also contribute to pain in the upper chest.
The diaphragm is a muscle found under the lower ribs. It can contribute to breathing problems, pain in the chest, ribs, and can cause sharp pain in the side known as side stitches.
The iliocostalis thoracis muscle can contribute to pain in the chest, upper back, lower back, and abdomen. Pain tends to be more concentrated around the shoulder blade and / or low back kidney area.