Gravity. It’s such a downer sometimes. While sitting our muscles will naturally try to put out less effort and transfer that effort on to the skeletal structure. Due to the weight of the shoulders and head and the spine flexes and slumps over and the shoulders hunch and rotate inwardly. The dramatic changes this can make on the spine over many years are sometimes shocking in an elderly person: how did they allow themselves to get to that point?
Without a real conscious effort to stretch, strengthen and keep good posture we are all headed in this direction. Pain will start to increase in between the shoulder blades. The pectoral muscles of the chest shorten. And, eventually it will cause shoulder impingement, especially for anyone trying to be active with inwardly rotating shoulders. Even the motion of jogging with inwardly rotated shoulders can cause impingement and tendinitis on rotator cuff muscles, especially the supraspinatus.
As the pectoral muscles and gravity pulls the arms down and into an inward rotation the hands also rotate inward so that the thumbs point at the body while in a natural standing position. In a correct anatomical position the thumb should point forward and part of the palms are visible when standing face to face.
Because of the structure of the shoulder joint the arm cannot raise properly while the thumbs are face down. The protuberances on the bone of the joint will inevitably impinge on the supraspinatis and, in doing so, cause tendinitis with pain deep in the shoulder under the deltoid often radiating into the top of the shoulder into the upper trapezious. Rotator cuff injuries take a while to heal and, when not followed by physical therapy, can lead to a frozen shoulder.
To avoid this mess and to have beautiful posture it is important to strengthen the back and external shoulder rotation muscles and to stretch the pectoral muscles and back into extension (opposite of hunching). Just 15 minutes a week (5 minutes three times a week) could save years of pain and lead to healthier, more balanced posture for life.