Two muscles are most important in moving the scapula (shoulder blade) as the arm is reached overhead. These are the upper trapezius (UT) muscle and the serratus anterior (SA) muscle. The UT goes across the top of the shoulder. You use the UT to shrug your shoulders. The SA comes from the scapula under the armpit around the side of the trunk. The SA attaches along the upper eight or nine ribs on the front of the body. The SA helps move the scapula.
Shoulder problems can occur if these two muscles don't contract and work together. There has to be just the right action between the UT and the SA. When the SA contraction is weak or the UT contraction is too strong, the scapula moves abnormally. It can even start to wing out instead of lying flat against the rib cage in the back.
The patient may end up with a problem where the shoulder joint pinches, called impingement. In this case the scapula moves up when it shouldn't. There are exercises to help with this problem.
In this study, physical therapists from the University of Minnesota measured the force of contraction between the UT and SA. Two groups of patients completed four different exercises. One group had normal healthy shoulders with no problems. The second group had shoulder pain or abnormal shoulder movement.
The exercises used a special push-up with scapular protraction. This means at the end of each exercise, the patient actively moved the scapulae forward on the rib cage as far as possible. The therapists helped patients practice the movement until the right motion and timing were present. Each of the four exercises was done five times with a two-minute rest period between sets.
The authors found the SA was most active during the military type push-up with scapular protraction. It was least active when performing the same push-up activity in the standing position against the wall. Two other positions (on hands and knees, and on toes and forearms) had SA levels between the two extremes. Overall results were the same in both groups.
This study showed that special exercises can be done to strengthen the SA without making the UT any stronger. This keeps the UT from overpowering the SA. Patients with scapular winging or shoulder impingement can benefit the most from these exercises. The patient can start with the easiest exercise (wall push up with scapular protraction) and progress to the hardest (full push-up with scapular protraction).
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