by Brian A. Bast, D.O.

Although referred to as a ball-in-socket joint, the shoulder socket is relatively flat and more of a suspended joint where ligaments and muscles account for the stability of the joint. Without a deep socket like the hip, the shoulder loses stability in return for increased range of motion. The important structures that give stability to the shoulder include ligaments, which connect bone to bone, and muscles, which are connected to bone by tendons. The ligaments are the innermost support structures and are covered by an intricate layering of muscles. The rotator cuff muscles (subscapularis, supraspinatus, infraspinatus, and teres minor) are the muscles that are the most intimately attached muscles of the shoulder and are surrounded and covered by larger more powerful muscles like the deltoids and the pectoralis major.

The shoulder relies on a delicate balance of muscle coordination and strength to perform without excessive wear on any one muscle. When a particular motion is repeated thousands of times in one practice, stroke flaws are magnified and certain muscles may be overworked. Or, a muscle may be placed in a difficult position where it may rub against nearby bone creating an impingement position. Dubbed “Swimmer’s Shoulder”, the most common swimming injury often involves one particular rotator cuff muscle, the supraspinatus, either being overworked or repetitively pinched. This injury can occur for numerous reasons, but the most common causes are overuse, improper technique and muscle imbalance.

A frequent pitfall in early swimming technique is to overuse the group of muscles that brings the arm closer to the body during the pull phase of the freestyle stroke. The muscles that bring the hand under the body include the pectoralis major, one of the strongest muscles around the shoulder, making it a great power generator. The pitfall is that this muscle may be relied on over other muscles if shoulder strength is not balanced. Ideally, in the freestyle stroke the hand reaches and enters the water finger tips first and then begins pulling water towards the chest along an imaginary line that splits the right and left side of the body. The concern is when the hand crosses this line to the opposite side of the body, putting the shoulder, albeit momentarily, in a bad position. In this position there are increasing demands on the smaller rotator cuff muscles that intimately surround the shoulder. Under these greater demands, rotator cuff muscles like the supraspinatus may become fatigued and inflamed and this muscle may rub against the ridges of the shoulder causing further inflammation and pain.

Key Points

1. Ample stroke technique at young ages. Coaching by someone experienced in swimming mechanics is essential for early stroke development and technique. Biomechanical flaws are often subtle and more easily recognized by a viewer and not the swimmer. Videotaping practice sessions is a useful tool, where stroke mechanics are reviewed with the swimmer.

2. Reinforcement of drills for all swimmers that focus on good technique. Drills that focus on proper stroke mechanics has a place in training regimens at all levels. While the amount of time dedicated to proper form will change as stroke mechanics are mastered reinforcement is important.

3. Core training provides a link in the kinetic chain between the legs, trunk and shoulders. This allows better streamline and less strain on the shoulders.

4. Strengthen scapula stabilizing muscles like the external rotators (teres minor and infraspinatus) which are on the back side of the shoulder. These rotator cuff muscles are often weaker than the opposing pectoralis major which is on the chest side of the shoulder. Strengthening these muscles can limit overuse of other rotator cuff muscles like the supraspinatus. Along the same thinking, stretching of the frequently tight pectoralis major and latissimus dorsi are effective in keeping the shoulder balanced.

The shoulder relies on a delicate balance of muscle strength and flexibility for optimized performance. Proper conditioning and stroke technique are necessary for long-term, injury-free, participation in the sport. Balanced strength allows for faster swimming because more muscles are engaged and working together.