One of the problems with repetitive use of the shoulder particularly under load or deceleration (as in throwing) is that the small rotator cuff muscles start to break down. Once they are damaged they do not function properly in stabilizing the shoulder, leading to injury. In addition, since much what we do in life, in sport, in strength training tends to focus on the large pushing muscle of the upper body (lats, pecs, deltoids) we tend to overdevelop these muscles and let the dorsal (posterior) muscles of the back and shoulder get relatively weaker. As a result we get muscle strength and flexibility imbalances that set up a cascade of events leading to shoulder injury.
The basic principle behind injury prevention in any healthy joint is to employ strategies that maintain the flexibility and strength balance between the opposing forces on the joint. This means that exercise programs need to be designed to strengthen weaker muscles and to stretch tighter muscles and other soft tissue around the joint. On the case of the shoulder we need to develop what is generally termed a posterior dominant shoulder. That is the muscles attached to the shoulder blades (which includes the rotator cuff muscles) must be strengthened while the muscles that surround the chest and front of the shoulder need to be stretched. Of course, not everyone has the same deficits so one prescription does not necessarily fit all needs. If you have an injury now, you should consult a Physician, Physical Therapist, Athletic Trainer or other qualified sports medicine professional.
There are however general principles that we can apply. One of the chief early indicators of pending shoulder problems is posture. Try sitting slumped forward, now lift your arms over head…now sit up straight, squeeze your shoulder blades together and lift you arms overhead. Notice the difference! As your Momma said, sit (or stand) up straight. You will be doing your shoulders a favor.
The rotator cuff muscles are small, postural muscles. As a result they must be strong but must also be able to contract repeatedly for extended periods of time. To train them we need to use relatively high repetitions with relatively low resistance in order to increase both strength and endurance. See the appendix for samples of a rotator cuff strengthening routine.
The Para scapular muscles are larger muscles that serve to help us maintain good posture. These muscles include the serratus anterior, rhomboids, middle trapezius, lower trapezius, teres major as well the thoracic spinal erectors. These muscles also serve to counteract the forces exerted by the pectoralis, anterior deltoids, latissimuss dorsi and coraco brachialis. These are the “pulling muscles” of the upper back and need to be trained in equal measure to their opposing muscles. This is where the idea of “push/pull” strength training programs comes from. See the appendix for some ideas on training these muscles. In general when you are strength training these upper back muscles you should be sure to use full range of motion. This means, for example, that when you do a rowing exercise, you retract you shoulder blades at the top of the movement and pull the weight all the way in to your chest. The are also a number of assistance exercises that you can do to help keep a strength balance in these muscles. Again, see the appendix.
n addition to maintaining a strength balance around the shoulder joint we need to maintain a range of motion balance. Short, tight muscles in the chest and front of the shoulder combined with stretched and (relatively) weak muscles in your upper back are a recipe for shoulder injuries. In addition, many of us are restricted in the upper back (thoracic spine) so this area usually needs attention as well. If these thoracic spine segments are severely restricted you may need the services of a Chiropractor, or Sports Physical Therapist to mobilize your upper back.
This article is intended as a general overview of factors that contribute to (non-traumatic) shoulder injuries. Many shoulder problems are preventable with a well-designed training program. If you already have a shoulder injury you should seek appropriate medical advice. If you do not have a shoulder injury now then incorporate a prehabilitation or injury prevention program into your week. In future articles, we will go into more detail and variations on shoulder injury prevention.