This month we take a closer focus on a piece of equipment you find in every gym. It's known generically as the pec deck, and I want to make it clear that I'm not referring to any particular brand of equipment. In
the past, I presented the first of a two-part discussion on shoulder instability. Before we get to part 2, I want you to see some practical examples of shoulder instability problems that are caused by common training
practices, as well as unusual problems that can occur.
The pec deck was designed to train the pectoralis major, the chest muscle that's commonly known as the pecs. The movement is similar to a dumbbell fly, but there are some significant differences. To begin with, the pec deck places your shoulders in a position of external, or lateral, rotation. Instead of lying on your bark, you're in a seated-or in some cases slightly reclined-position. At the end of the rep your upper arms are horizontal to the floor, a position of 90 degrees of flexion, and your forearms are vertical and pressing against the pads of the machine. Your shoulders are rotated externally, which can have important implications for some trainees.
The motion is completed as you move your upper arms backward to stretch your chest, and the final, stretched position includes horizontal abduction or even hyper-horizontal abduction of the shoulder. In this situation there are several possible causes of shoulder instability, some of which may overlap. When the shoulder is externally rotated, the ligaments in its front and bottom are stretched, and the stretch increases when the shoulder moves into horizontal abduction. This is not necessarily desirable.
Too much stretching of the ligaments will make them permanently loose, and that will cause shoulder pain for a variety of reasons. To begin with, the ball, which is the head of the humerus, will move too far forward in the socket, the glenoid fossa, during such movements as flat- and incline-bench presses, dumbbell and cable flys and pec deck. This can make the ligaments hurt, and you may also feel compensatory pain in the biceps tendon and rotator cuff muscles or tendons because they must work too hard to stabilize the shoulder.
What if you already have shoulder instability? If that's the case, performing any of the above-named exercises will cause pain in the front or hack of your shoulder. This leads to frustration, with you scratching your head wondering why you can't per for the exercises that everyone else can do. That's a common scenario with trainees who come to the Soft Tissue Center. Even so, they don't necessarily all have the same problem. The first priority at this or any treatment facility is to make a diagnosis. It's the health care provider's job-be he or she an orthopedist, sports chiropractor, physical medicine specialist or osteopath-to isolate your problem.
This isn't always easy, and shoulder instability is one of the most commonly missed diagnoses. If you're having a problem, it may be wise for you to seek more than one opinion. In any event do not attempt to diagnose yourself. If you've already developed shoulder instability, the most common form of which is known as anterior glenohumeral instability, then you must avoid the aggravating exercise for the time being. For a severe case you may have to eliminate it from your workouts entirely. The pec deck is a particular offender in this regard due to the extra stretch you get. It can be just too much movement if your ligaments are already overstretched.
The key conservative treatment for such injuries is to work on strengthening the rotator cuff muscles, including exercises for both internal and external rotation. Another problem that seems to occur after the patients use pec deck machines is known as thoracic outlet syndrome. It's a somewhat complex ailment to diagnose. The nerves to the upper arm leave the spine in the neck and them a bundle, known as a plexus. The nerves in the bundle travel by certain muscles behind the collarbone, or clavicle, in front of the first rib and past other muscles to supply the arm. Some people have extra bands of connective tissue around this bundle of nerves. If the bundle becomes compressed, the patient may develop tingling, numbness, pain, temperature differences-perceived or actual-and a variety of symptoms over large areas of the arm, forearm, hand and even armpit.
The pec deck can aggravate or produce this problem if you perform it a certain way. Dr. Sean Coughtin of the Soft Issue Center demonstrates the correct and incorrect performance styles. Note how the movement occurs in the shoulder joint. This position is the offending action. Don't let your shoulders roll forward when you're using a pec deck. During the past year at the Soft Tissue Center we've seen six cases of thoracic outlet syndrome that can be attributed to the patients' performing pec deck flys. If this is as common an occurrence as I believe it is, then there are hundreds, if not thousands, of similar cases around the country.
The solution is to avoid rolling your shoulders forward during this exercise-or simply avoid the machine altogether. If you feel shoulder pain when you're using the pec deck, you may have some degree of instability, and the pec deck may not be for you. If you train smart, you'll be able to train hard. There may be physical reasons that you're unable to perform an exercise. It's better to know than to keep making the situation worse.