Exercise Analysis - External Shoulder Rotation

During my tenure as a trainer at the local health club, I learned an interesting lesson. Before doing new-member orientations, I typically asked the newcomer what their exercise-related objectives were. In most cases, the answer was the same. Surprisingly, health and fitness were rarely mentioned and appearance-related goals took front and center.

Fortunately, even if you pay no heed to the benefits that resistance training brings, you will enjoy their positive effects because a program designed to make you look good will also bring many of the adaptations that make you feel good. However, there are exceptions. One is the development of a muscle group that is inconspicuous, but far from innocuous.

Most sports fans are familiar with the term rotator cuff because some of their favorite athletes have been derailed by injury to this susceptible area. But the average exercise enthusiast thinks little about working this underlying musculature, simply because it doesn’t show. But what the rotator cuff lacks in terms of flamboyance is made up by its critical role as a stabilizer of the shoulder. So, even though working it won’t make you look better, neglecting it can surely affect your ability to perform exercises that do!

There are four muscles that comprise the rotator cuff. All are attached to the shoulder blade at one end and the upper arm at the other, but they take distinctly different paths when spanning the shoulder to form this attachment. Two are external rotators that travel behind the shoulder and are particularly important because typical upper body strength training maneuvers don’t lend to their development. However, chest, shoulder and even upper back exercises do involve the opposing muscles that internally rotate the arm. Activities of daily living are also more apt to strengthen those muscles, so it’s common for a relative imbalance to be present. The end result is poor posture, increased risk of injury and a distortion of the appearance to which many hours are devoted to create.

To maintain shoulder integrity and prevent postural misalignment, attention must be paid to the external rotators of the arm; specifically, the teres minor and infraspinatus. These muscles turn the arm away from the body, so the basic way to exercise them is to perform this movement against resistance offered by a dumbbell. But it’s important to understand leverage and loading patterns to ensure your efforts are not wasted. Assuming an upright posture, holding a dumbbell in your hand and externally rotating your arm won’t do the trick, regardless of whether your elbow is straight or bent. Gravity is not pulling your arm into internal rotation in this case, so the muscle will not be shortening against the load you’re applying. Lying on a bench on your side so that your body is perpendicular to the floor and performing the same movement (preferably with the elbow bent at 90 degrees) will solve this problem.

Resistance training machines are equipped with cams that strategically vary opposition as movement occurs in order to match fluctuations in the target muscle’s capacity to create movement. You can do the same with free weights because the rotational force (torque) you work against is a function of both the weight you are using (which remains constant) and the length of the moment arm through which that force is applied. This varies as movement occurs, so if you understand where your muscle is more capable, you can manipulate the opposition to provide a consistently challenging degree of resistance. For example, if you perform dumbbell external rotation of the arm as described above, opposition will be greatest when your forearm is parallel to the floor and least as you reach end-range (your arm is fully rotated and your fist is pointing up toward the ceiling). Conversely, lying face down and beginning the movement with your fist facing the floor so that you end up with your forearm parallel to the floor will reverse that loading pattern, thereby allowing for maximal opposition at end range. Positioning your body at any angle between these two will spread the opposition over the intermediate portions of the range.

The posterior head of the deltoids is also an external rotator, so externally rotating the arm upon completion of dumbbell or cable movements designed to target this muscle (bent-over lateral raises, for example) is a good way to work the aforementioned external rotators while maximizing range of motion for the contracting rear delt. Isolated external rotation can also be done against the opposition offered by the weight stack of a cable machine. In this case, the pull of gravity is re-routed by the cable/pulley configuration, so you can effectively perform the movement standing, as long as the pulley is adjustable and you can position it at waist level. Regardless of your form of loading, however, it’s essential to limit motion to the shoulder joint exclusively when isolating your external rotators. To ensure this is the case, keep your upper arm directly down at your side throughout while holding the angle at your elbow constant. Other than your arm rotating back and forth, no other bodily movement should occur.

This article was originally published in New Living Magazine, which can be accessed on-line at www.newliving.com.





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