Most people lack adequate flexibility in the shoulder in one or more of the main shoulder movements but because we rarely have to use all of the motion, we don't miss it. Until we miss it.
Inflexibility in internal rotation is one of those movements. It's an awkward motion that is required for things like throwing or swimming or serving a tennis ball - anything overhead. You should have at least 70-80 degrees of motion (this is measured as in the image with the hand pointing to the ceiling as the starting point of measurement).
Most people have about 45 degrees or just over half of normal motion. This is rarely a problem until you use your arm overhead. Here's why.
The muscles that help control how well your humerus moves, the rotator cuff, anchor on the scapula (shoulder blade) and the humerus. Normal flexibility of internal rotation means that these muscles have normal length. Muscles that have normal length have the best chance at developing tension at the right time during their use (something called the length-tension relationship). As you lift your arm overhead, the rotator cuff muscles must contract at the right time and the right amount to keep the upper part of your humerus from shifting. If the muscles are inflexible, this timing will be off and the humeral head will drift up and squish the tissues that live in the space between the humeral head and the acromion. If you do this enough, you can abrade the rotator cuff and even tear it. A degenerative tear of the rotator cuff usually happens in a person over 60 years of age who decides to, for example, tackle a large painting project at home. She lacks normal motion of internal rotation (and probably has some weakness as well), doesn't know it and begins painting. The sweeping motions of the arm tax the rotator cuff and the combination of inflexibility with weakness allows the cuff to rub on the acromion. After a few days of this, the person realizes her shoulder really hurts and she can't lift her arm. This is when she ends up in her physician's office and usually is diagnosed with a rotator cuff tear.
The best way to know if you lack flexibility is to have a clinician measure it. But, if you can't get in to see someone here's another option.
To check the right shoulder, you'll need a helper and a tool (a carpenter's inclinometer or if you have an iPhone, you can download an inclinometer application).
- Lie on your right side with a pillow under your head.
- Slide your right arm out from under you until the upper arm is at 90 degrees to your body.
- Position your arm so your hand points to the ceiling. This is the starting position. Have your helper place the inclinometer on your forearm and adjust the forearm position until the inclinometer reads "0".
- Your helper should place his or her hand on the front of your shoulder and apply moderate
pressure. This is to keep your shoulder from moving and making it seem as if you have more rotation than you actually do.
- Allow your arm to drop toward the floor. When you have reached the stopping point, have your helper record the angle on the inclinometer. If it is less than 70 degrees, have your helper press down lightly until the movement stops. If by pressing down, your arm moves to ~ 70 degrees, all is well.
If your motion was less than 70 degrees with or without help, you should stretch your shoulder. You can use the same position as the test - sometimes referred to as a "sleeper stretch".
To increase the flexibility, I prefer something called an eccentric or resistance stretch. This stretches the muscle while it contracts. Apply a gentle pressure on your arm and, at the same time, lightly resist it. Now, push your arm downward while maintaining the tension in the muscles. Move until you feel tightness or an inability to move any more and hold it for five seconds. Release the pressure and go again. Do this five times.
This technique will increase motion in your arm quickly but your muscles have to learn to use the flexibility. So, keep doing the drill for one week. Then, stop for a week and re-test. If you're over the age of 30, I would check your shoulder internal rotation at least once every three months especially if you have a desk or more sedentary job.
DK
image source: www.shoulderdoc.uk.co
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