As the ball flew from the hand of the young, agile baseball pitcher, he felt something odd in his right arm. It went numb; then it tingled. And, for a brief moment, his arm felt lifeless. It felt dead.
It had happened before. Normally, Jimmy could stall. He would walk around, call the catcher out to the mound and gently shake his arm. The feeling would come back and although his shoulder hurt, he usually could make it through the inning. Today, though, he knew he would not make it. His arm hung lifeless by his side. He was done.
Jimmy had "Dead Arm Syndrome".
Dead Arm Syndrome (DAS) is a pain induced paresis. The word paresis means "a partial or slight paralysis". DAS is a condition in which a pitcher throws so hard that he paralyzes his arm from pain. But, pain from what?
Have you ever noticed the extreme flexibility of a baseball pitcher's shoulder? At the start of the delivery phase of the pitch, the hand is well behind the head. Normal rotation of the shoulder in this direction is about 90 degrees or the hand pointing up to the sky (the position you use when being sworn in - like the President). It is not uncommon for a pitcher to possess 120 to 140 degrees of rotation. This exceptional mobility is one of the attributes of great pitchers. It's a gift. A gift that sometimes comes with a curse.
The shoulder complex is very mobile by design. With four joints moving in three planes, you can place your hand in space through a very wide range of motion. Pitchers improve on the design partly from years of training (including stretching) and partly from their particular genetic profile. But, while this flexibility improves performance, it also increases the risk of a certain type of injury that typically occurs only in very flexible shoulders: a Bankart Lesion.
A Bankart Lesion is a tear of the cartilage (called the glenoid labrum) that forms the shoulder socket. In most cases of DAS, the pitcher has a Bankart Lesion. The pain comes from tearing the cartilage (although it has a meager blood supply, the upper margin does have small blood vessels and nerves), over stretching the attaching tendon (biceps), joint capsule and, in some cases, a mild stretch injury to the axillary nerve. When the tear is large enough, surgery is required to repair it.
One of the secrets to reducing your risk of a Bankart Lesion or for other problems associated with pitching is in the balance between the two rotation motions of the shoulder.
I have to get technical for a few moments. No way around it. But, if you have had DAS or know someone who does, this information is critical. So, take your time as you read this.
The rotation motions of the shoulder are referred to as internal and external rotation. To best understand these two motions, try this:
- Lie down on the floor on your back. Slide your right arm away from your body until it forms a 90 degree angle with your trunk.
- In this position, bend your elbow until it forms a 90 degree angle with the hand pointing up. You are now in what we call "neutral".
- From neutral, drop your hand back towards the ground. This motion is external rotation. When your hand hits the floor, you have moved through 90 degrees of motion.
- From neutral, drop your hand towards the ground. At some point in the motion, your shoulder will come up off the ground. This is the end of your internal rotation (see figure for example).
Normal motion of internal rotation, from the neutral position, is 70-80 degrees. This gives your shoulder about 160 degrees of rotation movement (90 of external plus 70 of internal rotation).
Baseball pitchers with DAS, in nearly every case, have less then 45 degrees of shoulder internal rotation but still have a combined motion of at least 160 degrees. They just have way too much motion in one direction and not enough in another.
The speed of a fastball for most college level baseball pitchers is 35 meters / second. The force exerted on the back of the shoulder to slow the arm moving through a normal amount of internal rotation (at this point, the ball has left the hand) is approximately 90 lbs. But, when a pitcher has 45 degrees of internal rotation, the time to slow the arm is reduced by nearly 50%. So, he has to generate a lot of force in much less time (this principle of force applied over a period of time is why airbags work so well). As a result, the force to slow the arm climbs to 162 lbs. Any wonder why injuries might occur?
If you or someone you know has DAS, be forewarned. This is, in nearly every case, secondary to tears to the glenoid labrum. Have your motion checked by a physical therapist or athletic trainer who works with sports related injuries. If you ignore it, you will very likely end up in surgery, a year of rehabilitation and may never throw a smoking fastball again.
Make today count.
Doug Kelsey
Author. Speaker. Therapist.
P.S. If you are a PT or ATC and would like to learn more about how we use the Sports Center Training System to rebuild athletes with shoulder tendonitis, tendonosis, and rotator cuff tears, join us for our next professional education seminar on August 4th-5th at Sports Center. Only 12 clinicians get access to this seminar this year and there are only a few spots left. Take advantage of the early registration period ending June 29th and save. As always, graduates get 20% off any seminar. Call Angie Francis at 512-206-0433 or email her at afrancis@sportscenteraustin.com to register today.
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