Throwing Performance and Shoulder Health Series Part IV: The Shoulder
Our series on shoulder health finally reaches the shoulder. We’ve talked about how important other areas of the body are to set the shoulder up for success, but without question the shoulder itself, in particular the rotator cuff must be trained as well. Researchers say angular velocities reach over 7000 degrees per second with other forces reaching ½ your body weight on the glenohumeral joint while throwing. For context, that’s 2-3 times as fast as your common ceiling fan on its highest setting or as fast as your washing machine during the spine cycle. Needless to say, the shoulder has to handle a lot of force while throwing and this is why it’s so important to train it properly.
Shoulder Mobility – A Predictor of Shoulder Injury?
Researchers have dissected the throwing motion countless ways to determine how the shoulder works in various parts of the motion and what factors may contribute to shoulder injury in throwing athletes. One aspect they have found is the ratio of internal rotation vs external rotation. As a result of the forces encountered in the motion, throwing athletes often show a loss of internal rotation range of motion over time. Some of this can be due to changes in the bones over time, and some may be attributed to soft tissue (muscles, tendons, joint capsule) changes. One scientific study showed pitchers with a loss of internal rotation range of motion were 2.5 times more likely to suffer a shoulder injury over a 3 year period. This phenomenon continues to be explored, but the big take home point in the meantime is shoulder mobility is important. The mobility exercise below is a great basic exercise to gain and maintain shoulder internal rotation range of motion.
The Rotator Cuff: The Safety Handle of the Shoulder
Last month we dove into the basics of anatomy around the scapula or shoulder blade. This month the focus is on the glenohumeral joint. This is where the head of the humerus (arm bone) meets the shoulder blade, making up what we commonly think of as the shoulder joint. The rotator cuff is a group of muscles that attach to both the humerus and the scapula. You can think of them as almost cradling the head of the humerus and when these muscles contract they compress the head of the humerus into the glenoid (shoulder socket). This is the primary purpose of the rotator cuff – to keep the humerus in the socket and prevent dislocation with movement. If you’ve ever driven with a very aggressive driver, you may have felt the need to grab onto the handle above you to prevent you from sliding around as he or she whips the car around on the road. Holding on to this handle keeps us in one place despite all the other forces pulling us in different directions. This is what the rotator cuff does for the shoulder and it’s especially important in high velocity movements like throwing. We talked above about the forces involved in throwing and it’s the rotator cuff’s job to maintain integrity of the shoulder joint throughout the motion. So, baseline strength is important to handle these forces, but the muscles’ ability to contract quickly to these forces may be the most important part.
What Does Shoulder Stability Really Mean?
When think about sports performance we think about strength and power in muscles, but we don’t talk about the nervous system’s role as much. Via a complex and amazing communication network, our brain must talk with muscles to determine where we (or our limbs) are in space and adjust muscle activity accordingly based on the task at hand. Have you ever tried to ride the train at the Denver airport without holding onto anything? This is a game I’ll play often and it’s a perfect example of the communication that must happen within our body to maintain balance. When the train stops or starts, forces are placed on our body. Our nervous system determines the amount and direction of those forces and tells the muscles to contract in a manner that counters this force to maintain balance. All this happens in fractions of second to keep us from falling over. This ability to maintain position and know where we are in space can go by different names such as proprioception, dynamic stability, neuromuscular control, or motor control, but it serves as a key aspect of shoulder health. If the rotator cuff’s primary job is to hold the shoulder joint together, it would make sense the faster it’s able to respond to outside forces, the more stable the joint will be. Long story short, it’s not all about strength in the shoulder. We also have to train these muscles to respond quickly to keep the humerus centered in the glenoid for optimal function.
The End of the Line – The Elbow
I know this series is on shoulder health, but the elbow is another area often injured in the throwing athlete. The reason for this is in line with the concepts we’ve talked about for the shoulder. Remember all of the regions of the body that comprise the throwing motion and how inefficiencies in one area can spell trouble for areas further down the chain? Well, the elbow is one of the last stops as the forces travel from the hips to the ball, so, much like the shoulder, it’s very reliant on what’s happened in the body before the forces even reach the elbow. For example, when we talked about the trunk, we talked about early and/or excessive trunk rotation or opening can lead to much larger forces and poor positioning of the elbow (see example left). This will place more stress on the MCL ligaments at the elbow – the ligaments often implicated in Tommy John surgery. So, being diligent and training other areas of the body and working with you coaches to develop good mechanics will not only lower your risk of shoulder injury, but help mitigate stresses felt at the elbow as well.
Hopefully over the course of this series, you’ve seen how shoulder health comprises much more than just the shoulder. We’ve talked about the hips, the trunk, the shoulder blade, and now the shoulder. All these pieces must work together to generate force and transfer that force to the ball while throwing. Inefficiencies in one area, can lead to greater stress/work in another, and all of these areas need mobility, strength, stability, and power to enable maximum throwing velocity while decreasing the risk of injury. If you include these concepts into your training program, you will be taking a solid step towards bettering your throwing performance. Good luck next season!
Dr. Eric Leeseberg is a physical therapist at Colorado In Motion and can be reached at Eric@ColoradoInMotion.com