Range-of-Motion: A Pitcher's Best Friend...or Not
As a pitcher, how do you know if you’re on the right path, or the wrong path? If you think about it, this goes much deeper than how well you perform, or how hard you throw. If you’re a talented thrower, most of that is going to be there regardless. The key is whether or not you’re setting yourself up to utilize your talents over a large window of time, and this all centers around how well your arm and body are actually handling the extreme forces associated with throwing a baseball. The better your body handles that stress, the less wear and tear it will undergo.
"It's not the mountain that wears you down..it's the tiny pebble in your shoe"
So how do you know how well this is happening? Well, this is where it gets tricky, because overuse injuries in baseball such as ligament tears, frayed labrums, and many others, don’t occur in just one instance. Rather, they are the result of repeated abuse over time. Think of it like water dripping on a rock. At first, the water will simply hit the rock and bounce off, however, over time, that same drop will start to structurally change the rock and create a divot. So which drop was it that created wear on the rock? The answer is all of them. Even though the first drops may have been far from creating the divot, they were just as influential as the last. This is why general markers such as overall feeling, although valuable in many ways, don’t necessarily tell the full story of how well the body is handling each and every throw. Everybody feels good until they are hurt, and by the time you actually sense something is wrong, it’s probably been going on for a really long time.
So how do you determine that something is wrong before you actually feel it? Well, think about every other machine in existence, and most of them have some type of check-engine or indicator light that signals a problem long before it starts to malfunction. Wouldn't it be nice if the human body had a similar type of mechanism? Even better, what if there was an "indicator light" pertaining specifically to the throwing arm of a baseball player?
Luckily for pitchers and throwers everywhere, this has been a focal point within the medical and research communities for the last couple of decades. Researchers have worked diligently to shed light on this topic by identifying mechanical markers that arise within overhead athletes, and then correlating those markers with injury. Thus far, a players’ shoulder range-of-motion (ROM) patterns have served as the gold standard in this process, and are highly regarded as one of the best ways to quantify how well an individual is handling the demands of throwing. Time and time again, this correlation has been shown in both prospective (i.e. prior to an injury) and retrospective (i.e. looking back after an injury has occurred) research studies, within varying age groups, and across multiple overhead sports.
"Think of these ROM Risk Factors as your check-engine light; long before a car endures damage or becomes dysfunctional, there is always an indicator light letting you know that something is wrong"
To provide you with a more specific understanding of what these patterns are, in addition to an overall greater sense of awareness surrounding injury, listed below are the primary ROM Risk Factors (outlined within the research) with a brief description of each.
DOMINANT TOTAL ARC MOTION DEFICIT (DTAMD)
Total Arc Motion (TAM) is essentially the total degrees of motion present within each shoulder, and is the summation of both Internal Rotation (i.e. arm laying forward) and External Rotation (i.e. arm laying back). If the TAM in the Dominant Arm is limited by more than 5º relative to the Non-Dominant Arm, then a player is considered to have DTAMD (1).
For example, if the TAM within your throwing arm is 167º, and the TAM in your non-throwing arm is 173º (i.e. 6º deficit), your chance of injury significantly increases because that's greater than a 5º deficit. However, if this deficit was 5º or less, you could eliminate this risk factor.
GLENOHUMERAL INTERNAL ROTATION DEFICIT (GIRD) + DOMINANT TOTAL ARC MOTION DEFICIT (DTAMD)
GIRD occurs when the Internal Rotation (i.e. arm laying forward) within the Dominant Arm becomes limited by 20º or more in relation to the Non-Dominant Arm. When GIRD is present in combination with DTAMD, a player is considered to be at a greater risk of injury (1).
In more simple terms, imagine a comparison between your left and right arms relative to the picture below. If your non-throwing arm is able to lay down towards the table by at least 20º more so than your throwing arm, you would be considered to have GIRD. Combine this with the DTAMD risk factor listed above, and your likelihood of sustaining an injury would be increased. On the contrary, if the internal rotation difference between your throwing arm and non-throwing arm is less than 20º, you could eliminate this risk factor.
GLENOHUMERAL EXTERNAL ROTATION DEFICIT (GERD)
GERD occurs when the External Rotation (i.e. layback) within the Dominant Arm is less than 5º greater than the External Rotation present in the Non-Dominant Arm. In other words, the throwing arm should have at least 5º more layback than the non-throwing arm. However, it should be noted that GERD largely assumes that osseous (bone) changes like Retroversion have taken place. Therefore, this risk factor may not be relevant to youth throwers with a low number of accumulated throws (2).
For example, if the layback in your throwing arm is 110º compared to 107º in your non-throwing arm (3º difference), your chance of injury increases because that's less than 5º. On the contrary, if your throwing arm has 110º of layback compared to 104º in your non-throwing arm (6º difference), you could eliminate this risk factor because your throwing arm has at least five more degrees of external rotation than the non-throwing arm.
DOMINANT SHOULDER FLEXION DEFICIT (DSFD)
DSFD occurs when the Dominant Arm becomes limited in Shoulder Flexion (i.e. arm overhead towards the table) by 5º or more relative to the Non-Dominant Arm. If a player exhibits this trait for any number of reasons, they are considered to be at a greater risk for injury (3).
For example, if you have 83º of shoulder flexion in your throwing arm, compared to 90º of flexion in your non-throwing arm (i.e. 7º deficit), your chance of injury increases as your throwing arm is limited by 5º or more. On the contrary, if your throwing shoulder exhibits 87º of flexion, compared to 90º of flexion in your non-throwing shoulder (i.e. 3º deficit), you could eliminate this risk factor.
In summary, the goal of this article was to provide you with a greater sense of awareness surrounding throwing-related injuries that occur in baseball players and overhead athletes alike. Too many people are misinformed on the matter, and are under the impression that throwing injuries are simply the result of bad luck. Fortunately, this couldn't be further from the truth, as most injuries in baseball occur from repeated abuse over a long period of time, with each throw taking its individual toll. Some individuals handle this abuse better than others; and although genetics and various other circumstances play a role, there are numerous preventative measures that can be taken to reduce your chance of injury. Understanding how well your shoulder is functioning and handling the stress from throwing is one of those measures. Once you know where you stand, we have solutions designed to help you maintain and improve.
Wilk, K. E., & Macrina, L. C. (2010). Correlation of Glenohumeral Internal Rotation Deficit and Total Rotational Motion to Shoulder Injuries in Professional Baseball Pitchers. The American Journal of Sports Medicine, 329-335.
Manske, R., & Wilk, K. E. (2013). Glenohumeral Motion Deficits: Friend or Foe? The International Journal of Sports Physical Therapy, 537-553.
Wilk, K. E., & Fleisig, G. S. (2014). Deficits in Glenohumeral Passive Range of Motion Increase Risk of Elbow Injury in Professional Baseball Pitchers. The American Journal of Sports Medicine, 1-7.