The Mechanics Of An Arm Injury – What To Expect From Stephen Strasburg

Stephen Strasburg’s injury Tuesday does not seem severe but as Washington Post writer Adam Kilgore puts it:

“The potential first step of their nightmare scenario unfolded Tuesday night when the Washington Nationals scratched Stephen Strasburg from his start against the Atlanta Braves after “having trouble getting loose in the bullpen,” General Manager Mike Rizzo said.”

Stephen Strasburg’s mechanics are indeed troubling to a few experts including Chris O’Leary of chrisoleary.com. He writes: “Like Mark Prior, Stephen Strasburg has some Inverted W in his arm action and a timing problem as a result (aka habitual rushing). This will significantly increase the load on his elbow and his shoulder and make him a very high risk draft choice. I could even see him pulling a Cole St. Clair and blowing up mid-season.”

In the same article O’Leary mentions two of Strasburg’s other bad habits, improper scapular loading and what O’Leary terms “hyperabduction,” covering nearly all of what O’Leary describes as high-risk mechanics on his website. In addition to some kinesiological evidence supporting the claim that these habits are dangerous, there is also observational evidence from O’Leary that these techniques are not practiced by successful pitchers (pitchers who pitch for a long time and are relatively injury free) and that they are practiced by frequently injured pitchers.


Hyperabduction occurs when a pitcher raises his pitching arm side (PAS) elbow above the level of their shoulders (the level of your shoulders it the imaginary plane that passes through your shoulders parallel to the ground when you are standing straight up on a flat surface) when their arm is in the “high cocked position”. It seems to lead to rotator cuff and labrum injuries. Hyperabduction can be seen quite clearly in the above photo of Craig Stammen.


Hyperabduction also seems to go hand in hand with the inverted W, both of which seem to seen being practiced by Jordan Zimmermann in the above photo. It should be noted

that his PAS elbow is above his shoulder level which is a sign of hyperabduction, though it is not as severe as the hyperabduction of some other pitchers. Zimmermann’s inverted W is quite obvious, however, and while “the Inverted W is [not] (that) bad in and of itself” it can lead to timing problems which can lead to injuries of the elbow and shoulder such as the UCL injury Zimmermann had last season.

In the above photo you can see the recently injured Tyler Walker about to plant his glove side (GS) foot while his PAS arm is nowhere close to being vertical indicating rushing. Rushing occurs when the lower body pulls the shoulders into rotation before the PAS forearm is vertical. O’Leary writes “I have a theory that this…problem is related to Bicep [sic] and Labrum [sic] problems in professional pitchers. The logic is that this could cause the pitching-side upper arm to externally rotate especially hard. This could put an increased load on the shoulder and the Biceps [sic] muscle (which inserts into the shoulder).” Walker–who also shows some tendency to use an inverted W and whose timing problems can also be seen with the help of a few expertly timed clicks in this video -was recently put on the DL for a torn labrum.



Other Nationals pitchers who appear to have timing and other mechanical problems include Matt Capps, Scott Olsen, and Tyler Clippard, who can be seen practicing improper scapular loading in the above picture. In the above photo Clippard pulls his elbows well behind the acromial plane (which is known as scapular loading and is fine) while raising his shoulders dangerously high (which is not fine), perhaps even to the point of having an inverted W. The combination of pulling the elbows behind the acromial plane (The acromial plane is an imaginary plane that passes through the shoulders and would be parallel to your bed if you were lying down.) and raising the elbows above shoulder level can be harmful to the shoulders.

strasburg2The most severe problems of any Nationals pitcher belong to Stephen Strasburg. Because of the extreme velocity with which he throws his pitches, the strain caused by mechanical flaws in Strasburg’s delivery will likely be amplified to a degree not seen in most other pitchers. In the photograph below we can see most of Strasburg’s flaws on display: his inverted W, his improper scapular loading, his hyperabduction, and indications of his timing issues.

There is, however, still hope for Strasburg. O’Leary writes that Strasburg shows significant variability in his mechanics, sometimes practicing safer mechanics: “there is a chance that Stephen Strasburg could have a career more like a John Smoltz…effective for periods of time but…also [struggling] with elbow and shoulder problems.” It is also worth noting that the theories mentioned in this article are simply theories, and though they seem reasonable, I haven’t seen a large study done on them yet.

While last night’s injury may not be serious, there is  at least some reason to believe that Strasburg will have more serious shoulder and/or elbow problems at some point in the near future. Whether he will get hurt again or not is up for debate, but we’ve got to make sure to enjoy him while we can.

Note: Chris O’Leary did not directly contribute to this article. The terminology (PAS, GS, etc.) and theory (scapular abduction, inverted W, etc.) in this article comes from chrisoleary.com. Any errors in the application and in my interpretation of O’Leary’s theories are my own.