Some guy on Twitter asked me why a system couldn’t be built based on PitchFX that would serve as an early warning system for injuries. Now, it can, to a small extent, but not a pure heuristic system like this guy wanted. A = B is not the case. There are things we can see, but they serve as notes and have to be put into context by someone and then hope that the pitching coach and organization agrees. Good luck with that.

The guy kept coming back to “velocity loss always precedes Tommy John.” Well, no. A later discussion with Corey Dawkins, ATC, showed why this is a confusing topic and why Twitter is a bad place for technical discussions.

First, we have to define a couple things:

* “incompetent” - the stage at which a ligament ceases to be able to perform its function properly. It does not mean a complete tear or a loss of function. The level of tearing where a ligament becomes incompetent is also a subject of intense debate among surgeons, though 33% is a reasonable figure.

* “chronic sprain” - pitchers often sprain their ligaments, rest, and heal. The ligament heals itself with scarring, the pitcher returns to play, everyone’s happy. It’s not 100%, but it’s functional. Scar, in general, is not quite as strong, though again, surgeons will debate the percentage. If he does it again, ESPECIALLY in the same place, the process recurs, but tends to not be as functional. There’s a slow descent that is insidious. Function (including velocity) can be lost.

* “insidious” - an injury that happens or gets worse in a slow enough fashion that it’s not noticeable. Ever see one of those videos where someone took a picture of themselves every day? Things change over time, but slowly enough that it’s difficult to notice without sufficient perspective.

Ok, now that we have that, let’s take a look at how this happens. Pitchers with chronic sprains will have a tendency to lose velocity over a period of time. Normally, velocity has more to do with the shoulder, but a player’s unconscious guarding is thought to have a lot to do with this. Once again, chronic elbow sprains can insidiously sap velocity.

Once a pitcher’s ligament is acutely injured to the point where it becomes incompetent, something weird happens. Not always, but often, a pitcher will see an uptick in velocity. It’s often small and unnoticed, but sometimes it’s significant. Some believe it’s a change in mechanics. Some believe its a loss/change of proprioception. The best theory I’ve heard was from a presentation at ASMI’s Injuries in Baseball Course several years back, where there was a gap in the body’s adjustment to the changed kinematics, according to Dr. Lyle Cain. I’m vastly oversimplifying, but it takes the body time to change, but the reaction comes up shy of the pain threshhold that would create guarding.

In traumatic sprains or at the point where the incompetent ligament becomes non-functional, there a massive loss of velocity, down to zero (“I can’t throw, skip!”) in most cases. That’s the stage where the guy is headed to surgery.

I hope that makes more sense. If you were following along on Twitter, it made much less sense and I should know better than try to explain technical issues in 140 character bites.

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