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Are asymmetries in the FMS acceptable in one-sided dominant sports?

baseball fms soccer softball volleyball

"I have a question about 3/2 asymmetries on the FMS.  I understand that 3/1s and 2/1s are never accepted or acceptable. 3/2s are acceptable on shoulder mobility and pitchers because of the adaptations in the shoulder from throwing." I assume it refers to the humeral torsion that occurs, a bony adaptation there.  "Are 3/2 symmetries ever accepted or expected in one-sided dominant sports on other patterns such as rotary stability or any unilateral pattern? And a few athletes that come to mind could be possible as one-footed dominant soccer players, football kickers, and baseball players."

All right, so let's go with this great question and one of a couple key things, you've got to remember FMS scoring. Remember, zero means I have pain with it.  That's never acceptable to have pain.  We know pain actually probably means you already have an injury, but it's certainly a robust injury risk prediction factor. One means I can't even do a movement with compensation or some alternative strategies, and 2 means I can do it with compensation or alternative strategies, and 3 means I can do it perfectly. Again, I'm going to just blow the misconception out that we're always seeking 3 in all patterns.  That's not the case.  There are some sports-specific patterns that we like to look at that we want to see a 3 on. 

So when we're saying asymmetry well, what matters with asymmetry is maybe not even the asymmetry as much as don't have a 0 or 1 first off, okay?  That's a very important fact.  Now let's look at 2/3 asymmetries.  Well, in pitchers in particular, this is really the evidence of testing hundreds and hundreds of pitchers over time.  We know that they have that shifted total arc, that shifted humeral torsion there that occurs, and that arc shift is normal and desirable.  What that causes in practice is a 3/2 asymmetry, and that's totally okay.  As a matter of fact, an elite level baseball player who has a 3/3 shoulder mobility and a bad Y balance test, I don't have research on this, I've just seen it time and time again.  3/3 shoulder mobility, bad Y balance test lower quarter, man that's a pitcher that's about to explode.  That means they have tons of mobility and not a lot of motor control.

Alright, this wasn't about just baseball players.  This is really about other sports, foot-dominant soccer players, football kickers, that type of thing.  And track athletes, I think, are a great one that are commonly cited for asymmetries. So let's look at the research.  This is one of my favorite studies on this. USA track and field is done by Dr. Chapman and Todd Arnold, their group there in Indianapolis. If asymmetry is present on the FMS, less improvement in race time over the course of a year.  So if you didn't have an asymmetry, you got faster over a year period.  If no 1s on the FMS, better improvement in speed over the year.  So what does that look like? 

Well, if you had a 14 or less, again, that's not the best way to analyze the FMS. We know that.  But this is 2014.  Done back in 2011, that was our best knowledge at that point in time. 41 with 14 or less 80 had a 15 or 21.  You look at the percent change in performance and those who were higher scoring, which again means fewer zeros and 1s, is how we want to think about that, they had a greater improvement in speed and these are in elite track and field and in elite track and field hundredths of a second obviously matter a big deal. Well, we see the same thing with asymmetries. Those with asymmetries did not see that increase in speed again.  So when we're looking at performance, we want to see, all right, do they have asymmetries or not?

Now let's look back to maybe a similar case as a pitcher with a 3/2 shoulder asymmetry. In track, when you're running around that oval, you've got the curves and you've got a consistently running one direction. Well, there can be some asymmetry that develops there in some of their performance patterns because of running around the track in the same direction over and over again. In that case, if I saw a 3/2 asymmetry in a well-performing athlete, I probably would keep it.  I wouldn't do much for it. Now, if I saw a 1 in any pattern, that means the person a 1.  You have to think about it. 

Let's think about it in a different perspective, not even from a symmetry perspective.  A 1 means the person doesn't have the movement variability to be able to perform a wide range of movement and therefore is going to stress tissue in a repetitive way.  And then secondly is going to have underperformance because they're not able to use all their tissue, all their movement in the way, all their muscles in the way they need to.  So that's basically it. In general, we were okay.  In some rotational sports, a 2/3 asymmetry though even in sports like golf and baseball, hitting the rotary stability, that rotary stability should be 3/3.  The active straight leg raise in  those players should be 3/3.  Really, pitchers and potentially active straight leg raise in short distance runners, I might consider a 2/3 asymmetry to be okay. But other than that, everything else should be symmetrical.  All the unilateral patterns should be symmetrical.  And that bears it out. Well, one of the things I think that if we kind of take it to the next level, you mentioned foot dominance in soccer players.

There's a good amount of research in the Y  balance test lower quarter that says that in non-athletes, in soccer players, in a bunch of different populations, that symmetry is -- right-left symmetry is exactly the same, and limb dominance doesn't affect it.  Basically what we want to think about when we're thinking about symmetry -- symmetry on the lunge, symmetry on the Y balance test, symmetry on rotary stability – in soccer, the vast majority of what you're doing is symmetrical running. Very little time is actually spent in that asymmetrical position.

So having that symmetry allows us the movement variability in both sides to be able to, again, disperse the stress across all our tissue.  Also to be able to develop power in all planes of our tissue.  So that's kind of a key thing there.  Again, multiple studies look at that that say limb dominance does not affect Y balance test lower quarter scores.  So, to me, when I look at the Y balance test, I'm looking at, okay, this is my three dimensional performance. 

Remember, FMS is looking at pigeon-holed movement. The Y Balance Test is looking at the other end of the spectrum where I can do numerous patterns to get there. Both ends of movement variability, the limited movement and then the unrestrained movement, both of them really are not affected by limb dominance or asymmetrical sports.  And again, remember, almost all our training is going to, whether it's cardio or cross training, is going to occur in a symmetrical pattern as well. The bottom line I like to say this is from Todd Arnold.  Todd Arnold is the performance physician for USA Track and Field.  He's been with them for three Olympics now.  We've won more gold medals in track and field than I think we've ever won, but his quote is,

"I've never seen a 0 or 1 to be a competitive advantage in elite track and field or any other sport for that matter." 

He's worked with pro baseball, pro basketball, lots of different sports, and the research bears that out as well. So I think this is a great bottom line that we need to consider in this topic.



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