The Asymmetry Debate – Advantages and Disadvantages

We have an awesome podcast this week in Chris Bishop. Chris is one of the world's most profound lower body sports scientists.

He publishes on all aspects of training but specializes in force plate testing and functional and non-functional asymmetries.  

Functional asymmetries refer to asymmetries that are important for performance. Conversely, non-functional asymmetries reduce performance and can be potentially injury-causing.  

DEEPER FUNCTIONAL and NON-FUNCTIONAL ASYMMETRIES 

In all my readings, one thing that has been clear to me is if the throwing arm does not have more external rotation than your non-throwing arm, or if you have a weaker throwing arm than your non-throwing arm, it can increases injury risks and reduce velocity.  

It should make sense. I use the catapult analogy.  

Imagine you could only pull a catapult back 10 degrees, with a hinge held together by a very small spring?  

Would the boulder be hurled through the air at a longer distance?  

Probably not.  

In contrast, you now pull the catapult back 20 degrees further, and the spring is 20% thicker and stronger. What would the effect be now?  

You are intuitively correct. The boulder would exit faster and travel further. These physics principles apply to the competitive baseball player or any throwing athlete.  

Lori Michener, a researcher at the University of Southern California, looks at upper extremity asymmetries in both strength and range of motion.  

I was an invited co-author on a research article looking at shoulder strength, and we found that pitchers were weaker than position players overall for both arms, which is frightening given that pitchers at the time did arm care training every day and position players did nothing at all for throwing-arm specific training.  

It should speak volumes to you that strength must be specific and address asymmetries between arms and between muscles.   

THE MAJORITY OF PITCHER'S THROWING ARMS ARE WEAKER THAN THEIR NON-THROWING ARMS 

In my professional experience, I have seen that over 50% of professional pitchers have weaker throwing arms than non-throwing arms, and I believe that could be a result of central nervous system fatigue during the season that may change in the offseason.  

Those who are using our product could quite simply answer this research question. Fatigue plays into asymmetries, and that is important.  

You could have a strong throwing arm versus the non-throwing arm, and if strength plummets during the season, now the throwing arm is weaker than the non-throwing arm, which is now fatigue-based asymmetry, and one that is on 6000 athletes are discovering with our product.  

Intuitively, you do not want your athletes throwing arms to become weak during the season, and asymmetries should be tested.  

If not, welcome to the insidious world of fatigue-induced compensation.

Fatigue causes weaknesses which in turn changes the throwing motion and results in altered tissue stress that can move from microdamage to a full-blown rupture.

On the topic of functional asymmetry, science tells us that external rotation increases during the season and that internal rotation of the shoulder is less on the throwing side relative to the non-throwing side.

RESTORING SYMMETRY

SOME CLOSING POINTS

I didn't want to dive deep into lower body asymmetries, but if you listen to Chris, you will see how much asymmetries can shift with fatigue and the importance of restoring them as it affects ground reaction force and the energy transfer between the ground, the body, and the baseball.

Since pitchers are generally unilateral in their delivery, drive leg and stride leg strength can change.  In my experience, I have tested single leg performance in pitchers and have seen stronger stride legs which makes sense because the stride leg must brace forward momentum and gravity.

We are not there yet, but we will be working on a way to evaluate lower body strength in the future.  

If you are interested in learning more about what you can currently do now with our dynamometer and platform to assess the lower extremities, please reach out to me directly, as the information is on a needs-to-know basis for now.

Keep training, keep assessing, stop guessing, and lessen asymmetries that are non-functional (increased length, reduced strength).  If you don't use our product, may the force be with you -but only at an optimized level.

Have a great weekend, and keep making gains pain-free!