Monday, April 21, 2014

Is The Non-Contact ACL Issue That Complex? - Part I

The following article is part I of a II part series on the complexity of the non-contact ACL injury.  Is the non-contact ACL injury really that complex?  With the abundance of research that has been done and is being done in this area, one would think that we would have figured it out by now.  Yet, we are still looking for “the answer”.  Many feel they have “the answer” yet injury rates continue to climb, athletes continue to return to sport with increased risk and their future joint health and performance continues to be compromised.  So one has to ask, why the complexity?  Isn’t it simply training?  The simple answer to that question is no but it also is not that complex.  Unfortunately training bad movement will simply strengthen bad movement.  No matter the level of the performance trainer, if they do not understand movement or how to assess movement, they cannot and will not improve movement but rather only make compensation strategies stronger.  For example, the US Olympic athlete here demonstrates a significant lateral shift.  In her training, she was squatting with a significant amount of weight with this lateral shift under the supervision of a very high level performance coach.  In this instance, she simply reinforced and strengthened her lateral shift, continued to further develop asymmetrical strength and endurance and set herself up for performance issues and potential injuries.  Is this the fault of the strength coach?  No.  If we don’t assess movement as a part of what we do, how can we quantify it, how would we know how to impact it and how can we determine if our interventions are changing it?  In athletics and especially high performance athletes, it is sometimes very hard to see unless you know how to assess.  If we don’t know how to assess it in the sciences and biomechanics, how can those in other fields be expected to know?  Or do we know how to assess?

In medical and biomechanical sciences, sometimes things tend to be overly complicated with the science and the scientific research and thought process that is done.  We look for a scientific reason and answer for every aspect of movement and correlations with correlation co-efficient of 1.0.  In reality, these correlation co-efficients rarely, if ever exist.  So why the complexity and is there a simple answer?  Yes and no.  Simply, movement is complex and confusing to assess.  When we see movements, like depicted here with this high school dancer, it is hard to determine what is the root cause or the main factor that is driving the movement we see.  Some would look at this particular example and conclude this is a foot problem due to the pronation that is occurring at the foot in this position.  Yet, in a closed kinetic chain, where one link is connected to the next, there is no way the foot could not move into pronation if the hip is adducted to this degree.  Try it.  In a standing position, move your hip in toward midline a little.  Now do it a lot.  What happens to your foot?  You feel your arch collapse and your foot pronates.  Yet, the same is true with the knee.  If the foot moves into pronation, then the knee must also follow along.  Try it.  Move your foot into pronation (collapse your arch) and look what happens to your knee.  Your knee moves into adduction.  So do you address the foot or do you address the hip?
To answer that question we must assess movement.  Based on what we know from the research is there a way to assess athletes in a way that uses the information we do know and which also leads us, through a process of elimination, to why they move the way they do?  Some have attempted to do this with an individualized test.  In these instances they attempt to use one test in isolation to determine if the movements are present.  That part is simple.  The single leg squat above is a clear indication of risk but does it tell us how to address the movement dysfunction?  No.  To get to the root cause, we must have a sequence of tests which lead us, through a process of elimination, to a root cause or causes (which we will speak about in a minute).  But, in the case above, there are some key concepts that can look at with an isolated test like this that starts to lead us to the root cause. 
Two of the key concepts we teach clinicians, coaches and performance trainers is very simple and yet aids in determining the root of such a complex issue. First, the weak link always falls first under loading and is a root cause contributing to the movement pattern.  Second is the link with the largest magnitude of deviation under load is a root cause that is resulting in movement observed.  Case in point.  Take these two athletes performing the exact same movement, a 31 cm step up.  Both of these athletes are demonstrating adduction past midline which would lead one to believe the root cause is at the hip.
However, in #1 (soccer player), her ankle is clearly in a neutral or near neutral position while her hip is in an adducted position.  What was observed on her was as she started load the extremity with this test that her knee fell into this adducted position first and as she progressed, her foot began to pronate.  Conversely, #2 (cheerleader), when she put started to load the lower extremity, what was observed was her foot fell into a pronated position which was then followed by her hip.  Using the concepts mentioned above, the weak link falls first and the link with the largest magnitude of deviation is the weak link, we can clearly see where the deviations are.  In #1 the weak link is the hip and in #2 the weak link is the ankle.  Considering this, the treatment for the same movement dysfunction would be completely different and one can speculate if treated the same, the outcome would not be as good. 
Using this concept one can then begin to determine where the root cause is and how one would address.  Simply determining this as a clinician, coach or strength coach will have an immediate and profound impact on injury rates as well as performance.  Performance, really?  Yes.  Look at the mechanics here.  Tell me how that cannot impact force production, kinetic energy transfer or symmetrical strength development.  Improvement of these would directly translate into improved vertical jump, improved sprint speed and improved explosive power.  In other words, improving these motions has a direct impact on performance. 
In part II of this series, we will talk about how to fully assess movement.  More importantly, how do we simplify so we can impact in a way that reduces injury and further drives performance.

Build Athletes to Perform…Build Athletes to Last!™

About the author: Trent Nessler, PT, DPT, MPT is CEO of A.C.L., LLC and is a practicing physical therapist with 15 years in sports medicine and orthopedics. He has masters in physical therapy and doctorate with focus in biomechanics and motor learning. He is the founder/developer of the Dynamic Movement Assessment™, Fatigue Dynamic Movement Assessment™ and author of a textbook “Dynamic Movement Assessment™: Prevent Injury and Enhance Performance”. Trent is also associate editor of the International Journal of Athletic Therapy and Training and Member of the USA Cheer Safety Council.  For more information, please see our website at

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