Is There A Secret Sauce? - Part III

Key to Identifying the Weak Link!

Over the course of the last 2 weeks we have been talking about various aspects of movement assessment and how we can positively or negatively impact that.  In our first blog in this series we spoke of the influence that both verbal and non-verbal instruction have on movement.  Knowing this, we can use that knowledge to facilitate more efficient change in order to reduce injury risk and improve performance.  In last week’s post, we talked about the influence of fatigue and how we can use the fatigue and vibration research to facilitate more rapid change in poor movement patterns.  So, although there is not a “secret sauce” this knowledge can give you a significant advantage when it is applied to movement correction.  Is it secret?  Absolutely not!  Unfortunately the research has been out there for more than 10 years but it often requires us to look at it differently in order to apply to the techniques we use in the clinic, performance setting or on the field.  So although it is not done or a standard of practice does not mean it is a secret sauce.

As we go around the country and abroad teaching people about movement, one debate always seems to bubble to the surface when it comes to movement.  The debate is, does the adduction in the frontal plane (or valgus displacement) that is seen coming from the lower lower kinetic chain (foot/ankle) or the upper lower kinetic chain (hip/core)?  In other words, is the pronation and lack of dorsiflexion leading to the adduction in the frontal plane or is it from an issue at the hip/core?  This is a valid question and unfortunately is often driven by one’s training or perspective.  In 2011, Man Fong et al published a study in the Journal of Athletic Training that looked at dorsiflexion range of motion and landing biomechanics.  What they found was that those who had lack of dorsiflexion also had greater knee valgus displacement during landing.  The conclusion is that lack of dorsiflexion must then lead to increased risk of frontal plane motion.  This lead to a big push to assess ankle dorsiflexion in order to determine risk of ACL injury.  However, if we consider that age old debate “Was it the chicken before the egg or the egg before the chicken”, it requires us to consider all the factors.  It you talk to a podiatrist, you may hear that everything is driven from the foot and therefore adduction in the frontal plane can and will be controlled by strengthening and controlling the foot/ankle.  Conversely, if you talk to a physical therapist that sees everything at the hip, then you may hear that everything is driven from the hip and therefore adduction in the frontal plan can and will be controlled by strengthening and controlling the hip/core.  Although both approaches may have beneficial results, is the outcome as good as it could have been IF the root cause was identified?

For example, in the picture here with a DI soccer athlete, the lateral displacement of the pelvis to the right is going to cause an increase in dorsiflexion on the right and decrease in dorsiflexion on the left.  Over time and if this is carried over to all activity that requires squatting (which it does), then this will lead to decreased range of motion of the left ankle.  This will also lead to altered strength and proprioceptive development throughout the entire kinetic chain.  So, in this case, is it the lack of dorsiflexion that leads to the lateral shift and hence adduction in the frontal plane with single limb activities or vice versa?  How can we possibly know?

As difficult and as complex as the problem is, it really comes down to common sense.  The lower kinetic chain is a closed chain and anything that can affect the top of the chain will affect the bottom and vice versa.  Considering this, poor control at the ankle/foot can and will drive adduction in the frontal plane.  Conversely, poor control at the hip/core can and will also drive adduction in the frontal plane.  So how do you know what to address?  Considering the above and basic biomechanics, then the following two statements make sense.

·        In a closed kinetic chain, the weak link will fall first which will then be followed by the rest of the kinetic chain.

·        In a closed kinetic chain, the weak link in the chain will present with the largest magnitude of the deviation.

So, in other words, the weak link falls first and the link with the largest magnitude of deviation is the main driver of the movement that is present. 

In this example, we see a DI soccer player that is performing a 31cm step up.  As she starts to load the lower kinetic chain, what we see is significant adduction in the frontal plane.  If we view her ankle at this point in the motion, what we see is that her ankle is in a relatively neutral position.  Based on the fact that we see her hip falls into an adducted position first and that her hip has a larger magnitude of the deviation, we can then conclude that the “root cause” of the adduction in the frontal plane is the result of weakness or lack of stability at the hip.  If you watched this athlete throughout the entire range of motion, what you would see is that as she continued to load the limb (continued her step up) that her ankle eventually starts to move into a pronated position.  But this only occurred as the result of the increase in magnitude of the adduction that was occurring at the hip.

Using this same motion with the following athlete, we see a completely different presentation.  In this athlete, we see adduction in the frontal plane but we also see a significant amount of pronation at the ankle.  As she began to load the limb in the step up motion, what was noted was that she immediately pronated (arch collapsed)  as she started to attenuate force through the limb and as she continue to progress up through the range of motion of the step up, this pronation increased in magnitude.  What we also saw was a fair amount of adduction in the frontal plane.  So, in this particular case, the weak link (ankle) gave first and had the larger magnitude of the deviation.  Considering this, it is the lack of ankle stability and severity of the weakness that results in an increase in adduction in the frontal plane. 

In both of these cases, applying some common sense and basic biomechanics aids us in getting a clearer picture of the root cause versus basing our interpretation on a preconceived philosophy.  In both cases, had they been treated the same, both would have had positive results.  But, does positive results equate to optimal outcome?  Far too often the two are considered synonymous when they in fact are not.  If you identifying the weak link in the chain this will result in optimal outcome, longer and sustainable results and a greater impact on current and future athletic performance.

We hope that you found this blog insightful and useful.  Next week we will discuss the importance of multiple single limb tests for determining symmetry.  As we stated previously, stay tuned and if you like what you see, SHARE THE PASSION!  It is the biggest compliment you can give.  Follow us on Twitter @ACL_prevention and tweet about it.  #ACLPlayItSafe and help us spread the passion.

Dr. Nessler is a practicing physical therapist with over 20 years sports medicine clinical experience and a nationally recognized expert in the area of athletic movement assessment.  He is the developer of an athletic biomechanical analysis, is an author of a college textbook on this subject  and has performed >5000 athletic movement assessments.  He serves as the National Director of Sports Medicine Innovation for Select Medical, is Chairman of Medical Services for the International Obstacle Racing Federation and associate editor of the International Journal of Athletic Therapy and Training.