Should We Re-Think How We Look At Movement

Throughout the course of the last several series of blogs, we have discussed a lot of the research around biomechanical risk factors, fatigue and how this should weight in our decisions when considering how to assess and treat movement.  On 9/12/16, we posted a somewhat controversial blog looking at the latest research on the Functional Movement Screen or FMS.  Although the FMS is an excellent tool for screening movement asymmetry and movement overall, what the research indicates is that it might not be that great at identifying movements that put athletes at risk.

So, considering what we have talked about and literature that we have reviewed over the course of the last several months, what should we consider when looking at risk factors for non-contact ACL injuries?  This is the question that everyone is striving to figure out.  As we all know, the non-contact ACL injury is a very complex problem and according to the literature, involves a plethora of factors that should be considered.  All too often, we think of movement as the only risk factor.  However, according to the literature, this is only part of the picture.  As a clinician, this is one of the most frustrating things about research.  So many great researchers are producing ground breaking evidence but yet they all appear to work in their own separate silos.  It appears that none of them bring together the body of literature to provide a more comprehensive approach.  To truly have a comprehensive look at risk, should we not include known demographic risk factors as well as movement risk factors.  Clinically we take the athlete's or clients history and our clinical exam to determine the root cause and from that we develop an intervention.  In research the clinical decision making process is all done in isolation and the findings are not leveraged to drive the intervention.  Understanding there are a lot of variables you need to control in research but end of the day, does this drive a comprehensive approach? 

 

Part of the restriction including all the "known" risk factors is that there is not a way to do this efficiently.  End of the day, in order to have a dramatic impact on non-contact injuries, we need to have an efficient way of implementing the body of research.  If it is not efficient, adoption will not happen and therefore our impact will be minimal.  If implemented all that we know today as risk factors using traditional methods, this would take 40 min to an hour per player.  For any of us that have done physicals, we know that is not possible.  So no matter how good your intervention is, if it is not efficient it will not be adopted.  Whatever we do must be efficient. 

On the flip side, there is a large movement to come down to 1-2 movements that identify risk.  This would address the efficiency factor but is that the answer?  We know clinically in order to assess an overhead athlete for a possible labral tear that we have to take into account the athlete's history, symptoms, and perform several provocative tests.  Could you do one provocative test?  Yes.  But, is your sensitivity and validity of your diagnosis of the root cause better when you consider all these factors and do several provocative tests?  Definitely.  However, looking at one or two movements might identify risk and may help to reduce risk by 40%.  But, is 40% good enough.  Are we satisfied with 40%.  If my child or athlete falls in that 60%, then no, that is not good enough. 

So, how do we do it better?  We do it better by combining all the known risk factors.  Until the advent of current technologies, we have not been able to do that efficiently.  With time of flight technologies and IMUs, we are starting to see ways in which we can do this.  A time-of-flight camera (ToF camera) is a range imaging camera system that resolves distance based on the known speed of light, measuring the time-of-flight of a light signal between the camera and the subject for each point of the image.  This is the type of technology that the Microsoft Kinect and other similar devices function off of.  An inertial measurement unit (IMU) is an electronic device that measures and reports a body's specific force, angular rate, and sometimes the magnetic field surrounding the body, using a combination of accelerometers and gyroscopes, sometimes also magnetometers.  This is the type of technology used by DorsaVi, Myomotion, BPM Pro and others.  Now that we have technologies that allow us to integrate all these factors, what should we consider in order to get a comprehensive view of risk.

So, if we have technologies to do this and in order to develop this comprehensive look at risk, the question becomes, what factors we should consider and which ones can measure or influence.  Approaching this from a physical therapy, athletic training or performance coaches perspective, there are factors that we can measure but we may not be able to do it efficiently, cost effectively as we need or influence once they become known.  For example, in 2006 Griffen et al looked at all the known risk factors.  Although we know that femoral notch depth and menstrual cycle influence risk, can we efficiently, cost effectively and reliably measure that clinically without the use of expensive equipment and time consuming procedures?  Approaching this from the clinical perspective, one should think about what factors would you consider in your typical history with an athlete or patient.  For that, we can look to the literature.

Based on the literature, some factors that should be considered from the history or demographics include:

• Age of the athlete - Griffen et al Am J Sports Med 2006
• Gender of the athlete - Prodromos et al J Arthro 2007
• Sport the athlete participates in - Griffen et al Am J Sports Med 2006
• Body Mass Index of the athlete - Brambilla et al Am J Sports Med 2015
• History of previous knee injury - Rugg et al Am J Sports Med 2014
• Previous history of concussion - Brooks et al Am J Sports Med 2016

So, we know these are the demographic risk factors.  But for us to have a truly comprehensive approach, shouldn't we combine this with known movement risk factors?  So in addition to the demographic factors, we also know there are things we should look at from a movement perspective.  These include:

• Performance and stability in single limb activity – Myers et al Am J Sport Med  2012
• Symmetry between the right and left side in single limb activity – Rohman et al Am J Sport Med  2015
• Presence of lateral displacement of the pelvis (lateral shift) during a squatting motion – Atkins et al J Strength Con 2013
• Core strength and endurance impact on single limb mechanics  – Frank et al Am J Sport Med  2013
• Control of the speed and magnitude of frontal plane motion during single limb activity  - Stearns et al Am J Sport Med  2014
• Impact of fatigue on single limb performance  – Brazen et al Clin J Sport Med 2010

One would think that if we combine only one or two of these factors and we can reduce injury rates by 40%, that if we combined all the known risk factors that the sum impact would be much greater than 40%.  Obviously, this depends on the intervention.  Next week we will discuss how we apply this to our interventions.

Dr. Nessler is a practicing physical therapist with over 17 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 >3000 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.