Does Injury Prevention = Improved Performance?

For years we have known that training improves athletic performance.  We also know that training reduces the risk for injury.  Yet, does decreasing the risk for injury also improve athletic performance?  That is a question yet to be answered.  Or is it really a question that has not been answered?  Is the answer there and we just do not know it.  In thinking about this logically, physiologically and biomechanically, if would make sense that since improvements in pathokinematics (abnormal movement) result in improvements in force attenuation (reduce injuries) then it would also result in improvements in force production (improve athletic performance).

Before we get too much in depth, we must first define pathokinematics.  This is a term new to most and one we define in our textbook, Dynamic Movement Assessment: Reduce Injures and Improve Performance.  Pathokinematics is defined as the pathological (abnormal) alignment of the lower kinetic chain (from pecs to the feet) during functional activities (sports) that results in abnormal force attenuation (overloads tissues resulting in injury) and force production (decrease power output) along the entire kinetic chain.   The purpose of this report is to provide an overview of the research on:

1. The impact of abnormal movement patterns have on the lower kinetic chain with regard to injury.
2. Identify a few of the causative factors related to pathokinematics.
3. Briefly examine the impact pathokinematic movement patterns have on athletic performance. 

Impact of Pathokinematics on Injury Rates

Lower extremity kinematics vary from athlete to athlete and from sport to sport.  However, there are several inherent movement patterns that make athletes more susceptible to injury.  Pathokinematics or abnormal movement patterns can include one or more components of excessive femoral adduction, internal rotation, genu valgum and pes planus.  However, due to the variability among athletes and demands of various sports, there may also be components of lumbar sidebending, lateral pelvic shift, decreased hip extension, excessive trunk rotation and scapular depression present which if observed might also lead to injury over time.  Research indicates if these pathokinematics can be altered or corrected then the risk for athletic injury is reduced.  Studies have shown that some of these asymmetries in fundamental movements can be identified with movement screens, such as the Functional Movement Screen (FMS).  The FMS is a combination of 7 foundational movements which are evaluated and scored based on how the participant performs the movements.  The FMS has been has been used effectively in predicting athletic injuries in professional football players.  The FMS has also be shown to be a useful to identify asymmetries and movement dysfunction when implemented as a pre-participation screening tool in athletics.  However, since this test is derived from pediatric reflexes, many question the correlation to sport.  There is also question about the ability of this assessment to “capture” the pathokinematics we “know” from the research that are directly correlated to increased injury risk.  The Star Excursion Balance Test (SEBT) is another movement screen used to assess lower extremity stability and to identify athletes at high risk for lower extremity injury.  In this test, subjects are in single leg stance and reach with the contralateral lower extremity while attempting to maintain balance and stability.  Subjects are scored based on ability to maintain stability and how far they are able to reach.  Improvements on this test have been correlated to reduced risk for injury.  However, do these isolated movements truly represent the mechanics that are present during high demand and fatigue induced play? Is there an even better way to evaluate these movements?  If the movement assessment where combined with proven fatigue protocols, would movements be more representative of what occurs in sport?

With athletics, ground reaction forces (GRF) can vary from 3-6 times body weight.  A multitude of  
factors can impact these ground reaction forces including surface, fatigue of the athlete, landing mechanics, etc.  Knowing the high GRFs associated with athletic activities, some studies have correlated the degree or severity of the “pathokinematics” to an increase in GRFs.  This may indicate why those athletes are at greater risk for injury with these higher demand sports (basketball/volleyball).  Several studies have shown pathokinematics also increase with fatigue and may be a contributing factor of why injuries occur later in the game (like soccer/skiing).  When combined with sports with high GRFs, then the risk is even greater.  As movement patterns break down, ground reaction forces increase with gait and impact, which may result from altered length tension relationships of the musculature of the lower kinetic chain.  The change in length tension relationships alters force production of this musculature at a time when there is an increase demand.  This results in the muscles’ inability to attenuate the force that is applied which equates to higher forces being distributed further along the kinetic chain and tissues being loaded in a biomechanically disadvantageous fashion.  The net result is not only an increased load to the tissue but when combined with valgus and rotational stresses, it creates a shearing stresses to the cartilage and ligaments.  Since cartilage and ligaments are weakest in shear forces, this could be one reason why, when combined with high load situations that it results in a ligamentous or cartilaginous tear, pain or reoccurrence of injuries with return to sport.  Hence, the more pronounced the pathokinematics and the higher the GRFs or physical demands of the sport, the higher the potential for injury.  However, one factor that has not been well investigated is the impact these movements have on athletic performance? 

What Movement Tells Us and Its Impact on Performance

Some initial studies do show implementation of a strengthening program can result in a reduction in the magnitude of these pathokinematics as well as a reduction of pain.  This has had an impact on performance through an increased tolerance with running in those with patellofemoral pain. There is also direct correlation between length tension relationships and the maximal contraction a muscle can produce and sustain, which is well documented in the research and excepted in the scientific community.  When pathokinematics are observed in athletes, these length tension relationships are drastically altered and hence would impact force production in the lower extremities and core.  As a result, there is a decrease in the efficiency (quality) of the movement, an increase in GRF, and decrease in maximal force the muscle is able to produce (strength) and sustain (endurance).  With an increase in the magnitude of pathokinematics, the impact this would have on loss in efficiency, strength and endurance and overall impact on athletic performance is apparent.  As further research continues to be performed on the impact on performance, results are showing improvements in pathokinematics correlate to an improvement in athletic performance. It is well accepted in the coaching community that if you can improve a player’s technique, you will improve their performance (efficiency of skill).  Just like a coach working with a lineman on his technique to drive from his hips to improve his power off the line, improving the efficiency of movement should have the same impact on performance.  It is well known and documented in the neurological literature that to improve performance on a given task that you need to train specific to that task.  Hence, to improve performance on the squat, you must train the squatting motion. 

So, the question then becomes, are there specific movements that we see in sports that if assessed would have a larger impact on the overall performance?   The difficulty also becomes determining what deficits are adding to the pathokinematics the athlete is presenting with and how do you address.  Looking at the athlete’s in single limb testing, it is evident if there is significant deficits when compared to the contralateral side.  Seeing this and knowing the deficits are more on the athlete’s dominate side and used in push off in sprinting, then we can see how improving these pathokinematics would add to increased power.  This will translate into improved time in the first 10 yards.  But exactly where are the deficits and how do you address?   If you address, will there be improvement in the movement and the overall performance?

As a result of the complexity and speed of the movement patterns in action, differentiating the various contributing factors leading to the overall presentation can be difficult.  There are multiple factors or variables contributing to the complexity of the movements observed.  Some of these include altered recruitment patterns, hip strength and endurance, core strength and proprioception.  Identifying and differentially diagnosing the “root cause” is essential.  This ensures the intervention’s impact on preventing injuries and improving athletic performance is as efficient and as impactful as possible.  Therefore, when evaluating movement patterns, using a standardized battery of tests to isolate the components of the complex movement may assist in assessing what may be contributing to the overall movement pattern observed with athletic activities.  Using additional standard orthopedic tests, to differentially diagnose causative factors, can assist in identifying the “root cause” of the movement pattern.  For example, knowing the gluteus medius is a femoral external rotator as well as a pelvic stabilizer in a closed kinetic chain, it will resist these motions during athletic activities.  Weakness or fatigue of this muscle would result in hip adduction, internal rotation as well as a trendelenburg pattern in single leg activities and/or running.  So, if a trendelenburg or hip adduction and internal rotation is identified with single leg hops or with single leg squatting motions, then an isolated and repetitive manual muscle testing of the gluteus medius (abduction, slight extension, slight external rotation) may give some idea of treatment strategies. 

However, if this same movement pattern is noted and the gluteus medius is strong, then assessing further down the kinetic chain may be indicated.  For example, excessive pes plantus can also result in hip adduction and internal rotation in a closed kinetic chain and therefore a more extensive evaluation of the foot and ankle may then be indicated.  Knowing the multifidus, quadratus lumborum and obliques assist in rotational stability of the lumbar spine, these muscles would also provide these same functions during athletic activities.  If there is an observed excessive trunk rotation during running gait and subsequent rotation to one side with plank test, then this may indicate weakness or fatigue of one or more of these muscles.  On the other hand, if there is excessive trunk rotation noted during running gait and excessive tightness of the iliospoas with a Thomas Test and corresponding weakness of the gluteus maximus with repetitive manual muscle testing, then this may correlated with the cross pelvic syndrome described by Panjabi.  In both of these examples, development of treatment strategies which improve the indentified “root cause” should result in improved movement during activity and hence improved athletic performance. 

A Current Case

The key, to have a true and profound impact on injury rates and performance is what you look at and interpreting what you look at.  If you do this well, the impact on both performance and injury rates is outstanding.  Case in point is a current project being conducted with D1 College Soccer players.  For the last 3 years, during physicals, the female soccer team has been undergoing the Fatigue Dynamic Movement Assessment™ of FDMA™.  The FDMA™ is a very physically intensive movement assessment that combines a fatigue protocol with an aggressive movement assessment (DMA™). Collectively, this assessment takes ~12 minutes per athlete, takes them to a state of ~80% VO²max then has them perform the DMA™ which consist of 80 repetitions and 3 one minute timed tests.  The average D1 athlete has a RPE (ratings of perceived exertion) for this test of 8/10.  Over the 3 years, over 100 athletes have been tested and the team has seen a 100% reduction of non-contact ACL injuries and 58.2% reduction of “other” lower kinetic chain non-contact injuries.  This has also resulted in ~60% reduction of total days on the DL for the team.  This means that key players are on the field longer and in the season longer which adds significantly to overall team performance.  In a prior, unpublished study, the DMA™ was used with high school athletes.  The athletes exercise programs were developed based on the results of the DMA™ and there was a significant improvement in the average vertical jump and 40 yard dash time for all 40 athletes tested.  Although these are not yet published, it highlights the impact that improvement in movement can have on performance.

Summary

Human movement is very complex interaction of multiple systems.  Deficient function of any one of these systems can result in pathokinematics which puts the athlete at risk for injury and impacts their performance.  Improvement in these patterns has not only resulted in a decrease in the potential for injury but initial studies also indicate an improvement in athletic performance.  With the use of standardized movement assessment combined with further differential diagnosis of the athlete’s individual movement dysfunction, the skilled practitioner, athletic trainer, personal trainer or strength coach can develop individualized programs that will have a direct impact on, not only their movement dysfunction, but aid in reducing their risk for injury as well as drive their individual performance.  Although the impact movement has on performance needs further and more extensive investigation, including this as a part of pre-participation physicals could aid in development of more individualized programs, reduce athletic injury and improve overall individual and team performance.   As more research is produced highlighting the impact these programs have on performance, it will result in more acceptance amongst the athletic and coaching community.

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