To Change Movement - We Must 1st Change - Part IV

Last week, we concluded our discussion talking about a recent study by Boren et al where they looked at MVC of gluteus medius and maximus for various exercises commonly used to strengthen the hip and increase stability in single limb performance.   

As a recap, what was found was five of the exercises produced greater than 70% MVC of the gluteus medius muscle.  These were:

• Side plank abduction with dominate leg on the bottom – 103% of MVC
• Side plank abduction with dominant leg on top – 89% MVC
• Single leg squat – 82% MVC
• Clamshell progression #4 – 77% MVC
• Front plank with hip extension – 75% MVC

Five of the exercises produced greater than 70% MVC for the gluteus maximus muscle.  These were:

• Front plank with hip extension – 106% MVC
• Gluteal squeeze – 81% MVC
• Side plank abduction with dominate leg on top – 73% MVC
• Side plank abduction with dominate leg on bottom – 71% MVC
• Single leg squat – 71% MVC

Discussion:  Based on the results of this study, it leads us to some indication of types of exercises we can do with our patients that will result in MVC of the gluteus medius and gluteus maximus.  That said, is this always the right kind of training and more importantly is this the most functional? 

The front plank with hip extension and the side plank shown here are great exercises for the glutes as well as the core.  This study as well as others show that improvements in these motions as well as the MVC of the associated musculature aids in stability in single limb performance.  But is this a start and end point?  One thing we must ask ourselves is, does this have carry over to full weight bearing upright positions?  Are the length tension relationships the same and is the neurological input to the system the same as when you are standing.  Full weight bearing upright postures result in very different neurological input to the system as well as muscle activation.  So, although this may be a great exercise and a great starting point, it is not or should not be an end point.  The goal of exercises we use toward the conclusion of rehabilitation and/or in preparation for return to sport or while in sport is to have similar MVC on these muscles in upright training postures.  This trains the body, the neurological system and the brain to maximally activate these muscles in more functional postures. 

When looking at the single limb squat motion picture here, according to the study, this has both high MVC of the gluteus medius and maximus.  This is also an exercise performed in upright full weight bearing postures.  But, is this position similar to that of sport?  If you compare this position to that of sprinting, is there a way we could do this same exercise that closer represents a true sprint position?  If you look at the epidemiology and video studies looking at mechanisms of injury related to non-contact ACL injuries what you typically find is rupture occurring in more of a landing position with the contralateral limb in either extension or slight extension and abduction.  So, although this is a great starting point, is this the end point?

Again this goes back to the initial discussion.  What we are discussing here is not taking the data simply as is.  Rather, we are taking the most current literature and applying practical application and knowledge to that.  But one KEY factor here.  Throughout this discussion, the practical application is back up with solid science as the foundation of why we make the modifications that we do. 

To dive into this discussion a little bit further, lets look at single limb symmetry.  We mentioned previously that studies indicate that asymmetry in single limb performance or movement is an indicator of risk.  Clinically we have known this and the research has started to prove and look at this a little more in depth in the last 5-6 years.  One measure of this that has come out recently is what is defined as the Limb Symmetry Index (LSI).  The LSI is a comparison of the injured limbs performance to the uninjured limbs performance on a battery of single limb activities.  One recent study clearly shows this.  In 2015, Rohman et al looked at single limb performance as a measure or indicator for an athletes ability to return safely to sport. 

Methods:  Retrospective case series of 122 patients who underwent ACL reconstruction and who received postoperative Standard Functional Tests (SFTs).  10 of the 12 individuals tests within the SFT were analyzed for change in limb symmetry index (LSI) and absolute function in each limb. 

Results: In all athletes, involved limb performance increase in all tests.  LSI significantly improved in 6 tests with 5 of the 5 of the tests which showder initial LSI below 90%.  These tests were: single leg squat, retro step up, single leg hop, crossover triple hop, and timed hop.  Retro step up and single leg hop showed LSI improvements greater than 10%. 

Discussion:  As impressive and exciting as these results are, there is one thing that must be considered when reading through the results.  Does improvement in the LSI scores result in decreased risk of re injury, improved performance and improved short and long term outcome.  The easy answer and logical answer would be yes.  But, that is not what this study showed.  There was not a retrospective analysis of re-injury rates, comparison of pre-injury performance to post injury performance measures nor comparison of short and long term outcome measures.    What we can conclude based on previous studies is that we know improvement in the LSI does reduce risk.  How much, that we do not know.  We also know that improve symmetry (not LSI) does result in improved sprint speed and vertical jump.  Does improvement in LSI (as measured here) also improve sprint speed and vertical jump?  That we don’t know.  Finally, we know that lack of symmetry adds to increased risk of osteoarthritis later in life and more patella-femoral pain syndrome.  Does improvement in LSI also equate to those same improvements?  That we don’t know.

So, based on these last 2 blogs, what do we know?  We know some great exercises that will aid in improving strength of the gluteus medius and maximus.  We also know we should consider progressions which bring athletes into more upright, sport specific postures.  We also know that there are ways to quantify and express single limb symmetry, Limb Symmetry Index (LSI).  We also know that if we can improve the stability during these testing positions, then we can improve LSI and potentially reduce risk.  So, this would tell us that we need to train to improve performance on these tests.

As basic as it sounds, to truly change movement, we must change the way that we think.  And although it is not 100% data driven, it is 150% science driven.  Move better, feel better, perform better and last longer.  That simple.   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.  #MovingToChangeMovement and help us spread the passion.

Trent Nessler, PT, MPT, DPT:  Physical Therapist | Author | Educator |Innovator in Movement Science and Technology.  Dr. Nessler is a physical therapist and owner of Athletic Therapy Services.  He serves as a practicing clinician and movement change consultant for practices and organizations looking to develop injury prevention initiatives and strategies.  He has been researching and developing movement assessments and technologies for >10 years is the author of the textbook Dynamic Movement Assessment: Enhance Performance and Prevent Injury, and associate editor for International Journal of Athletic Therapy & Training.  You can contact him directly at drtrent.nessler@gmail.com