Efficient Movement Drives Performance & Mitigates Risk - Part VI

Last week, we started our discussion about quadriceps weakness and how this can influence movement and a patient's perception on their functional ability.  This was specific to those who have had an ACL reconstruction.  However, that being said, I think there is a lot we can learn from this and which we can apply to any athlete.  It gives us some guidance on some things we can assess (isometric quadriceps strength and single leg squat/hop) as well as some thing we can do in our training to help reduce these deficits, improve performance and mitigate injury risk.

However, I think one question that comes out of this discussion is why does this persist after an ACL reconstruction if they are doing rehab and what can we do to change it.  Why does it persist?  I think there are a lot of complexity to this question.

One aspect is that there are neuroplastic changes that occur in the brain following an injury.  There has been an increasing body of evidence that is showing that there are changes that occur in the higher centers (brain) after an lower limb injury.  Studies are showing that some of the neuroplastic changes that are occurring remain after rehabilitation and after the athlete has been returned to play.  It is speculated that some of these neurological changes that occur could be one reason for the higher reinjury rates after an athlete returns to play.  If we could identify where these changes are, then this might guide us on what type of training we could do which would improve and reduce reinjury rates.

Grooms et al J Orthop Sports Phys Ther 2017 looked at 15 ACL reconstructed athletes who were cleared to return to sport and compared them to 15 matched controls.  Each participant filled out an IKDC (which we talked about last week) and had a functional MRI.  A functional MRI is an MRI that is done while the athlete is performing a task (pictured above).  In this study, the task was performing knee extension while having an MRI. 

What this study showed was that the athletes who had poor scores on the IKDC (their perceived functional ability of their knee) did in fact have diminished activity in the ipsilateral motor cortex and ipsilateral cerebellum.  What does that mean?  Essentially, this means that these athletes had altered activation in areas of their brains which is responsible for sensory, motor and sensory-visual-spacial processing.  We are going to dive into this subject a lot more on the next blog series but this information clearly guides us on types of exercises we can add to our rehab and our performance training that is going to improve input in these areas resulting in improved performance and mitigating risk of injury.

I touch on this here, because this may be one reason that we see some of the things we do in rehab.  For the athlete that has massive lateral shift (shifting weight to one side during squatting), this may be from these higher center neuroplastic changes.  In addition, the changes in the primary motor cortex could be one additional reason that the quadriceps have difficulty firing and why an asymmetry in quadriceps develop continues even at the point of return to sport.  So, how can we change this and can we use exercises to increase input to these higher centers?

Sadly, I think it is not as complex as we make it. Applying some simple concepts early on in the rehab process will aid in elevating a lot of this.  Some examples:

1. Correct a lateral shift ASAP.  The first time you start any type of squats, partial, sit to stand or whatever it is, correct the lateral shift.  Do not let this persist.  Training this motion and allowing this lateral shift starts creating these movement patterns as the default movement pattern in the higher centers.  This means this will be the movement they resort to when they sit, get down to the commode, sit in a car, on their bed ect.  This will then be the movement pattern they will carry over to functional squatting, training activities and sport.  WE must correct it and correct it right away.   
2. Start working recruitment of the quadriceps right away.  If they can't do the motion concentrically, start them doing it eccentrically.  Muscles are stronger eccentrically and I have often found we can use this to start recruiting muscles the athlete is having a difficult time recruiting.  Try this technique.  Take an athlete that can't do a long arc quad set or a straight leg.  Raise their leg for them up to the end range of motion then have them hold it.  Do this for a couple of reps then have them slowly lower it.  Do that for 5 reps then have them do it immediately concentrically after completing an eccentric contraction.  They can do it!  Why?  We have reengaged that synaptic pathway and got it firing again.  
3. Add BFR to your routine.  Blood flow restriction training is a great tool we can use to recruit more of the muscle.  By using BFR, you create a blockage of the venous return which causes a buildup of blood within the muscle (buildup of blood in the muscle resulting in back flow preventing more oxygenated blood from entering).  As result, muscle gets super pumped up and creates a hypoxic state.  This is due to less oxygenated blood coming in all while the task or load continues to be performed.  This decrease in O2 causes a fatigue and an increase in motor unit recruitment and more whole muscle activation.  This is how we get more of the muscle involved and greater recruitment of the whole muscle versus partial and hence more hypertrophy.  
4. BFR alone not enough - add electrical stimulation.  We know that electrical stim (ES) can aid in recruiting more motor units within the muscle when done with low level exercise (leg raises, short arc quads, long arc quads).  You can increase the impact of both the ES and the BFR by combining the two. 
5. Single limb performance - single leg activities are absolutely an essential part of your rehab
   
   program and early.  Obviously we want to stick within the guidance of the protocol, but the sooner you can start single limb exercises and single leg squats while controlling the frontal plane motion of the knee the less likely you are to have an issue with quadriceps weakness and risk of reinjury.  To promote desired motor patterns we are looking for, it is imperative that the athlete controls frontal plane motion, hip motion and motion at the foot an ankle.  Full kinetic chain stability is the key.  

All these techniques aid in increasing motor unit recruitment, more of the whole muscle contraction and aid in developing desired motor patterns in the higher centers.  This is just the beginning.   Keeping in mind, there are more ways to do this and in our next series, we will talk about specific training techniques we can deploy to create neuroplastic changes and help mitigate risk for reinjury.   What I will say, is if you add these techniques to your rehab process, quadriceps atrophy and weakness will not be an issue. 

That concludes this series.  Next week, we start to dive into some of the research related to the changes that occur in the higher brain centers and what specific strategies we can do to help retrain..  Stay tuned as I am super excited to share with you.  Have you followed my instragram @bjjpt_acl_guy lately?  If not, you are missing out.  I am constantly posting the latest research in injury prevention and sports medicine.  Don't miss out and please share with your colleagues, athletes and training partners and please be sure to follow us on instagrm @ bjjpt_acl_guy and twitter @acl_prevention.  Train hard and stay well.  #ViPerformAMI #ACLPlayItSafe

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 and ACL injury prevention.  He is the founder | developer of the ViPerform AMI,  ViPerform AMI RTPlay, the ACL Play It Safe Program, Run Safe Program and author of a college textbook on this subject.  Trent has performed >5000 athletic movement assessments in the US and abroad.  He serves as the National Director of Sports Medicine Innovation for Select Medical, is Vice Chairman of Medical Services for USA Obstacle Racing and movement consultant for numerous colleges and professional teams.  Trent also a Brazilian Jiu Jitsu purple belt and complete BJJ/MMA junkie.