Brian Schiff’s Blog

Perhaps one of the most researched topics is ACL injuries.  I have been studying and working for years in my clinical practice to find the best ways to rehab athletes following injury as well as implement the most effective injury prevention strategies.  Prior studies indicate prevention programs even when self directed can be successful.

However, on the whole injury rates have not declined over the past decade or so.  Much attention has been given to valgus landing mechanics, poor muscle firing, stiff landings, genetic difference between males and females, ligament dominance, quad dominance, and so forth.  The predominant thoughts today for prevention center around neuromuscular training and eliminating faulty movement patterns (refer to work being done by Timothy Hewett and Darin Padua).

We also know from a biomechanical standpoint that the hamstrings play an integral role in preventing excess anterior tibial translation, and as such hamstring strengthening needs to be a big part of the rehab and prevention program.  I believe in hamstring training that allows for activation in non-weaightbearing and weight bearing positions.  Common exercises I will use include:

• HS bridging patterns (double /single leg, marching, knee extension, stability ball)
• Nordic HS curls
• HS curls (stability ball, TRX or machine)
• Sliders – focus on slow eccentric motion moving into knee extension followed by simultaneous curls/bridge
• Single leg RDL (add dumbbells or kettle bells for more load)

Note: click on any of the thumbnail images above for a full view of the exercise.  From left to right: Nordic HS curls, sliding hamstring curls and single leg RDL).

A recent blog post entry by the UNC Department of Exercise and Sport Science (@UNCEXSS) has spurred my post today.  Click here to read their entry on optimizing injury prevention based on work done by Professor Troy Blackburn regarding the effect of isometric and isotonic training on hamstring stiffness and ACL loading mechanisms.  The research that was done holds promise for hamstring training designed to increased musculotendinous stiffness (MTS).

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I had the pleasure of listening to Darin Padua, PhD, of UNC present some of his latest research on ACL injury prevention last week. He has been doing research for some time. One of his studies (JUMP ACL) in collaboration with the military and several others has looked at prospective data and injury occurrence among college age subjects.

Much of the research to date on injury prevention has been done by Timothy Hewett and his colleagues. It has concluded that drop landing with a valgus collapse (hip abduction/IR with valgus knee moment) is a risk factor for injury. Interstingly enough, despite that knowledge and the proliferation of prevention programs, Darin mentioned that overall these prevention programs have not slowed the rate of ACL tears in the last decade. Why is that?  He also relayed that much of what we know now is based on 15 total cases.

The Jump ACL Study in a nutshell lasted for 5 years at 3 different military academies:

N = 5,700 cadets with no prior ACL surgery

• Soccer players = 1,690
• Tested from 2005 to 2008
• 39% female; 25% NCAA athletes
• 14,653 person-years of follow-up

N = 113 incident ACL injuries

• Soccer players = 29
• Mean time from testing to injury = 3.1 yrs
• N = 92 one ACL injury; N = 11 two ACL injuries

Some data (will be published) he discussed based on his findings revealed the following about high risk profiles for ACL injury:

• Hip flexion > 40 degrees at landing = 1.76x increased risk
• Hip adduction plus knee valgus = 3x increased risk
• Hip adduction plus knee varus = 27x increased risk

He also mentioned that the high risk profile does not correspond to the ACL injury event profile of:

• Hip abduction
• Lateral trunk flexion
• Knee valgus collapse
• Small knee flexion
• Tibial ER/IR

In the end, he suggests we need to better understand who to target (high risk profile clients) and what to modify (injury event profile) so we can better customize injury prevention programs that optimize proper movement and meet the needs of each individual athlete.  He reminded us that using the uninjured side for comparison is insufficient as faulty movement patterns already likely existed contributing to the first ACL injury.

So, assessing movement continuously and striving for excellent movement quality is a MUST if we are going to both prevent initial ACL injuries and reduce the re-tear rates for our athletes we send back to play.  He reports that those at increased risk simply have bad biomechanics.  His message provides more weight to having an advanced algorithm to identify asymmetry, poor motor control and flawed movement patterns in order to effectively prescribe interventions to address these things.

At UNC they use a PRIME assessment.  I am excited to learn more about it and have referred one of my female higher level soccer players to their lab for assessment as I look at this return to play decision with her now that she is just past 7 months post-op.   I think the hip/core obviously play an important role as I see so much deficiency in my female patients recovering from injury.

Clearly his findings with hip adduction and varus as a big risk factor seem to indicate it could be a top down kinetic chain breakdown as well upon impact based on the risk profile.  Pelvic stability or the lack thereof seems to be significant, only NOT in the same manner we thought about it before based on previous research available.  Stay tuned, as we have lots more to learn about ACL injuries and how best to tailor our prevention efforts.

It is widely accepted that decreased hip strength and stability leads to knee valgus. Excessive frontal plane motion and valgus torque increase the risk for non-contact ACL injuries. While we know that hip abductor weakness is more of an issue in females than males, the question remains to what degree other factors are involved.

Claiborne et al (1) noted that only 22% of knee variability could be linked solely to hip muscles surrounding the hip. In light of this we must look at the whole kinetic chain when assessing movement dysfunction and injury risk. In the most recent issue of the IJSPT, researchers sought to discover how activating the core during a single leg squat would impact the kinematics of 14 female college-age women. They excluded participants with current pain or injury to the lower extremities or torso, or if they had a history of any lower extremity injuries or surgeries in the past 12 months.

The participants were assessed for their capacity to recruit core stabilizer muscles using lower abdominal strength assessment as described by Sahrman (2). This testing model has 5 levels of increasing difficulty used to challenge participants to maintain a neutral spine. The draw back of this method is that it is done in supine versus the standing position of this study, but the author acknowledges this limitation. Out of a possible high score of 5, five of the participants scored a 1 or 2, while the other nine scored a zero.

For the study, a six inch step was used to assess 2 reps of a single leg squat. Each participant was asked to perform the test with the dominant leg to standardize conditions. They performed the reps under two conditions:

1. CORE – engaged abdominal muscles as they had been instructed to do so during the Sahrman test

2. NOCORE – no purposeful engagement of abdominal muscles

Results

• The CORE condition resulted in smaller hip displacements in the frontal plane but had no effect on hip angular range of motion – essentially there was less medial/lateral movement
• The CORE group did not exhibit any changes in knee displacement but did exhibit greater degree of knee flexion – this may suggest higher function assuming more knee flexion is desired during squat tasks in sports and functional activities
• Those scoring the lowest on the core assessments had larger improvements in performance when they did in fact activate the core musculature

How do we use this information to affect our practice?  Well, in terms of rehab it seems straightforward and many of us may already encourage patients to activate their core during treatment.  However, I think the greater contribution may come in injury prevention programs (particularly ACL programs) where we are looking at all facets of neuromuscular control and appropriate muscle activation patterns.

With any prehab or rehab strategy, we as clinicians, trainers and strength coaches are essentially trying to reprogram the brain to summon and execute a better motor pattern or strategy – feedforward training.  We know that healthy individuals tend to have better transverse abdominus and multifidus muscle activation, so it only makes sense to consider activation of local stabilizers as we work on global muscles.  Improving core and pelvic stability should only help reduce unwanted frontal plane motion.

With that said, the authors of this study readily acknowledge more work needs to be done with larger clinical populations (including EMG work) to more clearly identify what magnitude the core musculature has on lower extremity motion and displacement.

Keep in mind the proper program will always stem from your ability to assess movement impairment and tissue dysfunction.  I suggest beginning with a FMS in the athletic population and incorporating parts of that or the SFMA to compliment your evaluation in the clinic.  This will generally reveal the priorities for the corrective exercises.  For now, we can use this information in this particular study to be more intentional with our patients and clients suffering knee and hip dysfunction by adding this one simple step to our programming.

References

1. Claiborne TL, Armstrong CW, Gandhi V, Princivero DM. Relationship between hip and knee strength and knee valgus during a single leg squat. Journal of applied biomechanics. 2006;22(1):41.

2. Faries MD, Greenwood M. Core training: stabilizing the confusion. Strength & Conditioning Journal. 2007 ;29(2):10.

As I prepare to present at an ACL Symposium with some of my colleagues this weekend, I thought I would share some of the information I am presenting on injury prevention.

Research consistently shows that neuromuscular training is beneficial in reducing ACL injuries.  This type of training hinges on training our athletes to land, plant and cut on a bent knee while shifting the COM (center of mass) forward.  Too many times, I see female athletes land with stiff knees in an upright posture relying too heavily on their quads.

Emphasizing hip and knee flexion is vital in order to activate the posterior chain and provided a restraint to anterior tibial translation.  When it comes to landing and plyometrics, I feel strongly that we need to focus on repetitive drills that enhance power and teach ideal form.

These exercises should include single and double leg varieties, but more importantly they should challenge the body in the sagittal, coronal and transverse plane.  I have included a short video today that illustrates just a few exercises that I incorporate in my training sessions.

Stay tuned as I will share more details about prevention training in future posts.

For those who know me well, it is safe to say I am an “ACL geek” of sorts.  I love studying, reading and searching for the best way to rehab and prevent these injuries.  As I have grown in the profession, I have become increasingly concerned with articular cartilage damage and the long term effects it has on our young athletes.

Perhaps I am getting more concerned as my knees aren’t getting any younger either (lol).  Anyway, I truly believe we often underestimate how deleterious cartilage injuries can be long term.  In addition, I feel we, as rehab and conditioning professionals, need to better understand how our training impacts the cartilage regardless of whether patients had a concomitant bone bruise with their ACL injury or not.

One of my favorite prehab exercises is a single leg hop and stick (see below)

I typically begin with an alternate leg approach (push off right and land on left) prior to initiating takeoff and landing on the same leg to teach proper landing mechanics.  By now, we know increasing hip and knee flexion, as well as shifting center of mass forward reduces ACL strain and injury risk through a diminished extension moment.

However, what we may not know as much about is how an ACL reconstruction alters tibiofemoral joint mechanics at such a landing.   I want to share some interesting information from a recent article in the September edition of The American Journal of Sports Medicine.  The article by Deneweth et al. looked at tibiofemoral joint kinematics of the ACL reconstructed knee during a single-legged hop landing.

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