Monday, August 14, 2017
Last week, we started our discussion about how we assess movement efficiency in the MMA athlete and how that may guide some of our training. As we described last week, core strength is critical in mixed martial arts for both performance and injury prevention. The side plank test is an exceptional test for assessing the strength and endurance of the core and is often an exercise that is also used as a part of our training. This is a great exercise as there is a lot of EMG activity of the gluteus medius, internal obliques, quadratus laborum and transverse abdominus. During this movement, the EMG activity of the gluteus medius is very high and this is a critical muscle in stabilizing the core/hip/lumbar spine. The gluteus medius is the muscle that assists in stabilizing the pelvis during single leg activities. Here we see an athlete demonstrating a retrotrendelenburg, where you can see an arc from his upper body to lower body. This should be straight and when performed in this fashion this a movement pattern that adds to weakness of the gluteus medius. If this poor movement pattern is repeated over and over with every repetition and every training session, then this results in the athlete not training the muscles he is setting out to train and the impact on performance will be less than optimal.
This week we will continue this discussion as we look at assessing power generating movements and single limb performance. Considering this, one of the first movements we want to look at is the squatting motion.
Squat – In this test, the athlete is asked to perform 20 repetitions of a body weight squatting motion. During this test, you are assessing the ability to perform a squatting motion without a lateral shift (if a plumb line from cervical spine to sacrum is envisioned, the hips should remain equal distance from the plumb line throughout the motion). If there is deviation to one side or the other, this is referred to as a lateral shift.
Video – in the following video analysis we see an Olympic athlete demonstrating a right lateral shift during the squatting motion. This same motion is carried over to training and athletic performance.
Rational: The squat is a critical motion for athleticism. Improvement in the efficiency of the squatting motion has not only been shown to be associated with a reduction in injury risk but also associated with improvement in vertical jump and sprint speed. Reduction of a lateral shift results in symmetrical force attenuation and improved symmetrical force production. For the MMA athlete, this means greater force which can be generated with kicks and faster and more explosive takedowns. In addition, a lateral shift can indicate loss of motion in the ankle, knee or hip on the side they are shifting away from. This can guide preventative techniques which aid in reducing non-contact injuries during training and fights. In this picture, we see the athlete from the video shifting to her right side which could indicate a loss of motion in the left hip, knee or ankle.
Training Impact: For training purposes, the athlete is asked to squat using a resistance they can control throughout their range of motion without a lateral shift. If an athlete has a lateral shift, simply loading that and allowing them to continue with will result in greater variance in asymmetry right to left, bigger impact on athletic performance and increased injury risk. Once proficiency is maintained at a given weight, the athlete is then progressed through progressively increased loading. If a loss of motion is considered, this could also guide some additional mobility exercises that can be performed. If there is a suspected true loss of motion at the ankle, you would most likely see an asymmetry in the ankle motion in the plank test discussed previously. This will appear as an increase in plantar flexion on the suspected side during this test. In the training example here, this MMA athlete is doing a weighted squatting motion with kettle bells. Although this is a great exercise, the problem is that he is shifting to his left side during every rep. Allowing him to do this during his training is just adding to the problem and accentuating his asymmetry.
Next week, we will begin the discussion of single limb testing and look at ways we can assess these athletes and how this can guide our training. If you enjoy our blog, please share the passion and follow us on Instagram @BJJPT_acl_guy or on Twitter at @acl_prevention.
Monday, August 7, 2017
Last week we started the discussion on movement efficiency in MMA and we finished with the question, So, how do we assess that? So this week, let's begin to take a look at some of the movements that we assess in these athletes and how these equate to injury prevention and performance enhancement.
Testing the MMA athlete
Plank - In this test, the athlete is placed in neutral spine and neutral hip position, feet all the way together and head neck in neutral position. They are then asked to maintain this position for one minute period of time.
Rational: The plank is a critical position for assessing the stability of the core. The goal of this test is for the athlete to be able to stabilize while maintaining neutral spine position and neutral hip position. In this test, the athlete must sustain stability this position within 10⁰ of flexion and extension AND rotation. Maintaining stability in flexion, extension and rotation is critical to provide stable base for the lower kinetic chain to pull on, to generate force from and allow efficient kinetic energy transfer across the entire kinetic chain.
Training Impact: For training purposes, the athlete is asked to start training this basic movement correctly. The key to training is to ensure the athlete is maintaining neutral spine and hip position throughout their training. Once this achieved, movement and resistance can be added to this movement. In addition, the push up portion of the dynamic sumo stretch has a big carry over to this test therefore it is critical to ensure this movement is being performed correctly. Once this is perfected, an exercise like the plank crawl is a great addition to the MMA athlete’s core training routine.
Next we need to look at the core's recruitment in in combination with the pelvic and hip musculature.
Side Plank – In this test, the athlete is place in the neutral spine position ensuring that the athlete is not in a retro-trendelenburg position. The feet are placed on top of one another and the non-weight bearing arm is placed on the hip. Head and neck are maintained in a neutral position. They are then asked to maintain this position for one minute period of time.
Rational: The side plank is a critical position for assessing the stability of the core and the endurance of the gluteus medius. The goal of this test is for the athlete to be able to stabilize while maintaining neutral spine position and neutral hip position (hips not rolling forward or back). In this test, the athlete must sustain stability this position within 10⁰ of lateral sidebending (moving hips up or down toward the surface) AND rotation. Maintaining stability is critical to provide stable base for the lower kinetic chain to pull on and to aid in preventing internal rotation of the lower kinetic chain in single leg stance activities.
Training Impact: For training purposes, the athlete is asked to start training this basic movement correctly. The key to training is to ensure the athlete is maintaining neutral spine and hip position throughout their training. Once this achieved, movement and resistance can be added to this movement. Once this is perfected, an exercise like the side plank with the CLX is a great addition to the MMA athlete’s core training routine.
Side Plank with CLX
Next week, we will begin the discussion and look at ways we can assess these athletes and how this can guide our training. If you enjoy our blog, please share the passion and follow us on Instagram @BJJPT_acl_guy or on Twitter at @acl_prevention.
Monday, July 31, 2017
Throughout the history of this blog, we have talked about how movement assessment can be used in injury prevention and aid in performance enhancement. The association to sports like soccer, football and basketball are often easy for us to see. However, sometimes we think there are certain sports that may be immuned to or which this does not have as much application to. As a fan of MMA (mixed martial arts) and a student of BJJ (Brazilian Jiu Jitsu), coaches and athletes that specialize in these arts often think movement assessment has little application or that the sport is beyond it. However, these sports more than any other are dependent on quality of motion for ultimate performance and for injury prevention. Yet those that do use movement assessment for the sport often rely on outdated methodologies and primarily subjective measures.
Looking at the stats related to MMA and ACL (Anterior Cruciate Ligament) injuries we find some interesting key points. Most would tend to believe that most ACL injuries in the UFC or MMA occur with contact. A leg kick, knee bar or something of that nature. However, the reality is that most of the ACL injuries in MMA are non-contact in orientation. >70% of these injuries occur during a non-contact mechanism in training or during take down in a match. One of the most common combinations of movements associated with ACL risk is valgus and internal rotation that occurs at the knee.
As depicted here in the basketball athlete, this is sometimes easily seen in single leg stance or single limb activities. Most often we see this in running, cutting and jumping activities. Likely we have all seen a news reel or instant replay where a football or basketball player have a cutting movement resulting in these movement patterns and associated ACL injury. But how does this apply to the MMA athlete and how do we identify? Often these athletes are in such close contact with one another and the movement occur so rapidly that it is difficult to identify.
As previously mentioned, the majority of non-contact ACL injuries in MMA occur with takedown. As depicted in this picture, as the athlete shoots forward with his left leg, grabs his opponent and drives forward with the hips, this is when the injury occurs and usually to the stance leg (in this instance the left leg). It is the point where you are driving the hips forward that the knee will tend to fall in toward midline. This position not only creates a valgus stress at the knee but also results in an internal rotation moment. The combination of these two movements creates a tremendous amount of shearing stress to the ACL and the meniscus of the knee. Since these tissues are weakest in resisting of shearing forces, this is where a tear or rupture often occurs. Obviously, optimizing the technique is critical to performing correctly but identifying where the weaknesses are in the system will aid in preventing these pathological movements during.
Are knee injuries and ACL injuries that common in the MMA? This slide here represents just a few of the ACL injuries that have occurred in the UFC over the last 8 years. Some experts associate injuries to these athletes to equate to ~$118M in lost revenue. This loss in revenue associated with pay per view losses, sponsorships, etc. associated with each of these fights. Considering this, >70% of non-contact injuries in these sports (MMA, BJJ, Karate) occur to the lower kinetic chain with the knee representing ~80% of those. According to Harris et al Sport Health 2013 and Read et al Am J Sports Med 2017, professional athletes who suffered an ACL injury had a decrease across all performance measures after returning to sport following an ACL reconstruction and had a shortened athletic career as a result. In professional sports, this meant reducing not only their professional career by 2-4 years but also the income they could get during that time (as a result of the decreased athletic performance). When considering future performance as well as longevity of an athletic career, then obviously prevention of an ACL injury is critical. Considering the majority of these injuries are non-contact in orientation, then this is why we focus on non-contact injuries. In addition, non-contact injuries are also the ones that are most dramatically impacted (reduced) when properly identified and trained. Another aspect that makes MMA so susceptible to lower limb injury is the association of concussion and lower limb injury.
This really started to come to light in 2016 when Brooks et al Am J Sport Med and Gilbert et al Sport Health both published studies showing that athletes who suffered a concussion where at greater risk of lower limb injury. Not just a little but 1.6 to 2.9x greater risk of injury up to two years post-concussion. This is despite the fact that cognitive testing (Impact test which is used to determine an athlete’s ability to return to sport) had returned to base line levels. Considering that concussed athletes were found to be at greater risk of lower limb injury up to 2 years post-concussion, it makes us wonder how we could better test and train those athletes for safer return to play. The initial studies showed similar results in Division I athletes and further studies by Pietrosimone et al Med Sci Sports Ex 2015, Cross et al Br J Sport Med 2016, Nordstrom et al Br J Sport Med 2016 showed this had similar applications in professional football, lacrosse and soccer players respectively. Studies are showing that these athletes, despite unremarkable (meaning no signs of concussion) neurocognitive testing, when tested in single leg stance, their performance is greatly altered. Kristinaslund et al. Am J Sport Med 2013 and Myers et al Am J Sport Med 2012 showed that single limb performance was the single best test for assessing movement associated with successful performance in sport and movement associated with risk. Further, Howell et al Am J Sport Med 2015 may have discovered some of the underlying cause for altered single limb performance post-concussion. In this study they found athletes who had suffered a concussion had a greater displacement of their COM (center of mass) during single limb tasks. As depicted here, this displacement of COM alters force distribution through the lower limb which alters force production (performance) and force attenuation (injury). Considering, this not only guides us on how we should assess but also how we should train.
Next week, we will begin the discussion and look at ways we can assess these athletes and how this can guide our training. If you enjoy our blog, please share the passion and follow us on Instagram @BJJPT_acl_guy or on Twitter at @acl_prevention.
Monday, July 24, 2017
Last week we talked about the Read study and some of the implications that an ACL injury can have on an athletes performance after RTPlay. This week, we are going to disect this a little more the investigate what this means to the team and to the player.
Players starting in less games. One thing the authors spoke about was that players returning to sport post ACLR started less games following RTPlay. This can come from multiple factors including a coaching decision, a medical decision or player decision.
- Coaching decision. The coach may choose to not start the player due to their current performance. They see that the player is making less tackles which means more players are getting by them which may result in more yardage per carry for the opposing team or TDs. Net result is a decrease in the team’s performance. The coach may also see that one of their star players is no longer one of their star players. Coaches are there to win games and that depends on results of the individual players. If a player’s stats drop, that means an opportunity for another player to move up.
- Medical decision. We know that athlete who have an ACLR are at greater risk for other lower kinetic chain injuries. They also tend to have more knee problems and knee pain with RTplay. This may result in the ATC or MD pulling them out of play or modifying their play based on how their knee is responding.
- Player decision. This is one that typically does not last long. If the player is self-limiting their play, they may be pulled by the coach or cut from the team. A lot of times, athletes will suffer from Kinesiophobia (fear of movement) after an ACLR. This is where the athlete has not developed 100% confidence in their knee and its ability under the high demands of this sport, so they may self-regulate. This is most common with those who suffer a non-contact ACL injury and typically have kinesiophobia with explosive movements and cutting movements. Net result is a decrease in agility which may be one reason for a decrease in number of solo tackles.
Considering the above, what is the overall impact to the team and does this impact team performance. Keeping in mind what this study showed us, one of the things we know is that the athletes that did return to play were the better defensive players prior to their injury. That said, this study also clearly shows they did not return to the same level of play. For defensive players, one of the game performance measures is number of solo tackles. The number of solo tackles dropped dramatically and brought their individual ranking down from a star player to an average player. Taking star players out of the game can and will have a dramatic impact on overall team performance in individual games as well as overall seasonal performance.
On a personal level, what is the impact to that athlete? This is obviously the individual that is impacted the most. NFL players know this impact and it is one reason that in 2014 and 2015, knee injuries were ranked the #1 concern among NFL football players in the NFL Players’ Association. This is above concussion or any other injury. Why? Because they know how much this impacts earning potential. This has a direct impact on the NFL player’s earning potential in 2 ways. If their contract is up for negotiation, this is going to be based on prior year’s performance. If they are starting in less games and making less solo tackles, then they do not have as strong negotiating power as they may have had previously. In addition, what this study shows and what the athletes know, is that their professional football career is cut short. Although this study shows an impact, what industry experts say is that their professional career may be reduced by 3-4 years. On a multimillion dollar contract, that is a lot of potential income that they lose out on.
So why is this study so important? ACL injuries are common in the NFL. How common? Let’s look at the numbers by season.
- 2016/17 – 46 ACL injuries
- 2015/16 – 48 ACL injuries
- 2014/15 – 45 ACL injuries
- 2013/14 – 63 ACL injuries
Over four seasons that is 202 ACL injuries. If you look at the overall cost of those injuries, you must look at time loss, ACLR cost, rehab cost, positional replacement costs, emotional capital and impact to team performance. Industry experts put this cost at ~1M/player. Over 4 seasons, that is $202M in injuries.
Sadly, over 73% of those are non-contact in orientation. Studies suggest that you can reduce non-contact ACL injuries by as much as 80% if those athletes are properly identified and put on an appropriate program. So over four seasons, that is a potential $118M cost savings if they had been identified and trained appropriately.
So why is this not being done? One is time. How do you do that efficiently? Here is an interesting fact. 66% of all NFL ACL injuries are associated with 5 positions.
- Wide receivers – 19.4%
- Linebackers – 15.5%
- Cornerbacks – 11.7%
- Offensive lineman – 10.7%
- Defensive ends – 8.7%
What does it take to make a change? First and sadly, you need to tie it to performance. How does this impact athletic performance, team performance and revenues. The above study highlights the impact this will have to the individual performance of the player but also the impact this will have to the team’s overall performance. Secondly, we need to know we can somehow efficiently identify those at risk. With the advent of wearable sensor technology and the knowledge that 66% are associated with 5 key positions, then we now have an efficient manner to address. Finally, having a solution. Once those at risk have been identified, how do we change that? There are multiple programs out there that can efficiently impact these pathokinematics and improve the movements that put athletes at risk.
Insanity - To do the same thing over and over and expect a different outcome. Is it time for the insanity to be over or are we going to continue what we have always done and expect a different result? I chose the former.
Monday, July 17, 2017
Over the course of our last series “Is there a secret sauce” we provided some thoughts and research on several factors that contribute to altered biomechanics or pathokinematics that put athletes at risk for an Anterior Cruciate Ligament (ACL) injury. Throughout the history of this blog, we have attempted to correlate these same pathokinematics to not only ACL risk but also to changes in athletic and team performance. In this authors mind, there are two ways in which this impacts performance; directly or indirectly.
The direct impact is the impact that altered biomechanics has to force production and kinetic energy transfer. This direct impact results in muscles of the core and lower kinetic chain producing less force. This is the results of several factors including changes to length tension curves. Simply stated, due to the altered mechanics, the muscles of the core and/or lower kinetic chain are placed in a shortened or lengthened position. Knowing the impact that length (shortening or lengthening) has on force production, then the muscle cannot produce as much force or power as it could if it were in an ideal length tension relationship.
The indirect impact is after the injury occurs. The altered biomechanics resulting in a non-contact ACL injury result in an impact on future athletic performance. However, this concept of how these injuries impact future performance has not been fully investigated. That said, more and more studies are starting to investigate the impact on future athletic performance.
Case in point, a recent study by Read et al, Am J Sport Med2017, the authors looked at the impact of ACL injuries have on future performance in National Football League (NFL) players.
Results: At least 74% (28/32) players who had an ACLR RTPlay in the NFL for at least one season game. 61% (23/32) successfully returned to play for at least half of the NFL season (min of 8 games). In the seasons leading up to their injury, athletes who successfully returned to play started a greater percentage of their games (81%) and made more solo tackles per game (3.44 6 1.47) compared with athletes in the ACLR group who did not return to play. Athletes in the ACLR group retired significantly earlier and more often after surgery than the matched control group. In the season after ACLR, athletes who RTPlay started games 57% less times and had only 2.38 solo tackles per game compared to matched controls at 3.44 solo tackles per game.
Conclusion: Athletes who successfully returned to play were above average NFL players before their injury but not after.
Next week, we will start to dissect this a little more. Specifically what does this mean to the team's performance as well as the athlete's overall earning potential. If you are enjoying our blog, please share it and follow us on twitter @ACL_prevention and on Instagram at @Bjjpt_acl_guy
Monday, July 10, 2017
Gradients of Gluteus Medius Weakness – Part III
In our last couple of blogs, we have talked about the function of the gluteus medius in both an open kinetic chain and closed kinetic chain. We have also talked about how this muscle functions on both the femur and the hip and how weakness of this muscle will present itself at the femur versus at the hip. Although most understand the movement that occurs at the femur, identifying weakness that is represented at the hip is just as critical as it is at the femur. With the shear stresses that are imparted to the labrum of the hip during these motions, hip motion can have just as devastating effect on the hip as the movement can have on the ACL at the knee.
So now that we have identified it, how do we strengthen it? Easiest thing is to look at the function of the muscle. Before we get into specific exercises, let’s say one obvious thing, if you are going to strengthen this muscle, do it right! Every single day, we see physical therapists, athletic trainers and personal trainers who do these exercises wrong and just strengthen bad or compensatory movement patterns. In these cases, it is better to not do it than to do it. Because strengthening bad movement patterns sets them up for greater risk. To increase recruitment or maximal volitional contraction (MVC) of the gluteus medius, we need to think of it not just as strengthening the muscle. You have to change recruitment patterns and sequence of firing. Yes strength is a part of that but only a part. To change MVC during functional movement you must change motor plans in the primary motor cortex.
In 1998, Karni et al showed that in order to change a motor plan in the primary motor cortex (PMC), it required 3,000 to 30,000 repetitions. The authors also showed that you can employ techniques which result in quicker change and that there are also things that we do that will result in slower changes. From this, we have developed a saying.
Poor Technique = Poor Motor Learning = Poor Performance
Learn it, live it and teach it. Change in the PMC is critical to change how the muscle fires during movement. Based on the science, we know for every repetition that you do incorrectly, you then must do three reps to have a positive change on the PMC. Considering this then, you must do one rep to offset the bad movement, one rep to offset the previous bad rep and one rep to drive a positive change in the PMC. Sounds simple enough right? Sadly, even with highly educated individuals, we typically see athletes doing the exercise incorrectly under direct supervision. We then wonder why their movement has not improved that even when we are focusing on the right area and muscles. Identifying the previously mentioned movements is hard enough when doing it in an assessment let alone when we are doing exercises. There are numerous exercises to strengthen the gluteus medius in both an open kinetic chain and closed kinetic chain. Therefore, we will only cover two exercises in depth which work on the gluteus medius in a closed kinetic chain.
One such exercise, we call the lumbopelvic disassociation (LPD). You can view a video of this on our YouTube channel, by clicking here. This exercise is intended to do several things:
· Assist athletes in discerning lumbar motion from hip motion by improving proprioception through the hip
· Provide a closed kinetic chain exercise to start strengthening the gluteus medius
The video is intended to give viewers some pointers. Although the athlete may do it incorrectly, this video’s intent is to not only show the exercise but to show where people go wrong. This said, there are some common mistakes that people make in performing this exercise and which we can look for during performance of. Once you have viewed the video, take a look at the athlete in this photo performing the exercise, you see several key factors.
· Knee/ankle/foot are stable
· Non-stance leg is extended – this places the lumbar spine in extension and aids athlete in keeping neutral spine and not going into lumbar flexion during.
· Chest is up – promotes thoracic extension which also promoted lumber extension
· Hips are level
If you compare the above athlete to the athlete pictured in the next photo, you can see some slight variations that also lead to strengthening compensatory strategies. Keep in mind, this athlete is demonstrating minor deviations and is not even close to the magnitude of deviations that you would typically see when someone does this incorrectly. We use this example because it is even these slight changes that result in significant impacts to the MVC of the gluteus medius. In this case what we see is:
· Non-stance leg in extension and chest up – good
· Neutral spine position – good
· Retrotrendelenburg position of the right hip – indicated with the yellow circle and seen with the hips not being level and the left hip coming up (placing the right hip in a retrotrendelenburg position)
· Externally rotated position of the right foot – indicated with the red circle
The combination of the raising of the left hip and the external rotation at the right foot makes the retrotrendelenburg much greater at the right hip. If we allowed him to continue this with all of his training, we can anticipate that when he performs in single leg stance or single limb tests, that his natural tendency is going to go into a retrotrendelenburg on the right when performing single limb tests on the right. The simple correction is having him bring his right foot in slightly and drop his left hip down slightly.
What is pictured above is a retrotrendelenburg but keep in mind that this can also present itself as a trendelenburg. Easiest way to see both of these is to simply look at the hip position. Are the hips level during the course of this exercise? You have to watch closely during the beginning phases of this exercise as it may present itself here as the athlete rotating their hips out. If they do and we allow them to continue that, then we are again just reinforcing the bad movement patterns and strengthening their compensatory strategies.
Another common exercise used to strengthen the gluteus medius in a closed kinetic chain is side-stepping with a theraband. In this video, we again go through some specific pointers related to the technique and compensations. Even though this is one of the most widely used exercises for gluteus medius weakness, it is also one that is often performed incorrectly a majority of time.
· Having the band to high – higher the band is, the easier the exercise is. Placing the band at the ankles not only makes the exercise more difficult but also brings in higher recruitment along the lower kinetic chain.
· Band too loose – if the band is not tight at the starting position, it will be too easy throughout the motion and only stress the muscle at its weakest point in the length tension curve.
· Lack of core activation – keeping in mind the concept of specificity, if we train with increase in lumbar lordosis (lack core activation) throughout this exercise then this promotes lack of core activation when it matters the most.
· Allowing compensation during performance of the exercise. Common compensations are:
o Externally rotating with stepping out – this allows increased recruitment of the hip flexors and reduces MVC of the gluteus medius
o Standing when bringing feet together – this is a much easier position for the movement and maintaining this position throughout will aid in increased MVC.
Taking these few pointers and applying to your gluteus medius strengthening will not only make a huge difference in what the athlete feels but also aid in improving their mechanics with CKC movement. We hope that you found this blog insightful and useful. As we stated previously, stay tuned and 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. #ACLPlayItSafe and help us spread the passion.
Monday, July 3, 2017
Gradients of Gluteus Medius Weakness – Part II
Last week we discuss the function of the gluteus medius in both an open kinetic chain and closed kinetic chain. Now that we know the function of muscle, what kind of movements will we see? The most obvious is adduction in the frontal plane (like pictured in the above athlete). When we see movement like that and we have identified it is coming from the hip and not the foot, we know that the gluteus medius is playing some role in that. But what about the cases where the lower limb (femur) is stable? We know that the gluteus medius also has an impact on stability at the pelvis, so what kind of movement would we see at the pelvis and if we see movement at the pelvis, does varying movements indicate a gradient of strength of the gluteus medius?
According to Palastanga et al, we know that the gluteus medius “controls” pelvic rotation when the lower limb is stabilized. It is well accepted in the literature as well as the medical field that weakness of the gluteus medius can result in a trendelenburg at the hip during gait (walking). In the example pictured here, the right hip drops during stance phase on the left leg. The arrow indicates that it is weakness of the gluteus medius on the left side that allows the pelvis to drop on the right. With the origin and insertion of this muscle on the iliac crest and femur, shortening (or contraction) of this muscle would result in pulling the left pelvis down which would raise the right hip. This is seen a lot in patients who have suffered a neurological insult (stroke) and who have a gluteus medius weakness as a result. However, you can also see this in athletes. In athletes, you will not typically see this in walking gait, but you will start to see this in running gait and in jumping. Because of the ballistic nature of these movements, this occurs as a result of much higher ground reaction forces that occur with sports and are often much harder to see. If you look at the high school football player pictured here, you can clearly see a trendelenburg that is occurring with a single leg hopping activity. This trendelenburg is not apparent in his normal gait cycle. However studies show that jumping results in ground reaction forces that are 4-8 times body weight whereas walking is traditionally 1 to 1.5 times body weight. Hence, when we have an athlete do more difficult movements (single leg squat or single leg hop), then this lack of control at the pelvis then becomes more apparent.
But, we also know that with greater weakness comes more significant deviation. In the knee, this is represented as a larger increase in the frontal plane adduction and hence an increased adduction moment. But, if the lower limb is stable, how does that appear at the pelvis? Again, looking at some of the stroke literature, we know that patients who tend to have decreased MVC of the quadriceps that they hyperextend their knee. Why do they hyperextend their knee? Subconsciously, they have figured out that they cannot sustain a flexed knee posture so they hyperextend their knee to create more bony stability (created by bony stability with increased contact with femoral condyles and the tibial plateau). This position, although it provides stability, also results in a decrease in MVC of the quadriceps. Something similar to this occurs at the hip. As pictured here, what you see is a retro-trendelenburg. In this position, you see the athlete subconsciously position their center of gravity (upper body) further laterally which increases body stability (between the acetabulum and femoral head) and requires significantly less MVC of the gluteus medius. As a practitioner or examiner, if you don’t look for this and you are only looking for adduction in the frontal plane as your indication of gluteus medius weakness, then you may miss an opportunity to not only reduce ACL risk but also risk for a labral tear in the hip.
With severe weakness come severe deviations. In the knee, this means that adduction in the frontal plane is of such large magnitude that we are also now starting to see significant internal rotation of the femur. But what does that look like in the hip? In the hip, this results in a trendelenburg along with a rotation (what we define as a cork screw). In this scenario, the gluteus medius is so weak that the pelvis drops and rotates at the same time. Looking at the origin and insertion of the gluteus medius, the muscle is failing through its full range of motion and hence why these two movements occur in unison. This is most easily observed by the position of the contralateral limb (non-stance leg). If this leg comes way across midline like this, then there is both a component of hip drop as well as rotation that is occurring at the hip. In these cases and under high loads (jumping and running) the amount and magnitude of shear stress that is imparted to the labrum of the hip significantly higher than it is intended to take or that it is designed to take. In this volleyball player pictured here, you can clearly see the trendelenburg and rotation occurring in both single leg squatting motions as well as in single leg hopping motions. That said, not only is this athlete at risk for ACL injury but also hip injury. As a practitioner or examiner does not look for this, then they are missing an athlete that is at high risk for injury, especially in sports that require running and jumping.
Considering all the above, we can now grade our gluteus medius weakness based off the deviations that we see presented at the pelvis as much as what we see at the knee. At the pelvis, we would expect the following gradients:
- Trendelenburg – mild/moderate gluteus medius weakness
- Retrotrendelenburg – moderate to severe gluteus medius weakness
- Cork screw – severe gluteus medius weakness
Ok, so now we have it but what does all this mean for strengthening? Stay Tuned!
We hope that you found this blog insightful and useful. Stay tuned next week we will discuss how do we train the gluteus medius in both an open kinetic chain and closed kinetic chain. As we stated previously, stay tuned and 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. #ACLPlayItSafe and help us spread the passion.