Monday, June 26, 2017
Is There A Secret Sauce? - Part V
Gradients of Gluteus Medius Weakness
Throughout this series we have been discussing what the research tells us about what puts athletes at risk for injury. Not that there is a secret sauce but more that it is a contemplation of complexity of the issue and plethora of factors to consider when looking at. We have taken an in depth look of the current research to see what does it tell us and how we can use that knowledge to improve the outcomes with our interventions. In the last 2 blogs, we spoke a lot about adduction in the frontal plane in single limb performance and how important this is to identify in our athletes. We have also discussed how we can use this knowledge in our interventions so we can have better results.
When looking at lower kinetic chain mechanics, one of the easiest factors to identify is adduction in the frontal plane. Although the majority of research has been written around this deviation in relation to ACL injuries, we also know that this deviation has an impact on patellofemoral pain, non-contact ankle injuries as well as a shearing stress at the hip. So often, we tend to get caught up in the complexity of the issue and try to dissect to the minutest detail. Yet, is this really getting us anywhere? What the research shows and what we know clinically is that when looking at the big picture, it is often the larger movements, that when corrected, have a larger impact on overall lower extremity mechanics than when we focus on the smaller minute movements. For example, if we have a running athlete that demonstrates a significant amount of adduction in the frontal plane, slight pronation at the foot and lack of 5° of 1st MTP (metatarsal phalangeal) extension, correcting the adduction in the frontal plane will often do more for their injury risk and performance than focusing on the lack of MTP extension. Is the 5° of 1st MTP important? Absolutely but although both are important, in many cases, it is the larger movements that drive the smaller movements.
Over the course of the last 10 years, there has been a plethora of papers published looking at hip muscle activation and the impact that it has on adduction in the frontal plane. Specifically, many authors have looked at the MVC (maximal volitional contraction) of the gluteus medius during such activities and found that decreased strength (decreased MVC) and endurance of this muscle adds to an increase in adduction in the frontal plane. Although this has been well documented and vetted in the research, many still question the gluteus medius’ role in control of frontal plane motion. However, 2013 in the Journal of Strength and Conditioning Research, Mauntel et al showed that there was an increase in knee valgus in those who demonstrated decreased hip adductor and external rotation strength. They also found by increasing hip abductor and external rotator strength and endurance resulted in a decrease in knee valgus (adduction in the frontal plane) that was observed in single limb performance. The authors suggest, based on previous author’s data as well as their findings that reducing adduction in the frontal plane by targeted strengthening to these muscles would and does reduce the risk for injury. We also know that gluteus medius activation is also directly correlated to patellofemoral pain in athletes. According to a study published in 2012 in the British Journal of Sports Medicine, Morrissey et al found that those who demonstrated decreased strength and endurance (EMG activity) of the gluteus medius had an impaired ability to control frontal plane motion at the knee. Those subjects that demonstrated increased frontal plane motion were also more likely to complain of patellofemoral pain. In other words, as depicted here in this athlete, sometimes the obvious answer is right in front of us and we need to just look. Instead of trying to make a complex issue even that more complex, maybe we just look at the most obvious movement and find out how do we prevent that! The interesting thing is, when you do, in a majority of the cases, the little things correct themselves.
So, keeping with that philosophy, what muscle is it that results in a decrease in adduction in the frontal plane? Some studies suggest the gluteus medius and some suggest strengthening the abductors and external rotators. Are they one in the same? To find this out, we must go to two of the leading resources in this area. According to one of the most referenced experts in this area, F. Kendall Muscles testing and Function with Posture and Pain, we see that the manual muscle testing position for the gluteus medius in an open kinetic chain (OKC) is abduction, slight extension and slight external. Knowing this, in an OKC, the gluteus medius is both an abductor and external rotator. However, is this how the muscle functions in a closed kinetic chain? To determine this, we must look at another leading source N. Palastanga Anatomy and Human Movement: Structure and Function. According to Palastanga and due to both the attachment and fiber orientation of the gluteus medius, in a closed kinetic chain, it functions to both provide abduction and externally rotate the femur. During single limb activity, it is much more important in stabilization in both abduction and external rotation (preventing adduction and internal rotation) and also controls pelvic rotation when the lower limb is stabilized. From the function of the muscle, in both an open kinetic chain and closed kinetic chain, we can then determine what movements are associated with weakness of this muscle AND what types of movements will aid in strengthening of this muscle.
We hope that you found this blog insightful and useful. Stay tuned next week we will discuss how to identify those movements at the pelvis and what that means. 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.