Gluteal Amnesia II - General Overview
Hey readers! I am so glad you are here. In this 5-part blog series, I am untangling the mystery of gluteal amnesia. If you have not read part I of this series (“What do the Glutes do?”), I highly recommend you go back and read that first (click here). I will be using a lot of the terminology presented in part I over the course of this series, so it might be helpful for you to read that information first. In this installment (part II), I will explain:
What gluteal amnesia actually is
What are the possible causes for it
What are the potential implications of it
What is Gluteal Amnesia?
As discussed in part I, Dr. Stuart McGill, a researcher on back pain, is generally credited with coining the term “gluteal amnesia.” Gluteal Amnesia goes by many names in the literature, including dead butt syndrome, sleepy glutes, gluteal inhibition, and more.
In general, gluteal amnesia is a condition where the gluteal muscles become weakened and/or do not receive an adequate amount of input from the nervous system (sometimes referred to as “diminished neural drive” or “inhibition”). Your nervous system is responsible for telling which muscles to move, when to move, and how forcefully to move. If there is reduced neural input to a muscle, or muscles, such as in gluteal amnesia, that muscle(s) does not receive an adequate signal from the nervous system, causing reduced force production and dysfunctional movement. If your gluteal muscles become weakened, as can happen in gluteal amnesia, they cannot produce optimal force to move the hip joint safely and efficiently, again causing dysfunctional movement in the body, and possibly even injury.
Regardless of the cause of gluteal amnesia, your glutes essentially end up getting chronically lengthened beyond their normal resting length while your primary hip flexors (i.e. the prime mover muscles on the front of your hips that cause hip flexion) become too tight and/or short. Often gluteal amnesia is attributed to a life of chronic sitting; however, there are some other possible causes (discussed in the following section).
The consequences of gluteal amnesia are far-reaching and include: compromised strength development, muscle atrophy (discussed in part III), denervation (discussed in part IV), reduced proprioceptive functioning (proprioception is your body's internal GPS that senses where your body is in space at any given moment), limited healing capabilities, injury and/or pain in the hips or other joints in the body, reduced athletic performance, and increased risk of early degenerative changes to bony and cartilaginous structures.
As you can obviously see from the potential consequences above, gluteal amnesia is not a good thing for the human movement system. Also, it should hopefully be evident that your gluteal muscles are super important for optimal movement and functioning in your entire body. So, why does gluteal amnesia occur in the first place? Well, let's take a deeper look at the most common causes of gluteal amnesia.
What are Some Causes of Gluteal Amnesia?
Gluteal amnesia can be the result of many factors. Dr. Stuart McGill explains that the cause of gluteal amnesia typically results from one, or more, of the following:
Lack of use
Pain. Patients with hip, low back pain (LBP), and sometimes knee and ankle pain, are often clinically described to have reduced activation in the gluteal musculature. In fact, if you experience LBP or knee pain, and you have not been assessed for gluteal amnesia, you should go to a trained specialist (e.g. physical therapist, orthopedist, sports medicine doctor, etc.) to see if your gluteal muscles are contributing to, or causing, the pain. In fact, pain, swelling, and joint inflammation can cause gluteal amnesia, and vice versa (gluteal amnesia can cause pain in nearby areas).
Pain is a fascinating beast and causes some interesting effects in the human body. When your body experiences pain in the lumbo-pelvic-hip complex (i.e. lower back, abdomen, hips), knees, and/or ankles, your nervous system greatly reduces the neural signaling to the glutes. This reduced signaling is thought to protect your musculoskeletal system by limiting powerful movements that can come from the glutes, all with the goal of hopefully reducing pain and eliminating further pain. This effect can cause gluteal amnesia and subsequently interfere with healthy, normal movement in the hip, low back, knee, and even the ankle. Interestingly, this phenomenon of reduced neural signaling during pain has also been seen in the knee joint, and a few studies have documented it in the elbow and ankle joints. Think of it this way - when your nervous system detects pain in an area, it responds by essentially cutting that area off from its regular nervous signaling to hopefully reduce further pain.
Gluteal amnesia can also cause pain to develop in the low back, hips, knees, and/or ankles. If your gluteal muscles are weak and/or underactive, it may cause other muscles to take on the job of the glutes, potentially leading to pain or injury (see next section - "implications" for more information on this).
Poor posture. Poor posture is another big factor in gluteal amnesia. If your body does not have proper static (i.e. stationary) and/or dynamic (i.e. movement) posture, all of your muscles are at risk for injury and/or discomfort because poor posture can affect the length-tension relationship of certain muscles. Length-tension relationship refers to the resting length of a particular muscle and the tension that muscle can produce based on this specific resting length. All muscles have an optimal resting length-tension relationship. If a muscle is lengthened beyond its optimal length due to poor posture (as can occur to the gluteal muscles in gluteal amnesia), it simply cannot produce the necessary force for efficient movement. This is because the additional length affects how the muscle contracts at the cellular level (click here to read more about muscle contraction). If a muscle is shortened too much (as can occur to the hip flexors in gluteal amnesia), it also cannot generate sufficient force for safe movement. This is also because the shortened length affects how the muscle contracts at the cellular level.
An example of the effects of poor posture can be seen in people with an excessive anterior tilt of the pelvis. An anterior tilt of the pelvis means that the top of the hip bones move towards the front of your body, causing your “butt” to stick out (some people commonly refer to this as “cheerleader butt”). In people with an excessive anterior pelvic tilt, their hip flexor muscles can become too tight, while the glutes become too lengthened. This shortening and lengthening affects the length tension relationship of these muscles, putting the entire kinetic chain at a mechanical disadvantage. In fact, studies have shown that tight hip flexors result in a two-fold reduction of gluteus maximus activation during a bilateral squat, compared to those with typical hip flexor lengths. Thus, it is super important to keep your muscles at the appropriate resting length so that you can move safely in your environment. Maintaining proper posture is a good way to ensure your muscles remain at their optimal length-tension relationships.
Lack of use. Lifestyle is a big contributor to gluteal amnesia. In our current culture, we live very sedentary lives. Even if you are a regular exerciser, the simple fact remains that as a species, we are not nearly as active as our biology is programmed to be. Prolonged sitting (e.g. in the car, at a desk, on the couch, etc.) puts pressure on the gluteal muscles and puts them in a lengthened position. As discussed above, this increased length reduces the force output of the gluteal muscles, making it more difficult to safely move around in your daily environment. When external pressure is translated to muscle and fascia (such as from chronic sitting), the tissue can deform or change shape, and this can bring about pathophysiological responses in that area including, reduced blood flow, impaired lymphatic drainage, and mechanical cell damage.
Prolonged sitting also causes the hip flexors (e.g. Psoas, rectus femoris, TFL, etc.) to become tight, affecting the length-tension relationship of the hip flexors, and reducing their force output. The increased tightness of the hip flexors also reduces neural drive to the gluteal muscles, while the neural activation of the hip flexor muscles actually increases (known as "altered reciprocal inhibition"). Over time, the glutes can atrophy (meaning that the muscle tissue literally breaks down) and become even weaker. The process of muscle atrophy will be discussed in more detail in part III, so if you are a cellular biology nerd like me, stay tuned.
What are Some Implications of Gluteal Amnesia?
Gluteal amnesia can negatively impact your balance, gait, posture, overall movement, athletic performance, and it can lead to pain or injury in one or both hips, the lower back, knees, and/or ankles. If even one muscle in your kinetic chain is weak, it can limit force production and velocity of other muscles in the chain, hindering all types of movement in your daily life.
If the glutes do not work quite right as a result of weakness and/or reduced neural drive, other muscles of the body will compensate by attempting to do the job of the glutes. This is because weak muscles cannot produce enough force in functional situations, causing the synergists (i.e. helper muscles) to create the movement, known as synergistic dominance. Synergists are not designed to take on the role of other muscles, as they have their own jobs to do. Over time, synergistic dominance can cause injury and/or pain to muscles and joints in your kinetic chain. For example, if you have weakened/underactive glutes, you might have to chronically rely on your low back muscles when you stand up from a seated or bent-over position. This puts undue pressure on your low back musculature, possibly leading to low back injury and/or pain. Additionally, if your glutes are too weak to stabilize your lumbo-pelvic hip complex during functional movement, your knee stabilizers may take on that job, putting these muscles at risk for pain or injury.
The synergists that have to work overtime in gluteal amnesia include the hamstrings, low back muscles, and knee and ankle muscles. Indeed, weakness in the gluteal muscles has been implicated in many types of injuries including: anterior knee pain, ACL injuries, low back pain (LBP), hamstring strains, ankle strains, and more. And, individuals with chronic back pain often have reduced strength and neural activation in their gluteal muscles. Synergist muscles have their own jobs to do, and if they are busy performing the job of another muscle, the ability to perform their main job will suffer. This will put the entire kinetic chain at a mechanical disadvantage causing dysfunctional movement, and potentially injury.
The glutes are prone to inhibition, often referred to as "gluteal amnesia." This inhibition is often caused by pain, posture, and/or lack of use. When your body is experiencing pain, your nervous system reduces the input to certain muscles as a protective mechanism from further damage. In the case of poor posture (e.g. excessive anterior pelvic tilt), the glutes can become lengthened past their normal resting length. All muscles have an optimal resting length that allows them to exert the maximal amount of force in a minimal amount of time. When that length is altered (either too long or too short), the muscle cannot produce sufficient force for functional movement. In our very sedentary culture, our glutes can become weakened, lengthened, and/or underactivated, causing synergist muscles to pick up the slack. This means that the hamstrings, low back muscles, knee and ankle muscles often have to take on the job of the glutes, putting those muscles at risk for injury and/or pain because synergist muscles are not designed to take on the role of other muscles in the kinetic chain. Weak and/or underactive glutes can negatively affect the functioning of other muscles and joints, disrupting movement, athletic performance, fluid circulation, proprioception, healing, and tissue growth. Stay tuned for part III next week which will take a microscopic dive into the cellular processes that control muscle atrophy and hypertrophy in gluteal amnesia.
Please note, the information presented in this blog series is not meant to diagnose gluteal amnesia or treat active cases of gluteal amnesia. After reading this series, if you have concerns about your gluteal muscles, please follow up with your physician, physical therapist, or sports medicine doctor. If you have been diagnosed with gluteal amnesia, please continue to heed the advice of the medical professional that evaluated you. Also, please keep in mind that I have simplified some anatomical and biological information, so I can keep the focus on gluteal amnesia as best I can. If you feel like you need more thorough descriptions and explanations, please refer to my reference list at the end of each installment in this series. Also, a special thanks to my amazing husband for doing all of the artwork for this post. Matt - you truly are a very talented artist.
As always, the information presented in this blog post is derived from my own study of neuroscience, human movement, anatomy, and yoga. If you have specific questions about your gluteal muscles, please consult with your physician, physical therapist, or private yoga teacher. If you are interested in private yoga sessions with me, Jackie, you can book services on my website ("Book Online" from the menu at the top of the page), or you can email me at firstname.lastname@example.org for more information about my services. Also, please subscribe to my website so you can receive my weekly newsletters (scroll to the bottom of the page where you can submit your email address). This will help keep you "in-the-know" about my latest blog releases and other helpful yoga and wellness information. Thanks for reading!
~Namaste, Jackie Allen, M.S., M.Ed., CCC-SLP, RYT-200, RCYT, NASM-CPT
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