Hip Hip Hooray! Part Two
Updated: Aug 20, 2021
The Quads and The Psoas
YIKES THIS SUMMER HAS BEEN A DUMPSTER FIRE FOR WRITING. (But don't forget you can find me at Medium more often! Recent ones include Rejected Sperm Pickup Lines and If We Compared Male Athletes To Kangaroos In The Same Way We Compare Female Athletes To Male Athletes.)
In Hip Hip Hooray, Part One, we took a gander at the bony and ligamentous anatomy of the hip. In spite of all the aggressive forces that weave up and down, the hip is essentially just two bones, plus the sacroiliac (SI) joint acting like a fascinator on top.
In designing this photo collage, I feel that I have truly peaked as an artist. The angles. The hat's ribbons mirror the joint. The hair and chin as the hip bone and butt bone. The collar as the top of the femur. Honestly. It's beautiful. This should be Beatrice's official royal portrait.
So yes, it's just two bones, but attached to those two bones are so many muscles, it's almost hard to believe when you look at them. Just look at this video of all of the muscles stacking on top of each other. (All anatomy stills are, as always, from Essential Anatomy, the most amazing anatomy app.)
Today we're gonna look at the major muscle groups in the front of the hip joint: the quadriceps and the psoas. The quads and psoas have some wild shit going on. Especially the psoas. Like Homer Simpson's alcoholism, it's the cause of, and solution to, all of life's problems.
In our shoulder series, I compared all the shoulder muscles to the various Baldwin brothers. For the hip muscle groups, we're gonna look at Shrek, because Shrek is the fucking best.
The Quadriceps, AKA Princess Fiona
The quads are—duh—four muscles all stacked around each other. The quads serve two purposes: to straighten your knee and to flex the hip. (Remember that hip flexion is the direction of pulling your knee towards your chest.) If you're doing something like sprinting, your quads not only aggressively pull your leg forward for the next stride, but they also to help absorb the impact of landing as you go.
Your quads are princesses all the way. They're strong as hell, so they think they own all your shit. They think they do everything. Even when all they do is lounge in a prison tower and stare out the window being annoying, they're thinking about how excellent they are. In fairness, they ARE red-haired and hot and can do martial arts, so they've got that going for them.
The quads run from above and below the hip and across and around the kneecap. (Yellow asterisks below designating quads.)
Although there are four quads, I've shown just three in this pic. (On the right side of the picture, I also removed accessory muscles so you can see the quads better. The left side of the pic shows a more complete leg.)
These three muscles don't cross the hip joint. You can see they attach on the femur just below the hip joint, which means they only move the knee. But don't be fooled by only 1/4th of your thigh being attached above the hip. These muscles acting together can still produce a shit ton of energy at the knee level. If you've ever seen Carli Lloyd kicking a soccer ball, you've seen how beastly the quads can be.
The largest quad strength measurement I've been able to find is in young athletic men: 1,350 pounds of kicking force. Holy fuck. The kick from a horse's back leg can kill you and it comes in at about 2,000 pounds of force.
The quads have to work in perfect harmony in order to get the kneecap to slide evenly across the knee joint. If you have one batshit quad muscle pulling sideways, you're gonna have a bad time. People with trouble after total knee replacement often have issues with the patella (which doesn't usually get replaced) for this reason. The natural biomechanics are incredibly precise and even small shifts (like uh, a new metal knee being inserted) can cause big changes.
And then there's the fourth quad, the big one missing from the picture above, but shown below, in isolation on the right, in completion on the left. It sits on top of the three quad muscles shown in the above picture.
Rectus Femoris. A monster muscle. Rectus crosses the hip AND the knee like a boss, which means that she is capable of moving both the hip and the knee. Rectus does work when the leg is swinging forward during essential movements: walking, running, skipping.
Rectus is too important for one tendon, so she's got two tendons that attach up into the hip socket. Then at the bottom she joins the patellar tendon with all the rest of the quad muscles at the knee.
Why are two tendons important? Because they allow her to simultaneously exert force on the hip and also help stabilize it. And even though there are about seven muscles that flex the hip, rectus does about a third of the total work. So yeah, she's important in flexing the hip. Just like when Fiona is managing Donkey's well-meaning ineptitude, Shrek's angry self-esteem issues, and handling the fact that she's a decorative pawn in a repellent patriarchy, Rectus Femoris calmly commands much of the leg under pressure.
HOWEVER, PRINCESS, THERE ARE SIX OTHER MAJOR HIP FLEXORS AND IT'S NOT ALWAYS ALL ABOUT YOU. PSOAS MIGHT HAVE SOMETHING TO SAY SOON.
(I sympathize with the quads. I hate when not everything is about me.)
Persistently dominant quadriceps can lead to serious hip, knee, and back troubles.
In a normal, mechanically-sound knee, the quads produce a torque about 2/3rds greater than the hamstrings exert from the back of the leg. There's already a natural, significant muscle imbalance between the two. So just imagine if you skip training hamstrings for ten years, and then pick up running again. It's gonna be like skiing in South Park. You're gonna have a bad time.
Here's why the quads' sense of self-importance can be an issue. They're so strong and so powerful that they can start to dominate movement if they don't have appropriate controls. This dominance means that a person's body may lose the ability to extend. Highly dominant quads pull people into a slight forward bend. They'll struggle with getting their legs behind them in a full walking or running stride, for example, or even just standing completely upright. This persistent forward bend can lead us to....what do we have for them, Pat?... Crippling knee pain AND! Looooooooooooowerrrrrrr back paiiiiiiin!!!!!! Give the wheel a spin!
Why did I just switch into a game show host voice? I have no idea. Why does the sun rise in the east? Don't ask these questions.
What are the controls that help to prevent this quad dominance? The hip extenders: hamstrings and gluteus maximus. We'll get at them next time, but we have to talk about another flexor first. Fair warning, he's kind of an asshole.
The Psoas, AKA Pshrek
In the beginning of Shrek, he's this giant unsociable ogre who hides away from the world and does everything he can to handle his own life without help from anyone else.
Welcome to your Psoas. (Pronounced SO-azz.)
Iliopsoas—technically made of two (and sometimes three) muscles masquerading as one muscle—is the giant unsociable ogre of your body. It runs, amazingly, from one thoracic vertebra and all five lumbar vertebrae down across the hip and into your thigh bone.
Did you look at that image? Psoas runs...from your middle spine...along your lower spine...behind your digestive system...across the hip...and inserts into the leg. It's like a fifth of your body length. This thing can be SIXTEEN INCHES LONG! In spite of this, although you can access it if you palpate just the right spot between your hip and pubic bone, it's actually very deep in the body and largely inaccessible to probing fingers. (For this reason, I am extremely suspicious of people selling "psoas releasing" services.)
Psoas likes to work alone, because he's strong as hell and can handle a lot of jobs in the swamp of your body. He's a major hip flexor, yes. But he also externally rotates your leg and helps to bend you sideways, in the way you see sorority girls training their abs.
The psoas is psuper cool in even more ways. It's the only muscle that connects your trunk directly to your leg. The top of the psoas (near the spine) is responsible for postural positioning while the bottom (near the leg bone) is responsible for movement. So your body split-controls this muscle, using it for simultaneous functions of entirely different natures.
Furthermore, psoas shares tendons with the diaphragm (your primary breathing muscle in the rib cage) and fascia with the pelvic floor (the muscles you squeeze to stop peeing which are also important core stabilizers). That is a LOT of work for one muscle. It's like those quick-change magicians who always make me literally squeal at my TV.
PS if you missed Léa Kyle's quick-change performance on AGT this season, you GOTTA watch it.
All of this means that your psoas can exert influence on some of the most vital pieces of your body: lungs, digestive system, internal organ blood flow, etc. Can a weak, shortened, inflamed, gripping-for-dear-life psoas on someone with chronic forward lean and back pain also be affecting their breathing, digestion, and elimination? You bet your colon it can.
What helps to counteract quad and hip flexor dominance in the body? Your hip extenders: hamstrings and glutes.
Pshrek also has a neat feature that the other hip flexors don't have. Remember that he is a powerful hip flexor—he brings your knee up to your chest. But he also provides that same movement from the opposite direction: bringing your trunk down towards your leg. Imagine sitting in a chair. You know how you lean forward to stand up? Psoas leans you forward.
This is important, because this giant muscle doesn't just pull on your leg, he also pulls on and directly influences six vertebrae. This muscle can seriously affect your hip and back mechanics. Which is great, as long as psoas is strong and working harmoniously with the body. He can do wonderful things for a lower back. But the vertebral influence is not so great when our feisty ogre is weak, stubborn, or trying way too hard.
Because of his breadth of abilities and points of action, other muscles in the swamp turn to Pshrek for assistance when they need it. If your ab muscles are underutilized, the body might start calling on psoas to bear more of the burden of trunk movement.
Unfortunately, this can lead to him angrily trying to solve problems alone and making everything worse. Your psoas can begin to influence movements that aren't in his lane, like hip extension, internal rotation, and hip stabilization. Why? Because the root of the problem hasn't been solved (you need better ab strength), but Pshrek is really convinced that if he just gets furious enough, he can do something about it. Typical man.
This false sense of dominance can lead to chronic pain in a lot of places. When we get further in these hip blogs, I'll show you all the different weaknesses that can lead to your psoas doing quintuple or octuple duty in the body, and how to get it to calm the fuck down.
In the meantime, here are some other things to appreciate about your psoas and quads:
The psoas is up close and personal with a whole bunch of your internal organs. The kidneys and adrenal glands sit on a nice little psoas pshelf. The colon runs right on top of it as well, kind of like a rectal slip 'n' slide, if you will. (You probably should not, however.)
And the psoas is so important to healthy body function that it's one of the most commonly-used muscle markers of disease and predictors of mortality. A deteriorating psoas can be a sign of anything from diabetes to heart disease to cancer. People with small psoai tend to die earlier. And poorly-nourished people who increase the size of their psoai through adequate nutrition (not exercise!) while hospitalized end up leaving the hospital sooner than those who do not.
But it gets even crazier when it comes to your psoas. Because the psoas appears to be smack dab in the middle of anxiety, depression, and mood disorders. There's lots of research to show that lower back pain and psychological symptoms are linked. I've found this to be anecdotally true in the gym as well, though neither I nor science knows the ins and outs of it. And in a super cool branch of psych research, psoas features prominently in treating patients who have both lower back pain and PTSD.
Listen, I'm not saying that the psoas is the cause of anyone's depression. But for sure we underestimate the effect that our physical state has on our emotional state. I told you before that psoas major is connected to the diaphragm; your central breathing muscle. The diaphragm is a critical mediator of our sympathetic nervous system (aka the PANIC SYSTEM!!!!!) and our parasympathetic nervous system (aka the There Is A Sleeping Puppy Nearby System).
For people who are chronically stressed/anxious/depressed, we know that the sympathetic nervous system stays engaged, one result of which is altered breathing. These new breathing patterns are absolutely reflected into your psoas and all of its deep connections to the abdomen, pelvic floor, and low back. An Instagrammer I like, Caitlin Hogan, just did four really good posts about this.
We underestimate the effect that our physical state has on our emotional state.
What's that? You want more mystical-but-well-documented science about these muscles? Let's go back to the quads for a bit. The quads appear to be deeply related to the condition of one's heart.
(The following paragraphs are citing research only. I am not any kind of doctor and this is not medical advice. Heart conditions are not meant to be diagnosed or treated by blog. It's just interesting information! If you have any kind of heart concerns or are wondering if exercise could benefit your heart in particular, you must ask your doctor those questions.)
Chronic/congestive heart failure (CHF) is a chronic, debilitating condition(s) where the heart isn't able to work as powerfully or efficiently as it used to. One of the classic symptoms of CHF is exercise intolerance (shortness of breath, fatigue, etc). However, the amount of intolerance is not compatible with the drop in the heart's ability to work. In other words, even with a problematic heart, one would expect only a medium decline in exercising ability based on the output numbers. But people with CHF tend to have enormous problems with exercising ability. So what's the problem, if it's not all in the failing heart?? It's peripheral problems, where the blood vessel/skeletal muscle system in the rest of the body are also malfunctioning.
Which means that improving the peripheral problems—which we know can be done with better exercise and nutrition habits—leads to good outcomes in helping to manage CHF.
What do the quads have to do with it? They've been shown specifically to affect CHF outcomes. This study (and others) have found that the quads tend to get particularly fatigued in cases of CHF. And this study found that improving the quads improved the CHF symptoms. These are tiny but important studies. And larger studies find similar results. This one looked at 1314 subjects. Over the course of several years, they found that strong quads predicted lower mortality rates both in healthy subjects and in those with coronary artery disease.
Why the quads? Well, it's not only the quads, because forearm and grip exercises have been used to show improvements too. But leg pain is a common problem in CHF. So researchers believe that this enormous muscle group holds a particular place of importance when it comes to the flow and return of blood to the legs and back into the heart again. Having some major quad engines funneling fresh blood and nutrients into and out of the legs reduces the amount of work the heart has to do to get blood around your entire body.
Furthermore, loss of quad strength specifically has been demonstrated in other diseases like COPD, diabetes, and fibromyalgia. All of these diseases (including CHF) have shown that improving muscles with exercise has improved the livability of the conditions.
How on earth do all of these seemingly unrelated pieces merge together in the body? Remember that our systems, though separated for study, are not actually separate at all.
* Fascia, which surrounds each and every piece of your body, is highly innervated and provides critical neurological links between structures one might not expect to be linked.
* Muscles are essential to the blood and lymph systems, acting as pumps to get nutrients where they need to go.
* Inflamed tissue will let healthy neighboring tissue know that it's miserable, just like your grumpy Aunt Brenda when she doesn't approve of the city's snow plowing. Our bodies consort in ways that we can't even begin to understand. Just like how humans can affect each other's actions and opinions, so can your body parts. When Brenda's miserable, everyone in the neighborhood is miserable.
The science doesn't know why or how, and neither do I, but it's worth remembering when injuries don't quite go away or you steadily feel like a little bit of shit. I go to Ali Mischke, structural integrationist in Boston for fascial work for this reason and although I cannot tell you why she makes me feel like a new person, I can only say that she does, and usually in surprising ways. If you've been looking for a body treatment that you might not have tried yet, fascial integration might be a good option for you too.
Shrek and Fiona ended up together because they learned how to use their powers in collaboration. Same with your quads and psoas. In future parts of this blog, I'll show you how to integrate them. But before we do that, we know one thing damn well: Shrek and Fiona couldn't do shit without Donkey and Dragon.
In the next blog we're gonna handle the back of the hip joint: your hamstrings and your badunkadunk (glute maximus). Side butt (abductors) and groin (adductors) are gonna get part four. You'll be such an expert by then that you'll be totally ready for part five, when I throw a thousand videos at you to help you train your hips.
It's going tibia-kay, I promise. See you in part three.