If I were asked to identify a part of the body that is widely misunderstood, the hip flexors immediately come to mind. This may be partly due to the fact that we colloquially use the term ‘hip flexors’, since that’s easier to say than naming the specific muscles in the group, and partly because a large portion of people I talk with think they know what “flex” means, and they don’t.
Hip Flexors: What they do
The easy answer to the question ‘what do your hip flexors do’ is ‘flex your hip. Well, what is flexing your hip? More times than not, when I ask someone to flex their hip, they don’t know what to do.
Hip flexion may be more easily understood as bringing your leg up towards your torso (or decreasing the angle between your torso and your leg). It doesn’t matter if your knee is bent or straight (though most will perform this action by bending their knee at the same time).
What muscles are the “Hip Flexors”?
If you head in to see a bodyworker and tell them your hip flexors are tight, they’ll know what you mean. That said, the hip flexors aren’t a single muscle that has the common name of hip flexors, they are a group of muscles that work together to perform the action of flexing the hip. So what muscles are they?
The biggest and strongest muscle in this category is going to be the Psoas. I’ve explained a lot about the psoas in a previous post, so I’m going to direct you back to that post for more information. In short, it is the largest and strongest muscle of the hip flexor group, and lies deep under the abdominal contents along the back body near the spine. Psoas (major) hangs out with his friends Iliacus, which sits largely just inside the hip bone, and Psoas Minor, which a) is only present in ~40% of the population and is relatively weak, so we won’t worry too much about the psoas minor in particular.
Next up is rectus femoris, which is grouped in with the quadriceps (which most people know!) and aids in hip flexion because it crosses both the knee and the hip joint. It originates on the front of your hip bone (ASIS, or anterior superior iliac spine) and attaches down below the knee on your shin.
Also in the hip flexor group is sartorius, which holds the title of being the longest muscle in the human body. It runs from the front hip bone (ASIS), descends obliquely across the front of the thigh, and after joining in with the tendons of other muscles (gracilis + semitendinosis), inserts on the front, interior tibia. The sartorius is a pretty wimpy muscle, so think of it more as a helper than a powerful mover.
We also have the TFL, short for tensor fascia latae, which assists in hip abduction (moving your leg across your body) but also lends a hand in flexion, which often goes hand in hand with abduction. (Most of the time, you’ll bend your knee before trying to move it across your body, rather than trying to do so with a straight leg, which will offer a much smaller range of motion).
There are also a handful of small muscles on the medial (inner) thigh that also help with hip flexion. These are all minor players, so I’ll stick to just listing them for now, and we’ll talk about stretching them later. Here you’ll find pectineus, adductor longus, adductor brevis, and gracilis.
Many of these muscles also take part in other actions as well as stabilization, so keeping them happy will get you more than you might think.
Why are the Hip Flexors Relevant?
If your hip flexors are tight (and they probably are, because modern humans sit a LOT, keeping the hip flexors shortened, tight, and angry), there can be repercussions other than painful/tight hip flexors, though that can obviously be a symptom. Tight hip flexors can contribute to lower back pain (if the psoas is pulling either up or down too much on the pelvis, it will tilt it unfavorably in one direction or the other), knee pain, decreased hip mobility, lack of stabilization in the hips and core, balance issues, and more.
If you’re an athlete, the imbalance caused by too-tight hip flexors will cause you to lean forward in many motions (especially squats). Often times, your quads will be working harder than they should, and your glutes won’t be working hard enough if this is the case (there go those booty gains!).
Balancing the Hip Flexors
Most people will fall into the category of having overly tight hip flexors. If this is you, you’ll want to do some stretching and mobility exercises to improve the range of motion. I’ll have a much more in-depth hip flexor stretching routine coming your way shortly, but here are a few basics:
1. Start in a low, static squat, like this. Spend a little bit of time wiggling about to get comfortable, and hold the static stretch for 2 minutes.
2. Next, move into a runner’s lunge. To get there, start in a downward facing dog. Bring one foot between your hands, while staying on the ball of the back foot with your back knee lifted. Wiggle your back toes back as far as you can. Ensure your front knee is bent at a 90 degree angle, and your front knee stays behind your toes. Press back through your back heel, and try to ensure your hips are even with one another. Spend about 2 minutes here once you find the static position.
From here, put your back knee down into a low lunge. Walk the back knee back if you need to, and double check that your front knee has not come past your toes. If it has, walk your front foot up a bit more. From here, go ahead and sink your pelvis down towards your front foot/the floor. When you find a spot where you feel a good stretch but don’t have the immediate urge to get the heck out of that position, hold for 2 minutes.
Repeat the runner’s lunge and low lunge on the other side.
Sit crosslegged on the floor, and sit up as straight as you can. From here, hinge forward at the hips and start to fold over your legs. In this crosslegged forward fold, you may not get very far down, and that’s ok! Your goal is to move to a place where you start to feel some stretch in the back and sides of your hips, and maybe your low back. The goal is NOT to get your head down – instead, imagine that your sternum could reach the floor before your head does – you want to keep a straight(ish) spine. Hold for about 2 minutes when you find the right spot. Re-cross your legs so the opposite leg is in front, and repeat on that side.
Sit up and place the soles of your feet together and bring them in towards your pelvis. This is often referred to as a “butterfly“. It is a-ok if your knees are high in the air – you’re going to spend a few minutes here and let gravity and the magical stretch reflex do their work for some gentle release.
If you find yourself on the other end of the spectrum and have weak hip flexors, you’ll need to do a little work to strengthen them. Mountain climbers are your friend here – IF you move slowly and ensure you’re using the hip flexors to move your knee in towards your chest and not just momentum and accessory muscles.
Lying straight leg raises will also give you a lot of bang for your buck. Lie on the floor on your back with both knees bent and your feet flat on the floor. Extend one leg long, and slowly lift it as high as you can, flexing your toes back towards your face as you do so. Slowly lower the leg back down. While you perform this movement, make sure that your low back is staying down on the ground and not arching up.
Finally, a simple looking yet deceivingly hard exercise – standing single leg raises with a hold. If you’re super weak here, you’re going to want to start with your back against the wall, which will help make sure you’re not bending forward to achieve the desired motion. You’ll stand up straight, bring your weight into one foot, and bend the opposite knee and lift the knee until it is even with your hip on the same side. Hold here, 30 seconds. To amp this up, you can move away from the wall, but be mindful that your hips are even and you’re not leaning forward or back, especially when you’re holding. If you still find this to be super easy, try with a straight leg.
When most people come in for a first session with me, they have some knowledge of their body. Most people know about quads, hamstrings, calves, biceps, and a handful of other muscles, but most people have less overall knowledge of the rest of the muscles – of which there are a lot! Today, we’re going to take a look at the psoas.
Where is it and what does it do?
The psoas is one of the muscles that most people don’t know much about. The psoas is the largest and strongest of the muscles that flex the hip (quite accurately referred to as the hip flexors, as a group). Psoas major and its friend, Iliacus may often be referred to together as “Iliopsoas”, because at their lower attachment, they are usually indistinguishable. Just to throw a little more fun into the mix, we’ll also consider the psoas minor, since it shares a half a name with psoas major.
The psoas major is the longest, strongest muscle of this group, and is found deep to the abdominal contents. It originates from the lumbar vertebrae and travels down to attach on the lesser trochanter, on the back (top) of the femur.
The iliacus is shorter and wider, located deep in the abdomen, originates in the iliac fossa (better understood as the area just inside your hip bone), and attaches at the same spot as the psoas major.
The psoas minor is less relevant, largely because it is only found in around 40% of the population. It originates from the lumbar vertebrae (along with the psoas major) and attaches on the superior ramus of the pubis (so, on the pelvis as opposed to on the femur bone in the leg). Interestingly, it does the opposite of the psoas major – when present, it assists in bringing a posterior tilt to the pelvis (upward rotation).
Because of its location connecting the torso and the legs, your psoas is involved in a lot of different movements – walking, running, sitting, twisting. Hip flexion is the psoas’ major job (bringing your thigh towards your torso or vice versa depending on what position you’re in). In addition to hip flexion, it stabilizes your lumbar spine, and it assists in laterally rotating the hip and adducting it (rotating out and bringing the leg towards the midline).
Why is it relevant?
If you sit a lot (for example, you sit at a desk for work ~8 hours a day), your psoas is shortened while you sit. If you do this often and/or for extended periods of time, they can become short and tight. Short, tight psoas muscles may lead to low back pain (since the muscle originates on your lumbar vertebrae- remember?)
The photo above gives you a pretty good idea of one way the psoas can contribute to low back pain. When the psoas shortens, it gives a downward pull (blue arrow). Since you don’t want to go through life bent over, your body’s response is to right itself (white arrow), and this causes an increase in the lumbar curve (lordosis).
Short and tight isn’t the only problem the psoas can have. It can also become overstretched, which makes it weak. In this scenario, there is a flattening of the lower back, a posterior tilt to the pelvis, and resultant tightening in the hamstrings. The flattened lumbar curve makes one particularly susceptible to disc damage in that area.
Balancing tension in the psoas
Given modern human’s proclivity towards sitting (working at a desk, driving, watching tv, etc), the psoas is often tight, short, and needs to be stretched. But stretching the psoas shouldn’t be your go-to move: there are other considerations.
1. In the first scenario described above – where the psoas is shortened, tight, and yanking the lumbar spine into an increased curvature – the body is in a position where there is a strong pull downward on the psoas. Stretching a muscle that is already being pulled on isn’t the best idea. In this case, you’d be better off contracting the muscle and then relaxing it a few times instead of giving it a traditional stretch. (This contract-relax method is PNF stretching – there’s a good description here)
2. In the second scenario that we described above – where the psoas is overstretched, weak, and there is a flattening of the lumbar curve – the body is in a position where there is a strong upward pull on the psoas. This comes partly from overly tight glutes and hamstrings which are basically taking advantage of the weak psoas and pulling the tension posteriorly. If you stretch the psoas further, it will allow the glutes and hamstrings to pull even more, which puts an even greater load on the psoas – effectively making the problem worse. A better solution here would be to release the tension on the glutes and hamstrings, which will lighten the load on the psoas.