I would like to explain the difference between positional hip flexor tightness and functional hip flexor muscle tightness.
I’m getting way ahead of myself, so let me take a step back, and explain why I want to differentiate between the two. Hip flexors are one of my most favorite muscles, but they get a bad reputation and seem to be poorly understood by most of the people I come in contact with. Let’s first figure out one of their main roles in the body.
What Do Hip Flexor Muscles do?
We therefore start with the question, “What exactly does a hip flexor do?” Well, there are three main muscles that can pick a leg up off the ground. The third choice of the body is the anterior tibialis, also known as the shin. If this muscle works predominately, you inevitably end up with shinsplints on either one or both legs. It’s the furthest from the center of the body and has the least amount of power, and therefore you pay the price pretty quickly and feel it being overworked (actually pulled away from the bone) fast. No fun.
The second choice in the body is the quad (also known as a secondary hip flexor) on the front of the thigh. This muscle seems to be most people’s default muscle to pick the leg up. The problem with the quad working all the time is that in the muscle pairing scenario it knocks out it’s better half the hamstring and dominates that relationship. This limits how much the hamstring can work, but that’s another topic for another blog. 🙂
The first choice to lift the leg up off the ground is the hip flexor, which is a very internal muscle. Take a look at the picture below. This is a front view of your hips, and we have scooped out all of your intestines to get a better look. The hip flexor is made up of two muscles…the psoas and the iliacus. They have the same action, and are grouped together into a blended muscle known as the iliopsoas, or hip flexor.
The psoas starts at the twelfth thoracic vertebrae ( your spine has 3 kinds of vertebrae: 7 cervical or neck, 12 thoracic or middle back, and 5 lumbar or low back) and attaches to two parts of the vertebrae itself: the body, or main thick circular part, and what’s called the transverse process or the little wings that stick out on the sides. Here is a picture of what I am talking about:
Then the psoas comes down and attaches to the inside of the top of the femur or thigh bone. Notice It literally is therefore attaching your low back to your leg via your hip! Consider now it’s best friend and partner in crime, the iliacus. This muscle lines the inside of the soup bowl hip bone itself, and attaches to the very same place the psoas does on the femur.
What is hip flexion?
So what exactly is hip flexion, and why is that important? Well, when you flex a joint you bring it closer together, and when you straighten out that same joint you are extending it. Flexion and extension, two very basic movement concepts.
Here is my daughter Sarah in hip flexion: sitting on this bench glaring at me for fear I will steal her ice cream cone.
Here is my other daughter Annika’s right leg in hip flexion going over the hurdle during a track meet.
What’s the difference? They are both in hip flexion. The hip flexor muscle is being shortened in both cases. Let’s quickly look at a picture of a hip being flexed.
Aaah, but in the track photo, one hip flexor is being functionally shortened because she is actively picking her leg up with that muscle. In the beach picture, the hip flexor is being positionally shortened simply because she is sitting. The interesting thing is the body doesn’t know or care if your hip flexor is positionally or functionally shortened…all it knows is that the muscle is shortened.
So what? Hip flexor muscles need the glute muscle!
Well, let’s not forget that all muscles have a partner in crime that they are paired with. Quad has hamstring, back has stomach, bicep has tricep, and the list goes on and on. Hip flexor’s antagonist muscle is another one of my favorites: the glute, or bottom, or juicy bun-bun. 🙂
If one muscle like we listed in one of the pairs above works all day, every day, what do you suppose happens to it’s antagonist, or partner in crime? For instance, if you walked around in a bicep curl for five years, showing off your Popeye muscle, what would happen to the tricep or back of the arm? The answer is it has to relax. It has no choice but to relax. That is the nature of its relationship with the bicep: one muscle contracts, and the other relaxes. That is how movement takes place!
Sitting is not your friend
In the case of the hip flexor if it’s partner in crime is the glute, what is the body then going to do if you sit all day? Relax the glute, right? Right. However, is your hip flexor actually working to pick your leg up? Extremely unlikely, unless you can feel it in the front of the crease of the hip working. It is shortened, for sure, but only because you are sitting all day. Is your glute working? No. It can’t in the face of a positionally shortened hip flexor…from sitting.
We already talked about how wicked sitting was from a metabolic perspective, and now here it is, even more wicked, from a functional angle.
So, what’s dominant?
This is how I find people with what I call quad/calf/ low back dominance. Your hip flexor doesn’t work because it’s positionally shortened which knocks out your glute; therefore you have no hip flexor and no glute. That leaves the quad to pick the leg up off the ground which knocks out it’s antagonist the hamstring. Now the only muscle on the back half of the body to be left working is the calf. So the calf does the work of the calf, the calf does the work of the hamstring, and the calf does the work of the glute.
If you notice: most people have pretty good-looking calves, very little hamstrings, and little to no glute, to prove my theory. If your glute and hip flexor aren’t working, the body has no choice but to use your low back as the closest neighbor, which means the low back is acting as a low back and a glute. You ask a muscle to do it’s job, and somebody else’s job, and you are going to get complaints! Muscles are just like people: they like to do their job, and not do anybody else’s job.
So tell me, do you think your hip flexors are working for you functionally? Or do you find yourself in the quad/calf dominant category?
Leave me a comment below please!