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What is the Iliacus Muscle and What Does it Do?

Part of the iliopsoas muscle group, the iliacus muscle is an important muscle to keep flexible and strong so you can lift heavy and avoid pain.

Stretching from the top of your hip bone down to the top of your femur, the iliacus muscles are a twin pair or triangular-shaped muscles that are used to rotate the legs, specifically providing flexion to the hip.

This muscle is tucked inside the hip bone and is a muscle which is often ignored alongside its better known brother, the psoas major. However, it’s important to look after both muscles in tandem, as they are vital for providing the power to lift heavy weights, as well as perform functional movement like walking and running.

What is the function of the iliacus muscle?

Together with the psoas major, the iliacus flexes the hip. Both muscles are known as the iliopsoas

These two muscles are important in providing hip flexion and in stabilising the lower back. Furthermore, the two muscles that make up the iliopsoas are considered the most powerful muscle in the hip flexor group. They allow your hips to move and propel your lets forward.

anatomy of the hipSource: Wikipedia
Anatomy of the hip flexors

When lying flat in a supine position, the iliopsoas is responsible for keeping your torso straight. The iliacus muscle is located deep in your abdomen, and is responsible for the rotation and flexion of the femur. This is a muscle used while walking, and along with the psoas, can become tight, causing issues in the back and hip.

It is important to keep both muscles of the iliopsoas healthy and strong, as they also play a big role in functional fitness.

What causes iliacus muscle weakness?

Iliacus muscle weakness has many causes, and is linked to decreased ability to flex the hip joint, as well as difficulty bringing the trunk forward when standing up, or ability to walk up an incline.

Source: Photo courtesy of CrossFit Inc.

If you’re a runner, your stride will be shorter, due to the tightness of the muscle. It could also be linked to the development of an anterior pelvic tilt. You can also damage your iliacus muscle by improper or lack of stretching.

According to Breaking Muscle, this can also impact your weightlifting:

"Many have heard of the “power triangle” in weightlifting - in this position the hips are flexed and the trunk is forward. With weak iliopsoas muscles you will have difficulty getting into this position, which means you lose out on potential power you can create in this area. So, you may not make gains you would like in the lift. Iliopsoas weakness also causes instability at the squat portion of these lifts, which can cause discomfort to the athlete."

The trick to avoiding any issues in your iliacus or psoas muscles is regular stretching and strengthening. Building the muscles in the hip flexors will help agility, speed, and strength.

Exercises to stretch your iliacus muscle

As part of good mobility training, athletes should always devote some time to stretching their hips and releasing any tightness in the muscles

Low Lunge

A popular yoga move that will open up the hips, the low lunge will stretch your iliacus muscle (and should feel really good!) A low lunge is performed by staring off on your knees. Sit upright, and pull one leg forward, keeping the other leg flat on the ground. Push your hips forward to feel the stretch.

Iliopsoas stretch programs
Iliopsoas stretch

Always go to around 80% for any stretch as you do not want to hurt yourself or develop any scar tissue from trying to overcompensate. If your iliacus muscle is tight, only stretch so far as it is comfortable.


With your back flat on the ground and your knees pointing towards the sky, push off your feet to create a bridge. Use your hamstrings, glutes and core to hold the position. This is a great one for stretching the muscles in your hips and building strength in your lower back.

Side-Lying Iliopsoas Stretch

If your iliopsoas is particularly troublesome, try a side-lying stretch. Lying on your side with your knees at a 90 degree angle, grab the top ankle with one hand and pull the leg back. Make sure you don’t arch your back to reach your ankle, and use a strap if you can’t reach.

You should feel the stretch all along the front of your hip.

Exercises to strengthen your iliacus muscle

Once your iliacus (and iliopsoas) is nice and loosened up, it’s time to work on building the strength up so you can squat heavy and avoid hip issues.


A great exercise for core strength, V-sits target the iliopsoas muscles too. Starting by sitting upright on the floor, bright both legs up off the floor at a 45 degree angle, and learn your torso back.

Use your arms to balance, and hold this isometric movement for 5 – 10 seconds. The balancing aspect will engage your iliacus muscle and help build strength.

Hanging Leg Lifts 

While hanging from a bar, bring your knees up to your chest in controlled movements. Once again this will engage your core and iliopsoas, building strength in the hips. This exercise will grow your grip strength, and challenge your upper back muscles and hip flexors. It’s one of the exercises to master before you attempt an unbroken set of toes-to-bar, and therefore requires a strong and flexible iliacus muscle to perform.

Bridging Psoas March

Taking an isometric exercise and adding movement makes the exercise more dynamic and helps build more strength.

Using a resistance band and raised surface, perform the bridge as you normally would, with your feet on the raised surface. With the resistance band wrapped around both feet, engage your core and pull one leg towards you, and then the other, in a marching movement. The goal is to engage your hip flexors, so that is where you should feel the burn.

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