The iliopsoas is a bit of a mysterious muscle. Probably because it’s one of the most ‘hidden muscles’ in our body. To be precise it’s not even one muscle. There are actually two muscles: the psoas and the iliacus. Together they form the iliopsoas. This is an important muscle in your yoga practice, because a ‘short’ iliopsoas restricts you in your back bends, whereas a weak iliopsoas can restrict you in poses like Bakasana and Utthita Hasta Padangustasana C, where you hold your leg parallel to the floor while standing.
Iliopsoas: Psoas major and Iliacus
The psoas major (about 50 percent of the people have a psoas minor as well) originates from the 12th thoracic (T12) vertebra up until the 4th lumbar (L4) vertebra and inserts on the lesser trochanter of the femur. (It’s the top muscle on the picture.) When you engage your psoas you bend (flex) at your hip; lifting up your leg when you’re standing or bringing up your torso when you are laying down. (The psoar also externally (outwards) rotates your femur when your leg is abducted).
As said you engage this muscle to be able to do Utthita Hasta Padagustasana C, Bakasana (crow) and Navasana. Engaging it will also help you to fold forward deeper.
When you’re a little baby this muscle is ‘still sleeping’. Only when you start to walk or try to sit up it’s getting activated.
The iliacus originates on the iliac fossa (inside of the ilium) and inserts on the lesser trochanter of the femur. It joins the psoas major; sharing the same tendon on the lesser trochanter. The job of the iliacus is also to flex at the hip and to externally rotates the femur. So you use it in the same poses as you use your psoas major. You engage and strengthen it when you lift your leg and you stretch it in all your back bends.
Iliopsoas and stress
The iliopsoas isn’t only physically an important muscle; mentally as well. I’ve talked about the reptilian brain before. This brain wants to keep us ‘safe’. If we’re in danger the reptilian brain brings the body in fight or flight mode. The iliopsoas is the first muscle that gets activated, because this is the muscle we need to run or to curl up into a little ball. If we have a lot of stress the iliopsoas is activated (engaged) all the time. As a result it starts to take this shape by shortening which will lead to problems like: low back pain, sacroiliac pain, sciatica, disc problems, scoliosis, hip degeneration and knee pain. Eventually affecting our structural balance, flexibility, strength and range of motion.
But this is not all. Because of the location of the iliopsoas – close to our digestive and reproductive organs – a tight iliopsoas muscle constricts the organs, puts pressure on nerves, interferes with the movement of fluids and impairs diaphragmatic breathing. If you want to know more, check out the work of Liz Koch. She dedicates her ‘life’ to research of the iliopsoas.
The stress reaction also works the other way around. After a long period of stress – which engages your iliopsoas as you have seen – your iliopsoas shortens. Now the reaction starts to work the other way around. Maybe you’re totally zen again on a mental level, but now it’s your short iliopsoas telling your body and brain you’re still in danger and the stress reaction of your body keeps being switched on. Eventually this will exhaust your adrenal glands, leading to adrenal fatigue and it will deplete your immune system.
You’ll find more yoga anatomy on our Yoga Teacher Training Course page.