5 Body Parts You Didn't Know You Had

Sit Bones, Sacrum, Psoas, Piriformis, and Intercostals

Do you know your piriformis from your psoas? If you do, you are probably really into yoga because yoga introduces you to body parts you never knew you had. And once you know about them, you better believe you are going to stretch them out. 

The Sit Bones

The pelvis; the ischial tuberosity is the thick part of the ischium. Stocktrek Images/Getty Images

You may hear them called sits bones or sitting bones. Chances are you didn't hear of them at all until your yoga teacher told you to sit on them. Anatomically part of your pelvis (the ischial tuberosity, to be exact), the sit bones are quite literally the bones under the flesh of the butt that you sit on.

The Yoga Connection: The sit bones are often mentioned in yoga because they affect your posture in seated positions such as cobbler's pose (baddha konasana). It also affects forward bends like seated forward bend (paschimottanasana).

When you sit up straight, you're balancing on your sit bones. You might not feel it because it's a little fleshy thanks to the muscles there. Yet, if you gently rock back and forth while seated, you'll notice a difference and can feel the sit bones.


Sacrum, illustration

Did you know that there is a triangular bone at the base of your spine right above your tailbone? Well, that's the sacrum. It is a common source of lower back pain and home to a number of nerves. The joint where it connects to the hip bones is called the sacroiliac joint (SI joint, for short).

The Yoga Connection: The sacrum is mentioned often in poses in which you are lying on your back. It should usually stay down and your teacher will likely remind you of this often.

The sacrum is stretched and twisted in a number of yoga poses and it's easy to take it too far. That's why you're often told to "protect your sacrum" and one reason yoga movements are slow and deliberate.

Also, it's important to protect the SI joint, which can become misaligned and is a common source of pain in yoga students. Ask your teacher about ways to mitigate and prevent this, particularly if you've injured it before.


The Psoas

The Psoas Major Muscle
The Psoas Major Muscle. SCIEPRO / Getty Images

The psoas major is one of the groups of muscles that are called hip flexors. These work together to bring your leg and torso toward one another into a position of flexion.

The psoas inserts in the upper interior of your femur (thigh bone) at one end. It then passes through the pelvis and connects to several of the lower vertebrae as it fans out at the other end.

The Yoga Connection: Since the psoas is not a surface muscle, it can be difficult to identify and isolate. Its anonymity does not decrease its importance, though.

Indeed, the psoas is key to the cultivation of core strength and hip flexibility. It is particularly important in balancing as well as bending forward and backward.

Strengthening and lengthening the psoas is key for anyone suffering from back pain due to sitting too much. There are a number of poses for the psoas that is perfect if you're a desk jockey.


The Piriformis Muscle

Running right behind the psoas (figuratively, and somewhat literally) for the title of least famous muscle is the piriformis. Stretching this little muscle in your butt can have a big impact if you're dealing with sciatica.

The Yoga Connection: The piriformis is a key muscle in leg rotation, allowing us to turn it outward from the hip. It is also a key to the support system for the sacrum.

It's possible for this little-known muscle to become either too tight or too loose and cause all sorts of pain. When your teacher speaks of "pelvic alignment," the piriformis is often the target.


The Intercostals

External intercostal muscles
The Intercostal Muscles. MedicalRF.com / Getty Images

Ever feel sore around your ribs after a lot of back bending or twisting? Those are your intercostals talking. These muscles are responsible for the expansion and contraction of your rib cage when you breathe.

The Yoga Connection: The intercostal muscles connect to the ribs and your rib cage plays a big role in your practice. It not only allows the lungs to expand and contract, it also affects your posture.

Poses such as cow face pose (gomukhasana) and gate pose (parighasana) can do wonders for stretching and opening up the intercostals. It's easy to neglect these, but the chest is just as important in yoga as any other muscles.