The Psoas: That (Too) Often Overlooked Muscle That Directly Influences Our Back and Posture

Sophie Lyon
Jan 29
3 min read

Did you know that your lower back pain might be related to a deep muscle located at the junction between your torso and legs? This muscle is called the psoas, sometimes referred to as the “muscle of the soul” in certain traditions, given its key role in posture, mobility, and even emotional well-being. In this article, we’ll explore why the psoas is so important, how it can be the source of back pain, and what you can do to keep it healthy.

I- What Is the Psoas and Where Is It Located?

The psoas is a deep muscle that connects the spine to the femur (thigh bone) by passing through the inside of the pelvis. More precisely, it starts from the twelfth thoracic vertebra (T12) and the first lumbar vertebrae (L1 to L5), runs along the inside of the ilium, then merges with the iliacus muscle before inserting on the lesser trochanter of the femur. This combined structure is often referred to as the iliopsoas muscle.

Main Functions:

✔️ Flexing the hip (lifting the thigh toward the trunk)

✔️Slight external rotation and adduction of the thigh

✔️ Stabilizing the lumbar spine

« The psoas is much more than just a hip flexor; it is a messenger of our central nervous system, a true ‘muscle of the soul’ that mirrors our emotional state and shapes our overall posture. » — Liz Koch.

II- How Does the Psoas Affect Lower Back Pain?

📌 Too Tight or Overused: When the psoas is constantly contracted (due to poorly performed exercises, intensive training, or chronic stress), it can pull on the lumbar vertebrae, causing excessive tension in the lower back and contributing to lumbar pain.

📌 Too Short and Weak: Prolonged sitting (office work, frequent travel, etc.) or a lack of physical activity can shorten and weaken the psoas. A “shortened” psoas increases the lumbar curve (lordosis) and raises the pressure on spinal discs, potentially causing or worsening back pain.

📌 Pelvic Misalignment: A stiff psoas often creates imbalance in the pelvis, affecting overall posture. Other regions of the spine (thoracic, cervical) may compensate, resulting in chronic tension.

III- Anatomical and Functional Connections of the Psoas

With the Diaphragm

📌 The psoas and the diaphragm share common attachments in the lumbar region (around T12 to L3). Their proximity creates fascial and muscular continuity, so a tight psoas can limit diaphragm mobility and hinder breathing, and conversely, a tense diaphragm can increase tension in the psoas.

📌 With the Intestines and Reproductive Organs

The psoas is in direct contact with the intestines and close to the reproductive organs. As a result, intestinal inflammation (colitis, irritable bowel syndrome, etc.) or temporary inflammatory states (such as menstruation) can irritate the psoas and trigger lower back pain.

IV- Why and How to Care for Your Psoas

1. Regular Stretching

Targeted stretches of the iliopsoas help maintain flexibility and prevent tension.
Avoid sudden or overly intense movements: choose progressive, longer-held stretches.

2. Strengthening and Good Posture

Comprehensive core strengthening (planks, Pilates, yoga) supports the spine and helps prevent overuse of the psoas.
Adopt an ergonomic sitting position: adjust your chair height, keep your feet on the floor, and take regular breaks to walk and stretch.

3. Breathing Exercises

Working on diaphragm mobility (mindful breathing, cardiac coherence, etc.) can relieve tension in the psoas.
Learning to better manage stress and anxiety (which often cause the psoas to tense up) can also reduce back pain.

4. Hydration and Lifestyle

Drinking enough water and maintaining a balanced diet helps limit inflammation.
Gentle activities such as walking, swimming, or cycling can help keep your range of motion healthy.

5. Consulting a Professional

If pain persists, it’s essential to see a physical therapist, osteopath, or doctor to assess the situation, release tension, and develop a suitable rehabilitation program.

In few words

The psoas is a genuine pivot between the upper and lower body and plays a major role in spinal stability, posture, and respiration. Whether it’s too tight or too short, this muscle can significantly affect your comfort and may be responsible for lower back pain that’s sometimes difficult to pinpoint.

Taking care of it means taking care of your back and overall well-being. So, remember to include strengthening, stretching, and breathing exercises in your daily routine to keep your psoas flexible and healthy!

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