The Most Important Muscle You've Never Heard Of

A tight or weak psoas can cause several physical problems and hinder athletic performance. Learn how to fix it at

The human body is an integrated system. One small issue can throw the entire system out of whack. And sometimes, the root cause can be hard to find.

The psoas is one of the common trouble spots. You may have never heard of it, but that doesn't mean it's not important.

What is the Psoas?

The psoas major is a deep hip muscle that connects the lumbar spine to the upper part of the femur. The lower half of the psoas is joined together with the iliacus muscle—which is why the two muscle groups are often referred to as the iliopsoas. A major network of nerves, which connect the lower spinal cord to the deep abdominal, oblique, hip and quad muscles, travels directly through the psoas in most individuals.

The psoas is generally considered a hip flexor muscle—it shortens the distance between the thighs and torso. Hip flexion occurs when you drive your knees up when running or perform a Sit-Up. It also helps rotate your trunk and stabilize your lumbar spine.

RELATED: The 10-Minute Workout You Should Do Every Day

Why Should You Care About the Psoas?

There's this thing called psoas syndrome. And it's bad.

Sitting puts your hips in a flexed position. Sit for too long and your psoas tightens up. Have you ever been stuck in the car for a long time and felt like, when you got out, you could hardly stand up? That was your psoas fighting back at you.

Since the psoas travels through the pelvis and hips—one of the most mobile joints in the body—and is filled with a huge nerve network—tightness or  weakness can cause several serious problems, such as:

  • Lower-back pain
  • Difficulty standing up straight
  • Anterior pelvic tilt
  • Pain radiating down your thigh to your knee
  • Restricted breathing
  • Excessive lower-back curvature
  • Lower spine stress fracture
  • Scoliosis
  • Poor posture

You get the picture. A problem in this small muscle can cause a cascade of issues. Now imagine how it could affect your athletic performance. If your psoas is tight or weak, it could seriously impair your overall strength, speed, mobility and most important, your durability.

How to Fix Your Psoas

If you're experiencing any of the problems listed above, there's a good chance your psoas may be the culprit. If that's the case, you need to actively stretch and strengthen it.

Mike Boyle, co-founder of Mike Boyle Strength and Conditioning, recommends three moves, shown in the videos above, to correct a dysfunctional psoas. If you're experiencing psoas problems, perform these exercises at least four times each week. If your psoas seems fine, you should still add the moves to your routine two to three times per week to prevent future problems.

Box Hip Flexor Stretch

  • Position your rear leg on a downward angle.
  • Keep your abs tight.
  • Tilt your pelvis backward slightly.

Sets/Duration: 1-2x20-30 sec. each side

Psoas Holds

  • Hold your thigh up so it's above parallel.
  • Keep your back straight.

Sets/Duration: 3x10-20 sec. each leg

Plank Hip Flexion

  • Slide your leg forward.
  • Do not move your lower back.
  • Isolate the hip action.

Sets/Reps: 1x8-12 each leg

RELATED: 2 Exercises That Every Athlete Should Try 


  • Kirchmair, L., et al. (2008) "Lumbar plexus and psoas major muscle: not always as expected." Regional Anesthia and Pain Medicine. Mar-Apr;33(2):109-14.
  • Sutherland W., (1990). Teachings in the Science of Osteopathy. Portland, Oregon: Rudra Press, 279-281.
  • Michele A., (1962). Iliopsoas. Springfield, Illinois: Charles C. Thomas.
  • Tufo, A., et al. (2012). "Psoas Syndrome: A Frequently Missed Diagnosis." The Journal of the American Osteopathic Association.

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