Hidden deep within the hips lies one of the most essential—and overlooked—muscles in the human body: the psoas.
When functioning properly, the psoas can give you strong posture, fluid movement, faster running, and even pain-free squats.
But when it goes neglected, it can be the source of everything from back pain to stiff and awkward movement.
In recent online discussions and training deep-dives, fitness expert and content creator Adam Sinicki (aka the Bioneer) explained just how influential the psoas really is—tying it not only to your biomechanics but even to mental and emotional stress.
This guide breaks down exactly what the psoas does, what happens when it tightens up, and how to release and strengthen it for better performance and less pain.
What Is the Psoas (and Why Should You Care)?
The psoas major is a deep hip flexor that connects your lumbar spine to the top of your femur (thigh bone). It’s primarily responsible for lifting the leg and stabilizing the spine.
This movement happens every time you walk, run, kick—or even sit. The psoas is crucial in stabilizing the pelvis and maintaining posture, making it as much a supporting muscle as it is a mover.
Psoas and Its Partners: Iliacus and More
The psoas often works in tandem with the iliacus, a muscle that starts at the inner pelvis and shares a tendon with the psoas to attach to the femur. Together, this duo is called the iliopsoas.
Other hip flexors include the rectus femoris (part of the quadriceps), which contributes to more powerful leg lifts but operates slightly differently from the deeper, stabilizing psoas and iliacus.
What Happens When Your Psoas Gets Tight or Weak?
Sitting for long periods shortens and deactivates the psoas by keeping the hips in a flexed, compressed position. Over time, this leads to:
- Anterior pelvic tilt: The pelvis tips forward, creating an exaggerated curve in the lower back.
- Lower back pain: Due to the lumbar spine being pulled from the tight psoas.
- Inhibited movement: Difficulty squatting, running, or walking fluidly.
- Poor core and postural support: Since the psoas helps stabilize the spine, weakness affects your entire midsection.
Interestingly, there’s also the psoas minor, a smaller variation found in only 40–60% of people. Some researchers suggest this vestigial muscle might be linked to certain cases of back pain or increased spinal compression—but the jury’s still out.
The Psoas as the “Emotional Muscle”
There’s a fascinating and increasingly credible connection between stress and the psoas. Because it shares fascial and nerve connections with the diaphragm at the T12 vertebra, emotional tension—especially chronic anxiety—can manifest physically in the psoas.
“The psoas is activated in a fight-or-flight state to prepare the legs for running,” Sinicki notes. “If you’re always stressed, it gets stuck in high tension, and that leads to chronic tightness.”
This is why practices like diaphragmatic breathing, yoga, and meditation are often recommended for releasing deep muscular tension—not just through stretching but via fully engaging the breath and nervous system.
How to Strengthen Your Psoas
Rather than throwing random ab workouts at the issue, you need to specifically target the psoas and its support crew.
Recommended Psoas-Targeting Exercises:
- Leg Raises: Especially effective when performed slowly and from a lying or hanging position.
- V-Sits: These engage multiple hip flexors, including the psoas, through deep static contraction.
- L-Sits and Pike Pulses: Excellent for training both the iliacus and the psoas simultaneously.
- Marching Drills: High-knee drills, either standing or seated, allow focused flexion on one side at a time.
- Crawling Variations: As in bear crawls, where you flex the hips actively while stabilizing the core.
**Tip:** To hit the iliacus more specifically, do unilateral pike pulses or back-supported drills to lock the pelvis in place. This isolates action to the muscle attaching to the pelvis rather than the spine.
How to Release and Stretch the Psoas
If you’re dealing with tightness, static and dynamic stretching can help. For long-term change, striking the balance between strength and mobility is key.
Best Stretches for the Psoas:
- Warrior Pose: A gentle lunge variation that adds spinal extension to lengthen the psoas.
- Sofa Stretch (Hip Flexor Stretch): Prop the rear leg behind you to exaggerate hip extension.
- Crab Reach: Incorporates thoracic extension and hip openers in a flowing motion.
Always make sure your hips remain square and avoid compensating with trunk rotation, which can reduce stretch effectiveness. Combine these with breathing drills for more impact.
Don’t Ignore Asymmetries
Most people are naturally asymmetrical, due to one-sided dominance, organ placement (your liver is on the right), or repetitive movement patterns, especially in sports.
But if you’re only doing pistol squats or kicks on one leg, or spending hours sitting cross-legged the same way, your psoas may be tighter on one side—causing tilting and compensation issues throughout the kinetic chain.
To correct this:
- Balance your training between both sides (mirror reps, alternate leads).
- Use unilateral exercises like single-leg Romanian deadlifts to observe side-to-side imbalances.
- Incorporate corrective cueing (e.g., keep back foot pointing downwards in hip-hinges).
Could Other Muscles Be Causing the Problem?
The psoas rarely works alone. Tight hamstrings, weak abdominals, unstable glutes, and even poor ankle mechanics can force the psoas to compensate, adding tension and reducing efficiency.
The lesson: Addressing the psoas means approaching the body holistically.
Why Natural Movement Fixes the Psoas—Without You Even Thinking About It
One of the best ways to keep the psoas healthy over the long run? Varied, functional movement.
“If you just move a lot and in varied ways, the body organizes itself effectively,” Sinicki shares. “Trail running, uphill sprints, and swimming all train the psoas and its supporting muscles naturally.”
Try:
- Trail running (especially uphill)
- Swimming (great for decompressing the spine)
- Diverse bodyweight training circuits
- Outdoor activities that move you in unexpected ways (e.g., sand dunes, obstacles)
Final Takeaway: Listen to Your Body
If you’re experiencing chronic back pain, postural issues, or limitations in movement, the psoas could be part of the problem—but it’s likely not the only factor.
Use targeted exercises, mindful breathing, and active stretching to restore psoas function—but also pursue expert guidance and whole-body movement patterns to prevent future issues.
Your psoas might be hidden from view, but its impact on your health, performance, and even emotional balance is impossible to ignore.
“If you want to move like an athlete and feel younger for longer, prioritizing the health of your psoas is one of the best things you can do.”
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