Most yoga students are aware that the psoas is a central player in asana, even if the muscle’s deeper function and design seem a mystery. A primary connector between the torso and the leg, the psoas is also an important muscle off the mat: it affects posture, helps stabilize the spine, and, if it’s out of balance, can be a significant contributor to low back and pelvic pain. The way that we use the psoas in our yoga practice can either help keep it healthy, strong, and flexible, or, conversely, can perpetuate harmful imbalances.
The psoas is a deep-seated core muscle connecting the lumbar vertebrae to the femur.
The psoas major is the biggest and strongest player in a group of muscles called the hip flexors: together they contract to pull the thigh and the torso toward each other. The hip flexors can become short and tight if you spend most of your waking hours sitting, or if you repeatedly work them in activities like sit-ups, bicycling, and certain weight-training exercises.
A tight psoas can cause serious postural problems: when you stand up, it pulls the low back vertebrae forward and down toward the femur, often resulting in lordosis (overarching in the lumbar spine), which is a common cause of low back pain and stiffness; it can also contribute to arthritis in the lumbar facet joints. On the other hand, a weak and overstretched psoas can contribute to a common postural problem in which the pelvis is pushed forward of the chest and knees. This misalignment is characterized by tight hamstrings pulling down on the sitting bones, a vertical sacrum (instead of its usual gentle forward tilt), and a flattened lumbar spine. Without its normal curve, the low back is weakened and vulnerable to injury, especially at the intervertebral discs.
The way that we use the psoas in our yoga practice can either help keep it healthy, strong, and flexible, or, conversely, can perpetuate harmful imbalances.
To help you create balance in the psoas and keep your low back healthy, it is important to first understand the anatomy. Then you’ll see why the psoas is integral to asanas as diverse as navasana (boat pose) and setu bandha sarvangasana (bridge pose), and how to engage and stretch this massive muscle for optimal benefit.
How to Find the Psoas
Although the psoas is one of the most important muscles in yoga poses, it is also one of the most misunderstood. Many students and even teachers have only a vague idea of where it is located. The psoas originates from the lumbar vertebrae and forms a strip of muscle almost as big as a wrist along each side of the spine. Looking at the front of the body, you’d have to remove the intestines and other digestive organs, as well as the female reproductive organs, to be able to see the muscle in the very back of the abdomen. It proceeds down and forward, crossing the outer edge of each pubis, then moves back again to attach on a bony prominence of the inner upper posterior femur (thigh bone) called the lesser trochanter.
The psoas affects our posture and helps stabilize the spine. If it’s out of balance, it can be a significant contributor to low back and pelvic pain.
Along the way, the psoas picks up its synergist, the iliacus, which originates on the inner bowl of the pelvis (or the ilium) and joins the psoas on its path downward to attach to the femur. The two muscles work so closely together that they’re usually referred to as one, the iliopsoas. The other hip flexors include the sartorius, the tensor fascia lata, the rectus femoris, the pectineus, and the adductor brevis. Besides flexion, these muscles might also contribute to the internal or external rotation of the hip. This action is important for yoga practitioners to understand because the psoas may try to externally rotate the hip in poses where we don’t want external rotation, such as backbends or forward bends.
Awakening the Psoas
Now that you have a picture of the psoas in your mind, let’s see if you can feel it contracting. When the psoas contracts, it will pull the femur and the spine closer together (hip flexion). If you are lying on your back, contracting the right psoas will help lift your right leg off the floor as in supta padangusthasana, or reclining big toe pose. If the back of your leg is flexible, you may be able to bring it toward your torso past perpendicular, but the psoas stops contracting at about 90 degrees, when the leg is vertical. At that point, gravity is no longer pulling the leg back toward the floor, so the hip flexors can relax. On the other hand, if the back of your leg is tight and you can’t bring your leg to the 90-degree point, the psoas contracts the entire time you hold your leg up, even if you have a strap wrapped around your foot. By definition, this is an isometric contraction: the muscle is working, but not changing length. Anytime you’re holding a body part against the pull of gravity, it’s an isometric contraction.
Navasana is another yoga pose that strengthens the psoas isometrically. You can feel the basic action of the psoas in navasana while sitting on a chair. Sit tall on the front edge of the chair, with your arms stretched out in front of you, parallel to the floor. Then lean toward the back of the chair without touching it, while keeping your chest lifted. As soon as your body inclines backward past vertical, gravity is trying to pull your torso down toward the earth, and the psoas contracts to hold you cantilevered.
To apply this action in navasana, move to the floor and sit tall (up on your sitting bones, not rolled back on your tailbone) with your knees bent and feet flat. Wrap your fingers lightly around the tops of your shins and give a little pull to help lift your chest, then lean back until your elbows are straight. Let go of your shins, keeping your arms parallel to the floor, feet on the floor, and chest lifted. While this is a mild beginner’s version of navasana, you’ll be doing some nice isometric strengthening of the psoas as well as of your back and abdominal muscles.
If you’d like to move into the full pose, tip your torso back a little farther, lift your feet off the floor, and find your balance. Even with your knees still bent, the psoas has to work harder, as it’s now holding up the weight of your torso plus the weight of your legs against gravity’s pull. You can stay here for several breaths, or go ahead and challenge the muscle even more by straightening your knees. In the full expression of navasana, the psoas acts like a guy-wire between your spine and the thighs to hold the beautiful V shape of the pose. This is a challenging pose, working not only the psoas, but also the abdominals, the back muscles, and the quadriceps; if you are a beginner, try working regularly on the preparatory steps to gradually build strength for the full variation.
Releasing the Psoas
After you’ve warmed and worked the psoas through contraction, it’s an ideal time to stretch and lengthen it. In order to stretch any muscle, we must do the opposite of its action; in this case, we’ll need to extend the hip, moving the lumbar spine and the femur away from each other. Because the psoas is a big and potentially strong muscle, you’ll be able to lengthen it most effectively by stretching one side at a time in poses such as anjaneyasana (lunge pose) and virabhadrasana I (warrior pose I), where the hip of the back leg is in extension.
A good way to isolate the psoas stretch, whether you’re a beginner or an experienced practitioner, is to practice virabhadrasana I in a doorway. Find an open doorway (or a pillar) and step up close so that the right side of your body is just behind the door jamb. Step your left leg through the doorway, and place your right foot two to three feet behind you, with that back heel off the floor. Stretch your arms overhead and rest your hands on the wall. Bend both knees slightly, and align your pubic bones, navel, and breastbone with the door frame.
The whole key to stretching the psoas is in the tilting of the pelvis. Remember, a tight psoas tries to tilt the pelvis anteriorly (pulling the spine and top of the pelvis forward and down), so you must tilt the pelvis posteriorly to stretch the hip flexors. The door can help you achieve this action: simply move your pubic bones toward the door jamb, your upper pelvis and navel back away from the jamb, and draw your breastbone toward the jamb. These actions help you tilt the pelvis posteriorly, move the lumbar spine toward the back of the body (instead of letting the tight psoas pull it forward and down), and lift the rib cage vertically up out of the low back. Altogether, you’ll be lengthening the psoas and relieving compression and discomfort in the low back.
When you’re ready to deepen the stretch, straighten the back knee fully (let the back heel stay off the floor, especially if you’re a beginner or have knee or low back problems), and gradually bend the front knee more. If you’re not getting a deep stretch on the front of the right hip, redouble your efforts to bring the pubic bones toward the wall, and the navel away, and bend the front knee more. Hold the pose for a minute or more, keeping your breathing slow and steady to help the muscle relax into a deep stretch. Then repeat on the other side.
Setu Bandha Sarvangasana
Now that you’ve stretched your psoas, you’re ready to work on backbending poses, which require full extension in both hips. In setu bandha sarvangasana, for instance, tight and short psoas muscles will tilt the pelvis anteriorly as you lift your pelvis off the floor, causing sharp compression in the lower lumbar vertebrae. So it’s important to prepare your body for backbending by first stretching the hip flexors, especially if you lead a sedentary lifestyle.
When you’re ready to work on bridge pose, lie on your back with the knees bent and the feet flat on the floor, hip-width apart, heels pulled in close to your sitting bones. Place a block between your feet, grounding down through the big toe and inner heel, and squeeze a second block between your knees. The blocks ensure that your thighs remain parallel throughout the pose to prevent the psoas muscles from externally rotating the hips while extending them, which can contribute to low back compression and knee pain.
By incorporating poses that strengthen and lengthen the psoas, you can release habitual muscle-holding patterns, improve your low-back alignment, and create a more balanced posture.
When you begin to lift your pelvis off the floor, lift your tail-bone first. This simple action sets the pelvis into a posterior tilt, and, if your hip flexors are lengthened enough, helps you keep space in your low back. As you continue to roll up into bridge pose, press your pubic bones up into the skin of your lower abdomen. Hold the pose for 20 to 30 seconds. Repeat the pose two more times; as the hip flexors lengthen, you may find that you can go deeper and lift higher.
A well-balanced asana practice helps keep your muscles strong enough to do their job and flexible enough to allow full range of motion of associated joints. By incorporating poses that both strengthen and lengthen the psoas, you can release habitual muscle-holding patterns, improve your low-back alignment, and create a more balanced and spacious posture.
This article originally appeared in the Spring 2011 issue of Yoga International.