The Opinionated Psoas, Part 2

By Thomas Myers

By Illustrations by Andrew Mannie

Originally published in Massage Bodywork magazine, April/May 2001.
Copyright 2003. Associated Bodywork and Massage Professionals. All rights reserved.

FIG. 1A: In most four-legged creatures of our common acquaintance, the psoas major muscle does not touch the pelvis. Instead, it passes directly from the spine to the femur.
We left off last time discussing the psoas muscle, having concluded it was a hip flexor. We also put forward a set of arguments that suggested, in summary, the psoas is neither a significant medial nor a lateral rotator of the hip. In this issue, let's continue our discussion, looking now at the upper part of the psoas to see how it might affect the lumbar spine. As with last time, let us be certain of the following caveat: these are simply thought-provoking ideas, opinions untried in the halls of science -- in fact I am about to quote some scientific evidence against my argument. Take these ideas with a grain of salt, and believe only, as the Guatama Buddha said, in "when the writing, doctrine or saying is corroborated by reason and consciousness."

FIG. 1B: Your cat or dog will extend the femur (and stretch the psoas) in walking or running. If you manually extend the femur further, you will feel resistance, from both the tissues and the animal's willingness, well before the femur is lined up with the spine. As you approach that point, however, the animal's psoas will be curving around the hip joint.
In most four-legged mammals, the psoas muscle goes directly from the lumbar spine to the leg without touching the pelvis (Fig. 1A). Humans have swung the pelvis, and indeed the entire spine, up vertically in such a way that the resting position of the standing hip is much more extended than your dog or cat would be comfortable with (Fig 1B). The result for the human psoas is that it now is bent around the front of the hip joint, going forward from the femur to the iliopectineal rim of the pelvis, and then back from this edge to the spine (Fig. 1C). This convinces us it is a hip flexor, because of the forward and upward angle of the pull of the femur, but what does it say about the pull of the psoas on the spine?

What it says is something very similar: the line of pull of the psoas on the spine runs not directly from the origin to the insertion, but from the origin (the bodies and transverse processes of T12 to L5) down and forward to the rim of the pelvis, in front of the hip joint. Keep this in mind as we present our argument.

FIG. 1C: For a human, having the hip extended to where the femur is in line with the spine is the normal standing position. It is thus normal, in human standing, for the psoas to bend around the pelvis and hip joint in its journey from the spine to the femur.
If we look at the standard authorities' listings for the functions of the psoas on the lumbar spine, we find it is listed as a spinal extensor, or postural hyperextensor. In other words, if extra short or tight, it would lead to a swayback. Many expert opinions seem to vary indefinitely on the subject, often suggesting contradictory information. In Grant's Method of Anatomy, J. V. Basmajian writes, "The psoas has a minor effect on the lumbar segments of the column (increasing the lumbar curvature)."1 W. H. Hollinshead, in Functional Anatomy of the Limbs and Back, writes, "[The psoas's] pull upon the anterior portion of the lumbar vertebral column results in an increase in the normal lumbar curvature, thus producing lordosis."2 And Bogduk, this decade's authority, dismisses the psoas's effect on the lower back altogether: "Biomechanical analysis reveals the psoas has only a feeble action on the lumbar spine with respect to flexion and extension. Its fibers are disposed so as to extend the upper lumbar segments and to flex the lower lumbar segments. However, the fibers act very close to the axes of rotation of the lumbar vertebrae, and so can exert only very small moments, even under maximal contraction. This denies the psoas any substantial action on the lumbar spine."3

With almost no evidence at all other than my "reason and consciousness" -- my clinical experience -- I actively disagree with every sentence in this last quote. Nor am I alone. Some recent EMG measurements have shown in the human body a psoas contraction is often used to hold the lumbars posteriorly.4 Another authority, at least in my life, Dr. Ida Rolf, contradicts Bogduk by writing, "If the body is normal, the psoas should elongate during (trunk) flexion and fall back toward the spine."5 Suffice it to say there is some disagreement with regards to the psoas's function on the lumbar spine.

FIG. 2A: Lying on our back with our knees up approximate the normal hip position of a quadruped, and it is a good position to play with the different functions of the psoas.
To make sense of all these conflicting ideas, we need to dissect the psoas a little. Either of the above statements depends on seeing the action of the psoas muscle as a whole, as a singular and discrete unit of movement. But we know, from our study of other muscles, that 'one muscle, one action' is not always the case -- there are often several functions, sometimes conflicting, within any given muscle. Think about the deltoid. This is also one distinct muscle, in its fascial casing. If you abduct your shoulder, the deltoid acts as one unified muscle to lift the humerus to the side. But now swing your arm horizontally, still abducted, so that your hand comes around in front of you, and the deltoid splits functionally into three distinct muscles. The middle deltoid remains contracted as a fixation muscle, the anterior deltoid helps out in the horizontal forward flexion, while the posterior deltoid becomes its antagonist and must relax to allow your arm to go forward. Take the arm back behind you. The anterior and posterior sections of the deltoid reverse roles, with the posterior creating the movement and the anterior relaxing to allow it to happen. The middle part contracts the whole time to maintain the abduction.

FIG. 2B: With the back arched into hyperextension, we contend that the lower fibers of the psoas are brought primarily into play.
Although the predominance of mechanistic thinking in our anatomical training has led us to think of each muscle as being a discrete unit with a singular function, we can see from this example this is simply and obviously not true in the case of the deltoid. Could such an argument be applied to the psoas?

Our argument is going to be that while part of the psoas certainly acts as an extensor of the lumbars, this is not true for all of the psoas. We can be forgiven for thinking the psoas has only one line of pull. Look at our opening figure and the psoas major looks like a fusiform muscle (cigar or spindle-shaped, like the biceps brachii or femoris), with one clear line of tension. Look at Fig. 1A, however, and you will see clearly that the psoas in a four-legged animal is a triangular muscle. It has a wide base of origins, narrowing together to one pointed insertion at the lesser trochanter. In other words, it could be considered to be six separate muscles -- from T12 to the lesser trochanter, L1 to the lesser trochanter, and so on down to L5 to the lesser trochanter. Our contention is that the muscle, despite appearances, operates on the lumbar spine in a similar way to our example of the deltoid -- one muscle with different opposing functions within it.

FIG. 2C: In lumbar flexion, the upper fibers of the psoas assist the rest of the abdominals to lift the ribs and flatten the lumbars against the floor.
First let's get ourselves into a similar position as the rabbit. Since walking around on our "paws" is not so easy for us, just lie on your back with your knees up. Your hip is now flexed, and the psoas passes more directly from the spine to the lesser trochanter, without touching, or at least without changing direction around the rim of the pelvis.

In this position, if you lift your foot off the ground, the psoas would clearly contract to flex the hip and support the weight of the leg. You can feel this if you hook your fingers on the inside of the iliac crest, pressing down along the iliacus toward the psoas. For most folks, you do not have to press down very far to feel the psoas leap into action at the very first movement of the foot. This is the action of the psoas as a hip flexor, which is not under contention.

But now, try two other movements in this position. First, arch your lower back off the floor, taking yourself into an anterior pelvic tilt. This is also a hip flexion movement, and so should engage the psoas. I will wager, however, if most readers, put their hand again on the inside of the hip bone, they will not feel the outer part of the psoas contract as they perform this movement. Most of the power for this movement will probably come from the spinal erectors, contracting to bring the sacrum and the mid-back closer together. If you do the movement strongly, the iliacus, between your finger pads and the hip bone, will probably contract to flex the hip as well. The rectus abdominis and the other belly muscles will relax, through reciprocal inhibition, to allow this to happen. If you can, feel along the psoas muscle to the inner, medial fibers and you will find they are helping the erectors make this movement happen.

FIG. 3: With the idea that the different slips of the psoas could act in differing ways, we can see that the upper part would act on the lumbar spine in an opposing way to the lower part - the upper part pulling T12 forward into lumbar flexion, while the lower part would pull L5 forward into hyperextension.
Now try another movement: from lying on your back with your knees up, slowly curl into a crunch, lifting the head, ribs and thoracic spine off the floor. This time, I bet, you will feel the lower back pressed into the floor. The sternocleidomastoid and the abdominals (all elements of the Superficial Front Line of myofasciae -- see "Anatomy Trains," Massage Bodywork, April/May 2000) will contract to lift the head and rib cage off the floor. Since the abdominals are in use, the erectors, again by reciprocal inhibition, relax, allowing the lumbars to flex, or flatten into the floor. As you continue this action, the psoas will come into play as the lower rib cage is lifted, bringing T12 closer to the lesser trochanter -- in other words, using the upper part of the psoas to help create lumbar flexion. It is difficult to feel this because the abdominals are going to be fully contracting during this movement, making it more difficult to feel the psoas. But if you put your hand just outside the edge of the rectus abdominis and push into your belly before you start the movement, you may feel it is those outer, upper fibers of the psoas which contract to make this movement.

If this is the case, then we are seeing the psoas used for lumbar flexion, instead of solely lumbar for hyperextension, as most books will tell you. Now, let's go back to standing. In standing, the human hip goes way out to extension, as in Fig. 1B or Fig. 3, but the line of pull of the psoas, as regards the spine, changes only a little, because the muscle takes a turn around the lip of the iliopectineal ridge, just anterior and superior to the hip joint. The lower, inner fibers of the psoas will still pull L4 and L5 forward, pulling the pelvis along with them into an anterior tilt. The upper, outer fibers of the psoas will still pull T12 and L1 toward the front of the pelvis -- in other words, they will create lumber flexion.

Once again, this is an opinion only: the psoas is its own antagonist regarding lumbar flexion and hyperextension. The lower inner fibers tend to produce lumbar hyperextension; the upper outer fibers tend to produce lumbar flexion. If the muscle is balanced within itself, it will balance the lumbar spine in and of itself, without reference to the other muscles surrounding it.

What is the significance of all this, even if it is true? If you start from the premise that the psoas is a spinal extensor only -- as the books do, and as Ida Rolf did when I trained with her -- then the way to reduce a lumbar lordosis, or swayback, would be to lengthen the psoas, which lots of bodyworkers do. Or if you consult a physiotherapist or an athletic trainer, they will recommend you tone up the rectus abdominis (which obviously produces lumber flexion and will thus counteract the tendency of the psoas to produce hyperextension).

I have problems with both these solutions. If the psoas is tight and the lumbar curve is hyperextended, then adding more tonus to the rectus abdominis, on top of the tension already there in the psoas, is likely to put increasing pressure on the lumbar discs, increasing the possibility of a protruding or even a herniated disc.

But if we, as manual therapists, work to lengthen the psoas as a whole, we will not achieve our goal either. I worked this way for many of the early years of my practice, working the psoas as if it were a unitary thing. Now I differentiate the psoas into three muscles, like the deltoid -- and I work separately on the lower, middle and upper fibers of the psoas, depending on the individual pattern in the lumbar spine.

Although we do not have the space in a column to go into this in all its glorious details, we can still outline the strategic considerations. If we are looking at the lumbar lordosis, then what we want is to lengthen and loosen the lower fibers of the psoas, while retaining the fascial tension in the upper fibers. A look at Fig. 4 shows us how we can do this -- to reach the fibers that pull forward directly on L4 and L5, we must lengthen the fibers which run along the medial side of the psoas sausage. Because there are lots of visceral extras here, like the iliac arteries and the ureters, we need to be careful. Find the outside edge of the psoas, letting your supine client (with his knees up) lift his foot off the ground if you get lost, and walk your finger carefully over the bulk of the muscle, arriving on the inside slope. Again check where you think you are by having him lift his leg. The feeling for the client may be a bit scary because you being there is a novelty, but there should not be undue pain at all. Note: Please desist in the face of distress. Now the client can perform the stretch -- have them step onto the foot, and at the same time tip the pelvis into a posterior tilt to press the lower back against the table. You can repeat this several times, or until you feel the inner fibers of the psoas opening.

If we are looking at a flat back or a posteriorly tilted pelvis, then we have to start looking at the lateral rotators, but as far as the psoas goes, we want to lengthen the longer fibers and tone up those inner, lumbar extension-producing fibers. We don't want to work directly on the upper part of the psoas itself -- anywhere above the navel, really -- because of the possibility of damaging a kidney or its delicate blood supply. But a look at Fig. 4 assures us the upper fibers are also the outer fibers, so we can work on the lateral fibers of the psoas, secure we are working on those fibers that come from T12 -- L1 on their way to the pelvic rim.

Fig 4: It is very difficult (and dangerous for the client's kidneys) to reach the upper part of the psoas muscle directly. But we can reach those fibers specifically, as this diagram shows us, when we understand this simple equation: the outer fibers = the upper fibers, and the inner fibers = the lower fibers. The fibers from T12 and L1 pass down the outer edge of the psoas, while the fibers from L4 and L5 pass down the inner edge of the muscle.
Of course, I believe in the preceding opinion -- it works for me in my practice, and has significantly refined my work from the old "now let's get to the psoas," or the shotgun "pin-and-stretch" methods of my early career.

Of more general significance, however, is the idea the psoas can, by opposing itself in this antagonistic way, support the lumbar spine without help from the surrounding muscles. In other words, you could have washboard abs or washtub abs and still support the lumbar spine adequately. Just because you have a soft belly and breathe easily into the abdomen does not mean you will have a saggy lower back. Or if you prefer the rock-hard belly, you can still maintain adequate responsiveness in the lumbars (which is diminished or lost, for instance, in some dedicated runners).

Balance and movement in the lumbars depends on the balance among four layers of myofascial tissues -- the abdominals, the psoas, the quadratus lumborum and the back muscles. Understanding the complex role of the psoas in the middle, and acting to treat it like the several different muscles that it is, will help the others to release and maintain both stability and responsiveness in this central spring of the human mechanism.

Well, if we haven't lost you totally in this tour of the psoas, then we invite you back for one more swing at it next time, when we will explore what happens when the psoas on one side of the spine is significantly shorter than the psoas on the other.

Thomas Myers, Certified Advanced Rolfer(R), LMT, NCTMB, studied directly with Drs. Ida Rolf and Moshe Feldenkrais, and has practiced integrative bodywork for more than 25 years in a variety of cultural and clinical settings. Myers directs Kinesis, Inc. which develops and runs training courses internationally for manual and movement therapists. He served as a founding member of the NCBTMB, and as chair of the Rolf Institute's Anatomy faculty. His articles have appeared in a number of magazines and journals, and a book is now underway on his "Anatomy Trains" Myofascial Meridians approach. Myers retains a strong interest in perinatal and developmental issues around movement. His practice in Boston combines structural integration, physiological rhythmic sensitivity and movement. He lives, writes and sails on the coast of Maine.

1. Basmajian, J. V., Grant's Method of Anatomy (Lippincott, Williams Wilkins: New York, 1984) 264.
2. Hollinshead, W. H., Functional Anatomy of the Limbs and Back (W. B. Saunders: London, 1969) 265.
3. Bogduk, N., Clinical Anatomy of the Lumbar Spine and Sacrum (Churchill Livingstone: Edinburgh, 1997) 102.
4. Calais-Germain, B., Anatomy of Movement (Eastland Press: Seattle, 1992) 62.
5. Rolf, Ida, Rolfing (Dennis Landman: San Francisco, 1977).

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