To begin, let's say that an essential understanding of your psoas muscles means understanding what they do for you and, when too tight, what they do to you. That understanding points you to an effective way to free them, if they're tight and painful.
What your psoas muscles do for you is maintain your uprightness in sitting, your spinal alignment and balanced equilibrium when standing, and your efficiency of movement bending, twisting, walking and running. Your psoas muscles are initiators of movement and dynamic stabilizers.
To get your psoas muscles to function well, we first free them (which can be done a number of ways – and there's hard way and an easy way). Then, we integrate their movement functions with other movers and stabilizers of the body, and so normalize psoas functioning. That's a matter of movement training, which also involves awakening our ability to sense our psoas muscles. Without the integration step, your psoas muscles are likely to revert to their tight state. I'll say more, as we go on.
Understanding how psoas muscles play in movement simplifies our approach to setting things right. Having made such a statement, I will, of course support it. But first, I have to lay some groundwork.
"PSOAS" OR "ILIOPSOAS"?
Sometimes, one name is used, and sometimes, the other. The psoas muscles share a common tendon and end-point with the iliacus muscles, which line the inside of the pelvis, so the combination is called, the "iliopsoas" muscle. For brevity, I use the term, "psoas muscle".
"Economical", in this sense means, "getting the intended (not necessarily the most) result with the least effort." Where tension and movement are concerned, more is obviously not necessarily better; more efficient is better. The word, "graceful", applies, here. Graceful movement is economical movement; awkward movement is uneconomical or ungainly movement. Graceful movement conserves effort; ungainly movement wastes effort. For movement to be economical, it must be well-balanced and well-coordinated – a matter of integration.
The psoas muscles, being most centrally located as the deepest muscles in the body, help control the shape of the spine. By controlling the shape of the spine, they control our balance – how the centers of gravity of our major segments – head, thorax (or chest), abdomen and legs – line up.
To the degree that our movements cause these centers of gravity to line up vertically (when standing), to that degree, we have balance. To the degree that we have accurate, balanced movement and good timing, we have economical movement.
Tight psoas muscles distort the spinal curves, shorten the spine, change pelvic balance and cause ungainly (chunky, heavy, labored, awkward) movement. To the degree that the spinal curves are distorted, our alignment is distorted and to that degree, we are out of balance and our movement is un-economical / wasteful of effort.
ACTIVITY AND REST: MUSCLE TONE
The term, "tone", refers to the level of muscle tension: complete rest means zero muscle tone; complete activation means maximum muscle tone. Some people believe that the higher the tone, the better; others believe that complete relaxation is better. As you will see, where tone is concerned, it's neither; better-integrated is better, and better-integrated means more freedom to adjust accurately to changing conditions – freedom and balance.
Here's the key to understanding your psoas muscles and freeing them: Psoas muscles help regulate our changes of position as we move from rest into activity and from activity into rest by changes in their tone. They help maintain our balance and stability in those positions. They are central to movements from lying to sitting, from sitting to standing, and from standing to walking and running. If their tone is too high, they interfere with balance and stability as we move into different positions; their tone is almost never too low, and if so, usually indicates either neurological damage or a need to learn basic control.
With changes of position, the activity level of your psoas muscles changes, as follows.
• From Lying to Sitting – At rest or in repose, your psoas muscles have no job to do and should be at rest – which means relaxed and comfortable.
Your psoas muscles connect your legs to your trunk. When you move from lying to sitting, they help hold and move your legs as counterbalances, plus they help provide a sufficiently stable core as you move to the upright position. Overly tight psoas muscles create groin pain or deep low back (lumbopelvic) pain when changing position from lying to sitting. You may have the experience of a groin pull or of muscles seizing up in your pelvis or low back.
• When Sitting – Your psoas muscles connect your groin to your pelvis and low back and stabilize your balance in the front-to-back direction; your brain adjusts their tone for the right amount of front-to-back stability under the pull of gravity.
Overly tight psoas muscles that create too deep a fold at your groin and too much back arch contribute to groin pain and back muscle fatigue and soreness.
• From Sitting to Standing – As you move from sitting to upright standing, your psoas muscles must relax and lengthen to permit movement to a larger hip joint angle between legs and trunk.
Overly tight psoas muscles, which connect your groin to your spine, prevent you from coming to a fully erect, balanced stand. They hold you in a subtle crouch at less than your full stature, which you may not recognize because you're used to it – except that you hurt in certain movements or positions!
• When Standing – Your psoas muscles' well-regulated tone helps your back muscles to erect you to your full stature, with minimal lumbar curve. Through your psoas muscles, your brain adjusts your spinal curves (and balance) as you bend forward, lean back, move side-to-side, and twist and turn.
Overly tight psoas muscles do not lengthen enough as you stand straight; they pull from your groin to your low back, causing lumbopelvic or lumbosacral pain, a "pubes back" position, and excessive lower back curve. Your butt sticks out.
• From Standing to Walking – As you move step into walking, you first shift your weight onto one foot to free the other leg; the psoas muscles on the standing side relax and those on the walking side tighten to help you step forward. (For therapists, a detailed description exists in the ezine article, "The Psoas Muscles and Abdominal Exercises For Back Pain".) In healthy walking, your psoas muscles freely alternate, side-to-side, between higher and lower tone as you walk or run.
Overly tight psoas muscles shorten your stride and require your hamstrings and gluteus medius muscles to work harder to bring your "standing" leg back as you step forward. You end up with tight hamstrings and tight gluteus medius muscles (hip pain in back). In other words, your brain has learned to hold your psoas muscles at a level of tension that's related to the tension of other muscles.
You can not make a lasting change in one without changing the other because your brain maintains habitual patterns of movement among muscles (pattern of coordination); to change one, you have to change your entire pattern, or at least enough of it to reorganize your movement pattern. That kind of change does not occur "by deciding to move differently"; when you're walking, you can not conveniently put that kind of attention into your movements; you have to make it automatic, and there's a process for that, mentioned below.
In actuality, most people never experience complete relaxation or complete activation; they're stuck with elevated muscle tone somewhere in between, stuck with limitations of movement and posture, stuck with ungainly movement (taken as normal "individual differences"), stuck with some degree of muscle fatigue (often mistaken for weakness).
The reason: muscle memory.
People may attribute consistent tight psoas muscles to muscle memory. But neither the psoas muscles nor any other muscle in the body has a memory. Muscles have no control of their own. Memory resides in the nervous system; the nervous system controls the muscular system to coordinate movement and maintain balance, something no muscle can do on its own. No muscle controls any other muscle; the nervous system does that. To do that, it remembers (or we remember, both at a conscious and at a subconscious level) what movement and balance feel like and our nervous system coordinates (we coordinate) our movements to recreate and maintain those familiar sensations of movement and balance.
Muscles never work alone; they always work in concert with other muscles. What any muscle does affects our entire balance. Other muscles have to compensate for those effects on balance by tightening or relaxing. Your brain controls these entire patterns of movement and compensation with memories of movement ( "muscle memory"). To be more accurate, the term, "muscle memory" should be "movement memory".
Because your nervous system and muscular system cooperate as a whole, to try to change the movement and tension behavior of tight psoas muscles without changing the larger movement pattern of which they are a part is to work against the rest of the system and its (our ) memory of how movements go and feel. That's why methods of muscle manipulation (eg, massage, myofascial release, stretching) produce changes that are either temporary or slow in coming – and why psoas release by manipulation is painful: it works directly on sore, contracted psoas muscles against the conditioning of the entire movement system.
The psoas muscles are our deepest core muscles.
When people speak of the "core", they usually mean the muscles of the abdominal wall. But how is that the "core"? The core of anything, such as the Earth or an apple, is its centermost part. The psoas is a core muscle (as are the diaphragm, quadratus lumborum, iliacus and other muscles closest to bone); the abdominal muscles are "sleeve", to use terms used by rolfers.
Your brain coordinates the movements and tone of muscles; tone changes as position changes in movement. That's what is meant by "supple." Supple psoas muscles have the sensation of spaciousness, support, freedom and length at your body core. The term rolfers use is, "open core." When psoas muscles do their job of stabilizing the spine, they relieve the abdominal wall muscles of some of that task; your abdominal muscles have the sensation of relaxation and free breathing. The term rolfers use is, "free sleeve." Healthy psoas functioning gives the experience of "open core, free sleeve." Open core / free sleeve is the feeling of trunk / spine length, flexibility and stability.
So, we can see that efforts to free the psoas muscles without also improving their coordination with the rest of the musculature are grounded in, let's say, a partial understanding of how they function. That means that "psoas release" techniques, "psoas stretches", and psoas strengthening approaches need movement education (known as "somatic education," which involves brain-muscle training) to produce the result they seek – a stable shift to healthy psoas functioning .
Economical movement (least effort, good result) and easy balance are the goal – attributes you can develop by movement training that first frees the psoas muscles and then integrates them into economical movement patterns. First free, then integrate.
It's convenient to use the movements and positions in which the psoas muscles participate – from repose to sitting, from sitting to standing, from standing to walking (and by extension, to bending, twisting, running and other actions) – to evaluate their functioning and to free and integrate them.
Then, it's a brain-level training process that changes the brain's sense of movement and coordination. Beyond saying that we free and integrate movement, a description of the training process is quite beyond the scope of an article, but you can see steps in that process in video through the link, below.
There's an easier way and a harder way. This is the easier way.