The Anatomy of Core Stability
By Kelly Kane
Many teachers know the buzz word “core stability” and see that working the back and abs helps their clients transition out of back pain, but they may not know exactly why. Here, Kelly Kane, founder of the Kane School of Core Integration in New York City, provides a detailed look at the core muscles and how they work together to support the back and the whole body.
As humans we move in an upright relationship to gravity. We sit, stand, walk and run, often while carrying heavy loads such as our kids, bags and backpacks. When we do these activities we need to stabilize our pelvis and our low backs, and use the flexibility and strength of our hips to change levels, locomote and mobilize.
Unfortunately when the hips are tight and mobility in the hip joint is limited, movement is taken up the skeletal chain into the sacroiliac joints, sacro-lumbar junction and lumbar spine. The protocol for creating healthy backs should be to find good drop and glide of the femur bone at the hip joint, while strengthening the core stabilizers. In the Pilates venue we call this hip dissociation/differentiation and core stability.
Core Stability
The Core in Pilates refers to the muscles of the pelvic floor, the transverse abdominus, the lumbar multifidi and the diaphragm. This group of muscles encases our organs and supports our upper extremities and spine, but specific attention must be paid to strengthening these muscles.
Stability means absolutely no movement. Core stability assumes both the lumbar spine and pelvis remain immobile. In pelvic stability, the bones of the pelvis are stabilized in either a posterior or neutral pelvic position while the upper and lower extremities load the stabilizing muscles. Even the smallest rotation of the pelvis during movement means that the core stabilizers are working unevenly. Challenging the core stabilizers by loading the head, arms and legs on a stabilized pelvis will make these muscles stronger.
Lumbar stability is stability of all five vertebrae of the lumbar spine. When the vertebrae are stabilized in neutral pelvis, the small lumbar multifidi and the transversus abdominus (TVA) work in opposition to each other to stabilize each vertebra (see diagram below). When assessing lumbar stability, it is vital to assess the stability of each spinal segment. It is possible to have segmental stability in all but one of the spinal segments. The trick is strengthening the core stabilizers so that all of the spinal segments are stabilized. In a posterior pelvic orientation lying supine the low back muscles are taken out of the equation, but the lumbar vertebrae are stabilized because the abdominal muscles push the lumbar vertebrae into the ground, inhibiting their movement. In neutral pelvis the ASIS and the pubic ramus are level in the coronal/frontal plane. For most people the lumbar vertebrae will be arching anteriorly, assuming a natural lordotic curvature. For our purposes we will talk about core stability, as it relates to the Pilates repertoire, in neutral pelvis.
The Core Stabilizers
Pelvic Floor
The most important of the muscle of the pelvic floor for postural support is the levator ani (see diagram below) which is comprised of three very different units. The pubococcygeus originates at the left and right pubic tubercles and courses posteriorly, running lateral to the genitals. The two sides meet behind the anal opening and then bifurcate as it runs up the anterior surface of the coccyx. The iliococcygeus arises from the lower aspect of the two iliac fossa and inserts at the coccyx. The ischiococcygeus runs from the two ischial tuberosities to the coccyx. Pelvic floor strength is primary for low back health because it is literally the inferior anchor of the spine: all three aspects of the levator ani attach to the tailbone. These muscles form a cup or a diaphragm that has the capacity to contract in and up. The pelvic floor muscles support the inferior organs of the pelvis, such as the bladder, prostate, uterus and rectum.
Strength and balance in the pelvic floor is greatly affected by pelvic orientation (neutral, anterior or posterior). To feel this for yourself, try sitting on a chair feeling your SITS bones. Come into neutral pelvis by bringing the ASIS and the pubis in the same plane. You will probably feel as though you are a little forward on your SITS bones. Contract your pelvic floor by pulling the right pubic bone to the right tailbone, the left pubic bone toward the left tailbone, the SITS bones together, close the anal and vaginal opening or condense around the base of the penis and pull everything up. Now tuck the tailbone under and sit on the back of your SITS bones, taking a posterior orientation, and contract the pelvic floor in the same way. You will probably feel more contraction around the anal opening. Do the same thing in an anterior pelvic orientation by rocking forward on your SITS bones and contracting the pelvic floor. You will most likely feel more contraction in the anterior pelvic floor around the genitals. When you are executing your Pilates exercises with a neutral pelvic orientation you will be more likely to recruit the pelvic floor evenly front, sides and back.
Transversus Abdominus
The transversus abdominus (TVA) is the deepest abdominal muscle. It literally forms a girdle that encases our organs and supports our spine. At the pelvis, it attaches to the inguinal ligament, the iliac crest and the sacrum. It also has attachments to the lumbar spine by way of the thoraco-lumbar fascia. At the thorax it attaches to the inner surfaces of ribs seven through twelve and has fibers that interdigitate with the diaphragm. A healthy TVA is said to contract whenever we move; when we lift our arms, walk, turn our heads. When it contracts it axially elongates the spine and assists in spinal flexion and rotation. It also aids in respiration and contracts when we laugh, sneeze, cough or forcefully exhale. When the TVA contracts with the lumbar multifidi, it stabilizes each of the lumbar segments. It is the muscle that reduces the diameter of the waist and helps us “scoop.”
The TVA is extremely important to low back health. When it contracts and axially elongates, it literally decompresses the lumbar spine. As an intervertebral stabilizer, it protects the low back and the intervertebral disks by “stiffening” the spine so that it can sustain loading.
Hip Disassociation/Differentiation
The hip joint is the articulation between the femoral head and the acetebulum of the pelvic hemisphere. The femoral head is a ball and the acetebulum is a cup. The hip joint is happiest when the ball literally spins in the cup. When the hip flexes the ball scoops out the cup, as if a melon scooper were scooping out a melon. In hip flexion the scooping happens posteriorly, in abduction the scooping happens medially, in extension the scooping happens anteriorly. When there is an incapacity to scoop, mobility is reduced and the mobility will be taken up or down the skeletal chain. When executing this scooping action the pelvis half has to diassociate/differentiate from the movement of the femoral head. The capacity to stabilize the core allows the pelvis to stay in one position while the femoral head scoops or drops and glides in the socket.
The action of hip disassociation/differentiation happens when you reach your ischial tuberosities or sits bones as you descend to sit in a chair. The pelvis stabilizes and the femur heads scoop out your pelvis creating a deep crease at the front of the hip, as the photo at right demonstrates. This action is also the action that keeps the back happy when you are change levels to pick something off the floor. There should be the same action of pulling the abdominal muscles in, engaging the pelvic floor, reaching the sits bones back while mobilizing through deep flexion of the knee and hip joint to change levels. The action of deep knee and hip flexion requires sufficient strength through the quadriceps, hamstrings and gluteals. Many people don’t have adequate strength in their legs to squat 30-50 times a day to pick up the kids toys, get goodies out of the bottom of the fridge or lift a heavy bag of groceries. Correct biomechanics and a deep understanding of the core stabilizers and how to get good hip disassociation/differentiation are primary to any Pilates practice.
Kelly Kane, founder of the Kane School of Core Integration, has been teaching Pilates for more than a decade. She studied with Romana Kryzanowska, Hila Paldi and Irene Dowd, and completed the training program at the Pilates Institute in Santa Fe, two years of the BodyMind Centering teacher-training program and a certification in massage from the Florida School of Massage. Her manual therapy repertoire includes Structural Integration, CranioSacral Therapy and Visceral Manipulation, and she cultivated her manual perception skills through three years of human cadaver dissection at the New Jersey School of Medicine and Dentistry. Her expertise also includes GYROTONIC® and Continuum Movement.
Illustrations ©Elijah Leonard
Amy Leibrock
in Anatomy, Teaching Strategies
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Reader Comments (6)
This model of stability may prove useful for objects that don't move, however for organisms such as the human body it counter-acts our functional integrity. This region being labeled as the "core" contains many joints and membranous structures designed for sliding, gliding and movement in relation to one another. When we 'lock' down the core in such a manner we inhibit a variety of adaptive capacities in this region, transferring and isolating strain into the mobile structures above and below this region. If movement is traveling from the foot, up through the ankle, through the knee and suddenly stopping at the hip, due to the immobility of the pelvis/lumbars, we're bound to see problems arise due to excessive forces colliding with this "stabile" /immovable environment. This model may work fine if you're loading weight onto a brick wall, but try moving the brick wall and see how unstable/dysfunctional things become.
'Stability' in the human body relies on its ability to MOVE, react, and respond to the subtle and gross changes in dynamic load during movement. Take away these qualities and you're left with a highly strained, unadaptive and rigid system. Rigidity is not a friend of the human body unless you're a power lifter or the like. Rigidity will quickly deteriorate joints and tissues at the junctions where mobility meets immobility. Forces accumulate in these places because they have no fluid path to travel through. You see this quite frequently in individuals with fused portions their spine. The segments at the transition of the fusion/non-fusion frequently are the first to develop signs of dysfunction such as disc/joint degeneration, arthritis, arthrosis, or collapsed/herniated/protruding/bulging discs, etc..
The concept that the 'core' lays in the middle of the body also seems rather odd. What enables this core to move an individual and "stabilize" them? Aren't we moving and supporting ourselves via our legs witch ultimately connect us to the ground? I believe the core begins in the feet (medial arch), running up the deep posterior crural compartment of the leg, up through the adductors and into the bottom of the pelvis, within the pelvic 'bowl' and up the front of the spine. Where's the mention of the important psoas in this "core" model that Kelly talks about.
"Challenging the core stabilizers by loading the head, arms and legs on a stabilized pelvis will make these muscles stronger."
What is the definition of 'strength' here? Strength isn't just static loading potential, but more importantly functional dynamic loading potential. In everyday life we don't move like robots or block people... . Just take a look at the most talented of athletes and you'll see fluidity of movement and strength at it's peak.
Regarding the TA - "It also aids in respiration... "
In normal respiration? How so? Yes, it aids in forced exhalation, but should we be walking around consciously forcing our breath out? The 'controlling' and overuse of the TA is concerning. Something we don't ever hear about in the Pilates model of core stability is the effect of excessive engagement of the TA as it relates to intra-abdominal pressure systems and diaphragmatic function... as well as rib mobility. When the TA is sinched down like a corset, it decreases intra-abdominal volume thus increasing pressure with this cavity below the diaphragm. Consequently, the diaphragm must work much harder to contract and move downward, thus putting more strain on it and making breathing more difficult and decreasing overall volume of breath. This results in having to utilize the secondary muscles of respiration in the neck and intercostals excessively, creating an inspiration fixed breathing pattern and straining the cervicals.
Is our goal to really make breathing more difficult and less efficient just to achieve greater 'static' abdominal and lumbar strength? Straining the diaphragm by increasing intra-abdominal pressure via contraction of the TA will lead to a variety of potential problems that nobody would want... and are often have very lasting impacts on both the musculoskeletal body as well as the viscera (organs). Increased pressure and less diaphragmatic excursion leads to abdominal visceral immobility and restriction... potentially effecting physiologic function as well. This increase in pressure also fatigues the muscles of the pelvic floor which are designed, in part, to counter-act the downward pressure exerted by the diaphragm on inhalation.
Furthermore, adequate movement of the lumbar vertebral segments is limited or null, which compromises disc health and physiology. Without proper movement and articulation the discs will chronically dehydrate and physiologic health will become negatively impacted(cellular function and maintenance is altered due to chronic immobility and sustained loading.).
As far as th hip movement goes... Why shouldn't our movment in the legs be allowed to travel naturally up through the hips and into the pelvic innominates? After all, the two halves of the pelvis naturally tilt posterior and anterior alternately when we walk... If they don't we've got problems. The pelvis was designed and is capable of moving healthfully via the SI joints(granted they only have a few degrees of rotational ability and a few millimeters of translation allowable). Nonetheless, healthy iliosacral/iliolumbar function allows for a figure 8 type of motion to occur here during gait. This is a complex region of biomechanics and form closure/force closure to provide proper stability and function in the moving form we call a human being. When we 'lock' this region down we're asking for trouble... and it will be anything but stable or functional.
Ever notice how some avid Pilates folks walk like soldiers? With there legs swinging under their pelvis like sticks and the pelvis/lumbars perfectly stationary... NO contralateral movement as was originally intended in our bodies. Very rigid in the "core", rather than dynamic fluidity and complex autonomic coordination.
Now I'm sure I've ticked off some folks here, but that's not my intention. I just feel that we've bought into a belief system that has lacked adequate and educated scrutiny. I think Joseph Pilates contributed some valuable insights, and I'm sure he helped many people. But remember that this was a person who was searching, in part, for a means to help his rickets... He himself needed something as 'controlling' as Pilates... Most people in our culture today don't need excessive rigidity or more control in their lives. Our culture could actually benefit from being a little freer in the pelvis... more expressive in their movements and less controlling of things that are beyond their moment to moment control. If we had to think about everything we did in out "core" every time we moved, we wouldn't go anywhere. Thank goodness our bodies can perform all of that for us. And when it has trouble doing so due to the many allienating influences in our cultures (driving in cars, sitting behind desks, sitting at our computers, sitting down to eat, etc.) we can turn to things like pilates to help re-connect with these inhibited and lost regions of our bodies. But we need to know when is enough and let the body take over its job. I also think its extremely important that we look objectively at all disciplines before accepting them as accurate 'truths'. Unfortunately, the training for pilates doesn't provide the level of anatomical, physiological or biomechanical understanding/knowledge that is needed to analyze and objectively view it in this manner. So too many folks are adopting a belief system that they aren't capable of questioning appropriately, and they're teaching it to others as if it were anatomically and biomechanically accurate , safe and functional when it really is not in some ways.
At the end of the day, no matter what discipline you practice, the body (its anatomy and physiology) is your only accurate teacher and source of information. If what you're being told or what you're teaching doesn't correspond to the reality of the human body and its natural unimpeded function, then we must be brave enough and secure enough to begin posing important questions. Our greatest weakness in this discipline of 'strength and stability' lays in our neglect to ask these important questions and challenge that 'stability' to see if it will really hold true in the end.
I would be happy to have a dialogue on this topic... That's really why I chose to post this message. I hope nobody is offended by my comments or such.
Are you a Feldenkrais person? I like your post. I also like Kelly Kane's article as well. I am an "out-of-the-box Pilates teacher and although Kelly's info may not be in line with your knowledge of the moving body she by far surpasses many Pilates peeps out there, especially those zealous Classical teachers.
I am looking to get certified in Gyrotonics and I am wondering your take on this modality. It definitely embraces more freedom than does Pilates and works more in spirals. However, I know some folks who are so hypermobile in their backs that they cannot do Gyro. Would love your feedback.
Hi rebelred,
Although I'm fan of Feldenkrais, that's not my chosen field of inquiry. I'm actually a structural integration practitioner with an emphasis on visceral/peripheral nerve and cranial osteopathic manipulation.
I honestly didn't mean to ruffle any feathers with that post, but I think it's always healthy to examine everything from an educated, objective and unbiased point of view (including my own chosen profession). And I do agree that Kelly Kane makes a concerted effort to provide an educated experience for people.
As for gyrotonics, ...love it! I wish it was more recognized and utilized by folks. It opitimizes organic, spiraling, integrative and fluid movement that is so akin to our everyday lives and nicely matches the inherent design and function of the human body. We could certainly use more gyrotonic/gyrokinesis teachers out there. Especially seeing as how we, as a culture, seem to have lost touch with the natural and unencumbered movement within the pelvis and upper body. I think it also integrates and connects our movements with the ground (through the feet) in a very effective manner.
I think it would be wonderful to see more fluidity rather than more rigidity and 'bracing'. 'Life is motion' ....
...Legs were designed to move with the pelvis, not separate from... .
Kind Regards,
Forgot to mention this... Gyrotonics may not be appropriate for everyone, but such is the case with any movement/manual discipline. I would say it's more about the right approach at the right time, as it relates to each individuals needs/condition ....Rather than any single approach being superior to the next.