What muscles make up the “core?”
The core can be defined as the area between where your legs meet the hip(bowl) and the lower end of the ribcage. In Pilates, this is also called “the powerhouse”. In martial art and a lot of eastern philosophies it is referred to as the “hara”. The areas in question are the pelvic floor (or pelvic diaphragm), the pelvic bowl, the low(er) back (lumbar region), abdominal muscles/ the low side waist.
A.) The Pelvic Floor/Pelvic Diaphragm consists of:
- - central tendon of perineum
- - the left and right bulbospongiosus muscles
- - the left and right ischiocavernosus muscles
- - the right and left superficial transverse perineal muscles
- - internal and external anal sphincter (less important for Mula Bandha but important for ashwini mudra)
Inferior to the pelvic diaphragm, and overlapping it anteriorly, is the urogenital diaphragm whose fibers run transversely from the rami of the pubis and ischium on one side to those on the other. The urogenital diaphragm consists mainly of the sphincter urethrae muscles.
I also would like to mention the obturator internus which forms the lateral walls of the pelvis. (see also below under “pelvic bowl)
B.) The Pelvic Bowl:
The pelvic bowl is not merely the link between the thighs and the upper half of the body, it is also the foundation for the torso. There are a couple of muscles that all have a relationship with the femur (greater trochanter) like the piriformis, the obturator internus, obturator externus, gemellus superior, gemellus inferior and quadratus femoris – however, I would not list them under “core muscles” per se. I also would not list the “glutes” group (Gluteus maximus, Gluteus medius and Gluteus minimus) under “core muscles”. (just a feeling, although this is debatable.)
Muscles either within the pelvic bowl (or running through it) that I would list under “core muscles” (from the deeper to the more superficial muscles):
- - left and right iliacus
- - left and right psoas minor (counts as well as lumbar muscle)
- - left and right quadratus lumborum (c.a.w.a.lumbar muscle)
- - transversus abdominis (see also the abdominal section)
C.) The Lower Back (Lumbar Region)
Deep Back muscles that tend to be arranged in several layers, with the deepest ones consisting of small bundles passing from one vertebrae to another:
- - the intertransverse muscles that connect one transverse process to the next (sidebending)
- - the interspinalis muscles that connect adjacent spinous processes (extension)
- - the transversospinalis that run superomedially from transverse process to spinous process.
Intermediate Back muscles of the lumbar (lower back) region are a group of posterior muscles that form a layer superficial to those described just above. The intermediate back muscles run through the whole length of the spine (from the occiput/C1 to the coccyx) and are sometimes referred to collectively as the sacrospinalis or erector spinae.
As already mentioned, we are only concerned with the lower back or lumbar region portion of these muscles - they consist of three components:
- the iliocostalis (most lateral)
- the longissimus and
- spinalis (most medial).
Each of these is further divided into three subcomponents according to spinal region. Of interest for us here concerning the lumbar region is mostly the iliocostalis lumborum with its lumbar fascia and the longissimus thoraces. The next upper (and most superficial) layer of the lumbar/lower back region consists of the very very last inferior portion of the trapezius muscle and the lower parts of the latissimus dorsi.
D.) The Abdominals:
The abdominals consist of 4 layer of muscles, mentioned here starting with the innermost layer and moving to the outmost or superficial layer:
- - The transversus abdominis
- - The internal oblique
- - The external oblique
- - The rectus abdominis
The transversus abdominis is the deepest of the abdominal muscles. The fibers of the transversus are essentially horizontal. They terminate anteriorly in a broad aponeurosis. Contraction of these circular fibers reduces the diameter of the abdomen, i.e. “pulls in the belly” or increases lordosis of the lumbar spine. Contraction also tones the abdominal organs. This muscle is important for uddiyana bandha and nauli. It is being awakened and strengthened in Navasana. An easy way to feel the action of the transversus is to wrap your hands around the sides of your abdomen and cough.
The next layer consists of the internal obliques, a thin sheet- like muscle located on the side of the trunk that is in the front as well attached to a very broad aponeurosis. Its fibers cross diagonally upward and forward from the iliac crest, inserting on the lower ribs and the linea alba. Unilateral contraction of the internal obliques draws the opposite shoulder forward and bends the trunk laterally. This action accentuates twisting postures such as Parivrtta Trikonasana. Bilateral contraction causes compression of the abdomen and assists in flexion of the trunk. Contracting the internal oblique also contributes to the “air bag” effect described at the end of the text.
The external oblique form the next successive layer. This is a sheet like muscle with its fibers running “opposite”/perpendicular to those of the internal oblique. (Paul Grilley: "put your hands in your pockets") Unilateral contraction of the external oblique results in side bending and contra-lateral rotation of the spine and ribcage (contraction of the external oblique draws the shoulder forward). Also here, bilateral contraction causes compression of the abdomen and assists in flexion of the trunk. Both, internal and external oblique muscles work synergistically in rotation of the trunk. For instance, rotation of the trunk to the right combined with flexion involves simultaneous contraction of the right internal oblique and left external oblique. This interplay is essential in all twisting actions of the trunk for creating the “wringing effect” on the abdominal organs that so effectively eliminates toxins from the body, and you could say that the abdominals are the core prime movers in all twisting postures. Contraction assists in compressing the abdominal content and contributes to the “air bag” effect, protecting the lumbar spine.
The outermost layer of the abdominals consists of the rectus abdominis that lies inside a “rectus sheath” formed by the aponeuroses of the three preceding muscles. This is a long and flat muscle that is divided into four bellies by horizontal fibrous bands, giving it a “washboard” appearance. Contracting the rectus abdominis flexes the trunk forward, or if the upper body is fixed, lifts the pelvis. Important in Uttanasana and Tolasana. Tightness of this muscle limits the depth of back bends such as Urdhva Danurasana and Pursvottanasana.
Contracting the rectus abdominis assists the other 3 inferior layers to compress the abdominal content, producing an “air bag” effect (Sadie Nardini describes this as preventing the content of a filled sandwich to spill out to one side). It prevents hyperextension of the lumbar spine, protecting it when extended as in all back bends.
Why focus on the core as part of the yoga practice?
The core – is literally the core of your yoga practice, on and off the mat. The core is your connection to yourself, your power to uplift you, to transmute, transform and create, your strength and the ability to go within and reconnect (gather energy, access eternal internal wisdom).
Apart from that, on a physical level, a strong center protects the lumbar spine (intervertebral disks) see “air bag” effect mentioned above. Your foundation ignites the core and “lights your fire” so you can radiate and shine and bring illuminating energy into all areas of your life – and those of others.
Another viewpoint is that focusing on the core honors the holistic concept of Brahmacharya – directing into being (“creating”) from the inside out (from the divine, timeless, infinite, eternal “level” to the human plane of existence. ) As planets rotate around the sun or petals circle around the central part of a flower, the limbs (“extrem”ities) should also be in service of the spine (the core, the hara) and not the other way round.
Besides the physical core, what are some emotional and energetic benefits of working from the center?
Literally centeredness on all levels. Clarity of mind and emotion – knowing who you are, what you want, what you feel and what you need right NOW. The ability to stay calm in times of transitions and stress. The ability to be aware without judgement, hence the ability of transmutation. A greater reservoir of available energy and the ability to seize ones' potential to the greatest extend, being (or becoming) a true “individual” while at the same time being connected to the core of existence – the part that is in all of us.
These are excerpts from my certification interview. Questions by Sadie Nardini (http://www.sadienardini.com/)
Copyright (Interview passages) Chiaradina Cerweny. Please do not use any passages without contacting me. Thank you for your understanding!
Radiate Variety in Unity. Chill. Life is not to be imitated. :)