By Florence Bowen, DOMP

Take a deep breath in.
Fill up your lungs, your belly, and relax the space between your sit bones.
Take a deep breath out.
Observe the deflation of the belly, the retraction of your lower ribs and lungs.
That is one rep.
You are now one step closer to a stronger, more functional inner core.
Wouldn’t it be great if core work was that easy? Well, it kind of is.

The inner-core unit

The core is far more than just your six-pack muscle. Underneath those washboard abs are layers of muscles that work together in a synergistic fashion. The deep core (or inner core) can be thought of as a canister or a barrel. The top is formed of the thoracic diaphragm and all of its extensions, the bottom is formed by the pelvic floor muscles and the transversus abdominis and multifidus muscles wrap around the middle or sides of the barrel. Ideally, when we breathe in these structures all relax, expand or stretch and when we breathe out they contract together.

The thoracic diaphragm is a muscle which lies between your lungs and all of your abdominal organs. It is the main muscle that draws air into your lungs when you breathe and it does this in collaboration with the abdominal muscles to control intra-abdominal pressure.

The parachute shaped muscle also plays a key role in core strengthening.

Connections to the core muscles

The thoracic diaphragm has extensive fascial expansions which form connections to surrounding structures and the abdominal muscles. Think of fascial expansions as a web or cling wrap, it is a complex layer of connective tissue that clings to and encases bones, muscles and organs.

The thoracic diaphragm anchors itself to the lower six ribs and blends with the deep transversus abdominis fascia (your belt or corset like muscle), it also extends to the sternum (breast/chest bone) and xiphoid process where it blends with the linea alba ( the line between your six-pack muscle) and the rectus-abdominis muscle (your six-pack muscle). Below, the thoracic diaphragm anchors itself to the lumbar spine where it blends again with the transversus abdominis fascia and the hip flexor muscles.

By extensions and fascial expansions, when you breathe in you are stretching and loading your thoracic diaphragm and abdominal muscles simultaneous. A greater stretch of the tissues before the active shortening of the same tissues will generate a stronger more powerful contraction. Think of an elastic band, the more you stretch the band the more it will propel into space when you release the tension. This is the reason I say in my group movement classes “if you aren’t breathing, you aren’t using your core to its max potential”.

Diaphragmatic breathing is often prescribed during the immediate postpartum period. The simple act of breathing has demonstrated to aid in the healing of diastasis-rectus abdominus (the overstretching of the space between your six-pack muscles) that occurs in 100% of pregnancies.

Breath and benefits

Breath work, mindfulness and meditation have all been shown to reduce stress and anxiety, but why? This is because part of the neurological supply to the thoracic diaphragm comes from the cranium and the parasympathetic or “rest and digest” part of the nervous system. The vagus nerve, the tenth cranial nerve, supplies motor and sensory innervation to the crura of the diaphragm. Deep belly breathing, moving the thoracic diaphragm up and down increases the activity of the vagus nerve. This enhances the effects of the parasympathetic nervous system which leaves you feeling more calm and at peace.

Take home points

Do not undermine the potency of the breath!

Next time you take a deep breath in, you are doing much more than just oxygenating your body. You are also strengthening your inner core unit while you down-regulate your nervous system.

References:

Bordoni, B., Purgol, S., Bizzarri, A., Modica, M., & Morabito, B. (2018). The influence of breathing on the central nervous system. Cureus, 10(6).

Lee, D., & Hodges, P. W. (2016). Behavior of the Linea Alba During a Curl-up Task in Diastasis Rectus Abdominis: An Observational Study. The Journal of orthopaedic and sports physical therapy, 46(7), 580–589. https://doi.org/10.2519/jospt.2016.6536

Young, R. L., Page, A. J., Cooper, N. J., Frisby, C. L., & Blackshaw, L. A. (2010). Sensory and motor innervation of the crural diaphragm by the vagus nerves. Gastroenterology, 138(3), 1091–101.e1015. https://doi.org/10.1053/j.gastro.2009.08.053