Human movement is a dynamic process. The ability to maintain or change our posture, to move from point A to point B, or to lift and manipulate objects of varying weights etc., requires integrated and adaptable coordination.
Movement requires constant adaptation (both conscious and subconscious) to the context and demands of the specific task. I wouldn’t want to use the same amount of force to scratch my eye than I use to push a thumbtack into my notice board. I don’t need the same amount of tension in my body to push a shopping trolley down a supermarket aisle than I would need to push that same trolley up a grassy hill.
In short, movement requires a dynamic, adaptive interplay between stability and mobility. For lack of a more precise term, we can call this process “dynamic stability”.
Yet, when we think about the function of the “core”, we somehow tend to completely forget about the dynamic aspect of dynamic stability. The term “core stability” conjures up vague notions of sucking in belly buttons and rigidly bracing abs. However, core stability – and by extension spinal stability – is not a static bracing strategy but a dynamic process. A constant interplay between stability and mobility.
How, and how much, I “turn on” stabilising tension in my body is going to depend entirely on what I’m doing at the time. Am I walking? Am I carrying a 5kg bag in one hand? Am I lifting a 50kg load into the car? Am I deadlifting 100kg? If I employ the same core stability strategy for lifting 100kg weight than for lifting a cup of coffee, I’m going to run into trouble. And vice versa.
The body is hardwired to regulate this system more or less automatically, but things can and do go awry for various reasons including injury, illness or habitual dysregulation through inefficient posture or exercise strategies. Learning how to work with the body’s in-built stability system makes a phenomenal difference to how we feel and move.
The Integrated Spinal Stabilisation System
The simplest way to visualise the spinal stabilisation system is to start by thinking of the trunk, or the “core” as a cylinder.
The top of the cylinder is the Diaphragm, the large dome-shaped muscle that sits between the chest cavity and the abdomen and is the primary muscle of respiration (breathing).
The bottom of the cylinder is the pelvic floor, which is made up of multiple muscles and connective tissue structures. The walls of the cylinder are made up of all the muscles and connective tissues around the abdomen, along with the muscles along the spine.
As we breathe in, the Diaphragm moves downwards and, in a normally working system, this downwards movement increases the pressure in the space between the ribcage and the pelvis. This pressure – known as intra-abdominal pressure (IAP) – pushes out against the abdominal wall, lengthening and loading the muscles and connective tissues of the “core” and pelvic floor. From the outside, we (should) see this as an expansion of the front and sides of the abdomen.
Intra-abdominal pressure (IAP) is a key influencer of spinal stability and the body’s ability to generate, adjust and sustain IAP is necessary for good “core” function. Generating, adjusting, and sustaining IAP depends to a significant degree on the movement of the Diaphragm. If the Diaphragm is not free to move downwards, the system will not work optimally.
Sucking in the belly button and bracing the abdominal wall inwards towards the spine is a commonly taught “core activation” strategy, but one that actually impedes the body’s in-built stabilisation system. Pulling inward restricts the movement of the Diaphragm and the subsequent distribution of loading around the abdominal wall.
It is essential to appreciate the Diaphragm’s dual function as both the major driver of breathing and a key stabiliser of the trunk and spine. It means that our “core” function is inherently tied to our breathing function. Good core function depends on integrating these two functions, and on being able to adapt to imposed demand.
The first step in assessing “core” function, then, to assess diaphragmatic breathing. Next, we have to consider how the movement of the Diaphragm integrates with the function of the abdominal wall during rest and movement. A detailed assessment of breathing mechanics and spinal stabilisation is included in both the comprehensive and standard assessment protocols.
