When we talk about core strength, we don’t typically mention the diaphragm, the primary muscle of respiration – yet it is located right at the centre of the abdomen. The diaphragm is a dome-shaped sheet of muscle and tendon and separates the chest (or thorax) from the belly. In very simple terms - the diaphragm contracts during inhalation, which causes air to be drawn into the lungs, and relaxes during the outbreath which forces the air back out again.
Now, what does the diaphragm have to do with core strength? For starters, it attaches to a number of stabilisers, such as the ribs, sternum and (lumbar) spine. In terms of surrounding muscles, imagine your abdomen like a pressurised container – with the pelvic floor being the bottom, the deep abdominals and back muscles forming the sides, and the diaphragm acting as the lid on top. If any of these components don’t work optimally, the container will start to lose pressure and weaken the base – your core.
The diaphragm also connects to the thoracic and lumbar erectors, the QL (the ‘back muscle’) as well as the psoas (main hip flexor) – all of these are involved in moving the spine, and giving it stability. Conversely, this means that impaired function of any of these muscles will lead to a knock-on effect.