The deep core is primarily made up of four key muscle groups:

1. Transversus abdominis

The deepest of the six abdominal muscles, the transversus abdominis, wraps around the entire abdomen, sitting below the visible ‘abs’ we commonly refer to when talking about the core.

Also known as the corset muscle due to the way it wraps around the centre of the body, its sheer size means it provides important stability to the spine and pelvis while helping to maintain internal abdominal pressure (ie keeping all the organs where they’re supposed to be).

2. Multifidus

In comparison to the transversus abdominis, the multifidus muscles are very small. “These muscles run along the length of the spine, providing stability and support by controlling small movements of each vertebra,” Norris explains.

But despite their size, the multifidus muscles are still strong, which is thought to be down to the way they’re constructed.

3. Pelvic floor muscles

Your pelvic floor muscles kind of do what it says on the tin – they sit at the base of your pelvis, providing a ‘floor’ that supports the pelvic organs and stabilises the pelvis.

“They also play a crucial role in controlling bladder and bowel function,” Norris adds.

4. Diaphragm

Although the diaphragm is primarily talked about for its role in breathing, it’s also an important for maintaining core stability. Despite being a thin, dome-shaped muscle, the diaphragm is responsible for controlling intra-abdominal pressure (which pushes out waste such as urine, poo and vomit), reducing stress on the spine and supporting the trunk area.

In fact, a 2023 study into the role core stabilisation exercises could play in the treatment of lower back pain stated that, while the diaphragm is often overlooked as a core muscle, anyone who requires “any form of core stabilisation exercises for low back pain rehabilitation should consider [it]”.

Deep core exercises: 3 moves to improve balance and ease lower back pain