Core muscles are the most controversial set of muscles. You will see people doing funny things in the name of core training. Let us get down to the basic layering of the core muscles.
The deep layer: This is the weakest layer of the core as it consist of vertebra , ligaments and 2 small muscles interspinalis and intertransversarii.
The function of this layer is to process the information to the brain about the spinal components or the position of the spine. This layer does more of neurological function and less of stability function.
The middle layer: This is the strongest layer of the core which gives stability to the spine. This is the layer which is the most important for us when it comes to strengthening the core. These are the set of muscles we need every day every minute of our life.
This layer contains the muscles transverse abdominis, multifidi , quadrates lumborum , semi spinalis thoracis, psoas.
This is the layer which contracts and forms a tight band around the spine holding the air inside , to make it strong also called as the hoop tension effect.
The superficial layer: This layer does not support the spine but is more used during the movement of the spine. So practically the core stability exercises does not have an effect on these set of muscles. Yes these muscles are rectus abdominis , internal and external oblique’s and the erector spinae group.
Also the cadaver studies have shown that all of us are born with 4 or 6 or 8 packs of muscle. It is just hidden under a layer of fat.
The superficial layer doesn’t work on the stability of the spine, so by doing work for the deep core muscles , it won’t lead to a flat stomach or 6 pack abs.