If you are looking to have those 3D abs, this is the way to get it!
These muscles help bend your torso to the side, help rotate your torso to the left and right, and perhaps most important, actually act to resist your torso from rotating, which helps to stabilize and protect your spine.
I split my abs training into parts, I work the rectus abdominis, the middle part, then the external/internal obliques (the ones highlighted in the picture), and lower abs. I cannot isolate this parts completely but I can target them as the muscle that works primarily.
So for each part, I have a different routine, and I switch it sometimes for variety and for intensity purposes.
When I have a client who is a beginner I don’t recommend this routine untile I make sure that his core is strong and I do that by giving him lower intensity exercises and prepare him progressively.
Of course working your abs alone won’t get you that well-desired six pack unless you get rid of the fat that covers them(in most of the cases) and you do that by having a caloric deficit.
But I will talk about this in another article.