It’s not really a proper guide, like, it doesn’t make sense anatomically. Upper and lower “sixpack” muscles aren’t different muscles, the squareness of them is just fascia on top holding things together. I don’t know what definition of “core” they have here, it also makes no sense. If you want to exercise, good, but find a better guide.
Is the vertical for variety, or does one need to do all?
It’s not really a proper guide, like, it doesn’t make sense anatomically. Upper and lower “sixpack” muscles aren’t different muscles, the squareness of them is just fascia on top holding things together. I don’t know what definition of “core” they have here, it also makes no sense. If you want to exercise, good, but find a better guide.