Legs, from the knee to the waist....a lot of the rest is genetics, not work
I would say that I sort of have a staring problem with my current SO....she is about 5 7, overall pretty small frame, a C chest but nothing to knock you head off with. I have been with her for awhile, enough that I should be a little more used to it, but I still find myself uncontrollably staring at her. It's distracting.... I think what makes me so glued to her are about 4 things, that if a woman has it, I am a leering teenager again:
--- When I look at her legs from the side, there are 3-4 cords of muscle, all coming up from the knee. The hamstrings themselves are separated....if you are a man and you have seen this, you know what I mean.
--- Her back has a contour of muscle over the shoulder blades. When that has no clothes over it = lights out.
--- When she runs, her butt doesn't move. It has literally no give to it. It's like grabbing a honeybaked ham.....again, if you have seen this, it's all over.
--- Her forearms have veins on the posterior side, so when she grabs anything it is incredibly hot to me.
A woman can NOT have a whole lot of other stuff, but the raw athleticism of those 4 things will pretty much trump everything else. Pure genetic beauty of a pretty face is one thing.....I will find them impossible not to look at, but it's not necessarily sexy, as in I feel a little growl when I see them.
When I see a really in-shape woman though, it is like there is this mammalian brain that says to me "We make babies, strong like bull with that one. Make very fast hunters. Survival value of offspring is very high in this one."
So if that is "primal", that is how I feel.