I can't really organize my thoughts (or even collect all of them that I might have on the subject) so I'll just write a bunch of disorganized stuff about this off the dome.

There's not NO element of like, power and strength, but considering my oeuvre is huge scary women in general, that's not something exclusive to just the muscle-bound ones. "This woman would probably break every bone in your body if she fucked you" is kind of an omnipresent factor whether I'm drawing muscle, fat, hyper, etc. cuz they're all gigantic and like 8 feet tall at the shortest lol

Huge, rounded, bulging shapes. Muscles that take up space, that fight against one another for room, that have a sense of monstrous, overwhelming gravity. That expand and contract enormously with every exaggerated movement. That serve to inconvenience their owner and all those around them with their enormity, while simultaneously not hindering them in any way that matters.

On a visual level violently flexing, expanding musculature has obvious parallels with sexual release, and as such there is an appeal with working out/bulking out as a kind of replacement for intercourse, physical exertion and the act of becoming an inhuman behemoth a surrogate climax.

The contrast between a pretty face, dainty hands, etc. and an impossibly massive figure. A figure that's loaded with an inhuman amount of beef but still maintains a decidedly feminine silhouette. Or not; the disparity between a cute face on a body that'd put even the largest male bodybuilder to shame is also hot.

Individual muscles/muscle groups is a hard one because I could prob focus on amping up any of them and get all hot and bothered over them. The fairly obvious ones are biceps/triceps, lats, calves, pecs, and neck. And thighs, obviously. And ass. And y'know, enormous forearms tapering into comparatively small hands are also pretty nice. And you know, can't have enormous arms without massive delts, so...