It's one of those words that has a singular and a plural version that changes the meaning slightly.
"Muscle" singular is the concept / idea of strength, size, power, beauty etc.
"Muscles" plural are all the individual bumps and bulges like biceps, pecs, quads etc.
'Girls with Muscle' then is like saying: "Girls with Power" / "Girls with Strength."
Or mid-worship a girl could say: "Feel that? That's all muscle" - That's all power / strength
It's the same with "Exercise" (concept) vs "Exercises" (push ups/pull ups/curls etc.)
Anyway, I agree with you. "Muscle" sends the mind racing more.
Muscle is both a count noun and a mass noun, so it's both.
This. That’s why in English people say “I like your hair.” Not, “I like your hairs.”
Interesting in chat/threads with other muscle addicts the term commonly used is ‘muscle’ instead of ‘muscles’. Even referring to overall body ‘muscle’ instead of overall body ‘muscles’. Just me I’m sure but I find the word ‘muscle’ much more erotic!