When I watch TOS I'm always struck by how unbuff they all are, especially Nimoy, in comparison to what is considered standard today.
This. Nimoy really has no muscle tone,he has arms like Gumby. Shatner at least has some arm muscles but nothing like you would see in a main character who takes his shirt off a lot on TV today (and a higher body fat, though I'm by no means calling him fat in TOS), yeah. I watched ST: TMP the other night and wondered at the choice of them putting Spock in that sleeveless white thing. (Not that I don't find him attractive, it's just that on TV and in movies today all the women are stick thin and all the men have huge muscles much of the time.)
(Off topic: That's also why I was amused while watching "Kid Monk Baroni," though: if I was casting an actor to play an athlete, Nimoy would be my last choice.)
Sulu looks ok without a shirt, but he's so skinny.