Gym boy

I was at a party earlier this evening, and as I was getting dressed and leaving one of the other guests said to me "so you're a gym-boy?" in a fairly pleasant and conversational sort of way. I froze. I was, of course, dying to hear what was going to come next but at the same time horrified that this sort of thing means so much to me. He went on "you have a very muscular butt...". Butt? I was hoping for shoulders, again.