I find that in the context (and I suppose in the confines) of the gym, straight men are more vocal in their praise of another man's fitness progress.
I photographed two bodybuilders before a competition early this year, and they complimented each other's skills so much that even I blushed.
I remember when I started frequenting a gym that was close to my office. There was a guy that I always run into in the locker room. He always goes with his girlfriend (now wife) and like routine they'd kiss before parting ways in the locker room entrance.
I noticed right away he has excellent musculature, but never said anything for about four months. I never initiated a conversation once, not even the bro-nod.
One time, it was just two in the locker room, he said "your biceps are getting bigger man." I didn't put two and two together that he was talking to me for maybe a few seconds. When I turned around and asked if he was talking to me (d-oh), he said "yeah, I noticed you started lifting heavier dumbbells than usual."
I was speechless for a bit, I guess it surprised me a great deal that he was actually paying attention to my progress, since I started going to the gym.
I eventually introduced myself and we became friends. We barely talk anymore though. I switched jobs far from the gym and he moved to the west coast to start a family.