[quote=@Chrononaut]
I'd use fetid after describing the smell first, but it's not really properly used in the context of a gym setting (how bad can someone actually smell after exercising?). 

[/quote]

As someone who's exercised in a tiny dojo crammed full of people, I can tell you from first hand experience that things can get VERY smelly in an hour.

But you are correct, Fetid isn't the right word. I've seen that word used to describe things like the smell of corpses. A work out is fairly mild in comparison to something like that.