This is a tough one. Granted every gym is at some point going to have a certain air of 'musk' about it so we all except that when we work out, its not going to smell like a bed of roses but out of respect  we do what we can to minimise our impact on others nasal senses.

However every once in a while, and maybe through no fault of their own there is always an exception to the rule, and this poses the question of when is it polite to say something, and more importantly who should say it?

Approaching the subject of ones personal hygiene and body odour in any situation is difficult enough, but in the gym even more so as it's a natural environment to sweat and perspire but there comes a time when enough is enough so what do you do?

Approach the individual and politely comment that you are having trouble working out yourself because you keep retching each time they raise a dumbbell, or approach the manager of the gym, explain the situation and let them have a quiet word?