I don't do spin classes, but re the guy who breaths very hard.....

I know that when I have to do zone 5 efforts as part of any of my workouts, yeah I probably sound like I'm going to pass out, but rest assured I'm OK. We're all just different. The hubby, who has big lungs almost never sounds out of breath even when he's at top effort, me on the other hand, though I process oxygen better than he does, I heave like an out of control set of bellows. Let the guy do his workout and don't worry about him.