Lungs aren't muscles, they are just bags. It'll be the muscles around your rib cage, core and the diaphragm that is strong to do that.
Well of course I meant the groups of muscles that activate the lungs, didn't think it was necessary to list them. Just can't imagine the diaphragm or intercostals getting that powerful through natural training. I mean it's a hot water bottle.....I've been known to struggle to blow up a balloon before!
![Big Grin :D :D](/styles/default/xenforo/vbSmilies/Normal/biggrin.gif)
That being said, I just had a look on youtube, and there's some pretty averagely built guys doing it, so perhaps some just have super diaphragms naturally. Think I'll hold off trying it, as when someone finds me passed out, I'll have hell of a job explaining it.