Ive read in a weider book that when you do breathing squats supersetted with dumbbell pullovers it stretches your rib cage better. I smell BS.
I've read that the world is actually flat and that the world is only 6000 years old.
Just because someone says something doesn't change the fact that it isn't so.
PV: you could technically lengthen the ligaments in the intercostal region and thus the small muscles there. But the cartilage that cements all of that would hinder this and cartilage is very slow growing and would be deformed or tear first (disslocated rib, etc).