I tried to switch to vaping high nic (20mg liquid) - i think i may have scarring on my wind pipe (my throat still hurts from vaping that high nic, and breathing is still sometimes painful, which is pretty bad news)
Lungs do recover, but dont count on it. Quit today, and take it seriously.
Watch thank you for smoking, its great for stopping.
One of my friends from decades ago had asthma right through his teenage years, and was extremely thin and weedy. Couldn't exercise much without coughing fits and similar.
He took up swimming (!), and although it was slow going at first he eventually developed good lung capacity. And became a body builder. :)
Suspecting the same thing would work for anyone with not much (or damaged) lung capacity.
I smoked for 23 years and was diagnosed with COPD at about year 17. I still have serious lung issues but they do get better, slowly. Also I want to say that my body has adapted to function better in lower oxygen availability environment - as long as I don't burst cardio over a level I'm not accustomed to, I can keep it up for hours esp. endurance