Hi,
As a 43 year old ex-smoker I know what you are going through, keep training the improvements when they come feel amazing. I am training now for the Marathon de sables so run and cycle every day.
It is annoying, that my own stupidly in smoking makes the starting so much harder, but I can run 5 miles then walk 2 minutes then run again, on the bike I cycle 12 miles a day. Even with this level of training, sometimes you feel you are only battling against the damage done by smoking and not improving, as you should
Some good advise to kids, DON’T SMOKE EVER!