Just to be fair I did do some quick research and a lot of what Fisting Kittens is true.

The lungs can and do regenerate if the the smoker stops before a irreversible disease like cancer is contracted, but I would hardly call the rate astonishing. The people at the Canadian Cancer Society (sorry I could find anything from the AMA) say:

Is damage caused by smoking permanent?

Not if the smoker stops soon enough. In smokers who have stopped before the onset of irreversible heart and circulatory disease, the body begins to repair itself. Normally, after a year of non-smoking, the risk of a heart attack is reduced by half. After 10 to 15 years of non-smoking, it's about the same as that of someone who has never smoked.
The most popular thing that came up in the search engine after I put in "smoking damage regeneration lung" was and article called "Teenage Smoking Causes Permantnent Lung Damage" that says:

A study published in the Journal of the National Cancer Institute has shown that smoking in the teenage years causes dramatic and lifelong DNA damage in the lungs. In fact, the young smokers could be at a permanently higher risk of developing lung cancer, even if they later quit.

This information comes at a time when surveys by the Centers for Disease Control and Prevention (CDC) indicate that the percentage of high school smokers rose from 34.8 percent in 1995 to 36.4 percent in 1997.

In this study, researchers tested for DNA alterations in the non-cancerous lung tissue of patients being treated for lung tumors. The healthy tissue was tested for the number of DNA alterations per 10 billion cells. Researchers found that former smokers who started between age 7 and 15 had an average of 164 genetic alterations. Ex-smokers who started between ages 15 and 17 had on average 115 alterations. And among former smokers who did not start smoking until after age 20, the number of DNA alterations averaged 81.

Experts say that DNA alterations in the lung tissue occur when chemicals in tobacco smoke fuse with genes in the DNA and cause mutations that can significantly increase the likelihood of cancer.

But that has nothing to do with short term athletic performance, so it doesn't really apply here.

The American Lung Association List the Following as a timeline of the benefits of quiting smoking:

When smokers quit, within twenty minutes of smoking that last cigarette the body begins a series of changes.

At 20 minutes after quitting:

blood pressure decreases

pulse rate drops

body temperature of hands and feet increases

At 8 hours:

carbon monoxide level in blood drops to normal

oxygen level in blood increases to normal

At 24 hours:

chance of a heart attack decreases

At 48 hours:

nerve endings start regrowing

ability to smell and taste is enhanced

The first year after quitting:

At 2 weeks to 3 months:

circulation improves

walking becomes easier

lung function increases

1 to 9 months:

coughing, sinus congestion, fatigue, shortness of breath decreases

1 year:

excess risk of coronary heart disease is decreased to half that of a smoker

Long-term Benefits of Quitting

At 5 years:

from 5 to 15 years after quitting, stroke risk is reduced to that of people who have never smoked.

At 10 years:

risk of lung cancer drops to as little as one-half that of continuing smokers

risk of cancer of the mouth, throat, esophagus, bladder, kidney, and pancreas decreases

risk of ulcer decreases

At 15 years:

risk of coronary heart disease is now similar to that of people who have never smoked

risk of death returns to nearly the level of people who have never smoked
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