Anyone who has been to a marathon on Okinawa has witnessed a few of the die-hard locals smoking cigarettes before and after their race, but they are usually part of that group just out for the day trying to finish. They feel they can smoke and still go slow for a long time. Maybe even beat the time they put up last year.

Inhaling smoke from tobacco does many things to the body that significantly compromises airway and blood flow, severely limiting the ability run fast and race to your potential. For example:

Smoking a cigarette immediately increases carbon monoxide in your blood. Instead of floating around harmlessly, carbon monoxide poison latches onto hemo-globin, the molecule responsible for transporting oxygen from your lungs to your muscles. This means less oxygen is getting delivered to your muscles during exercise, resulting in early fatigue and oxygen debt.

According to Australian sports physiologist David Pyne, inhaled smoke causes an immediate 2-3 fold increase of resistance inside the airways of the lungs. One primary cause of this resistance is chronic swelling of the mucous membranes due to constant smoke-related irritation.

Over time, another factor that will slow you down is the accumulation of tar. A pack a day smoker inhales about 2 cups a year, so it does not take long for air exchange to become compromised in the lungs. In effect smokers end up with a smaller lung surface area than non-smokers.

Along with maximal oxygen consumption, lactate threshold is much lower in smokers compared to non-smokers. Lactate threshold is that running speed when lactic acid begins to accumulate in the blood, a sure sign that your muscles are not getting enough oxygen to meet the demand. Anyone who runs knows that the earlier you have to start breathing hard, the sooner you must slow down.

Nicotine in tobacco causes blood vessels to constrict, decreasing blood flow to muscle while increasing in blood pressure and heart rate. The heart of a smoker therefore has to work harder than a nonsmoker in order to deliver the same amount of oxygen to the muscles.

Smoking increases the amount of plaque deposited in the arteries. Eventually vessels become narrower and less elastic, with blood flow eventually becoming restricted. Once this happens, endurance is permanently reduced.

Smokers produce more phlegm and often have irritation of the entire respiratory track, making breathing during fast running very difficult.

All of these factors make running more of a chore for smokers. Sure, some smokers are blessed with the ability to run, but the truth is they would feel a whole lot better and run much faster if they quit. Smokers will never run fast relative to their potential, and as long as they continue the habit you can bet they will progressively get slower.

Some smokers may be able to run, and some runners may be able to smoke, but neither will ever be able to win.