Even though both substances are very harmful to your lungs and can severely affect your training, I have known some great athletes who smoke either cigarettes or marijuana or both. I have listened to many debates about which is more hazardous to your health and training without coming to any set answer. The only thing each side was able to agree on is that if you want to be in the best shape possible, don't do either.
However, for those of you looking to quit and cant decide which one to quit first here are some interesting facts to help you make your decision.
Marijuana contains THC which is a bronchial dilator. This means its opens up your lungs to clear out anything hazardous like smoke and dirt. Cigarettes contain nicotine which does the opposite and makes it harder to cough anything up.
When equal amounts of Marijuana and Tobacco are smoked, Marijuana deposits four times as much tar as Cigarettes. This is because Marijuana joints are unfiltered and are more deeply inhaled.
In a study at the University of California San Francisco frequent Marijuana and Cigarette smokers went through test using a spirometer. This device measure air flow when breathing in and out. The experiment also measured individuals lung capacity (how much air your lungs can hold) and air flow rate (how quickly you can blow out air). With Cigarettes there was a straight relationship showing the more Tobacco the individual used the worse he did on all of the experiments. The same could not be said about the Marijuana users who actually showed an increase in air flow and lung capacity up to a certain level.
Both Marijuana and Cigarettes are shown to cause throat irritation, coughing and tar build up.
Remember the best way to stay fit and healthy is to refrain from both so stay smoke free my friends!