Even if your a heavy smoker, after a month, the smoke and resin starts to dissapate from your lungs. So, if a boxer smokes in between fights{couple of months}, then trains for 3 months, it won't affect him that bad. I'd say that most boxers who smoke, don't smoke that much, unless they are partying. Alot of other sports stars smoke. Usually in sports that don't take as much endurance. I remember a former 3rd baseman for the Cinti. Reds{baseball}, Buddy Bell, used to smoke in between innings. Some football players{American football}, even smoke. All I say is, If you can smoke, and still perform at the highest level, than you are a beast, and more power to you.