Smoking a single cigarette will greatly increase the level of Carbon Monoxide (CO) in your blood for a good hour or more. When we get burn or smoke inhalation victims in here (emergency room), we have to ask them if they are smokers before we treat them, because the normal level of CO in a smoker would be a treatable toxic level in a non-smoker. In other words, if you smoke and have a slightly to moderately high CO level, we basically ignore it medically because it's normal for them. If you don't smoke and have a high CO level, we watch you for a while.
Carbon Monoxide is a deadly poison. It is the number one fatal cause of accidental poisoning deaths in the US. Interestingly though, it is an important component of smooth muscle contraction and digestion:
So the CO has a relaxing effect on smooth muscle, but it is common knowledge that CO and Nitric Oxide (NO) are potent vasodilators, allowing more blood to flow into various tissues. You would think that this would help in an exercise effort, but you have to remember that the vessels are dilating because the blood is actually getting thinner in useful oxygen, and the body is trying to adapt the bloodflow to maintain a decent usable oxygen level in the tissues (perfusion). I say "usable" oxygen here because CO is NOT usable oxygen. When a CO molecule contacts a red blood cell, it attaches irreversibly to the cell, permanently lowering its capacity to deliver good oxygen to the tissues. Normal red blood cells live about 120 days, so that's about four months that you are stuck with a crappy red blood cell. Multiply this times how often you smoke, and how much you smoke (non-filter, filter, lights, whatever), and it's obvious to anyone with common sense that smoking has a deleterious effect on an athletic performance which depends on good perfusion such as bodybuilding or strongman or sports, etc. I can't imagine that it wouldn't have an effect on powerlifting, too. Don't powerlifters ever get out of breath? Why make it harder to catch it again?
Smoking won't kill you right away, but in training it's like putting a governor on a race bike. You're kinda shooting yourself in the foot. And it's not even that fun, is it? If you wanna smoke, smoke weed for cryin' out loud! At least then you'll want to eat.