No. At least not primarily. Smoke (assuming cigarette smoke, not weed) contains nicotine as the active agent, which is a cardivascular stimulant. That means that if anything, having a cigarette will slightly sharpen your reflexes (only momentarily though, and not above the level of a non-smoker - it's more appropriate to say that addicted smokers who have not had a fag in some time have slower-than-normal reflexes as compared to the average non-smoker, which might be the answer to your question).
Secondarily, smoking causes, among others, pollution of the lungs by tar deposits and deterioration of blood vessels, both lowering oxygenation of the body. This may manifest, in heavy and long-time smokers, in a wide variety of adverse conditions, including slower reflexes and lower muscle output.