You would be surprised,people who smoke a lot of weed,tend to smoke a LOT of weed. Ive trailridden with really fast guys who stop and smoke their pipe so hard they are hyper ventilating and literally cant get enough. I dont smoke and would be going 4 mph after a while if I did. It turns out different humans have different amounts of receptor sites that absorb THC,for some a puff is a major buzz,for others they can smoke all day just to keep them at their level of..............what ever level they need to be. I guess its more a mental addiction but some live by the weed. If somebody thought they would be faster in a Grand National main event after smoking and most likely they wouldnt be tested some would take the chance. In their head they are faster. Yes its a drug just like alcohol is a drug.