Admittedly, this is a pretty ridiculous question. I am an avid runner as opposed to a cocaine user, but I have a natural curiousity about human anatomy. If rigorous exercise raises blood pressure and speeds up the heart, resulting in a stronger heart, then why doesn't the heart have a similar response to cocaine use, which also raises blood pressure and speeds up the heart?
When you run your heart doesn't immediately go from 60 beats per minute to 120 bpm. Instead, when you exercise, you work your way up. Coke has an immediate effect. Your heart rate can go from normal to sky high within minutes.
Coke puts stress on your heart, increases heart rate, blood pressure, body temperature, and sweating. It also increases speed of respiration, dilates the pupils, decreased sleep and appetite. It can decrease seizure threshold and is associated with seizures, strokes, and heart attacks in susceptible individuals.
Now it sort of seem like I am proving you point here. However, ask anyone who has ever done coke if they have had a crash. When you come down from coke you become so irritable you can be intolerable. You can become antisocial and aggressive. Besides that, after you come down your body is undernourished and basically not in a healthy state. You feel and look like crap.
When you are a runner and you come down from the “runner's high” you still feel pretty good. With coke you feel like hell. Also, when running you get all those natural endorphins. Coke is artificial.
There's a lot more information out there. Check out erowid.com for more answers. It's a great non-biased website about any drug you could imagine.