i was exercising on my treadmill a few minutes ago, pushing myself really really hard (i wanted to burn off all the fattening stuff i hate for dinner). i was trying to keep myself pumped, to keep myself going, and i was listening to "cassie" by flyleaf. i tapped out the rhythm on the treadmill bars while i was running, and it suddenly kicked into high gear! i ran with it for as much as i could, and i was trying my hardest to get it to stop, but it wouldn't turn off! i finally unplugged it and then i collapsed on my floor, breathing rapidly, my heart racing, and shaking like crazy.

that was about twenty minutes ago, and my heart still hasn't slowed to normal, and i can still feel it beating strongly in my fingertips and behind my ears.

i know for a fact that i pushed my heart rate over 200 (my treadmill has one of those built-in pulse taker things) before i finally stopped, and i'm freaking out about this!

i'm fifteen, i weigh about one-forty, and this is not my first time exercising -- i don't exercise regularly, but i still do a few times a week. i pushed myself harder than i ever have before, and i'm wondering if this could be some sort of freakish heart attack.

someone please tell me what this is!