I'm a 22 year old female, and about 6 months ago, whenever I would do any sort of moderate physical activity (i.e.: playing wiffle ball with the kids, swimming, jogging) I get this weird rapid heart rate that starts very suddenly. My heart rate will go from feeling normal, to all of the sudden feeling like it is going to beat out of my chest. It almost feels like it's in my throat. It lasts anywhere from 10 seconds to as long as 5 minutes and the stop is always very sudden. It won't gradually slow down, it will all of the sudden stop and go back to a normal heart beat sometime after I stop exerting myself. This is NOT a normal increased heart rate from exercise, I know what that feels like and it is nothing like this. I get a sudden urge to grab my chest and crouch down when this happens. There is no pain involved at all, just a very scary feeling. The only thing that sometimes helps is if I inhale air, like an air bubble. This started as something that would only happen once in awhile when I exercised, but now it happens every single time. It does not occur AT ALL unless I'm doing some sort of physical activity. Can anyone tell me what this could be caused by?? I do not smoke nor do I have asthma.