I have a question. Im doing HIIT and my heart rate and everything goes up as high as its supposed to. But what Im not sure about is what happens if your heart rate doesn't drop too much before sprinting again? Does it HAVE to drop? Its not as if I cant do my sprint hard enough. Does my <a href="http://www.hiitguides.com/difference-between-aerobic-and-anaerobic-training/">HR</a> still HAVE to drop significantly?