After 5 minutes of jogging, sprinting, jogging sprinting HIIT, my heart rate is already pounding. A pounding heart rate means I'm burning calories. If I'm doing this fasted or with not a lot of food in my belly, then I'm burning even more.

So, is there a specific time frame I should be doing HIIT to get shredded? Or is 5 to 10 minutes sufficient enough?

I've lost much of my visible six pack and am desperate to get it back.