HIIT is a type of interval training exercise. It incorporates several rounds that alternate between several minutes of high intensity movements to significantly increase the heart rate to at least 80% of one's maximum heart rate, followed by short periods of lower intensity movements. This allows for the body to burn the maximum number of calories in a short period of time.

What also makes HIIT popular among people is that it can easily be adjusted to meet all levels from beginner to expert in the same session.