High Intensity Interval Training is doing one exercise for short bursts and having small rests in between. The idea of HIIT it that the intensity is so high throughout that you only need to do 30 minutes of it! You are working in your aerobic & anaerobic zones which helps to speed up your metabolism and also improve your cardio and lactic thresholds. We use HIIT for most of our classes and incorporate different elements in each class.