How do HIIT workouts work?
HIIT is a cardio session arranged as short bursts of very hard work. The whole point of high-intensity training is to kick up the intensity of your cardio. In order to qualify as true HIIT, you'll need to push yourself to the max during every set. That's why they're short—anywhere from 20 to 90 seconds, typically.
Is a 20 minute HIIT workout enough?
All you need is 7 minutes. The sweet spot is somewhere in the 20-30 minute range. If your workout lasts any more than 30-minutes, you're probably not working hard enough to optimize the benefits of HIIT.
Is HIIT better than cardio?
HIIT is definitely better at burning calories and helping you shed unwanted pounds. The biggest reason is the anaerobic form of exercise. It burns more calories than cardio both during and after exercising.