Todays HIIT training does not consist of only doing one set per exercise, but rather is considered more circuit training or cardio training. For circuit training, one exercise is done either to failure or for a given amount of time or reps, and then one moves to another exercise, and so on, eventually completing a circuit which they then must repeat. The constant work causes an extreme calorie burn, but the variation in exercise allows for recuperation of the worked fiber. When looking at HIIT in a cardio aspect, it is often prescribed as a given time of high intensity, followed by a given time of low intensity in a 1:1, 2:1 work to rest ratio. The lower intensity allows one to recover enough so during each bout of high intensity they can go at maximal intensity. This fluctuation allows for not only a large calorie burn during exercise, but also post caloric burn.