HIIT workout involves short bursts of intense exercise alternated with low-intensity recovery periods. Interestingly, it is perhaps the most time-efficient way to exercise. Typically, a HIIT workout ranges from 10 to 30 minutes in duration. Despite how short the workout is, it can produce health benefits similar to twice as much moderate-intensity exercise. HIIT workouts stimulate the burning and using up of fat and calories, HIIT workouts also produce muscle building anabolic hormones. As such it can be a very effective way of developing lean muscle.