A High Intensity Interval Fitness Application HIIT. HIIT Random Interval Workout is meant to get you in awesome shape in as little as 5 minutes by giving different exercises each day at random. The idea to confuse your muscles by doing a different exercise routine each day. This is proven to get you into top physical shape and prevent your body from plateauing. The exercise is changed every 30 seconds at random. You can select how long your want your total workout routing to be.