Taking HIIT a step further, this time of workout can be broken down to a few more varieties. AMRAP stands for "As many rounds as possible," Tabata is based on a study done specifically for athletic performance as few years ago in Japan that was designed around 20 second intervals of 170% intensity with 10 second rest in between for a total of 8 rounds or 4 minutes. And a time challenge just takes a series of exercises that once performed gives you a total time that you are able to complete it in. The goal is to continuously beat your time using the same series of exercises again & again.