Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. High-intensity interval training (HIIT), also known as high-intensity intermittent exercise (HIIE) or sprint interval training, is an enhanced form of interval training. It is an exercise strategy which alternates periods of short intense anaerobic exercise with less-intense recovery periods. HIIT is a form of cardiovascular exercise which generally consists of sessions of 9 to 20 minutes. These short, intense workouts provide improved athletic capacity and condition, improved glucose metabolism, and improved fat burning.