HIIT, or high-intensity interval training, is a training technique in which you give all-out, one hundred percent effort through quick, intense bursts of exercise, followed by short, sometimes active, recovery periods. This type of training gets and keeps your heart rate up and burns more fat in less time. “A high-intensity workout increases the body’s need for oxygen during the effort and creates an oxygen shortage, causing your body to ask for more oxygen during recovery,” says Eric Salvador, NASM, NSCA, head instructor at The Fhitting Room in New York City.  “This afterburn effect is referred to as excess post-exercise oxygen consumption (EPOC) and is the reason why intense exercise will help burn more fat and calories than regular aerobic and steady-state workouts.”