Given its popularity and prevalence, with each practitioner aiming to put their own spin on the concept, the public understanding of what constitutes a HIIT workout has become blurred.Īccording to the American College of Sports Medicine, HIIT is defined as a style of training utilizing short, intense work periods performed between 80 and 95 percent of a person’s maximum heart rate. You'll find this style of training everywhere, from boutique fitness studios to big box gyms that offer group classes. High Intensity Interval Training allows you to pair hard-hitting exercise periods with short rest breaks for a wide range of health benefits. If what you're looking for is a style of workout that will challenge you to give all-out effort without exercising for hours, however, you only need to understand one four-letter term: HIIT. THE FITNESS WORLD is so full of acronyms that you might sometimes feel you need to pack a glossary in your gym bag to decode one term from the next.