Charday Penn // Getty Images 10 min read IF YOU’RE LOOKING for a style of workout that will push you to your limits without needing to exercise for hours, you only need to understand one four-letter acronym: HIIT. The term stands for high intensity interval training, and it describes a protocol that pairs hard-hitting exercise periods with short rest breaks for a wide range of health benefits. You'll find this style of training everywhere, from boutique fitness studios to big box gyms that offer group classes. Given its popularity and prevalence, and with each practitioner aiming to put their own spin on the concept, the public understanding of what constitutes a HIIT workout how to implement the protocol within a larger training routine has become blurred . Let's cut through the hype cycle and determine exactly what you need to know. Here’s what HIIT is, what it isn’t, and the safest (and most effective) way to use it in your training. What Is HIIT?…