What it stands for: high-intensity interval training
Some people add "simply" to their high-intensity interval training, putting an "s" in front of HIIT. And if you've ever tried one of these short-but-super-intense workouts (think Tabata drills) then you'll know why. While the benefits of HIIT are numerous (Check out the top 8 here), the feeling while doing them is killer. But like many fitness endeavors, the more you put into HIIT, the more you get out of it!