Whatever your exercise of choice may be, chances are pretty good you’ve heard of the term high intensity interval training, or HIIT. But what is HIIT really, and how can you use it to make the most out of your workouts?
It’s a common—and legit question—whether you’re a fan of cardio like running or indoor cycling, or prefer to lift weights or strength train. While you might not know exactly what HIIT is, you may have an idea in your mind about what it entails. Burpees, anyone?
But like many workout protocols in the fitness field, there are some misconceptions about what HIIT really is, and what it can do for your fitness routine. Here’s what you need to know about this popular type of training.
What is HIIT?
There’s a lot more to high intensity interval training than its name alone suggests. In fact, HIIT refers to a very specific and particular type of training—and it’s possible to do interval training without actually doing a real HIIT workout.
The hallmark of HIIT is repeated, extremely hard bouts of work interspersed with periods of recovery. During your work intervals, you’ll be challenging yourself nearly to your max, Noam Tamir, C.S.C.S., founder and CEO of TS Fitness in New York City, tells SELF.
It’s the opposite of going for a long, easy run where you ration your energy in order to sustain the activity for longer. And it’s a little different from what you probably have seen labeled as “HIIT” in gen-pop exercise classes, says Tamir. Most protocols called “HIIT” would actually be more accurately described as circuit training or interval training, he says.
When your body is going all-out during true HIIT, it relies on your anaerobic pathways (breaking down glucose without oxygen) to produce the energy it needs to fuel you. This provides an immediate supply of energy, but the amount is very limited—which means the length of time you can sustain that max effort is quite short, says Tamir.
In fact, in true HIIT, you’d likely limit your work intervals to about 20 seconds, he says. Then you’d give yourself ample recovery time, usually at about a 2:1 or 3:1 ratio of rest to work. So if you were doing 20-second sprints, you’d rest for 40 seconds to one minute before beginning your next interval. (This is different from what many people call HIIT, where their work periods are way longer and rest periods much shorter, meaning they can’t go as all-out.)
Recovering before the next interval is essential: Forcing your body to repeatedly acclimate between two very different states provides excellent cardio conditioning, Franci Cohen, M.S., personal trainer and exercise physiologist, tells SELF. “The rest periods are needed to prep the body and enable it to truly perform at its max during the high-intensity spurts,” she adds.
As for how to determine whether you’re working at that near-max level? To help gauge whether you’re working hard enough, fitness pros use a rate of perceived exertion (RPE) scale that describes effort levels on a spectrum of 1 to 10, with 10 being an all-out, giving-it-everything-you-didn’t-think-you-had level of intensity. “Work intervals during a HIIT session should be at near maximum (e.g. 9),” Cohen says.
What are the benefits of HIIT?
The benefits of true HIIT are performance-based, especially for those looking to improve at a certain sport: “It’s really for athletes,” says Tamir. “With true HIIT, you’ll maximize your explosive performance and speed.”
There are other benefits too, including increases in VO2 max (how much oxygen you can use during exercise) and improvements in insulin sensitivity (how responsive your cells are to insulin), blood pressure, and cardiovascular function, according to a 2017 review published in the journal Sports Medicine.