woman using ropes to exercise

Whether you’re a couch potato, a fitness fanatic, or a gym unicorn — meaning that you sparkle instead of sweat and hit the gym once in a double rainbow — you’ve most likely heard the buzz about High-Intensity Interval Training (HIIT).  You probably know that it involves sweating up a storm while puffing and panting like an old steam engine. Beyond those basics, you’re sure that it’s very intense training and that you do a variety of movements in intervals. The name says it all, right?

Well, actually, it really doesn’t.  HIIT might have claimed the third spot in the National Academy of Sports Medicine’s (NASM) 2017 fitness trend forecast, but there’s way more to it than its name suggests. We’ve got some good news, though: we’ve sat down with Allan Misner, a NASM-certified personal trainer who dropped more than 50 pounds by adding HIIT to his fitness routine, and Craig Ballantyne,  the Author of The Great Cardio Myth: Why Cardio Exercise Won’t Get You Slim, Strong, or Healthy & The New High-Intensity Strength Training Program that Will.  They’re going to help you read between the letters — so you can get super strong, fast, and agile, without sacrificing the precious muscle tissue you’ve worked so hard for.


Sweet, Sweaty Science

If you’ve ever wanted to torch calories, melt fat, and build muscle, you’ve probably heard that you have to burn more calories than you take in. “However, when you do basic cardio [chronic cardio] for long periods of time, your body signals that it needs more food to keep up its new energy needs,” Misner said.  “You are only burning while you’re working, and you’ll often eat more offsetting the calories burned.”

HIIT— all-out, balls-to-the-wall, giving-it-everything-you-didn’t-think-you-had bursts of exercise, followed by short recovery periods—spikes your metabolism not only during your workout, but that burn keeps going through a process called excess post-exercise oxygen consumption (EPOC).  It also cranks up your growth hormone levels and your muscle cells’ protein turnover — that’s the healthy breaking down and rebuilding of your muscles’ tissues — reversing age-related muscle loss. Muscles burn more than fat: that’s the reason you’ll feel accelerated fat burning going on for hours as you recover on the couch, watching TV.  “It’s like magic or sweet, sweaty science,” Ballantyne said.  


HIIT Decoded

woman mountain climber exercise

“When you hear someone say they do 45-minute sessions, they are not actually doing HIIT because their intensity is not high enough,” Misner said. In order to qualify as true HIIT,  you’ll have to push yourself 100% for the full work phase. For example, if you’re doing a sprint, you have to imagine a bear is chasing you, and if you don’t give it everything that you’ve got for the full work phase, that bear will catch you.  No, it’s not comfortable. It’s not fun. That’s the reason HIIT sessions are super short—anywhere from 20 to 90 seconds.  

From burpees to bodyweight squats: this level of intensity takes some getting used to. If you’re working hard enough, your body temperature will skyrocket.  After the second or third set, unless you have a thyroid issue, you’ll start to drip sweat. You’ll also be in “oxygen debt”, meaning that it’ll be very, very hard to breathe. And, your muscles will burn, baby, burn.


HIIT the Gym

“If you are healthy enough to exercise, after being cleared by your doctor, you can use HIIT,” Misner said. “The amount of work you can do at 100% will be different than my 100%, but as long as you are pushing that upper limit and paying attention to your body, you shouldn’t have any issues.” If you’ve never “HIIT” the gym, your work phase should be 20 seconds, and your rest phase should be 80 seconds—a 1:4 ratio. 

If you’re moderately fit, according to the Journal of Strength and Conditioning, the “golden” ratio is 2:1, which means after 4 minutes on the assault bike, you’ll want to rest for 2 minutes before you put your pedal to the metal. (Another popular workout similar to HIIT, is Tabata Training, where you’re on for 20 seconds, off for 10 seconds, and rest for 8 rounds. The key advantage? Your basic workout is done in 4 minutes, not including your warmup and cool down.)

woman running catching breath

One last piece of advice: HIIT is “like running a factory at full-hilt, making the conveyor belts go faster and faster.” “Intervals…exhaust the supplies of the factory by turning up the conveyor belt,” Ballantyne said. “When you finally slow down, during your recovery from short burst exercise bouts, the factory workers have to work hard to stock up the supplies again”.  So, ladies: please rest, between sets, between workouts. (HIIT is so intense, you’ll only want to do it one or two times per week.) And, when you stop hitting full recovery, your workout is over.

Now you’re primed and ready for your first HIIT session. Just remember this formula: working harder + rest = higher oxygen intake = greater calorie burn.