Your sister-in-law does HIIT and so does that one friend from your pilates class. Oh, and your impressively fit co-worker also does HIIT? You may be wondering what it is they know that you don’t. So, just one more question: What the heck is HIIT?
Exercise enthusiasts and self-care warriors out there are naturally curious about this buzzworthy workout that promises big results in just minutes at a time. You care about your fitness, your cardiovascular health, your metabolic conditioning, your body composition, and, naturally, getting that exercise endorphin boost.
From your happy-hour buddies to celebrities like supermodel Karlie Kloss, it seems like everyone is incorporating HIIT in their workout routines. Yet, you have lots of important (and sometimes already conflicting) things vying for your limited time and need to know if HIIT is right for you.
So let’s start with the basics.
The Deets on HIIT’s Popularity
HIIT stands for high-intensity interval training, sports medicine specialist Zarinah Hud, MD, says: “It’s an exercise routine in which you give maximum effort at high intensity bursts, followed by a quick rest phase and repeat this interval.” These rest phases and high-intensity intervals add up to your desired workout length. For example, a HIIT routine could consist in running on the treadmill at an all-out sprint for 30 seconds, resting, then repeating the sprint–rest sequence several minutes.
I’ve done HIIT right in my living room with jumping jacks or burpees, some motivating music, and my cell phone timer, all while the baby was asleep upstairs.
HIIT is so popular not only because it can be snuck into even the busiest schedules but because studies have shown that it can burn significantly more calories and provide greater cardiovascular benefits in a much shorter time than steady-state, moderate workouts. For instance, Hud says, “A well-known study done by the Journal of Physiology showed that 10 one-minute sprints was equal to several hours of steady-state cycling in burning fat.”
Tyler Spraul, a certified strength and conditioning specialist and head trainer at Exercise.com, explains that on top of more efficient fat burning, HIIT can really help you increase your speed and power as well, since it’s “focused on training how you operate at higher levels of intensity.”
“HIIT earns some bonus points here,” he tells HealthyWay, “because it will increase your total work capacity as well.”
More Points for HIIT
Most women struggle to find enough time in their busy days to work out but still want to make fitness and wellness a high priority in their lives. If this describes you, Spraul points out that “HIIT is a great choice when you’re short on time and still want to get a challenging workout in.”
Bosses in their offices? Check. Busy grad students after class? Yup. Moms with a baby who will only sleep for 30 minutes at a time? Regardless of their individual fitness goals and schedules, HIIT stands to benefit them all.
Although both Hud and Spraul stress that too much HIIT can be counterproductive (more on that later), Spraul explains that HIIT is terrific for “your heart and cardiovascular system, which then carries over into just about every area of your overall health.” HIIT has even been shown to be a big helper for your VO2 max, which will contribute to your efforts to become a healthier, stronger athlete.
In short, high-intensity bursts of anaerobic exercise, interspersed with rest, can burn tons of calories and improve overall fitness and health in a New York minute.
Of course it’s cool from a time-management and accessibility perspective that you can do HIIT pretty much anytime, anywhere, with no equipment besides your body and a clock. Simplicity for the win!
This type of exercise is also a big hit (pun intended) with those who “tend to get bored of monotonous sets and reps,” according to Spraul, which could be the antidote for long, dull runs on the treadmill.
The Science Behind the Big Claims
One of the keys to success in HIIT is to realize the sweet spot of your anaerobic threshold, which of course requires appreciating the different between aerobic and anaerobic exercise.
Simply put, aerobic refers to moderate, steady-state exercise that uses your large muscle groups. Anaerobic exercise is shorter in duration but way higher in intensity (think sprinting) and makes use of your “fast twitch muscles,” according to a paper published in the World Journal of Cardiology.
Hud explicates, saying it’s “well documented in the literature that high-intensity workouts burn significantly more total calories and fat calories overall when compared to a conventional steady-state aerobic exercise routine, such as jogging.”
Hud says the so-called after-burn phenomenon is one of the reasons HIIT is so effective. Simply put, HIIT burns fat not only during the exercise but also “for hours after you’ve completed the routine.” Your body uses more energy than usual to recover, which means the calorie burning goes on for about two hours.
So what’s the takeaway for you? The after-burn phenomenon can add between 6 and 15 percent more calories to the overall energy expenditure associated with the workout, according to both Hud and the American College of Sports Medicine (ACSM).
Spring Into Action: How do I try HIIT?
You can do HIIT with tons of different types of exercises, like cycling, swimming, or even calisthenics, although it originated with running as the exercise of choice when the Finnish Olympic track team used interval training to win gold in the early 20th century. As the story goes, around 1910, Finnish running coach Lauri Pihkala started recommending that competitive runners “should include more training that included alternating fast and slow runs,” according to an article from The Science of Running. His method helped two Finnish runners, Paavo Nurmi and Hannes Kolehmainen, achieve victory at the 1912 Olympics.
Though most of us aren’t aiming for Olympic gold, HIIT is still a great choice. Whether you’re running on the open road or doing it indoor style on a spin bike at the gym, a good beginner’s HIIT workout will look something like this: a nice and easy warm-up followed by alternating a short period of super hard effort with a rest period, repeating the interval process until you get to the end of your desired time. Hud recommends anywhere between 15 and 30 minutes of HIIT exercise, and Spraul says, “20 minutes is probably about the optimal time, [though your workout] can vary based on your goals and fitness level.”
And of course, don’t forget to do a nice relaxing cool down.
When it comes to figuring out the right effort level to exert, don’t worry if you don’t have any fancy equipment. You can just go by feel. During the high-intensity phases, Hud advises going to “75 to 80 percent of your maximum heart rate for two to three minutes,” a level of effort marked by “[not being able] to hold a conversation.”
During your “active recovery” stages, she says to shoot for “40 to 50 percent of your maximum heart rate for two to three minutes,” which you can also think of as being able to hold a conversation with a “mild” effort.
We’ve got a video series you can use for for designing your own at-home HIIT workout, or you can consider turning to a trainer to help you put together a personalized routine.
Choose your favorite “fast twitch”–inducing workout. Maybe it’s running, maybe it’s cycling, rowing, hand-cycling, burpees, jumping jacks, swimming, rope-climbing…whatever. Just make sure it’s something you feel confident going all out with. Some more suggestions for low-tech workouts include jump squats, lunges, mountain climbers, or push-ups.
After completing your normal warm-up, choose how many reps you’ll do (so there’s no cheating once you get tired) and what timing structure you’ll use for your intervals. The ACSM says that using “a specific ratio of exercise to recovery” can “improve the different energy systems of the body.” For example, “a ratio of 1:1 might be a three minute hard work (or high intensity) bout followed by a three minute recovery (or low intensity) bout.”
Our HIIT video series includes exercises for core, full body, upper body, lower body, glutes, and cardio.
Another HIIT strategy is called the “sprint interval training method,” according to the ACSM, which explains that “the exerciser does about 30 seconds of sprint or near full-out effort,” followed by around four minutes of recovery. Then you repeat this interval process three to five times depending on your experience and fitness levels.
Again, don’t forget to cool down! Andrea Fradkin, associate professor of exercise science at Bloomsburg University, was quoted in a New York Times science blog post as saying that although cooling down doesn’t necessarily prevent future muscle pain, it does prevent a “buildup of blood in the veins,” which can cause fainting, dizziness, and an all-around gross feeling (believe me, I know).
So, what to do? Just “walk for a few minutes at the end of a workout and you’ll maintain normal circulation to the brain,” according to Ross Tucker, a physiologist who contributed to the same post. Another option is dialing down the same exercise you’ve already been doing and continuing it at a comfortable talking pace until your heart rate returns to normal.
Watch out for noob mistakes.
High-intensity interval training can help you score some pretty impressive benefits, but Spraul stresses that “it’s just one tool in the toolbox, and should be programmed intelligently as part of a larger approach to your fitness goals… Don’t try to do too much at once!” He emphasizes that when it comes to HIIT, “sometimes less is more.”
Both Spraul and Hud agree that one to three HIIT sessions a week should be okay (closer to one if you’re a beginner) as long as you have a good fitness base and you allow yourself enough recovery time in between. Otherwise, both of them mention that you’d be setting yourself up for an overuse injury.
Never exceed four HIIT workouts per week, and never do HIIT for more than 30 minutes at a time, says Hud. Spraul warns that “If you’re in pain, chances are you don’t need more HIIT and need to try something else for a bit to recover.” As with any new exercise regimen, it’s definitely important to consult with a physician to make sure you’re healthy enough for intense exercise.
Another potential pitfall? Dropping the ball on the nutrition front. When a workout this intense is on the table, Hud advises her patients to “stay away from ‘restrictive diets’ and go for a balanced meal, which would include a moderate amount of complex carbohydrates and lean protein a couple of hours before and after the HIIT routine.”
Nutrition-wise, the most important thing after a hard workout is replacing glycogen, which helps to prepare your muscles to repair themselves. According to Hud, “Research supports a 3:1 ratio of carbohydrates to protein within 30 minutes of finishing a HIIT workout is best for replacing energy stores.”
Trail mix or almond butter on whole wheat toast are great choices.
Thoughts From the Trenches
As a longtime exercise enthusiast, yogi, runner, bike commuter, and hobby triathlete (all pursuits that keep me both fit and sane) I’ve definitely tried incorporating HIIT into my routines before. And boy did I feel great when I powered through my routine…until 20 minutes or an hour or two later when I got a splitting headache, almost without fail.
HIIT sadly doesn’t work for me as a regular part of my routine because I have a headache disorder (daily chronic migraine) that causes certain increased vascular activity to trigger a really, really yucky headache. For me personally, that means being resigned to spending hours on the road, treadmill, or yoga mat instead of just a few minutes in ass-kicking mode to get the results I want.
In a broader sense, it means HIIT isn’t for everyone and affirms the importance of consulting with a trusted healthcare provider before implementing a routine that might hurt or incapacitate you.
Hud and Spraul both mention the importance of having “a good fitness base” before you embark on a high-intensity interval training journey. Like with any exercise, it’s important to make sure you won’t hurt yourself and that it’s safe to go all-out. Especially with HIIT, given the extreme nature of the “on” periods, you could harm yourself if you’re not quite up to the task.
Of course, even if your girlfriend can’t join you in your newfound HIIT regimen, that doesn’t mean HIIT won’t be the magic key to upping your workout routine.
HIIT has hard science and anecdotal evidence from trainers and athletes on its side, so whether you go for HIIT or another approach to achieving your fitness goals, start slow, listen to your body, and give yourself plenty of rest and recovery time between sessions so you can keep going strong.