Everything You Need to Know About Your Heart Rate and HIIT

The key to reaping such rewards? Tapping into your ideal HIIT heart rate. The short bursts of moves should challenge your beats per minute (BPM) to an intense level before a brief recovery. Keep reading to learn why your heart rate plays such an important role, what your goal BPM is, and how to use your HIIT heart rate to get the most out of your workout.

But first, what is HIIT?

HIIT workouts are characterized by intense intervals of activity followed by short breaks. In the case of Barry’s and OTF, this sequence is repeated throughout a 50-minute class. However, shorter HIIT workouts exist, too. In fact, you can enjoy health benefits from even just 15 to 20 minutes of HIIT movement. 

“HIIT is a method of cardiorespiratory training that involves relatively short periods of near maximal or maximal efforts alternated with lower exertion recovery periods,” says NASM master instructor Tony Ambler-Wright, MS. “These alternating intervals of work and rest can vary in duration depending on the intended goals and structure of the training session. Generally, ratios ranging from 1:1 to 1:5 (work: rest) are used to provide adequate recovery within each interval.” For example, you might sprint for a minute then walk for a minute; perform burpees for a minute then do a plank for a minute.

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What are the benefits of HIIT?

HIIT workouts are typically full-body workouts that offer a host of physical and mental benefits. What’s more, since they don’t take as long to perform as steady-state cardio, they’re great for folks with limited time to move their bodies. “One of the greatest benefits of HIIT is time efficiency; you can reap myriad positive health outcomes consistent with regular physical activity in a fraction of the time,” Ambler-Wright says. “With that said, it’s not easy.”

During the tough intervals, you should feel every part of your body putting in the work. Or, as Devan Kline, the co-founder and CEO of Burn Boot Camp describes it: You put all of your effort into your muscles, making your heart pump harder, thus improving the overall blood circulation to your body. As a result of exercising the heart muscle, your heart becomes stronger and healthier, which helps reduce the risk of heart disease.

Another benefit of heart rate training is increasing your VO2 max. This refers to the maximal amount of oxygen your body can utilize. "It's commonly used to test the aerobic endurance or cardiovascular fitness of athletes," says Lindsay Ogden, personal trainer and small group program manager for Life Time health clubs. "VO2 is important for heart health as it represents how much oxygen your heart can pump and how much of that oxygen the rest of your body can use."

Ambler-Wright adds that HIIT benefits also include improved resting metabolic rate, substrate metabolism, body composition, insulin sensitivity, and cognitive functions. HIIT workouts have also been shown to decrease the risk for cardiovascular diseases, breast cancer, metabolic syndrome, osteoarthritis, and rheumatoid arthritis known to cause lower back pain—all of which were detailed in a recent scholarly review. 

Why does heart rate matter in HIIT?

If you wear a heart-rate tracking device, take a peek at it throughout your next sweat sesh. You'll likely be surprised at how much it ebbs and flows as you cycle through periods of maximum work and recovery. Paying attention to your HIIT heart rate is important because your BPM can illustrate if you're actually pushing yourself or not.

Generally speaking, your HIIT heart rate should stay on the steeper side throughout the whole workout, according to DeBlair Tate, a certified fitness coach. Ensuring you're in the right range will help you reap the most benefits from your exercise—not only in the thick of it but afterward, too. "The greater the intensity of the intervals, the greater the demand for the oxygen needed for you to recover. This forms an oxygen deficiency in our body and increases our metabolism for up to 48 hours after working out," Tate says.

What should your heart rate goal be for HIIT?

A good guideline is to strive for 70 to 90 percent of your maximal heart rate during the high-intensity sessions, and 55 to 65 percent during recovery, according to Len Kravitz, PhD, coordinator of exercise science at the University of Mexico and author of HIIT Your Limit. "The level of intensity during the work intervals stimulates many positive changes in the heart as well as positive changes in the muscle cells," he shares.

The most basic way to find your max heart rate is to subtract your age from 220 and then apply the percentages. So someone who is 30 years old would have these targets:

High-intensity: 133 to 171 BPM

Low-intensity: 105 to 124 BPM

(Note that these are basic generalizations, and every body is different so your actual max could vary from this, and can only truly be determined in a lab.)

If you don't have a heart rate monitoring device, you can monitor your effort by checking your breathing instead. If you can chat with your friend while you're in the middle of your HIIT workout, you likely have enough energy to increase your output and speed up your heart rate.

How long should you stay in the high heart rate zone?

According to Tate, when you're at your peak performance, you're in the top heart rate zone. Throughout a 45-minute to one-hour workout, she says you should spend 10 to 20 solid minutes at high-intensity levels to see results. "You burn more calories per minute than with the lower heart rate workouts," she shares.

However, there are two times when this is difficult: when you're first starting out and when you're an advanced athlete. Newbies may struggle to push themselves to an uncomfortable level, while experienced fitness enthusiasts will have to exert much more energy to reach those sky-high BPMs. Ogden recommends beginning with shorter high-intensity intervals and longer low-intensity intervals so you can get through the workout.

What happens if you go above your max heart rate?

If you’ve ever taken an OTF class, you may know the thrill and/or fear of surpassing 100 percent HIIT heart rate. What will happen? “Technically, if you go above your predicted max heart rate, then it wasn’t truly your max,” Ambler-Wright says. 

Morbidly, if you truly surpass your actual max heart rate—particularly if you have a history of arterial disease or heart attack—you could overload your heart. That’s the worst-case scenario though, not to mention extremely uncommon.

How often should you do a HIIT workout?

When people start geeking out over tracking their heart rate, they may start to do tons of HIIT workouts to see faster results. Unfortunately, it doesn't work that way. According to Kravitz, if you feel exhausted and over-the-top sore after your routine, it may mean you've trained too hard or too long. "Most people can tolerate the varying intensities of HIIT quite well, but they just need to modify the workout for their fitness level," he explains. His recommendation is to perform no more than three HIIT workouts per week on non-consecutive days.

Also, Tate reminds fitness fans that heart rate tracking isn't only about cardio. In fact, you can amp up that BPM through many forms of exercise, including bodyweight strength training, typical weightlifting sessions, sports-centric workouts, and so on. "Most people do HIIT cardio, but you can also go full intensity for any type of workout," she says. "Remember that the purpose of HIIT is to go full steam—80 to 95 percent of your max heart rate—for a short time, followed by a period of low intensity. No matter how you do it, the goal remains the same."

Frequently asked HIIT heart rate questions

Will my heart rate decrease as I get fitter?

According to Ambler-Wright, your max heart rate won’t necessarily dwindle as you get fitter. “What you may find is that as you become more fit, the relative intensity required to reach your maximum heart rate might be much higher than it was when you were less fit,” he says. “In essence, at a given workload, your heart rate will be lower the more fit you get.”

What is the ideal HIIT workout length?

Remember: You don’t have to exert yourself for a full 50 minutes to enjoy the benefits of HIIT. “The ideal HIIT workout varies anywhere from 10 to 30 minutes in length,” Ambler-Wright says. 

The reason you can get away with these shorter workouts is due to the intensity of the movement. “The benefits of HIIT are truly derived from the intensity at which you’re challenging yourself, so it’s imperative to be able to go hard for the recommended duration and be able to repeat it for the recommended number of times,” says Ambler-Wright. 

You want to hit that target heart rate—that’s why 30 minutes is the sweet spot. “Extending the total workout length often comes at the expense of maintaining that high intensity necessary for each work interval; so, what was intended to be a HIIT session ends up being more of a moderate-intensity session, which commonly makes up most a large portion of people’s exercise activities.”

Who will get the most out of a HIIT workout?

Everyone can benefit from HIIT workouts. The beauty of the workout modality is that its modifiable. “High intensity is relative to the person, so they can determine just how hard they want to go,” Ambler-Wright says. “In fact, researchers have found that benefits can be realized by doing as few as three rounds of 20-second intervals at the hardest tolerable intensity followed by two minutes of recovery. Tack on a two-minute warm-up at the beginning, and a three-minute cool-down at the end, for a total of just 10 minutes of exercise.”

Who shouldn’t do HIIT workouts?

HIIT workouts require an intense exertion of energy. As such, you need to be up to the task if you’re going to engage in it. “Individuals who are injured or who have bone or joint pain should perform HIIT using a mode of exercise that minimizes impact forces on the body and/or doesn’t involve the affected body part,” Ambler-Wright says. (Cycling, working out on an elliptical, and swimming are all great examples.) “Additionally, those individuals who are at higher risk based on their cardiometabolic health status should seek medical advice and clearance prior to initiating a HIIT program.” That can include smokers, as well as people with diabetes³, high cholesterol, and/or high blood pressure.

Overall, HIIT is a challenging, inspiring workout modality for most to consider. If you have increased cardiometabolic risk factors, though, Ambler-Wright says that the biggest safety consideration is that you may be at an increased risk of an acute cardiovascular event, like a heart attack. There’s also “the potential for increased musculoskeletal injury depending on the mode, frequency, and volume of HIIT one performs,” he adds.

Ready to get started? Click play on the video below for a HIIT workout at home: