Understanding Changes in Resting Heart Rate

Robert J. Myerburg, MD, is a professor at the University of Miami Miller School of Medicine who for 31 years served as chief of the school’s division of cardiology. “We have known for a long time that a higher heart rate is associated with increased risk for heart disease,” he says.

The people in the new study were healthy, he points out. The new study findings may not apply to people with heart disease.

Don’t panic about these findings, says Kousik Krishnan, MD. He is director of the Arrhythmia Device Clinic at Rush University Medical Center in Chicago. “People who have a heart rate that goes up over time may have some other underlying condition,” he says. “If you have a resting heart rate that is over 100, ask your doctor to do a physical exam to see if something else is going on.”

Suzanne Steinbaum, DO, says the study provides empowering information. She is a preventive cardiologist at Lenox Hill Hospital in New York City. “Resting heart rate gives us an indication about our heart health,” she says. “The best way to keep your resting heart rate down is aerobic exercise.”

This means that if your resting heart rate is edging up, your activity level has probably taken a dive. “You are still in control,” she says. “Start exercising more and see a doctor to make sure something else isn’t going on.”

Mid-life resting heart rate of 75 plus beats/minute linked to doubling in early death risk

And an increase in the rate for men in their 50s is associated with a heightened risk of heart disease over the next 11 years, the findings show.

Resting heart rate-the number of heart beats per minute when the body is at rest-usually changes with age, with lower rates indicative of better cardiovascular fitness and more efficient heart function. A resting heart rate of 50 to 100 beats per minute (bpm) is considered to lie within the normal range.

The researchers wanted to find out what impact a resting heart rate at the higher end of the normal range might have on long term health and risk of early death (before the age of 75), and if changes in the rate over time might be important.

They studied a randomly selected group of men aged 50+ from the general population, all of whom had been born in 1943 in Gothenburg, Sweden.

In 1993, 798 out of a total of 1450 filled in questionnaires on lifestyle, family history of cardiovascular disease, and stress levels. And they were given a comprehensive medical check-up, which included their resting heart rate.


This was divided into four categories: 55 or fewer bpm; 56-65 bpm; 66-75 bpm; and more than 75 bpm.

Resting heart rate was measured again in 2003 and 2014 among those who were still alive and willing to take part at these time points (654 and 536, respectively) to track any changes in rate between 1993 and 2003 and any treatment for, or deaths caused by, heart disease/stroke or anything else, up to 2014.

During the 21-year monitoring period, 119 (just under 15%) of the original 798 men died before their 71st birthday; 237 (nearly 28%) developed cardiovascular disease; and 113 (just over 14%) developed coronary heart disease.

Men whose resting heart rate in 1993 was higher than 55 bpm were more likely to be smokers, less physically active, and more stressed than those whose rate was lower.

They were also more likely to have other cardiovascular disease risk factors, such as higher blood pressure and weight.


But a resting heart rate of 75+ bpm in 1993 was nevertheless associated with around a twofold higher risk of death from any cause, from cardiovascular disease, and from coronary heart disease, compared with a resting heart rate of 55 or below.

And a resting heart rate that was stable between 1993 and 2003, when the men were aged 50 to 60, was associated with a 44 per cent lower risk of cardiovascular disease over the next 11 years compared with a resting heart rate that had increased over this period.

What’s more, every additional beat increase in rate was associated with a 3 per cent higher risk of death from any cause, a 1 per cent higher risk of cardiovascular disease, and a 2 per cent higher risk of coronary heart disease.

This is an observational study, and as such, can’t establish cause, added to which the research was restricted only to men, and the age of the participants may itself have been an influential factor, note the researchers.

But the findings have clinical implications, they suggest, in that monitoring changes in resting heart rate over time may be important for uncovering future cardiovascular disease risk.

The new Charge 2 fitness tracker ($150) is the best Fitbit device I’ve ever tested, and I’ve used every one of the company’s products (except for its very first tracker). I’ll even take that a step further: Backed by Fitbit’s easy-to-use mobile app and opt-in leaderboard, Charge 2 is the best fitness-focused, non-smartwatch wearable you can buy right now.

After a week of using the wristband tracker day and night, I have only three complaints.

The bad stuff about Fitbit Charge 2

1. Charge 2’s screen is hard to read in bright sunlight

Outside on a sunny day, Charge 2’s OLED screen, like many other Fitbit device screens, becomes hard to read. I’ve grown to expect this, not only with Fitbits — Surge is the exception because it has a monochrome screen — but with most other wearable displays as well.

The first-gen Apple Watch does the best job of making workout (and other information) easy to read on sunshine-y days, and the Apple Watch Series 2 promises a display that’s twice as bright.

2. You can’t swim or shower with Fitbit Charge 2

Fitbit finally released a wearable, the upcoming Flex 2, designed for use while swimming or showering. Other wearables, such as Garmin’s vivosmart HR+ ($220), have had this “superpower” for some time now. Apple’s new Watch Series 2 will track swim workouts as well. So Fitbit’s belated dive into the pool comes none too soon.

Despite many things to like about Charge 2, it unfortunately can’t go in the pool or shower with you.

3. You can’t pause an exercise with Charge 2

Let’s say you select “Walk” as an exercise to track and, while you’re out, need to stop at the store to buy a couple of items. Unlike with Fitbit’s Blaze and Surge fitness watches, you can’t pause Charge 2’s exercise tracking. It’s a minor annoyance, but it’s still an annoyance.

The good stuff about Fitbit Charge 2

Charge 2 moves the Fitbit activity-tracking ball forward in several important ways.

1. Cardio Fitness Level and Score

Charge 2 is the first Fitbit device that calculates your “Cardio Fitness Score,” a numerical rating that’s based on resting heart rate, age, gender, weight, and other data. Charge 2 also tracks your “Cardio Fitness Level,” which ranks your fitness score from “Poor” to “Excellent.”


Cardio Fitness Score and Level before the author took a 15-minute run (left) and after (right).

It’s useful to know how your cardio fitness stacks up to others in your gender and age range. If nothing else, it encourages you to keep up the pace. If you’re not satisfied with your score, Charge 2 can help you increase it through more intense exercise.

2. Charge 2 Interval Workout mode

High-intensity interval training has been shown to increase cardio fitness and health. Fitbit got the memo, and it added its first interval training workout mode to Charge 2. The feature helps make Charge 2 an even better device for athletes, in some respects, than Fitbit’s higher-end Blaze or Surge.

With Charge 2, you can determine interval durations and set how frequently you want them to repeat, to seriously up your fitness game. I configured a workout in which I run for three minutes and then walk for three, then repeat, for a total of 30 minutes. Charge 2 vibrates to tell you when to change speed.

Other apps and fitness watches let you create interval training sessions, but it’s great to have this capability in a slim, lightweight wearable like Charge 2.

3. Relax mode

Fitbit’s “Relax mode” in Charge 2 provides guided breathing sessions of two or five minutes, to help you destress. The feature is easy to initiate, too. You just tap the Charge 2’s button to toggle through a few screens, then hold it in to start. (Apple’s watchOS 3, which is expected to be released Sept. 13, will feature a new, similar “Breathe” app.)

4. Charge 2 Reminders to Move

Alta was Fitbit’s first device with its “Reminders to Move” feature, which vibrates your wrist at 10 minutes to every hour (12:50 p.m. and 1:50 p.m., for example) if you haven’t taken at least 250 steps during that hour.

Charge 2 also includes Reminders to Move. And unlike Alta, Charge 2’s screen shows how many steps you took during the past hour, so you know how many more you need to “win the hour.”

Reminders to Move will also be available for Flex 2 and, soon, Blaze.

Other Charge 2 goodies worth a mention

In my tests, Charge 2’s battery lasted between 3.5 and 4.5 days. That’s impressive compared to some other Fitbit devices I tested. It also beats the Apple Watch’s 18-hour battery. You can expect to charge up Charge 2 about twice a week.

Fitbit’s “PurePulse” heart-rate sensor in Charge 2 seems accurate, at least compared to the readings from my Polar chest strap. I did see some brief but noticeable differences between the two heart-rate readings I received during intense cardio workouts. However, the average and maximum beats per minute (bpm) readings for each workout only differed by a few beats between Fitbit’s and Polar’s readings.

Charge 2 automatically tracks sleep and a variety of exercises. You can choose from several clock faces, too, including my favorite, which shows time, date, the day’s total steps, and your current heart rate. Also, like Alta and Blaze, you can easily switch Charge 2’s bands. Or you can opt for a “special edition” rose gold or black gunmetal case ($180) each.

Charge 2, like a growing number of Fitbit devices, displays calendar, text-message, and caller-ID alerts from your nearby smartphone. You can’t respond to any of these alerts as you can with a smartwatch, however.

A great upgrade to Charge HR

Charge 2 surpasses its predecessor, Charge HR, in every way. Charge 2 also advances Fitbit’s activity tracking capabilities and the data it provides users. The device costs $150 — the same price that Charge HR initially cost (it’s now $130).

Now that I’ve spent time with Charge 2, it’s hard for me to recommend any other Fitbits, though I have not yet tested Flex 2. For example, Fitbit Blaze lacks some of Charge 2’s key features, and it’s bigger and bulkier — though it also has a color screen and acts a bit more like a watch. Surge, Fitbit’s top-of-the-line tracker, has only one advantage, in my opinion: built-in GPS.

The bottom line: If you’re looking to buy a new Fitbit, do yourself a favor and seriously consider Charge 2.


Cardio fitness has been getting a lot of attention from major health organizations like the American Heart Association. And for good reason. As Fitbit previously reported, people with low cardiorespiratory fitness have a 56 percent higher risk of death from heart disease than those who are the most fit. ‘Cardiorespiratory fitness is one of the most powerful predictive risk factors for premature cardiovascular disease there is,’ says study co-author Timothy S. Church, MD, PhD, MPH, professor of preventative medicine at Pennington Biomedical Research Center at Louisiana State University in Baton Rouge. ‘It’s right up there with smoking, diabetes, and family history.’

But as you’ll see below, preventing heart disease isn’t the only reason you should care about your Cardio Fitness Score. In fact, it’s something everyone should be monitoring, says Church.

‘I think the continued evolution of physical activity tracking and measuring devices is creating a huge potential opportunity for the widespread use of fitness as an important health marker.’

Need more convincing? Read on for five more compelling ways improving your Cardio Fitness Score can positively affect your health.

Reduce belly fat. Having a healthy body mass index (BMI)-a measure of body fat based on height and weight-doesn’t mean you can avoid exercise. Researchershave found that healthy middle-aged men with high cardiorespiratory fitness scores tend to have lower amounts of visceral fat-a type of fat found deep within the abdomen that’s associated with health conditions like heart disease and type-2 diabetes-regardless of their BMI. Even at the same BMI, men with high cardiorespiratory fitness have, on average, 23 percent less visceral fat than those who are the least fit.

Sleep better.A recent reviewof sleep research concludes that regular exercise can help adults fall asleep faster, sleep longer, and wake up less. One of the studieslooked specifically at the relationship between sleep quality and cardiorespiratory fitness, and found that the better middle-aged adults did on a treadmill test, the less likely they were to have sleep complaints. Otherstudiesfound decreased physical activity leads to an increased risk for insomnia.

Prevent diabetes. When researchers evaluated the health of a group of people who had risk factors for type-2 diabetes (family history, hypertension, etc.) but hadn’t developed the disease yet, one metric stood out: VO2 max-the gold standard for measuring cardiorespiratory fitness. Individuals at risk for type-2 diabetes had a VO2 max 15 percent lower than a control group. The study authors wrote, ‘This raises the possibility that decreased VO2 max is among the earliest indicators of insulin resistance and type-2 diabetes.’

Combat anxiety.Numerous studiesshow the positive effect regular exercise has on anxiety. In a 2016 study, researchers found that women with panic disorder who performed aerobic exercise three times a week for 12 weeks experienced a significant reduction in anxiety symptoms as well as a significant improvement in their cardiorespiratory fitness.

Dodge the blues. A 2016 meta-analysis in Preventive Medicinefound that people with low cardiorespiratory fitness have a 75 percent increased risk of depression; people with medium cardio fitness levels have an increased risk of about 23 percent.

Ready to boost your Cardio Fitness Score? Check out these workout suggestions:
5 Simple Ways to Boost Your Cardio Fitness
The Two-Sprint Workout That Gets You Fit
Cardio-Fitness-Boosting Running Workout

This article is not intended to substitute for informed medical advice. You should not use this information to diagnose or treat a health problem or condition. Always check with your doctor before changing your diet, altering your sleep habits, taking supplements, or starting a new fitness routine.

Danielle Kosecki

Fitbit news editor Danielle Kosecki is an award-winning journalist who has covered health and fitness for more than 10 years. She’s written for Glamour, More, Prevention, and Bicycling magazines, among others, and is the editor of The Bicycling Big Book of Training. A New York native, Danielle now lives in the Bay Area where she doesn’t miss winter at all.

How do I track my heart rate with my Fitbit device?

Learn how Fitbit tracks your heart rate day and night, and see tips to get a more accurate reading.

Skip to:

  • How does my Fitbit device detect my heart rate?
  • How do I check my heart rate on my Fitbit device?
  • What are heart-rate zones?
  • What is my resting heart rate on my Fitbit device?
  • How do I improve the accuracy of my heart-rate reading on my Fitbit device?
  • What is my cardio fitness score?
  • Are the LEDs on my Fitbit device safe?
  • Why is my heart-rate reading blank or frozen on my Fitbit device?
  • Are there other factors that can affect my heart-rate reading?
  • Why is there a difference between the heart-rate reading on my Fitbit device versus another device?

How does my Fitbit device detect my heart rate?

When your heart beats, your capillaries expand and contract based on blood volume changes. To determine your heart rate, the optical heart-rate sensor in your Fitbit device flashes its green LEDs many times per second and uses light-sensitive photodiodes to detect these volume changes in the capillaries above your wrist. Then your device calculates how many times your heart beats per minute (bpm). The optical heart-rate sensor detects a range of 30-220 bpm.*
We use green LEDS because they maximize the signal detected from the capillaries near the surface of the skin. The optical heart-rate sensor also uses infrared light to determine when the device is on your wrist to improve the accuracy of your heart-rate data.
*This range applies during sleep; while you’re awake, the range is 40-220 bpm. On Fitbit Versa, the range is 30-250 bpm.

How do I check my heart-rate on my Fitbit device?

On most devices, swipe up on your clock face to open Fitbit Today . See your current heart rate and either your heart-rate zone or resting heart rate (if not in a zone). Swipe to see your time spent today in each heart-rate zone and your cardio fitness score.
If your device has an Exercise app, you can check your real-time heart rate and heart-rate zone during a workout. Note that heart-rate tracking is disabled while swimming.
On Fitbit Ionic and Fitbit Versa series, the heart-rate value appears gray if your watch is searching for a stronger reading.

What are heart-rate zones?

Heart-rate zones can help you optimize your workout by targeting different training intensities. Fitbit estimates your maximum heart rate with the common formula of 220 minus your age, and calculates 3 heart-rate zones based on that number. Occasionally during intense exercise, you might notice your heart rate go above your Fitbit-calculated maximum heart rate.
For more information about zones, see the American Heart Association’s Target Heart Rates article.

Default Zones

Icon Zone Description
Below 50% of your maximum heart rate
Your heart rate may be elevated, but not enough to be considered exercise.
Between 50% and 69% of your maximum heart rate
This low-to-medium intensity exercise zone may be a good place to start for those new to exercise. It’s called the fat burn zone because a higher percentage of calories are burned from fat, but the total calorie burn rate is lower than more intense exercise zones.
Between 70% and 84% of your maximum heart rate.
In this medium-to-high intensity exercise zone, you’re pushing yourself but not straining. Most people should target this exercise zone.
Greater than 85% of your maximum heart rate.
This high-intensity exercise zone is for short, intense sessions that improve performance and speed.

Custom Zones

Instead of using the 3 zones based on your maximum heart rate, you can create a custom zone to target a specific heart rate:

  1. Tap the Today tab and tap your profile picture > Heart Rate Zones.
  2. Enter your custom zone.

On, log into your dashboard and click the gear icon in the top right. Click Settings > Personal Info and enter your custom zone.

What is my resting heart rate on my Fitbit device?

Resting heart rate is the number of times your heart beats per minute when you are still and well rested. This metric can be an important indicator of your fitness level and overall cardiovascular health. The typical resting heart-rate range for adult Fitbit users is 50-90 beats per minute. Active people often have a lower resting heart rate. For more information, see the Fitbit Blog.
Fitbit uses your heart-rate data from when you’re both awake and asleep to estimate your resting heart rate. For best results, wear your device to sleep.

How do I improve the accuracy of my heart-rate reading on my Fitbit device?

As with all heart-rate tracking technology, accuracy is affected by personal physiology, device location on your arm, and type of movement.
For a more accurate heart-rate reading:

  • Wear your Fitbit device on top of your wrist, and make sure the back of the device is in contact with your skin.
  • When you’re not exercising, wear your device a finger’s width above your wrist bone.
  • During a workout, experiment with wearing the device higher on your wrist (2 finger widths) for an improved fit. Many exercises such as bike riding or weight lifting cause you to bend your wrist frequently, which could interfere with the heart-rate signal if the watch is lower on your wrist.
  • Consider tightening your wristband before a workout and loosening it when you’re done. The wristband should be snug but not constricting (a tight wristband restricts blood flow, potentially affecting the heart-rate signal).

What is my cardio fitness score?

Cardio fitness score, Fitbit’s estimate of your VO2 Max, is an indicator of overall fitness that can help predict performance for endurance-based activities including running, biking, and swimming (source). For more information, see What is my cardio fitness score?

Are the LEDs on my Fitbit device safe?

The LEDs on your device have very low power so they won’t burn your skin, and they’re programmed to shut down if your device freezes or can’t find a signal.
Note that the LEDs continue to flash if you turn off heart-rate tracking.

Why is my heart-rate reading blank or frozen on my Fitbit device?

Occasionally your device may have difficulty getting a strong signal, especially during exercises that cause your arm to move vigorously. If your heart rate is blank or frozen, try to relax your wrist and stay still for up to 10 seconds. On Versa 2, you might also notice a spike or dip in your reading as your device finds your heart rate. In both cases, normal tracking should resume shortly.
For additional troubleshooting steps, see Why don’t I see my heart rate on my Fitbit device?

Are there other factors that can affect my heart-rate reading?

Several factors can affect your heart rate, including air temperature, stress level, physical body position, and medication use (source).

Exercising in cold weather can make it more difficult for your device to track your heart rate, as environmental conditions can affect skin perfusion (the amount of blood that flows through your skin).
Spikes in your heart rate during sleep may be caused by sudden movements (for example, waking up and getting out of bed), or a weak signal due to wrist placement.
Review our tips in How do I improve the accuracy of my heart-rate reading on my Fitbit device? For any concerns about your heart-rate data, contact your physician.

Why is there a difference in my heart-rate reading on my Fitbit device versus another device?

At times, you might notice slight variations between your heart-rate reading on your Fitbit device versus on another device (such as a chest strap or another wrist-based heart-rate tracker) due to the differences in technologies.

Differences between heart-rate readings on your device and on exercise equipment are likely due to wrist or hand position. Make sure the back of your device is in contact with your wrist and that your band is snug.
Note that you might notice slight variations in your heart-rate readings on Versa 2 as compared to readings on another Fitbit device. We optimized the algorithm used to track your heart rate on Versa 2 to complement our latest hardware.

Fitbit heart rate monitoring explained

Tracking heart rate is a huge feature of Fitbit’s smartwatches and fitness trackers – and drives the data we demand from our wearables. But how does Fitbit track heart rate – and is it accurate?

Thanks to the in-built heart rate monitor found in the Inspire HR, Fitbit Charge 3, Fitbit Alta HR, Fitbit Versa and Fitbit Ionic, you’re able to gauge not only your heartbeat activity during workouts, but also tap into wellness features and some of the best sleep tracking in the business.

We get stuck into how it works, and why you’d want to try it out:

Why does Fitbit track your heart rate?

By tracking your heart rate, Fitbit can better establish facts about your body and offer better insights. Fitbit uses its heart rate sensor for:

1. Real-time 24/7 heart rate
2. Resting heart rate
3. Average heart rate
4. Calorie burn information
5. Heart rate via sleep for Sleep Stages
6. VO2 Max via Cardio Fitness Score
7. Breathing via Relax app

How does Fitbit measure heart rate?

Similar to how we covered the tech for the Apple Watch heart rate monitor, let’s give a quick breakdown to how pretty much all wrist-based heart rate monitoring works.

Photoplethysmography essentially works upon one simple premise: blood is red because it reflects red light and absorbs green light. So by using green LEDs and pairing them with photodiodes, Fitbit uses its own in-house PurePulse technology to detect the amount of blood flowing through the wrist.

When your heart beats, this flow, and as a result the green light being absorbed is greater. These lights are then flashed hundreds of times per second in order to gain the most accurate BPM (beats per minute) data.

Naturally, while every company dabbling with this optical sensor technology is working from the same blueprint, but the accuracy of the readings will come down to how each company’s algorithms interpret the data.

How accurate is Fitbit heart rate data?

Like with any optical heart rate solution, Fitbit’s PurePulse technology is solid but not without its issues. Fluctuating between high heart rate and low heart rate during interval training can often prove to be problematic for the heart rate monitor to keep up with. As we say though, Fitbit’s trackers aren’t alone in this problem.

If you sense your Fitbit device isn’t quite tracking your heart rate correctly, there are a couple of things to keep in mind. When you’re not exercising, wear your device a finger’s width below your wrist bone. And when you are exercising, consider wearing the device slightly higher on your wrist for more accurate readings, since some exercises will cause your wrist to move frequently.

Naturally, as with any wrist-based monitor, you’ll also need to make sure the back of the watch is touching the skin at all times, while also ensuring it isn’t strapped too tightly onto your wrist.

How to view your heart rate on a Fitbit

Below we’ll get into the intricacies of the heart rate monitor, but it’s worth pointing out how you can actually view your heart rate data, too.

Depending on the device itself, you should be able to see your current BPM on the home screen or by swiping. For detailed info from your exercise or on resting heart rate, you’ll need to head to the Fitbit app’s dashboard and tap through to the Heart Rate section and select the day you want to view. The same also applies to the Fitbit web app.

Resting heart rate while you sleep

Heart rate tracking isn’t just about exercise. Fitbit’s trackers are also able to keep track of your resting heart rate — a metric which refers to the heart rate measurement when you’re awake, calm and have not recently exerted yourself.

In order to estimate this, Fitbit interprets data taken from when you’re awake and when you’re asleep, meaning that those who take their device off before bed won’t receive the most accurate results.

Read next: How to use wearables to lower your resting heart rate

Typically, your resting heart rate is higher than your heart rate while you’re asleep, so don’t start panicking if you notice that the figure is higher than the lowest number you see in your graphs.

VO2 Max for serious fitness data

While VO2 Max – the metric which essentially calculates the maximum amount of oxygen that an individual can utilise during intense exercise – has made its way onto a large number of sports watches and even hearables, Fitbit has a different name for it – Cardio Fitness Score.

To access your score, simply head to the heart rate section of the Fitbit app and swipe the graph across. The higher your score, the better your fitness, and Fitbit will help determine where you sit on the scale by looking at your age, gender and resting heart rate. For more on understand the metric, read our VO2 Max guide.

Fitbit heart rate zones

Heart rate zones are essentially groupings, which allow you to adjust the intensity of your training based upon how long you spend in certain stages.

When you set up a Fitbit account you’ll be assigned your maximum heart rate, which is configured by the usual method — 220 BPM minus your age — and from there your heart rate zones are also established.

Essential reading: How to train with heart rate zones

At the top is what Fitbit labels as your Peak Zone, which means your heart rate is above 85% of its maximum. Next below is your Cardio Zone, which covers the ground betwee 70% and 84%, before scaling down to the the Fat Burn Zone when your heart is pumping at between 50% and 69% of its maximum. Anything below 50% of your maximum heart rate is considered Out Of Zone.

How to customise Fitbit heart rate zones

It’s all well and good knowing about your heart rate zones, but it’s also nice to have a bit of control over them. And there are two ways to customise them.

If you’re working from the Fitbit app, head to Account from the app dashboard and scroll down to Heart Rate Zones in settings. From there, you’re able to add a custom zone and also adjust your max heart rate.

To change the same things from the Fitbit web app, head to the dashboard, select the gear icon, select Settings and then Personal Information.


Using heart rate tracking to keep calm

Heart rate variability, which is calculated by looking at the time in between heartbeats, is another measurement used by Fitbit to keep a track on your heart. However, since this is focused on tracking fluctuations, things like a user’s age, body position, the time of day and health status can all affect readings.

Fitbit’s Relax app, available on the Charge 3, Ionic and Versa, measures the beat-to-beat changes in order to recommend a personalised breathing pattern during each guided breathing session.

However, these are more of a real-time way to get you to focus on relaxing, as opposed to something you view in the companion app and keep a track of in the long term. You’re able to choose a session lasting either two or five minutes, and all you need to do is follow the circle on the screen for inhaling/exhaling. Sparkles will show after around 20 seconds if you’re aligned to the device.

You can read more in our heart rate variability guide.

Working out that calorie burn

Firstly, your Fitbit device will take into account your basal metabolic rate (BMR), which is the calories that burn by maintaining necessary body functions like breathing, heartbeat, and brain activity.

This BMR accounts for around half of your daily calories, with this estimated from the gender, age, weight and height you enter when setting up your device. And with the tracker resetting the stats at midnight, this is why you’ll notice calories already burned when you wake up – your still burning as you sleep. Naturally, Fitbit will also be adding on the calories you burn through activity.

If you’re looking for more on this, we’ve gone into detail about how calorie burn estimates actually work.

Fitbit heart rate data by device

Naturally, with Fitbit’s heart rate tech involved in both fully fledged smartwatch and fitness trackers with smaller screens, what you see depends on which device you have on your wrist.

The devices which actually offer heart rate monitoring are the new Fitbit Inspire HR, Fitbit Ionic, Fitbit Versa, Fitbit Charge 3, and the Fitbit Alta HR. And while the PurePulse tech is consistent throughout, meaning the results should be the same no matter which tracker you wear, things are displayed slightly differently. For example, heart rate zones display a little differently on the live readout across devices.

Fitbit SpO2 sensor explained

The newest Fitbit devices – the Charge 3, Versa and Ionic – come with an SpO2 sensor for tracking blood oxygen levels. Currently you cannot tap into this information, although the sensors are “on” for Fitbit to collect data for its own research.

The first place we’ll be able to make use of it is with Sleep Score, Fitbit’s new way to analyse your sleep data. This is currently in beta, but when it rolls out it will use the SpO2 sensor to track any breathing disturbances through the night. Eventually, it will let Fitbit alert users if it thinks they might be suffering from sleep apnea.

One of the easiest, and maybe most effective, ways to gauge your health can be done in 30 seconds with two fingers. Measuring your resting heart rate (RHR) — the number of heart beats per minute while you’re at rest — is a real-time snapshot of how your heart muscle is functioning.

It’s easy to do. Place your index and middle finger on your wrist just below the thumb, or along either side of your neck, so you can feel your pulse. Use a watch to count the number of beats for 30 seconds and double it to get your beats per minute. Repeat a few times to ensure an accurate reading. While a heart rate is considered normal if the rate is between 60 and 100 beats per minute, most healthy relaxed adults have a resting heart rate below 90 beats per minute.

All in the numbers

Your resting heart rate, when considered in the context of other markers, such as blood pressure and cholesterol, can help identify potential health problems as well as gauge your current heart health.

“In certain cases, a lower resting heart rate can mean a higher degree of physical fitness, which is associated with reduced rates of cardiac events like heart attacks,” says Dr. Jason Wasfy, director of quality and analytics at Harvard-affiliated Massachusetts General Hospital Heart Center. “However, a high resting heart rate could be a sign of an increased risk of cardiac risk in some situations, as the more beats your heart has to take eventually takes a toll on its overall function.”

In fact, research has found that a resting heart rate near the top of the 60 to 100 range can increase your risk for cardiovascular disease and even early death.

For example, a 2013 study in the journal Heart tracked the cardiovascular health of about 3,000 men for 16 years and found that a high resting heart rate was linked with lower physical fitness and higher blood pressure, body weight, and levels of circulating blood fats. The researchers also discovered that the higher a person’s resting heart rate, the greater the risk of premature death. Specifically, an RHR between 81 and 90 doubled the chance of death, while an RHR higher than 90 tripled it.

While a low resting heart rate often suggests greater physical fitness, some situations can make your RHR too low, which may cause occasional dizziness or fatigue. “This may be the result of the electrical nodes of the heart aging, or not transmitting electrical signals correctly,” says Dr. Wasfy. “You should report these symptoms to your health care provider.”

Check your resting heart rate early and often

Dr. Wasfy recommends checking your resting heart rate a few times per week and at different times of the day. Keep in mind that the number can be influenced by many factors, including stress and anxiety, circulating hormones, and medications such as antidepressants and blood pressure drugs.

Talk with your doctor if your resting heart rate is regularly on the high end. There are ways to lower it and keep it within its proper range. One example is keeping your cholesterol levels in check. High levels restrict blood flow through the arteries and damage blood vessels, which can make your heart beat faster than normal to move blood through the body.

Another reliable way to lower your resting heart rate is to exercise. “Even small amounts of exercise can make a change,” says Dr. Wasfy. However, the intensity of the exercise is key. One study that involved 55-year-old adults found that just one hour per week of high-intensity aerobic training (about 66% of maximum effort) lowered RHR more efficiently than a low-intensity effort (33% of max effort).

Tips for measuring your resting heart rate
  • Do not take your RHR within one to two hours after exercise or a stressful event. Your heart rate can stay elevated after strenuous activities.
  • Wait at least an hour after consuming caffeine, which can cause heart palpitations and make your heart rate rise.
  • The American Heart Association recommends checking your resting heart rate first thing in the morning (but before you get out of bed).



The unique presentation of this tachyarrhythmia in our patient was a diagnostic challenge for the expert panel of our cardiologists and electrophysiologists. In the absence of availability of an electrophysiological study and a 12-lead capture of this arrhythmic event, we believe that the most likely mechanism of this arrhythmia could be atrial fibrillation with 1:1 conduction in the probable setting of co-existent multiple bypass tracts considering presence of possible fibrillatory waves, the irregular nature of the rhythm during its slow phase and the patient’s past history of paroxysmal atrial fibrillation. Without a 12 lead capture and an EP study, one could argue a possible differential diagnosis of a teleartifact (most likely a paper-speed artifact) however it is excluded because the paper speed was set at the regular standard (25 mm/s) and the telealarm morphology on the monitor was consistent with the one on the recorded telestrip excluding the possibility of a recording speed error. The true nature of this tachyarrhythmia is also suggested by the obvious co-existing clinical facts not otherwise explained by an artifact and these include the patient’s symptomatology (chest pain followed by a transient syncopy during the event), non-artifactual nature of the QRS morphology, elevation of the downward trending troponin value (most likely induced by a demand-supply mismatch from this extreme tachyarrhythmia in the setting of an underlying occlusive CAD), and confirmed functional appropriateness of the telemetry monitor. The wide QRS morphology during the slow phase of the tachyarrhythmia could be possibly related to a deceleration-related aberrancy .

With normal cardiac physiology, it is known that following the action potential (AP), the absolute refractory period (ARP) prevents another AP until the channels are reset at the AV Junction. The ARP of the AV Node lasts about 0.2 seconds limiting the heart rate to 300/min in theory. Following the ARP is the relative refractory period (RRP), and the stimulus needs to be greater than before, as the original electrical potential across the membrane hasn’t been fully restored. So, 300 beats per minute is not sustainable for long, as the stimulus needs to be progressively greater each time to generate the next AP. Another possible factor is the cardiac myocyte action potential duration which is normally about 200 msec which again theoretically would limit the heart rate to about 300 beats per minute. Heart rate conduction above 300 beats per minute would thus involve the presence of at least a bypass tract, shorter cardiac myocyte AP duration and also probable selective cardiac myocyte activation. A literature search has revealed several reports of extreme tachycardia. In 1943, Joseph Edeikein reported two cases; first case was of a 47 year-old female with myocardial ischemia who experienced two separate non-fatal paroxysms of supraventricular arrhythmia; one with a ventricular rate of 310 beats per minute lasting for 12 hours and second with a ventricular rate of 303 beats per minute lasting for 34.5 hours. The second case he reported was an infant aged 22 days that died after two days of sustained tachycardia with conducted ventricular rates reported above 300 beats per minute . Smelin et al reported a case of spontaneous atrial flutter in an adult with 1:1 conduction at rate of 300 beats per minute . In 1949, Silverman et al reported a fatal case of supraventricular tachycardia in an infant with a rate of 365 beats per minute . Lisowski et al studied atrial flutter in perinatal age group and the effect of maternally administered antiarrhythmic agents and they had reported a fetus with fatal rapid 1:1 atrioventricular conduction at 480 beats per minute which was probably the fastest human heart rate reported to date in the standard medical literature . A non-medical literature search has also revealed a case report of a Danish audiologist, Ole Bentzen, who died laughing while watching the movie “A Fish Called Wanda” in 1989. His heart rate was reported between 250 and 500 beats per minute, before he succumbed to cardiac arrest . Our case thus describes the fastest human heart rate ever reported. The patient spontaneously converted back to normal sinus rhythm after about 20 seconds and didn’t require cardioversion. Could an autonomic dysregulation (with history of his quadriplegia) in the setting of possible underlying concealed multiple bypass tracts have played a role in precipitating this extreme tachyarrhythmia remains a question of debate?

Heart Rate Records

Human heart rate can range from 20-30 at rest, to over 200 during maximum exercise (and also disease). Extremes of heart rate are also possible with certain medical conditions (see Heart Rate FAQ). This discussion is about heart rate extremes (maximum and minimum) in healthy individuals.

Resting Heart Rate

The average resting heart rate is around 70 beats per minute, with athletes having a lower level due to an enlarged and more efficient heart from training adaptation. (see the Resting Heart Rate Chart).

According to the current listing for the Guinness World Records (and also in the printed books since 2009), the lowest resting heart rate on record is 27 bpm (beats per minute) belonging to Martin Brady (b. 24 March 1969 in the UK) – tested at the Guernsey Chest and Heart Unit, Channel Islands, UK on 11 August 2005.

At the time of the 2004 printed edition Guinness World Records (Guinness Book of Records), the lowest heart rate on record was 28 bpm as recorded by Spanish cyclist and five time Tour de France winner Miguel Indurain, who was tested at the University of Navarra, Pamplona, Spain, in 1995.

There are other (unconfirmed) reports of Lance Armstrong having a low resting heart rate. According to his official website, he has a resting heart rate of 32-34 bpm (with a maximum heart rate of 201 bpm).

Maximum Heart Rate

We have no records of maximum heart rate. A rough estimation of someone’s maximum heart rate is using the commonly used formula of 220 minus your age in years (220-age). This implies that as you get older, your maximum heart rate decreases. It is not uncommon to see maximum heart rates well over 200 during maximal exercise tests. Peak levels may be achieved transiently. For records sake, a heart rate should be at a peak level for a set time, maybe 10-15 seconds. Resting heart rate levels are measured at ‘steady state’, often averaged over a one minute period.

If you want to test your maximum heart rate, it is best measured during a maximal exercise test, in which the body is pushed to its limit. In this case, you must ensure you are medically fit and used to pushing yourself to the limit as it can put excessive demand on the heart.

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Related Pages

  • procedure for measuring Heart Rate.
  • see Resting Heart Rate FAQ
  • more Fitness Testing Records and other Sporting Records
  • sporting records from the Guinness World Records

Want to check your heart rate? Here’s how

Learn what is a normal heart rate and how to find your pulse with your fingers or a device

Updated: February 6, 2019Published: October, 2016

Measuring your heart rate is any easy way to gauge your health, as it provides a real-time snapshot of your heart muscle function. For most adults, a normal resting heart rate—the number of heartbeats per minute while at rest—ranges from 60 to 100 beats per minute. A normal heart rate can vary from person to person. However, an unusually high or low resting heart rate can be a sign of trouble.

What is a normal heart rate

A normal heart rate for adults is typically 60 to 100 beats per minute. A heart rate that is slower than 60 beats per minute is considered bradycardia (“slow heart”) and a rate that is faster than 100 beats per minutes is termed tachycardia (“fast heart”). There are some experts who believe that an ideal resting heart rate is closer to 50 to 70 beats per minute. Regardless of what is considered normal, it’s important to recognize that a healthy heart rate will vary depending on the situation.

Among healthy people, a slower heart rate can be due to being physically fit, a medication, or sleep patterns. However, a slower heart rate can indicate a sign of disease including heart attack or other heart disease, certain infections, high levels of potassium in the blood, or an an underactive thyroid.

On the reverse side, a fast rate in healthy people can be because they are exercising, nervous or excited, using a stimulant or are pregnant. The health conditions that are associated with a fast heart rate include most infections or just about any cause of fever, heart problems, certain medications, low levels of potassium in the blood, an overactive thyroid gland or too much thyroid medication, anemia, or asthma or other breathing trouble.

By monitoring your heart rate, you can help track trends and patterns that are personal to you.

How to check your heart rate

According to the Harvard Medical School Special Health Report Diseases of the Heart, it’s easy to check your pulse using just your fingers, either at the wrist or the side of the neck.

  • At the wrist, lightly press the index and middle fingers of one hand on the opposite wrist, just below the base of the thumb.
  • At the neck, lightly press the side of the neck, just below your jawbone.
  • Count the number of beats in 15 seconds, and multiply by four. That’s your heart rate.

To get the most accurate reading, you may want to repeat a few times and use the average of the three values. For a resting heart rate measurement, you should also follow these steps:

  • Do not measure your heart rate within one to two hours after exercise or a stressful event. Your heart rate can stay elevated after strenuous activities.
  • Wait an hour after consuming caffeine, which can cause heart palpitations and make your heart rate rise.
  • Do not take the reading after you have been sitting or standing for a long period, which can affect your heart rate.

You can also use different types of heart rate monitors to check your heart rate. But be aware that most have not undergone independent testing for accuracy. One option is a digital fitness tracker. The most reliable ones use a wireless sensor on a strap that you wrap around your chest. The sensor detects your pulse electronically and sends the data to a wristwatch-style receiver that displays your heart rate. Others have sensors on the back of the wristwatch itself. These sensors, which are slightly less accurate, determine your heart rate by measuring blood flow through the skin.

Various smartphone apps to check your heart rate are also available. For most of these, you place your finger on the phone’s camera lens, which then detects color changes in your finger each time your heart beats.

Treadmills, elliptical machines, and other exercise equipment found in fitness centers and some home exercise rooms often feature handgrip heart rate monitors. These rely on trace amounts of sweat from your palms and the metal on the grips to detect the electric signal of your heartbeat. But experts don’t recommend these to check your heart rate, as they are notoriously inaccurate.

– By Julie Corliss
Executive Editor, Harvard Heart Letter

As a service to our readers, Harvard Health Publishing provides access to our library of archived content. Please note the date of last review on all articles. No content on this site, regardless of date, should ever be used as a substitute for direct medical advice from your doctor or other qualified clinician.

Fitbits with heart rate

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