Smart watches health: Best smartwatches for heart health monitoring

Best smartwatches for heart health monitoring


By Kaylyn McKenna

/ Essentials

CBS Essentials is created independently of the CBS News editorial staff. We may receive commissions from some links to products on this page. Promotions are subject to availability and retailer terms.


Don’t just keep track of your workouts this summer, monitor your heart’s health too. Smartwatches can be incredible tools for monitoring your heart health. They provide an easy way to keep tabs on your heart rate, get alerts on unusual cardiac activity and even take ECGs. 

  • Related: How we select our products

If your doctor has told you to keep an eye on your heart health — or if you’re looking to get more active, or just interested in gaining new insights on your health — check out these terrific smartwatch options for heart health monitoring.

Top products in this article

Apple Watch 8 (41mm), $329 (reduced from $399)


Samsung Galaxy Watch 5 (40mm, Bluetooth), $229 (reduced from $270)


Garmin Venu 2 Plus, $400 (reduced from $450)


Why a smartwatch with heart monitoring is important

Keeping a close eye on your heart rate is useful for a number of reasons. It can help you track how hard you are working out, help you manage chronic conditions and possibly even let you know when something is wrong.

If you’re shopping for a smartwatch for heart health monitoring, it can be hard to know where to start. There are a ton of new features that can sound a bit complicated if you’re new to heart monitoring.  To help, we’ve compiled this guide to help you understand what to look for and which smartwatch will be right for you.

Best smartwatches for heart health monitoring

These smartwatches have the features you need to monitor your heart rate, take ECGs and more.

Apple Watch Series 8

Apple via Amazon

The Apple Watch Series 8 is a durable smartwatch that is swim-proof, dust-proof and crack-resistant with advanced heart monitoring features. It has a number of health-tracking features, including an optical heart sensor, an electrical heart sensor for ECG, a blood oxygen sensor and a new body temperature sensor. 

You can tap into yoga, meditation and other workout programs via Apple Fitness+. (Apple Fitness+ is a subscription service. It costs $9.99 a month; Apple Watch buyers get the first month free.) It also comes with a new crash detection feature, which detects where the wearer is in a severe car crash and alerts emergency services.

Apple Watch 8 (41mm), $329 (reduced from $399)


The 45mm version of the Apple Watch Series 8 does everything the 41mm version does, except it does it bigger. 

Apple Watch Series 8 (45mm), $359 (reduced from $478)


Samsung Galaxy Watch 5


The Samsung Galaxy Watch 5 offers ECG functionality when paired with a compatible Samsung Galaxy smartphone. You can take the ECG on your watch and then open the ECG report on your smartphone to dive into your data. 

The Galaxy Watch 5 features an advanced bioactive sensor that collects more accurate data compared to the Galaxy Watch 4. This data can be managed and tracked in the Samsung Health app. It also offers an advanced workout algorithm, hear rate monitoring and sleep-tracking technology.

The Galaxy Watch 5 is available in 40mm and 44mm display sizes. It is also available in five colors. 

Samsung Galaxy Watch 5 (40mm, Bluetooth), $279


Samsung Galaxy Watch 5 (40mm, LTE), $249 (reduced from $330) 


Samsung Galaxy Watch 5 (44mm, LTE), $279 (reduced from $360) 


 Google Pixel Watch

Best Buy

The Google Pixel Watch features a round face with customizable watch faces and tons of band options. It offers an all-day battery life, with up to 24 hours on a single charge. The Watch includes the Google Home App to adjust your thermostat or connect to your smart home devices. Users can play music, track fitness activity and receive notifications from their connected phone. 

The Google Pixel Watch is the first Android smartwatch to include integrated Fitbit features. The watch’s health features include heart-rate monitoring, workout tracking, sleep tracking and more. Google advised that fall detection will be available in 2023. The watch comes with a free six-month subscription to Fitbit premium and three months of YouTube Premium.

The Watch comes in black, silver and gold.

Google Pixel Watch, $280 


Garmin Vivoactive 4

Garmin Store via Amazon

The Garmin Vivoactive 4 uses Garmin’s Pulse Ox technology to track your energy levels, respiration, menstrual cycle, stress, sleep, heart rate, hydration levels and more. It can stream downloaded music from Spotify and Amazon Music. When paired with your smartphone, the watch can receive notifications.

This Garmin smartwatch features more than 20 preloaded GPS and indoor-sports apps. Want a personal trainer on your wrist? This watch can show you animated workouts via your watch screen.

Available in a variety of colors. The price listed below is for the black watch, as pictured.

Garmin Vivoactive 4 (black), $280 (reduced from $330)


Garmin Venu 2 Plus


The Garmin Venu 2 Plus offers advanced heart and health tracking. The smartwatch samples your heart rate multiple times per second and lets you know if it stays too high or too low when you’re resting. It also helps gauge how hard you work during activities, even while swimming. Garmin also recently introduced an ECG app, which is available on the Venu 2 Plus

Garmin Venu 2 Plus, $450


Fitbit Charge 5


The latest in the Charge line from Fitbit, this well-equipped activity and health tracker packs advanced technology into a slender device and features a color touchscreen. The smartphone-enabled device helps you manage stress and stay on top of heart health and sleep.

The Fitbit Charge 5 boasts a 7-day battery life on a single charge.

Fitbit Charge 5, $100 (reduced from $150) 


Amazfit Bip 3


What’s so great about the Amazfit Bip 3? It features a colorful 1. 69-inch screen to display incoming calls and texts. It’s loaded with sensors, too, to monitor your heart rate, blood oxygen level, sleep quality, and stress levels. You can even take it swimming with you — the Amazfit Bip 3 is IP68 water resistant.

Amazfit Bip 3, $45 (reduced from $60)


Top features to look for in a smartwatch for heart monitoring

Here are some features to look for when evaluating smartwatch options for heart monitoring. These features can be useful for athletes, those with chronic health conditions or anyone that wants to track their heart metrics. None of these features or readings is a substitute for medical care or formal cardiological tests.

Heart rate monitoring

The most basic function to look for is heart rate monitoring. Almost all smartwatches and activity tracker include heart rate monitoring, but some include more advanced monitoring options like heart rate variability monitoring, stress tracking or heart rate alerts. Heart rate alerts can be adjusted based on your own normal resting and active heart rate (what is normal varies from person to person), to provide an alert if your heart is beating outside of it’s normal range for a sustained period of time.

When combined with activity tracking, heart rate reading can help you assess how hard you are working during a workout and how many calories you are burning. This is one of the more popular uses of smartwatch heart monitoring.

ECG capabilities

Many people aren’t aware that smartwatches can take ECGs, but the Apple Watch has had ECG functionality for several generations and both Samsung and Google have started offering the feature as well. ECG stands for electrocardiogram (also called an EKG). It is a test that measures the frequency and strength of the electrical signals generated by your heart while it is beating and contracting. The purpose of this test is to check for abnormal cardiac activity such as atrial fibrillation (a type of irregular heart rhythm).

Fall Detection

Fall detection isn’t technically a heart health feature. However, if you or the person that you are shopping for need a heart monitoring smartwatch due to a cardiological condition that can lead to falls or fainting, it may help. Fall detection turns your smartwatch into a trendy, more high tech Life Alert device. If the watch detects a fall it will give you the option to call 911 or a designated emergency contact or report that you are alright. If you don’t clear the notificaion within a set period of time it will then automatically send an alert to emergency services or your emergency contatct.

Phone pairing

You’ll want a smartwatch that can either pair with your phone or provides a compatible mobile app to view data. This allows you to view reports on your heart rate, exercise activity, ECG readings, blood oxygen, stress levels and other recorded metrics. If you have an iPhone, you may prefer an Apple Watch 8 for easy pairing. Similarly, Samsung Galaxy smartphone users may get more out of a Samsung Galaxy Watch 5.

Related content from CBS Essentials:  

  • Best smartwatches in 2023: Apple Watch, Samsung Galaxy Watch, more
  • Google Pixel Watch vs. Apple Watch 8: Which smartwatch is best?
  • Apple Watch 8 vs. Samsung Galaxy Watch 5: How to choose the best smartwatch for you
  • Amazon just slashed the price of the Samsung Galaxy Watch 5
  • Best early Amazon Prime Day 2023 smartwatch deals

Kaylyn McKenna

Kaylyn McKenna is an expert on deals, travel, luggage, home and more for CBS Essentials. When she’s not scouring the internet for the best deals on new luggage or robot vacuums, she spends time with her goldendoodle, Harley, our resident canine correspondent and dog treat expert.

First published on December 16, 2022 / 2:44 PM

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Best smart watches for health monitoring 2023

Two decades ago, if you wanted to monitor your blood pressure, get tested for sleep apnea, or even track your health and fitness goals, you probably had to go to the doctor. Now, the smart watch revolution is upon us, and all that data, which can keep you healthy and safe, is available with a flick of your wrist. Amazing, right?

But with so many health-monitoring devices on the market, how do you know which one is right for you? That’s where we come in. At Asurion, we take care of you and your tech, whether you’re looking for help choosing the best watch for your health or trying to protect your favorite home tech. Here’s our guide to the best smart watch for health monitoring.

Best all-around smart watches to monitor your health

The best watch for health monitoring is the one that offers the most important features for you. Your top priorities—fitness progress, weight loss, heart health, stress management, better sleep—should inform the smart watch you wear. And it’s OK to love the way your watch looks and feels. If you prefer a large screen, the Apple Watch Ultra™ features a large 49mm screen. And the Google Pixel® Watch is designed with a round, customizable face with many band options.

You’ll also want a smart watch that has a compatible app, so you can view your data on your mobile devices. . This way, you can get updates about your heart rate, activity level, Electrocardiogram (ECG) readings, which check your heart’s rhythm and electrical activity, and even your blood oxygen and stress levels.

So, if you have an iPhone®, consider pairing it with an Apple Watch® 8. If you have a Samsung Galaxy® smartphone, you’ll get the best results by pairing it with a Samsung Galaxy™ Watch 5.

Top smart watches for heart rate monitoring

Most smart watches and activity trackers offer basic heart rate monitoring. This feature can help you tailor your workout to meet your fitness goals—whether you want to lose weight or improve overall heart health. Heart rate monitoring can also help you manage chronic conditions like arrhythmia and atrial fibrillation.

If you want more advanced heart rate tracking, look for a smart watch like the Garmin® Venu 2 Plus or the Withings ScanWatch®. Both sample your heart rate multiple times per second and alert you when your beats per minute are too high or too low. That can be useful for people who have high blood pressure, are watching out for an accelerated heart rate (tachycardia), or are worried about their heart beating too slowly (bradycardia).

Best smart watches for taking ECG tests

Devices like the Apple Watch Series 8 and the Samsung Galaxy Watch 5 come with built-in electrical heart sensors that let you take an ECG, a painless test used to quickly monitor your heart’s health, right from your watch. This saves you an expensive, time-consuming trip to the doctor and gives you peace of mind.

You’ll need to download the compatible ECG app, and then, while wearing your watch, open the app for a quick, approximately 30-second reading. Your watch will send the results to the smartphone you’ve paired with it.

Regardless of the results, if you aren’t feeling well or are experiencing any symptoms, call your doctor right away.

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Top smart watches to check your blood pressure

If you want to stay on top of your health, it’s important to regularly check your blood pressure, which is a key indicator of risk for heart attack and stroke. Now, you can do it right from your smart watch.

If you calibrate your device with a traditional blood pressure monitor (the kind that uses a cuff attached to your upper arm), then models like the Samsung Galaxy Watch 5 can take your blood pressure using built-in sensors.

Meanwhile, the BP Doctor Pro from WearWiz comes equipped with its own inflatable cuff built into the watch strap and shows a digital reading of your blood pressure on the screen within a few seconds, making it one of the best smart watches for your health.

Top smart watches to track your sleep

Need a good night’s sleep? Look for a watch with built-in sleep tracking. One option: The Fitbit® Sense 2, which breaks down your sleep data each month and pinpoints how you can improve it.

Another option: The Apple Watch (the SE, Ultra, Series 3, or newer versions). It comes with its own app that lets you set your bedtime schedule and find out how well you slept by recording your movements, your heart rate, and other data. It’ll even check your sleep trends over the past 14 days.

Top smart watches for detecting falls

The technology isn’t perfect, but some smart watches can now detect when you fall, and automatically call emergency services, which might save your life. Typically, watches with this feature will buzz and sound an alarm to warn you that a call is being placed to 911, and you’ll have to cancel if it’s a false alarm.

Watches offering fall detection in their 2023 models include the Google Pixel Watch, the Apple Watch Ultra, and the Garmin Forerunner 45S.

Top smart watches to track your fitness

Health-monitoring watches, along with simple fitness trackers, have come a long way from simply counting steps and otherwise motivating you to workout. Now these devices have a wide range of features, from sturdy, waterproof watch cases to built-in GPS and powerful Wi-Fi.

If monitoring your activity is your focus, look for a watch with a built-in fitness tracker, like the Garmin Fenix 7X Sapphire Solar or the Garmin Vivoactive 4.

If you like to exercise for long stretches—think running and hiking—look for a smart watch with long battery life like the Amazfit® T-Rex smart watch, which can run for 40 hours when you’re not using GPS, or the Apple Watch Ultra, which lasts up to 36 hours on a single charge.

Top smart watches to track your menstrual cycle

For women who want to track or predict their menstrual cycles, check out a smart watch like the Apple Watch Series 8. It features Cycle Tracking, as well as a skin sensor to track body temperature changes and predict ovulation. You can also get period reminders and fertility predictions on Garmin watches like the Venu that comes with a menstrual cycle tracking widget.

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Professional health watch with accurate pressure measurement, automatic measurement of pulse, temperature, oxygen, arrhythmia alarm and remote data control Health Watch Pro №80M (black)

Professional health watch with cuff pressure measurement, automatic measurement of temperature, pulse, oxygen, respiration, arrhythmia monitoring and remote monitoring Health Watch Pro №80M is the flagship among watches and bracelets in the field of pressure measurement accuracy. In addition, the watch does a great job with tasks such as automatic data monitoring and critical value alerts.


Due to the fact that the users of the watch are not only athletes, but also the elderly, for whom control should be as simple and clear as possible, the watch is equipped with a full touch screen.

To scroll between menu items, use “swipe” to the left or right, and to enter any menu item, just click on its name 1 time. Additionally, 2 mechanical buttons are installed on the case: the top one – takes you to the main screen and turns on the device, the bottom one – activates a quick transition to the pressure measurement section. Health Watch Pro No. 80M has several interchangeable main screen screensavers – both classic image screensavers with a digital or analog dial, and informational ones, where, in addition to time, the results of the last measurement of heart rate and body temperature, as well as steps taken per day and calories burned, are displayed. The watch interface is completely in Russian, which makes it easy for anyone to master control. Moisture protection allows you to wash your hands in the watch (waterproof IP67), but it is absolutely impossible to take a shower or swim in the watch due to the presence of holes for air supply from the compressor to the cuff. Permissible wrist coverage varies from 15 to 23 cm (+ – up to 120 kg).


Health Watch Pro №80M is the first device on the market capable of measuring blood pressure with two fundamentally different methods:

  • cuff (like a blood pressure monitor a)
  • optical (like a smart watch).

Each method has its own advantages, and given that the Pro No. 80M is equipped with both methods, the watch can be called ideal.

Feature #1. CUFF. The measurement is made by the most accurate classical oscillometric method, just like a conventional medical carpal tonometer does. In this case, the accuracy of the data will be at the level of a carpal tonometer. This method is needed for everyone who is important to understand the exact pressure, regardless of the reason for which the pressure has risen or decreased, whether it be physical activity, stress or hypertension. The disadvantage of the method (as well as any tonometer) is that it cannot be used at the moment of movement: in the process of walking, running, working. To take a measurement, you need to stop, and ideally take a sitting position. However, this is compensated by the presence of optics in the watch, which is able to assess the pressure directly on the move in motion (see feature No. 2).

Cuff measurement rules: Measurement must be taken while sitting at rest (ideally 1-3 minutes after any physical activity), even if the person just walked up to mu. The same rule applies to working with any tonometer, but few people know about it.

Feature #2. OPTICS. This is the standard method for assessing pressure and is used in all other devices (without a cuff). The main task of optics is to understand how much the pressure has grown from physical activity, for example, a person is walking on the road right now, running, or doing physical work, and you need to understand how much the pressure has risen from the norm at the moment in order to understand whether you need to rest for avoidance of overload and hypertensive crisis. The disadvantage of this method is that it may not give the most correct data when measuring pressure at rest, since it is completely based on the analysis of blood flow, which at rest is almost always lower than at the time of activity, which contributes to obtaining underestimated data at the moment, when the pressure in a person jumped not because of physical activity, but, for example, because of a disease. And in this case, at rest, the pulse can be low in a person, and the pressure is high – such an anomaly can rarely be caught by an optical method. However, this drawback is compensated by the presence of a classic cuff in the watch and at rest, measurement can be done using it, like a conventional tonometer (see feature No. 1).

Optical measurement rules: measurements must be taken while moving or in the first few seconds after stopping, standing, not sitting and not giving yourself a break.

Feature #3. AUTOMETERING WITH OPTICS. Pro №80M are able to automatically evaluate the pressure with optics every 10 minutes. You go about your business, and the pressure is under control 24/7. The monitoring results are built in the form of daily statistics, which reflects the dynamics of pressure changes during the day under the influence of physical activity. You will clearly understand at what moments of the day a person experiences overloads and in the future you will be able to adjust the activity mode in order to avoid overloads. The disadvantage of the method is that at the moment of rest, the results can be underestimated (in fact, auto-measurement is performed by the same method as described in Feature No. 2), but it is fully compensated by the presence of a cuff (see feature No. 1).

The results of cuff measurements will also be displayed in the general statistics in the electronic log. And if the watch is used by a loved one living in another city, you can control the received data remotely from your smartphone from anywhere in the world.

The electronic log records all measurements, both Cuff and Optical. Measurement of blood pressure with a cuff is marked with a tonometer icon, and an assessment with optics is marked with a clock icon.

Feature #4. CALIBRATION FOR WORKING PRESSURE. This setting is intended to improve the accuracy of pressure estimation by the optics. In order to take into account the individual characteristics of a particular person when measuring pressure, the watch is able to take into account the factor of the individual level of working pressure, which is different for each person and changes with age and under the influence of hypertension. By setting the working level of human pressure in the settings, the watch will automatically make an adjustment for each measurement made by the optics.

Feature #5. VESSEL AGE. Adjustment for the “age” (state) of the vessels is designed to improve the accuracy of pressure estimation by the optics. Considering that with age, the state of blood vessels in a person changes – this significantly affects the change in the level of pressure. The “older”, that is, the more worn out the vessels of a person, the less they are able to control pressure surges and vice versa. The rules and logic for setting the clock to the age of the vessels are indicated in the instructions, however, its logic is simple: initially we set the value of the biological age of a person, however, if the clock underestimates the pressure data, then the age needs to be increased (that is, the vessels are not older than), and if they underestimate – lower (that is, the vessels are in excellent condition for age).


How does the watch measure body temperature? (read)

Health Watch Pro №80M is capable of measuring body temperature in 2 modes: a) from the surface of the wrist (the temperature of the upper tissues, which is exposed to the external environment), b) in the armpit (thermal insulated space, where the temperature is almost identical to the temperature of the internal organs).

1) To measure the temperature from the surface of the wrist, it is enough to scroll to the “Temperature” section and wait 10 seconds, after which the value in °C will appear on the screen. In this mode, the clock will reflect the current temperature of the area of ​​the skin on which the measurement is made.

2) The watch is capable of continuous temperature monitoring with an interval of 10 to 60 minutes, for this you need to enable automatic temperature monitoring in the settings. All received data will be stored in the electronic log “Temperature” in the application. In this mode, the watch will give a signal when the temperature rises above the critical level, which you can also set in the corresponding section in the settings.

In wrist temperature monitoring mode, it’s not so much the data you see on the screen that matters, but how much it has changed. Since, for example, if you take a measurement on the street in winter at -10 ° C, when the bracelet itself and the skin on the hand can cool, the bracelet will show the actual temperature of the surface of the hand, which can drop to 30 ° C or lower, but this is not means that the temperature of the internal organs is at the same level. Therefore, the reference data of the bracelet when measuring temperature from the surface of the wrist can be considered if the ambient temperature is in the range from 26 to 36 ° C, in other cases it is better to focus on changes.


How does the watch measure heart rate? (read)

Feature #1. The presence of an interval measurement mode, in which the heart rate monitor will be activated every 10 minutes (or with another set interval) and record the current heart rate level, saving the data in the heart rate history.

Feature #2. On-screen graphs with a history display of the results of the measurement of all parameters. Pro №80M has graphs: pulse, pressure, oxygen, body temperature and respiratory rate. Graphs contain the history of the last 6 hours. This feature will allow you to have an understanding of the trend in parameter changes over the past period without resorting to a smartphone: in the morning you will understand what the measurement results were for the night period, and in the evening you will be able to understand how the day went, for this you just need to look at the graphs right on the watch .

Feature #3. Alarm about reaching an abnormal value of the pulse. The anomalous threshold level is set from a value of 100 U/m and above. And at the moment when the heart rate monitor is operating in automatic mode, the fact that the pulse exceeds the critical mark is accompanied by vibration and a flickering alarm screensaver with the inscription “Arrhythmia”.

The history of heart rate measurements taken in manual and automatic modes will be stored in the application in the measurement log, which is located in the application on the main screen in the “HR” section.


How does the watch measure blood O2? (read)

The oxygen level can be checked on the watch in manual mode by scrolling to the appropriate section – “SpO2”. The measurement will start automatically, and how much time remains to wait until the end, it will be clear on the percentage scale. The received data will be displayed on the watch screen. The reference level of oxygen in the blood is in the range of 96-99%. Read more in this article. Also, when the automatic data monitoring mode is activated, the assessment of blood oxygen saturation will be performed automatically at the interval you set from 10 to 60 minutes. The collected data will be stored in a special section in the application.


The watch can monitor the number of hours spent sleeping. To be analyzed

  • Total sleep time
  • Sleep phase analysis: deep, light, active
  • Sleep time
  • Wake-up time
  • Sleep time

Additionally, sleep and wake times will be displayed on the bar graph.


The watch is equipped with an accelerometer that will record the number of steps taken, distance and calories burned. The data received for 24 hours will be displayed on the watch screen, and also saved in the application in the activity log, which will save the history for the entire period.

If you are counting calories while losing weight, you should know how to correctly interpret the data displayed by the bracelet, since the bracelet only displays the number of calories that a person burns as a result of physical activity, does not include basal metabolic calories. Details – in the article How the bracelet counts calories burned.


The Health Watch Pro №80MM is a professional health watch for those who need comprehensive control over everything at once: heart activity, heart function, blood pressure and physical activity. The bracelet is suitable for a person of any age. And being anywhere in the world, you will be able to monitor the health data of a person close to you, even at a distance.

how they work, what they measure and can they be trusted? But some researchers doubt whether to trust them with their health.

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Digital clocks with additional functions have been around since the 1970s. One of the first “smart” watches was the Seiko UC-2000 – they not only showed the time, but also served as a calculator, had a built-in Japanese-English translator and games like Tetris.

They were accompanied by a pocket keyboard, with its help it was possible to write text up to 2000 characters, save it in notes on the watch and print it on a special printer.

In the early 2000s, Microsoft released Smart Personal Object Technology (SPOT) watches that worked via FM broadcast. They stopped using the company’s technology in 2008, but the idea of ​​smartwatches has survived. And in the 2010s, watches and bracelets from Apple, Samsung, Sony and others entered the market, the functions of which work via the Internet.

The first “smart” bracelets were developed for professional athletes to track physical performance and calculate the load. Soon, trackers began to be worn by amateurs, as well as those who do not play sports and lead a sedentary lifestyle.

If earlier the bracelets had only a pedometer and a heart rate monitor, now manufacturers are adding more and more new features.

For example, Amazon has released a “smart” Halo bracelet that can determine the percentage of subcutaneous fat and understand the wearer’s mood by voice, while Apple, Garmin and Fitbit promise that their watches will track the level of oxygen in the blood.

Some smart devices help improve sleep for people who suffer from nightmares, including those caused by post-traumatic stress disorder (PTSD). The watch analyzes body movements and heart rate – based on this, it “understands” when a person is having a nightmare and begins to vibrate.

Smartwatch features are on the rise, but they are more commonly used to view notifications and track physical activity. The medical usefulness of such devices often raises questions – both from buyers and researchers.

2018 survey reveals which smartwatch features are most commonly used by Npd

How smart bracelets work and how accurate measurements are

Trackers are usually worn on the wrist. They measure performance using built-in sensors, you can track progress on the watch and in the application on your smartphone. The accuracy of trackers depends on the algorithm laid down by the manufacturer and the actions of the owner.

Pulse measurement

Smartwatch measures heart rate using photoplethysmography. The light coming from the sensors in the watch hits the skin, most of it is absorbed by the tissues of the body, the rest is reflected.

Thanks to the green LEDs, the watch can measure the volume of blood passing through the wrist at any given time. Blood is red, so it reflects red and absorbs green light. When the heart beats, blood flow to the wrist increases, and so does the amount of absorbed green light. In the period between strokes, on the contrary, it decreases. So thanks to the LEDs, the watch can measure the number of heartbeats per minute, that is, the pulse.

This is how heart rate sensors work Theconversation

Fitness bracelet is not a medical device, so the pulse is measured with an error. At rest, it is small, but a simple walk can be enough to increase the error and distort the signal.

The more intense the physical activity, the less accurate. For example, the disturbance caused by walking at 100 paces per minute may be indistinguishable from a heart rate of 100 beats per minute – this will lead to an error in the calculations. And while running, the sensor will most likely not work.

Left shows resting heart rate, right shows walking. Theconversation

A study that tested seven smartwatches on 60 volunteers found:

  • the devices were more likely to get their heart rate off when the person was walking—the median error was up to 8.8%;
  • were less likely to make mistakes when a person rode a bicycle – most watches had an error of less than 5%.

The result of measuring the heart rate of four identical Garmin watches while walking Theconversation

One of the reasons for the inaccuracy of the pulse measurement is the green LEDs, they are not as accurate as the red ones used in medical devices. According to Mikael Matson, a researcher at the Karolinska Institute, although red LEDs help to more accurately determine the pulse, they do not work well during movement, unlike green ones. Therefore, manufacturers of “smart” watches install green LEDs.

In addition, severe sunburn, tattoos, sweat on the skin or a loose strap may affect the measurement accuracy.

Step counter

The accelerometer, a device with a counterweight that reacts to the movement of the body in space, helps to count steps and determine the speed of movement. It recognizes the acceleration of the fitness bracelet and reacts to hand movements.

Some devices additionally use a gyroscope that takes into account three-dimensional movement in space, which allows you to:

  • determine how the hand moves during movement;
  • more accurately recognize the nature of the movements of the owner.

For example, a gyroscope bracelet can detect that a person is running in place, exercising, or simply waving his hand strongly.

Smart watch shows the number of steps taken CNet

Fitness trackers analyze all hand movements during the day, so the algorithm may mistakenly count some of them as steps. Moreover, if a person shuffles, limps, or simply moves slowly, the tracker may not register such movements.

Driving a car, using a computer mouse, changing clothes, taking a shower, and actively gesticulating can cause false positives for the pedometer.

Calorie counter

Devices from different manufacturers calculate calories burned differently. Some take into account indicators of activity and physical condition, as well as height, weight, age and gender of a person. Others work only on the basis of activity data – some take into account its type: running, walking, cycling, swimming.

The accuracy of calories burned calculation depends on the mathematical model used in the tracker — the more data it takes into account, the more reliable the result. A study by scientists from Stanford University and the Swedish School of Sports and Health Sciences showed that the difference in the number of calories burned per 10,000 steps can range from 400 to 800 kilocalories.

Measurement accuracy also depends on the level of fitness, the quality of exercise and body composition. Not all bracelets take into account these indicators.

Pressure measurement

Some devices use a pressure sensor to measure pressure. Others – a pulse rate sensor, it works on the basis of a pulse oximeter or photoplethysmogram.

The most accurate readings are given by a medical tonometer. It measures pressure in the shoulder area, where the arteries are deep under the skin, while smartwatches measure on the wrist. Blood pressure at the wrist is usually higher and more difficult to measure due to the proximity of the arteries to the skin.

To accurately measure blood pressure with the smart watch, your hand and wrist must be at heart level. But even in this case, the readings of the bracelet will be less accurate than those of the tonometer. The error will increase if the skin on the wrist becomes covered with dust or sweat, as well as if you measure the pressure in motion.


The altimeter, or altimeter, works with atmospheric pressure sensors. Atmospheric pressure is highest at the surface of the earth and as a person rises up, it decreases. To determine altitude, the altimeter compares the new pressure reading to a previously known sea level.

Altimeter smartwatches need to be calibrated almost daily to match a known reference altitude. While flying in an airplane or after a change in atmospheric pressure, the altitude reading may be incorrect.

Altimeter in Garmin Geoawesomeness


Stress level

Determine the stress will help the indicator of heart rate variability – the interval between heartbeats. Based on it, smartwatches Apple Watch, Samsung Galaxy Watch and some Fitbit trackers report stress levels. Variability is affected by age, body position, time of day, health status, and emotional, physical, and mental experiences.

The human heart does not beat in the same rhythm. For example, in healthy young people, the heart rate for one cycle of breathing, inhalation and exhalation, can change by 10-15 beats per minute. When a person is in a stressful situation, variability decreases – the heart rate can only change by two beats per breath cycle.

Heart rate monitor maker Valencell says it’s best to measure stress when you’re stationary – wrist movements can interfere with the measurement.

For clinical research, scientists use algorithms that “clean” readings from noise. But fitness trackers may not have enough power for such calculations. In addition, without context, it is impossible to know whether changes in rhythm are caused by stress or positive excitement.

Valencell believes that it is possible to increase the accuracy of measurements with the help of devices that would be attached not only to the wrist, but, for example, to the heart. More data will help measure stress, too: Fitbit released a watch with an electrodermal activity (EDA) sensor to track the body’s physical response to stress.

Sleep monitoring

The fitness bracelets use two sensors to monitor sleep: an accelerometer monitors movement, and a heart rate monitor monitors heart rate, duration and stages of sleep.

Some bracelets additionally take into account the level of oxygen in the blood. Its decrease during sleep can affect the quality of sleep and lead to sleep apnea and daytime sleepiness.

Sleep consists of successive phases: REM sleep and slow or deep sleep, which includes three cycles. A person goes through all the phases several times a night. In the phase of deep sleep, a person stops moving, and the pulse slows down and becomes monotonous. During REM sleep, breathing increases and heart rate and blood pressure increase.

Sleep history: breakdown by phases and graphs. Application for smart bracelet Fitbit Wareable

In 2018, scientists in Beijing tested six bracelets from Apple, Samsung, Jawbone, Fitbit, Huawei and Xiaomi and found them to be accurate, without significant errors.

However, sleep doctor Mikhail Poluektov explains that trackers provide a “raw” array of data that is difficult to interpret without special education: the owner of a “smart” watch receives information that he cannot use.

Alan Schwartz, director of the Sleep Disorders Center at Johns Hopkins Medical Center, says that most sleep-tracking devices only assume whether a person is sleeping or not – often they mistake inactivity for sleep. But trackers can give a rough idea of ​​the sleep schedule, and if the user does not have health problems, this is enough. The main thing is to treat the data with a share of criticism, Schwartz believes.


An electrocardiogram (ECG) is a test that reads the duration and strength of the electrical signals produced by the heartbeat. During an ECG, electrodes are used to measure the electrical activity of the heart.

A medical device usually consists of ten electrodes placed on different parts of the body. In smart watches, there are fewer of them, for example, in the Apple Watch Series 4 there are two: one electrode on the back of the watch – above the wrist, the second – on the side of the wheel. To make an ECG, you need to put one hand with the watch on the table, and attach the other finger to the wheel and wait for the watch to take readings.

Asus’ VivoWatch BP also uses two sensors to measure ECG and works without having to sit and raise your hand during measurements.

Experts are not sure whether such functions are more useful or harmful. For example, some cardiologists doubt that constant ECG measurements will help young people – on the contrary, erroneous warnings can lead to anxiety and strain on hospitals because of those who see a doctor.

What to do with readings

The effectiveness of fitness bracelets has not yet been studied, but what research is available defines trackers as not accurate enough to be used for sports or medical purposes.

Is it possible to lose weight with smart watches

Scientists at the University of Pittsburgh have suggested that people who wear fitness bracelets should lose weight faster because they constantly monitor their condition.

They tested this hypothesis – the experiment involved 470 people from 18 to 35 years old, who were put on a low-calorie diet and prescribed physical activity. Some participants controlled their diet and workouts on their own, others with a wristband.

After two years of research, it turned out that the group with bracelets lost less weight than the group without them. Scientists have concluded that the activity tracker does not provide benefits in losing weight.

Another experiment lasted eight weeks with 78 participants. The researchers wanted to find out which method of losing weight is more effective: with a trainer, with a tracker, or with both. The subjects were divided into three groups:

  • The first to lose weight with the help of a trainer: once a week, during an hour-long session, the trainer talked about nutrition, proper sleep and other things necessary for losing weight. Participants were also given booklets about diet and weight loss strategies. They were in control of their own lifestyle.

  • The latter monitored their activity and weight daily using trackers.

  • Still others combined the methods of the first two: met with a trainer and used bracelets.

There were no dramatic differences in weight loss between the groups. The researchers decided that the systematic use of the tracker gives the same effect as monitoring activity with the help of a trainer. The best results were shown by the third group, which worked out with a trainer weekly and used the tracker daily.

A recent study conducted in 2020 by the University of Sydney found that the use of activity trackers increases the physical activity of people without chronic diseases. Tracker users walk more, averaging 2,000 steps a day.

Detect disease with smart bracelet

Stanford University study says smartwatches and fitness bands can help detect Covid-19.

Researchers analyzed fitness bracelet data from 32 people with coronavirus and found that 26 of them had changes in heart rate, number of steps per day, or sleep time. Thus, the symptoms of diseases could be detected in advance based on the extreme increase in resting heart rate.

Participants shared data from their fitness trackers. The bottom two panels show the change in a person’s heart rate before and after the onset of symptoms – Day 0 Nature

A similar experiment was carried out at Mount Sinai Medical Complex. For six months, 297 healthcare workers were required to wear smartwatches for at least eight hours a day and talk about their condition daily. The watch showed significant changes in heart rate readings in the seven days before the coronavirus was confirmed.

Mount Sinai also found that 7 to 14 days after diagnosis, heart rate returned to normal and no longer differed from that of those who were not sick.

Dependency on trackers

The University of Bath studied the impact of technology on the health of people aged 13-18 for two years.