•The ability of the ECG application to accurately detect AFib and sinus rhythm in ECG recordings has been validated in a clinical study involving approximately 590 subjects. ECG application heart rate classification is compared to single-lead multi-channel ECG heart rate classification performed by a board-certified cardiologist. Among the classifiable records, the ECG application was able to correctly identify AFib 99.5% of the time and sinus rhythm (SR) 100% of the time.

•In the study, the ECG app determined 11.5 percent of records were inconclusive, including those deemed too poor quality to analyze. When these inconclusive records were included, the ECG application returned AFib results 86.5% of the time for AFib subjects and SR results 91.1% of the time for sinus rhythm subjects. Real-world performance can have higher uncertainty and poorer recorded results.

•The accuracy of the ECG application PDF report was assessed by comparing it with a standard lead I ECG recorded at the same time. Key features of the ECG waveform, such as PR and RR intervals, QRS duration, position and amplitude, and the presence and amplitude of P waves, were compared and found to be statistically equivalent within an acceptable margin of error. A comparison of simultaneous single-lead multichannel electrocardiograms and board-certified cardiologist heart rate classifications recorded by the ECG application had 96% agreement. No adverse events were observed during the clinical study. 


Follow these instructions to record an ECG on your Fitaos watch.

1.Wear the watch just above your wrist bones on the wrist you selected during setup. Note: The watch should be snug but comfortable.

2.Open the ECG app on your watch and follow the on-screen instructions.

3.Sit comfortably, rest your arm and wrist on a table, and keep still.

4.Place your thumb and index finger on the metal ring around the watch face to start a recording.

5.Keep your fingers in place, and remain still for the entire 30-second recording.

6.After the recording is complete, you can view the ECG app result on your watch. Please see below for more information about results you might see.



·Make sure the ECG app is available for your Fitaos watch. Go to

·Make sure the ECG app is approved for use in your country. Go to

·Review and complete the setup in the Fitaos Connect app on your smartphone (see ECG App Setup).

·The ECG app can be found in the Apps and Activities menu on your Fitaos watch. For help finding this menu, please refer to how to Start an Activity in your Fitaos watch user manual.



·Review and complete the setup in the Fitaos Connect app on your smartphone (see ECG App Setup).

·Water and sweat can cause a poor recording. Clean and dry your wrist and your Fitaos watch.

·Dry skin, cold skin, a hairy wrist, wearing the watch on your wrist bones or too much movement can prevent the ECG app from recording your ECG.

·Use moisturizing lotion on your hands and wrist.

·Remove the watch, and rub your wrist gently to warm the skin. Put the watch back on, and try again.

·Wear the watch just above your wrist bones toward your elbow.

·Remain still during the recording.



·Sit comfortably, relax, and try to remain still.

·Rest your arms on a table while you take a recording.

·Check the fit of the Fitaos watch on your wrist. The band should be snug. The back of your Fitaos watch must be touching your wrist. Wear the watch just above your wrist bones toward your elbow.

·Use your thumb and index finger on the metal ring around the watch face.

·Move away from any electronics that are plugged into a power source to avoid electrical interference.

·Water and sweat can cause a poor recording. Clean and dry your wrist and your Fitaos watch.



You may not be wearing the watch on the wrist you selected while setting up your Fitaos watch. You can either wear the watch on your other arm or change your user profile Wrist selection. To change your wrist selection, please refer to Setting Up Your User Profile in your Fitaos watch user manual, and select Wrist.

Understanding Your Results

After you complete an ECG recording, you will see one of the following results in the ECG app.


A sinus rhythm result means your heartbeat pattern appears normal. It indicates that the upper and lower chambers of your heart are beating in sync.

Note: A sinus rhythm result only applies to that specific recording and DOES NOT mean your heart always beats normally.


An AFib rhythm result means your heartbeat pattern appears irregular. AFib is an irregular heart rhythm caused by your heart’s upper and lower chambers not beating in sync. You should speak with your doctor if you receive an AFib rhythm result.

Left untreated, AFib can lead to serious health consequences. The irregular heart rhythm causes improper blood flow in the heart, which can lead to stroke, heart failure and/or other medical problems.

AFib can be temporary or persistent, but it is a manageable condition when treated by a doctor and with medication. Many people with AFib live healthy lives. Sometimes people with AFib do not have symptoms. However, others may experience one or more of these common symptoms:


If your heart rate is over 120 beats per minute (bpm) or under 50 bpm, the ECG app cannot check for AFib heart rhythms. In these cases, the result will be inconclusive, and your heart rhythm could not be classified. If you get this result repeatedly or you do not feel well, then you should speak with your doctor.

A heart rate below 50 bpm can be caused by taking some medications or by certain heart conditions. Some people with high fitness levels may also have a heart rate below 50 bpm.

A heart rate above 120 bpm is common while exercising and for a short time afterward. It can also be caused by high stress levels, an infection, dehydration, alcohol use or certain heart conditions, including AFib.


An inconclusive result means your heart rhythm could not be classified. This could happen for several reasons, such as moving too much or poor skin contact during the ECG recording. Try resting your arm on a table, and make sure the watch is snug on your wrist. If you get this result repeatedly or if you do not feel well, then you should speak with your doctor.



  • Many of the personal health and activity insights offered by Fitaos wearables come directly from or by analyzing heart rate data1. This includes features such as all-day stress tracking, Body Battery™ energy monitoring, respiration rate, sleep tracking and even how many calories you burn. Your heart rate can also reveal details of your cardiorespiratory fitness, measured in terms of VO2 max, when paired with walking speed, running speed or cycling power data (on compatible devices).

  • The human heart beats 2.5 billion times over the course of an average lifetime. With each heartbeat, oxygen, nutrients, hormones and other vital resources are delivered throughout your body by way of the circulatory system2. How your heart beats from one moment to the next is regulated by your autonomic nervous system. This vital nervous system sends instructions to your heart to physiologically prepare you for the challenges of life and environment.


  • Devices that offer all-day health insights based on heart monitoring data rely on the Fitaos Elevate™ heart rate technology sensor, an optical (PPG) sensor built into the back of the device. It detects your heart rate by shining a green light through your skin, which is reflected by the red cells in your skin’s blood vessels.
  • When your heart beats, the muscular contraction of the heart itself pushes a rush of blood through your circulatory system. The cycles of this pulsing blood flow are your heart rate, or pulse, and can be detected throughout your body. Your Fitaos watch conveniently measures your heart rate at the wrist.
  • The other option for measuring heart rate is to pair a compatible heart rate strap with your smartwatch. A heart rate strap measures the electrical signals that fire in your heart as it beats. However, this method is typically only used during recorded activities (running, cycling, cardio training, etc.). Wearing an elastic strap around your chest isn’t practical for round-the-clock monitoring, but these heart rate straps can provide reliable data even during the most vigorous, high-intensity physical activity.


  • The key to getting more insight from heart monitoring data is to examine the available information from multiple perspectives. For example, HR is the most common way of looking at heart monitoring data. Reported as beats per minute (bpm), this metric describes how fast your heart is beating in terms of how many beats would occur in a single minute at the current rate.
  • Many people find that HR provides valuable insight into exercise intensity, and they use it to guide their efforts during physical activity. An elevated HR outside of physical activity or an HR that’s too low when sedentary can each be a sign of health concerns. Compatible Fitaos watches can even be configured by the user to alert them to HRs outside of a preselected range.
  • HRV is another measure that Fitaos uses to transform your heart monitoring data into personally meaningful insight. Your heart doesn’t beat regularly like a metronome. Instead, the length of time between one heartbeat to the next is always changing. Typically measured in milliseconds, these changes aren’t huge, but they can provide a tremendous amount of information.
  • This is because your heart and how it beats from one moment to the next is regulated by your autonomic nervous system. As a result, the combination of HR and HRV data can be analyzed and interpreted to reveal changes in the balance between sympathetic and parasympathetic branches of your nervous system. The sympathetic branch dominates the rhythm during moments of stress when the body feels that it’s time for action. The parasympathetic branch is more dominant during quieter times. Analyzing the activity of these branches provides the basis for our all-day stress tracking, Body Battery energy monitoring and even some sleep tracking metrics.


  • RHR and HRmax are essentially the lower and upper limits of your HR. They are both important for various reasons. However, despite some similarities, each needs to be considered separately.
  • Your RHR changes from day to day. The RHR of normal adults can vary anywhere between 60 and 100 bpm, and some athletes can see an even lower range than that. Typically, a lower RHR reflects good cardiorespiratory fitness levels (VO2 max), adequate sleep, low stress and abstention from stimulants such as alcohol and tobacco.
  • Fitaos wearables typically measure RHR while you are asleep, usually not long before you wake up. Consider sleeping with your watch for the most accurate measurements of your RHR.
  • Your HRmax is the fastest your heart can beat. Unlike RHR, your HRmax doesn’t change from one day to the next. It is also almost entirely unaffected by your fitness level, so getting into great shape won’t increase your HRmax.
  • Everyone’s physiology is unique, and that includes your heart. Some naturally beat a bit faster than others, and some are a bit slower. As a rule, however, your HRmax will decline as you get older. This insight is widely used to estimate an individual’s HRmax with help from the following formula: 220 – age = HRmax bpm3. If you know your own true HRmax, you can enter it on your watch or in the H Band app.


  • Heart rate zones are an easy way to see and guide the intensity of your efforts during an activity.
  • Personalizing your heart rate zones set the stage for improving the effectiveness of your workouts over time. Avoid overdoing it in your recovery sessions, dial in better endurance training, and instantly see when it’s time to pick up the pace for a more stimulating workout.
  • With compatible Fitaos devices, you can customize activity-specific heart rate zones for running, cycling and swimming. These can be used in addition to the zones you configure for your general activity profile.


  • Several widely used methods exist for personalizing your heart rate zones. Setting up your heart rate zones based on percentages of your maximum heart rate (%HRmax) is the most common way. Other common methods when used with compatible devices include heart rate zones as a percentage of heart rate reserve (%HRR) and factoring in your lactate threshold heart rate (%LTHR) into the mix. Each of these methods uses your maximum heart rate as a key reference.
  • Which method is best for you? It really depends on a combination of what you are familiar with and the resources you use for training advice. One benefit of heart rate zone training is that it allows you to follow training programs and execute workouts at the recommended intensity. Customizing your zones according to %HRmax or following a program designed with %HRR zones in mind means you will be slightly underdoing it, especially during lower-intensity segments.
  • How you configure your personal heart rate zones does not impact advanced performance metrics such as VO2 max, training status, training load, load focus, or aerobic and anaerobic training effect feedback available on compatible Fitaos devices. Overestimating or underestimating your maximum heart rate can, however, affect the reliability of these metrics.


  • Your maximum heart rate is relatively stable and declines slowly as you get older. This is different from your resting heart rate, which reflects changes in fitness, recovery status and dietary choices.
  • If you already know your maximum heart rate, simply enter your maximum heart rate in the user profile settings of your device or in the Fitaos Connect app. If you don’t know your maximum heart rate, it will be automatically estimated by using the common formula of 220 minus your current age.
  • This formula for estimating maximum heart rate is utilized in guidelines from the American Society of Sports Medicine, which notes that while more complicated formulas exist, alternatives have not proven to be universally more reliable in practical usage4. According to this method, a 42-year-old person would have an estimated maximum heart rate of 178 bpm (220 — 42 = 178). Your maximum heart rate is likely within +/-12 bpm of this estimated value.
  • Estimating your maximum heart rate is a good place to start. However, knowing your own maximum heart rate and using it to personalize your heart rate zones unlocks the full potential of this training tool.
  • A variety of test protocols exist to determine your own personal maximum heart rate. You may also encounter your personal maximum heart rate during especially vigorous workouts that include sustained maximum-intensity efforts or during 5K/10K race events.
  • Tests to help you achieve your maximum heart rate are extremely demanding by design. Always consult a health professional before performing a maximum heart rate test if you are unsure of your abilities or doubt your capacity for strenuous physical activity.


  • Compatible Fitaos devices can automa
  • tically update your maximum heart rate using your performance data. If a heart rate higher than your currently set maximum is identified and passes a reliability threshold, your personal maximum heart rate is updated on the device or in the Fitaos Connect app.
  • This feature can be turned on or off in the Physiological Metrics -> Auto Detection menu of the device.


  • Heart rate zones offer insight into the current intensity of your performance. To anticipate the fitness or performance benefits of a workout, you should consider the combination of intensity, duration, recovery and repetition. This is true for specific workouts and within the broader picture of your training plan.
  • Heart rate zones remove the guesswork from the intensity element of that formula.
  • By focusing different workouts in different zones, you can create a well-rounded training regimen that helps you gain strength, endurance, power and other benefits. In general, the lower zones are best for warmup and recovery, while the higher zones lead to improvements.
  • The following are descriptions of our default heart rate zones. The zones may not match these descriptions if you customize them for different training purposes.

ZONE 1 (WWARMUP): 50–60% of MAX HR

Training in zone 1 feels like a relaxed, easy pace with rhythmic breathing. It improves your heart’s abilities to pump blood and your muscles’ ability to use oxygen. Brisk walking is a typical zone 1 exercise.

ZONE 2 (EASY): 60–70% of MAX HR

Training in zone 2 is at a comfortable pace, where you’re breathing more deeply but can still hold a conversation. It’s good for recovery and basic cardiovascular training. Light jogging typically falls into zone 2.

ZONE 3 (AEROBIC): 70–80% of MAX HR

Zone 3 training is done at a moderate pace, where it’s more difficult to hold a conversation. This strengthens your lungs and heart for more endurance. Easy running is done in zone 3.


In zone 4, you are moving at a fast, almost uncomfortable pace with forceful breathing. It improves anaerobic capacity and lactate threshold. Fast runs fall into zone 4.

Zone 5 (MAXIMUM): 90–100% of MAX HR

When you reach zone 5, you typically are at a sprint pace that is difficult to sustain for long. Breathing is labored. Zone 5 training builds power as well as anaerobic and muscular endurance.

Stress Tracking


  • Stress is your body’s natural response to the challenges of life and environment. It is an elevated physiological state that prepares you to react quickly to whatever comes next. All-day stress tracking on your Fitaos smartwatch is based on a well-established and scientifically validated understanding of your autonomic nervous system (ANS)1.
  • Stress levels (0–100) are estimated by the Firstbeat Analytics engine, primarily using a combination of HR and HRV data. This data is recorded by the optical heart rate sensor on the back of your device.
  • Divided into sympathetic and parasympathetic branches, your ANS regulates your physiological systems to best match the expected demands of your current situation. The sympathetic branch dominates when it’s time for action. Your pulse quickens, blood vessels dilate, digestion is interrupted, and adrenaline flows. This is sometimes referred to as the fight-or-flight response. In quieter times, the parasympathetic branch is more dominant, and your body enters what is referred to as rest-and-digest mode. This is when your body can repair itself and replenish resources depleted during more hectic times.
  • Sleep is an especially important opportunity for your body to recover, and, predictably, the parasympathetic branch of your ANS is typically the most active when you are asleep.
  • Stress levels are not measured by your Fitaos device during physical activity because the strain of physical activity itself can be considered stressful. The impact of physical activity is best measured and understood in other ways. Public speaking and running up a flight of stairs can both send your heart racing, but the underlying reasons why are fundamentally different.


Your physiological parameters and your body’s response to stressors are unique. Accordingly, the analytics used to monitor your stress levels are designed to recognize and adapt to your own personal situation. You can improve the quality of the insight gained by wearing your device as much as possible, especially while you sleep, because that is when your stress levels will typically be lowest. This helps create a better understanding of the full range of stress and relaxation states that you experience.

Wearing your device intermittently will still provide some insight into your stress. The details and precise levels, however, may be less personalized compared to what you would see with more consistent usage.


  • Your stress data reveals your physiological states throughout the day, corresponding to activity occurring within your ANS as it works behind the scenes to regulate your body’s responses.
  • You can configure select Fitaos devices to alert you when your stress level is unusually high. The alert encourages you to take a moment to relax, and the device will prompt you to begin a guided breathing exercise with the relaxation breathing timer.
  • The stress chart on your device or in the Fitaos Connect™ app will show orange bars when your stress level is above 25. Below level 25, the stress chart turns blue. This contrast is the key to identifying stressed and relaxed states.
  • Around level 25, activity within the sympathetic (stress: fight-or-flight) and parasympathetic (recovery: rest-and-digest) branches of your ANS is roughly equal. At higher levels (25–100), sympathetic activity is more prevalent, preparing you for action. Lower levels (0–25) indicate your parasympathetic system is the more active of the two.
  • What your stress data doesn’t tell you is why these various states are occurring. That is why it’s important to increase your own awareness of stressors in your life and how your body responds. This is how you can make the most of the stress data your Fitaos device collects and how you can work toward finding effective stress management strategies.
  • For example, elevated stress levels may stem from pressure at work, social anxiety or from something as simple as encountering an aggressive driver on the highway. Elevated stress levels could also be the result of happier situations, such as the excitement of a new job, the thrill of a first date or the jitters a runner feels the morning of a big race. Keep in mind that excessive exercise, consumption of stimulants, poor nutrition and getting sick can also produce higher than normal stress levels.
  • Regardless of why you experience stress, the key to a healthy, well-balanced lifestyle is to offset these draining experiences with relaxing moments and good quality sleep.



  • All the various cells in your body need oxygen to function properly. Your circulatory system, which includes your heart, lungs and blood, all work together to import oxygen from the environment into your cells.
  • Oxygen is extracted from the air that fills your lungs when you inhale. It is mixed into your blood supply and pushed throughout your body with each heartbeat. A pulse oximeter measures how much oxygen (compared to maximum capacity) is in your bloodstream as it travels around your body.
  • If you think about your blood as a train and oxygen as the passengers on that train, a pulse oximeter is telling you how crowded the train is compared to maximum capacity. When every seat in the train has a passenger sitting in it, then the train is operating at 100% capacity.
  • Compatible Fitaos wearables use a combination of red and infrared lights with sensors on the back of the device, which can estimate the percentage of oxygenated blood (peripheral oxygen saturation, SpO2%) available in your blood. Generally speaking, this value should be 95% or higher in most settings, but this value can be influenced by altitude, activity and an individual’s health. Numbers below 90% may be considered low, according to the Mayo Clinic.
  • Your device is not intended for medical purposes, and any questions about your Pulse Ox reading should be answered by your physician or other qualified health care professional. Pulse Ox not available on Fitaos devices in all countries.

Sleep Tracking

Sleep Tracking

  • Advanced sleep tracking in compatible Fitaos devices takes into account multiple factors to help you understand your sleep1. In addition to the basics, such as when you fell asleep and when you woke up, you can see times when you were awake and how much time you spent in key sleep stages (light, deep, REM). You will also see when those stages occurred during the night.
  • Sleep times and sleep stages are identified using a combination of heart rate, heart rate variability and body movement data. Age information that you enter during setup and detected personal physiological baselines provide valuable context for the analysis and improve the reliability of your sleep tracking.
  • Compatible Fitaos devices also track your respiration rate and blood oxygen saturation (Pulse Ox) levels during the night. Adding this information to your sleep chart offers a more comprehensive view of your sleep.


  • Sleep is crucial to your physical and mental well-being. Regularly getting enough quality sleep promotes good health, can improve your mood, helps maximize the benefits of exercise and provides many additional benefits.
  • Check your sleep data, and look for changes and trends over time. This will help you gain insight into the often-complex relationship between what you do when you are awake to how well you sleep at night.
  • A bad night’s sleep is easy to explain away in the moment, but recognizing longer-term trends can be a powerful motivator for lasting change. And when things are going well, you benefit from the confidence that comes from evidence you are on the right track.
    Select Fitaos devices with advanced sleep tracking also include a sleep score. Nightly scores (0–100) may be paired with personalized insights derived from your own activity and lifestyle data. These tips appear when an opportunity is identified to help you understand how factors such as daily stress levels, activity patterns and bedtimes influenced your sleep.


  • Your nightly sleep score is calculated based on a combination of sleep duration and sleep quality factors. How long you slept is compared to globally accepted age-based recommendations2. Quality aspects of your sleep score come from a combination of sleep architecture, stress data, interruptions during the night and other factors3.
  • Sleep architecture refers to how much time you spent in light, deep and REM sleep stages and the patterns formed by transitions between these stages during the night. The stress element is an analysis of heart rate variability interpreted to reveal the balance of sympathetic vs. parasympathetic activity occurring within your autonomic nervous system. When your heart rate is low and your heart rate variability is high compared to normal, it is a strong indication of parasympathetic dominance, meaning your body is stressed and actively replenishing resources depleted during the day.
  • Other contributors to your sleep score include restlessness, the number of times you are awake for longer than 5 minutes, and the total amount of time you spent awake.


  • In a sleep laboratory, sleep stages are identified with specific brain wave and neuronal activity patterns. These patterns are typically reflected physiologically as changes in heart rate, heart rate variability and respiratory patterns. Identifying these physiological changes while you are asleep provides valuable clues for recognizing sleep stages in real-world conditions outside the confines of a sleep laboratory.
  • Studies indicate that each sleep stage plays a role in your mental and physical recovery processes.


Light sleep is the first stage of sleep. Eye movements and muscle activity slow during light sleep as your body gets ready for deep sleep.


As you transition to deep sleep, eye and muscle movements stop completely. Your heart rate and breathing slow. At this point, you become difficult to rouse and are disoriented if awakened. It’s generally agreed that deep sleep has a myriad of health benefits. For example, it helps aid muscle recovery.


REM sleep is considered the final stage of a sleep cycle. Dreams are common during REM sleep. REM sleep stages tend to start short and grow longer throughout the night. The REM sleep stage is believed to be when your brain has a chance to process and make sense of data. It may even be linked to how you learn new skills.


In general, it’s best for sleep to be continuous through the night, with few to no stretches of awake time


Older Fitaos devices and those without integrated wrist-heart rate monitoring capabilities use movement-based sleep tracking to analyze wrist or body movement captured with an accelerometer. This algorithm also considers the time of day and provides more basic insight into sleep. It can estimate whether you are awake, in a light level of sleep or a deeper level of sleep. However, detection of specific sleep stages is not possible in these devices.