How much do you know about all the health data your Apple watch can track? The Apple watch itself, without any additional apps, can track a whole lot of information about your health. This falls into a few categories: heart rate measures, activity measures, endurance measures, energy measures, and a couple of other measures. A lot of which can be viewed on the Apple Watch itself, and even more can be viewed in the Apple Health App on your iPhone. To help you gain some knowledge on not only all the wonderful things this beautiful piece of tech can track, but what it all means, I've compiled everything you need to know.
With any of these measures, they likely aren't perfectly exact. There are many articles out there that discuss the preciseness of the Apple watch. The accuracy of any fitness tracker can vary based on the quality of the tracker and how well it is worn.To learn more about keeping monitoring accurate, check out this information from Apple.
The watch has the following sensors built in that are used to track data:
Pedometer: measures your steps
Altimeter: measures the height of your position.
Optical heart sensor/ photoplethysmogram (PPG): This is found on the back of the watch. The watch uses green LED lights paired with light sensitive photodiodes to detect the amount of blood flowing through your wrist at any given moment.
Magnetometer: measures magnetic fields
Accelerometer: measures acceleration aka how fast you are moving
Gyroscope: detects orientation or angular velocity
Ambient light sensor: detects light levels in your environment. Often used by sleep tracker apps.
GPS: tracks your location
Electrical heart sensor: The Apple Watch 4 series and later can take an ECG/EKG reading using these sensors located at the back and on the crown of the device.
Heart Rate Measures
Resting heart rate: just as it sounds, it is your heart rate when you’re not doing anything. This number should be between 60-100 BPM. A lower resting heart rate may indicate better heart health and cardiovascular fitness. It is affected by stress, hormones, caffeine, medications and how active you are. Some athletes have resting heart rates as low as 40 BPM.
Walking heart rate average: your average heart rate when walking around. This is affected by your pace. A lower walking heart rate may indicate better heart health and cardiovascular fitness.
Low heart rate warning: Bradycardia is defined as less than your average so typically <60 BPM. An apple watch will warn you if you get below 40-50 BPM (you can set this yourself under Apple Watch Settings-Heart) and stays there for 10 minutes when seemingly at rest/inactive. At this low heart rate, you are not going to be adequately perfusing your brain and limbs.
It is caused by:
Problems with the sinoatrial (SA) node, sometimes called the heart’s natural pacemaker
Problems in the conduction pathways of the heart that don’t allow electrical impulses to pass properly from the atria to the ventricles
Metabolic problems such as hypothyroidism (low thyroid hormone)
Damage to the heart from heart disease or heart attack
Certain heart medications that can cause bradycardia as a side effect
High heart rate warning: Tachycardia is defined as greater than your average or > 100 BPM. An apple watch will warn you if you get above 100-150 BPM (you can set this yourself under Apple Watch Settings-Heart) when seemingly at rest/inactive for 10 minutes.
There are multiple types of tachycardia including:
Atrial or supraventricular tachycardia (SVT) is a fast heart rate that starts in the upper chambers of the heart. Some forms of this particular tachycardia are paroxysmal atrial tachycardia (PAT) or paroxysmal supraventricular tachycardia (PSVT).
Sinus tachycardia is a normal increase in the heart rate. In this condition, the heart’s natural pacemaker, the sinoatrial (SA) node, sends out electrical signals faster than usual. The heart rate is faster than normal, but the heart beats properly
Ventricular tachycardia is a fast heart rate that starts in the heart’s lower chambers (ventricles). This type of arrhythmia may be either well-tolerated or life-threatening, requiring immediate diagnosis and treatment. In this condition, Electrical signals in the heart’s lower chambers fire abnormally. This interferes with electrical impulses coming from the sinoatrial (SA) node, the heart’s natural pacemaker.
Heart arrhythmia warnings: The Apple Watch can look out for atrial fibrillation. AFib is an irregular heart rhythm (arrhythmia) . It occurs due to the upper chambers of your heart (atria) beating out of sync to the lower chambers (ventricles). It can be temporary or persistent. Oftentimes, there are no additional symptoms. Your watch looks at the heart beat rhythm to check for irregularities. It is not constantly looking for it and in many cases people may not get a notification. If you do get a notification, and are not already diagnosed with AFib, let your doctor know.
ECG (on Apple Watch 4 series and later): ECG app uses the electrical heart sensor built into the Digital Crown and the back crystal of Apple Watch Series 4 or later to record a single lead ECG similar to a Lead I ECG. The ECG app then provides a result of sinus rhythm, atrial fibrillation, or inconclusive, and prompts the user to enter any symptoms such as rapid or pounding heartbeat, dizziness, or fatigue
Heart rate variability: a measure of the variation in the time interval between heart beats. Apple watch calculates HRV by using the standard deviation of beat-to-beat measurements captured by the heart rate sensor. The gold standard for assessment is analyzing a long strip of an electrocardiogram but it can also be assessed by fitness trackers.
HRV is controlled by your autonomic nervous system (ANS). ANS has two subsystems: parasympathetic (rest and digest) and sympathetic (fight or flight).
High heart rate variability means that your body is responsive to both sets of inputs (parasympathetic and sympathetic), the nervous system is balanced, and your body is capable of adapting and performing well.
Low heart rate variability means that one branch (usually sympathetic) is sending stronger signals to your heart than the other. This is good when you are exercising but if you’re not doing something active a low HRV indicates that your body is working hard for another reason.
HRV is affected by:
Training factors including training volume, intensity, new stimuli, and balance between rest/workouts
Lifestyle factors including diet & nutrition, alcohol, circadian rhythm & sleep habits, and stress
Biological factors including age, gender, genetics, and chronic health conditions
Heart Rate Recovery: The decrease of heart rate following the end of exercise caused by the reactivation of the parasympathetic nervous system. It is measured one and two minutes after the end of exercise. Faster heart rate recovery is linked to better athletic performance. Slower/abnormal heart rate recovery is linked to cardiovascular disease and all cause mortality.
HRR= HR at end of exercise minus HR set time later
Normal values are:
Abnormal: <12 BPM
Normal: 15-20 BPM
Superior: >20 BPM
Cardiovascular Endurance
VO2 Max: The measurement of the maximum amount of oxygen a person can utilize during intense exercise. It is a common measurement
used to establish the aerobic endurance of an athlete. A higher level of VO2max indicates a higher level of cardiovascular fitness and endurance. The only accurate way to measure VO2 max accurately is to wear a face mask and measure the amount of oxygen flowing through the mask and to your lungs.
Apple watch uses a metric known as “Predicted VO2 Max” and is based on your heart rate activity during exercise. It is measured during rigorous outdoor walks or runs for at least 20 minutes. Since the relationship of the heart rate and the VO2 max varies between everyone, it’s not a perfect indicator of your VO2 max, but with regular testing, you can see the trends of improvement or decline in relation to your own VO2 max baseline.
VO2 max = 132.853 - (0.0769 x W) - (0.3877 x A) + (6.315 x G) - (3.2649 x T) - (0.1565 x H)
W = Weight (in pounds)
A = Age (in years)
G = Gender factor, G = 0 for females and G = 1 for males
T = Time to complete the 1-mile walk (in minutes)
H = number of heart beats in 10 seconds at the end of the 1-mile walk
Hearing Health
Environmental Sound Levels: The Noise app tracks decibel levels of the ambient sounds around you, helping you identify when the sound levels of the environment could negatively impact your hearing. It can be helpful to understand how long you’re exposed to sound levels as they can affect your hearing.
Headphone audio levels: this is represented by the volume of your headphone audio measured in A-weighted decibels (dB). This is most accurate when using Beats, Apple headphones or speakers/headphones connected via wire
Activity Related
Total mileage walking/running: detected by the GPS app, this tracks your total distance in the day.
Flights climbed: a flight of stairs is counted as approximately 10 feet of elevation gain (16 steps). This can be helpful if you're trying to increase how often you go up or down the stairs, or when tracking inclines with running/hiking.
Walking pace: the amount of time it takes you to walk a mile during a walking workout. As speed goes up, pace comes down. Measured as minutes/mile in the app. Walking speed is considered the sixth vital sign. Norms for walking speed are measured in meters/second. Click here to convert your walking pace (minutes/mile) to gait speed (m/s) and to see gait speed norms.
Steps: your watch tracks your steps per day using its pedometer. It counts any step-like movement including walking, running, stair-climbing, cross-country skiing and household chores.
10,000 steps per day came from a pedometer called the "10,000 step meter". Your actual step goal depends more on your steps at baseline. Most adults take 4,000 to 6,000 steps. 30 minutes of recommended daily exercise is estimated to be another 3,000 to 4,000 steps.
Sedentary: 5,000 steps/day
Low active: 5,000 to 7,499 steps/day
Somewhat active: 7,500 to 9,999 steps/day
Active is more than 10,000 steps/day
Highly active is more than 12,500 step/day
The chart above demonstrates what step goals for different populations should be.
Running pace: the amount of time it takes you to run a mile during a running workout. As you get faster, your speed goes up and your pace goes down. This is again measured in minutes/mile.
Exercise minutes: one of the three rings. The 30 minute per day goal is set due to the American Heart Association’s guidelines for exercise.
Get at least 150 minutes per week of moderate-intensity aerobic activity or 75 minutes per week of vigorous aerobic activity, or a combination of both, preferably spread throughout the week.
Add moderate- to high-intensity muscle-strengthening activity (such as resistance or weights) on at least 2 days per week.
Spend less time sitting. Even light-intensity activity can offset some of the risks of being sedentary.
Gain even more benefits by being active at least 300 minutes (5 hours) per week.
Wheelchair specific: For wheelchair users, the rings are Roll, Exercise, and Move. Instead of a Stand goal, the Roll goal encourages you to roll or stretch every hour. For your Exercise and Move goals, Activity measures pushes, so active calories are calculated more accurately. Sensors are configured to address different surface types, inclines, and transition moments, such as moving from a wheelchair to a seat at your desk, or from your chair to your car.
Wheelchair distance: the distance traveled by pushing in your wheelchair. It only tracks wheelchair distance in an outdoor wheelchair workout in the workout app.
Wheelchair pushes: the approximate number of wheelchair propulsions detected by the apple watch throughout the day.
Stand hours: one of the three rings. How many hours per day you get up and moving. This is beneficial as at sedentary jobs it is helpful to get up and about once per hour to decrease stiffness.
Standing time: You probably have already gotten the notification to stand up. Each hour at the 50 minute mark, you get a stand reminder. On top of that, your Apple watch tracks your total stand time in a day as well as how long you stand each hour. This way you can know exactly how much you are actually up and about.
Energy Related
Resting Energy: The measure estimates the energy your body uses each day while minimally active. It is an estimate of your BMR (basal metabolic rate). It is measured in kcal. It is not 100% accurate and many people have reported issues with it being all over the place. It would be best to look at the average over a longer period (like month or year) than the daily.
Active Energy: an estimate of energy burned over and above your resting energy use. It is measured in kcal. Active energy includes activity such as walking, pushing your wheelchair, and household chores as well as exercise. This means it makes up your EAT (exercise activity thermogenesis) and NEAT (non-exercise activity thermogenesis). You’ll see this as your move goal under activity.
Total Energy: an estimate of total energy burned in the day. Again, not 100% accurate but an average can give you a look at what your estimated TDEE (total daily energy expenditure is). This can be useful when determining how much food you should be eating in a day.
For more information on TDEE, EAT, NEAT and BMR check out this post. You can use this calculator to look at what your estimated TDEE and BMR are supposed to be.
Other Data
Fall detection: On Apple Watch Series 4 or later, an alert appears and allows the user to easily call emergency services or dismiss the alert. If the user is unresponsive for about a minute, an emergency call will be placed automatically and a message will be sent to the user’s emergency contacts. All falls detected are recorded in the Health app. This feature is automatically enabled for users 55 years and older and can be turned on for anyone in the Apple Watch app on iPhone.
Breathe/mindfulness: The Breathe app reminds you multiple times per day to focus on breathing. It guides you through a series of deep breaths, and it reminds you to take time to breathe every day. While it is not triggered by stress, it can help relieve stress. It does track your “Mindful Minutes” per day, so you can see how often you are taking time to focus on breathing.
To adjust your Breathe reminder settings:
Choose how long you want to breathe, then let the animation and gentle taps help you focus. When you find a duration that you like, you can make it the default from your iPhone:
Open the Apple Watch app on your iPhone and tap the My Watch tab.
Tap Breathe, then scroll down.
Tap Use Previous Duration.
You can also change the length of each breath:
Open the Apple Watch app on your iPhone and tap the My Watch tab.
Tap Breathe, then tap Breath Rate.
Tap to change the number of breaths per minute.
Cycle tracking: this can be done on your iphone or on your apple watch using the cycle tracking app. This allows to track symptoms, menstruation occurrence, and predicts the start of your next period. Cycles vary from month-to-month and person to person. It can be used to estimate your fertile window. While not something automatically tracked by the watch, it is still a helpful app to use.
Where to find these measures:
References
“Bradycardia: Slow Heart Rate.” Www.heart.org, www.heart.org/en/health-topics/arrhythmia/about-arrhythmia/bradycardia--slow-heart-rate.
“Counting Your Steps.” 10,000 Steps, www.10000steps.org.au/articles/counting-steps/#:~:text=Sedentary is less than 5,000,than 10,000 steps per day.
Deusen, Mark Van. “Heart Rate Variability: The Ultimate Guide to HRV.” WHOOP, 10 July 2020, www.whoop.com/thelocker/heart-rate-variability-hrv/.
“Healthcare - Apple Watch.” Apple, www.apple.com/healthcare/apple-watch/.
Rosenbloom, Cara. “Who Decided We Should All Take 10,000 Steps a Day, Anyway?” The Washington Post, WP Company, 28 Jan. 2019, www.washingtonpost.com/lifestyle/wellness/the-10000-step-goal-isnt-based-on-science-but-its-still-a-decent-idea/2019/01/25/7bdf4946-1e7f-11e9-8b59-0a28f2191131_story.html?arc404=true.
Shaffer, Fred, and J P Ginsberg. “An Overview of Heart Rate Variability Metrics and Norms.” Frontiers in Public Health, Frontiers Media S.A., 28 Sept. 2017, www.ncbi.nlm.nih.gov/pmc/articles/PMC5624990/.
“Tachycardia: Fast Heart Rate.” Www.heart.org, www.heart.org/en/health-topics/arrhythmia/about-arrhythmia/tachycardia--fast-heart-rate#:~:text=Tachycardia refers to a heart,BPM) is considered too fast.
Tudor-Locke, Catrine, et al. “How Many Steps/Day Are Enough? for Adults.” International Journal of Behavioral Nutrition and Physical Activity, vol. 8, no. 1, 2011, p. 79., doi:10.1186/1479-5868-8-79.
Tudor-Locke, Catrine, et al. “How Many Steps/Day Are Enough? for Adults.” International Journal of Behavioral Nutrition and Physical Activity, vol. 8, no. 1, 2011, p. 79., doi:10.1186/1479-5868-8-79.
“VO2max Norms.” Topend Sports, Science, Training and Nutrition, www.topendsports.com/testing/norms/vo2max.htm.
“IOS - Health.” Apple, www.apple.com/ios/health/.
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