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Apple Watch
16 metrics in Kaizora
The tracker that brings the most into Kaizora today: heart rate, sleep and its stages, steps, workouts, and more, all through one Apple Health export.
Who It’s For
For iPhone users who want all-day and all-night data without thinking about it.
Where to Buy
United States
See at Apple, Apple Watch, United States (opens in a new tab)Not an affiliate link
Canada
See at Apple, Apple Watch, Canada (opens in a new tab)Not an affiliate link
What It Measures in Kaizora
Heart Rate, Resting Heart Rate, Walking Heart Rate Average, Heart Rate Variability (SDNN), Heart Rate Recovery, Respiratory Rate, Peripheral Oxygen Saturation and Sleeping Wrist Temperature on models that measure them, Estimated VO₂ Max, Step Count, Apple Exercise Time, and the sound level around you. Workouts become activities, and nights become sleeps, with light, deep, and REM sleep.
- Heart rate
- Heart rate variability
- Sleep and its stages
- Steps and exercise
- VO₂ max
- Blood oxygen
- Respiratory rate
- Temperature
- Sound level
How It Gets to Kaizora
Through Apple Health: export all your health data from the Health app on your iPhone and import the file. It also brings in what other apps and devices write to Apple Health, except those with their own connection in Kaizora.
Strengths
- Measures all day and all night without your thinking about it.
- Apple Health gathers data from many other apps and devices, so one export brings in a lot.
Limits
- Needs an iPhone.
- The export is a file you make by hand, often hundreds of megabytes, so your data is as recent as your last export.
- Apple measures heart rate variability as SDNN, which can’t be compared with the RMSSD other trackers report.
- Its VO₂ max is an estimate from walks and runs, not a laboratory test.
About What It Measures
How Accurate Is Your Watch's VO₂ Max Estimate?
How watches estimate VO₂ max from heart rate and pace, what validation studies found, why your estimate can be several points off, and how to get a trend worth following.
How Does Alcohol Affect Your Sleep?
Why a drink helps you fall asleep and then disrupts the second half of the night, what it does to REM sleep and heart rate, how much it takes, and how to see the effect in your own data.
How Loud Is Too Loud for Your Ears?
Why safe listening is a dose of loudness and time, the 85 dBA workplace limit and the WHO's 80 dB for 40 hours a week, how each 3 dB halves your safe time, and how to follow your exposure.
How Many Steps a Day Do You Really Need?
Where 10,000 steps came from, what meta-analyses of step counts and mortality found, why the benefit levels off at 6,000 to 10,000 depending on age, and how to count steps consistently.
How Much Deep and REM Sleep Do You Need?
What deep (slow-wave) and REM sleep do, roughly how much of a night each takes, what two large reviews say about change with age, and why chasing your watch's stage numbers can backfire.
How Much Exercise Do You Need Each Week?
The WHO's and the US guidelines' 150 to 300 minutes of moderate activity, how vigorous minutes count double, why any amount helps, and what a watch's exercise minutes do and don't count.
How Much Sleep Do Adults Need?
The AASM's 7 hours or more and the National Sleep Foundation's 7 to 9, what short and long sleep are linked to, why time in bed isn't time asleep, and how to judge your own sleep.
How to Estimate Your Maximum Heart Rate and Training Zones
Why 220 minus your age is only a rough guess, the Tanaka formula, how guidelines turn a maximum into moderate and vigorous zones, and how to find your own maximum.
How to Find Out Where Your Time Goes
Why guesses about your own hours are unreliable, how time diaries and timers record them instead, what a calendar does and doesn't tell you, and how to turn what you find into a target.
What Can a Smartwatch ECG Tell You, and What Can't It?
What a single-lead watch ECG records, what its classifications mean, what the Apple Heart Study found about irregular rhythm alerts, and why it can't detect a heart attack.
What Can Basal Body Temperature Tell You About Your Cycle?
How progesterone raises your waking temperature after ovulation, why the rise confirms ovulation only after it's happened, how to take a reading that's comparable, and how it compares with a wearable's wrist temperature.
What Does Your Sleeping Wrist Temperature Tell You?
Why watches and rings report temperature as a change from your own baseline, what moves it, how it follows the menstrual cycle and illness, and why it isn't a thermometer.
What Is Heart Rate Recovery, and What Does a Slow One Mean?
How far your heart rate falls in the minute after hard exercise, the 12 bpm threshold from the landmark study, what moves it, and how to measure it the same way each time.
What Is VO₂ Max, and Why Is It Linked to Living Longer?
What maximal oxygen uptake measures, typical values by age and sex from the FRIEND registry, the evidence linking fitness to lifespan, and how to raise yours.
What's a Normal Breathing Rate at Rest and During Sleep?
The 12 to 20 breaths a minute range, why a rising rate is one of the earliest signs of illness, how watches measure it overnight, and how to count it yourself.
What's a Normal Oxygen Saturation, and Can You Trust a Pulse Oximeter?
The WHO's 95% to 100% range, when a low reading is an emergency, what makes oximeters read wrong, including skin pigmentation, and how to take a reading you can rely on.
How to Bring Your Apple Health Data Together With Your Bank and Nutrition Data
A step-by-step guide to putting your iPhone's health data, your food diary, and your bank statements in one history, without counting anything twice.
Why Your Devices Disagree About Your Weight and Your Steps
Two scales give two weights, and your phone and your watch count different steps. Here's why, which number to trust, and how to keep the comparison fair.
How Accurate Are the Sleep Stages From Your Watch or Ring?
What deep, light, and REM sleep really are, how a wearable estimates them, what studies against sleep lab recordings found, and which sleep numbers are worth tracking.
What's a Normal Resting Heart Rate, and What Makes It Change?
The 60 to 100 bpm range, why your own normal matters more than anyone's average, what moves resting heart rate up and down, and how to follow it over months.
What Is Heart Rate Variability, and How Should You Track It?
What HRV measures, why SDNN and RMSSD give different numbers, and how to follow your own trend instead of comparing yourself with anyone else.