Several devices, one account

One value, one source#

Every value in a day, such as the night's length, the resting heart rate, the steps or the weight, is stored once and carries the name of whoever wrote it: a connected service (Polar, Oura, Withings and so on), an app on your phone that wrote into Health Connect (named, for example, “Garmin Connect · via phone”), the paired Garmin watch app, or your own entry. We do not average two devices into a third number. A second source helps in two ways: it fills a signal the first one lacks, and it covers a day the first one missed.

Some sources are the same device seen through two doors, and the app knows it. The Garmin link and a Garmin export are one watch. A Fitbit read through Google Health and a Fitbit read through the older Fitbit connection are one band. The night, the HRV and the steps of one device are never counted as two, and a baseline built from one door carries on through the other.

Which source is used#

The rules depend on the kind of signal.

The night#

One night is kept for each date. Three rules shape it.

What counts as the night. The night of a date is sleep that reaches into the window from 21:00 to 09:00 on your own clock. Sleep that lies wholly between 09:00 and 21:00 is a nap and is counted as one. A date with no sleep in the night window keeps its daytime sleep as the night, so a person who works nights is not handed a sleep debt for the sleep they had. A sleep shorter than 30 minutes or longer than 16 hours is not accepted as a night at all.

Which device's night. When more than one device measured the same night, a connected service's night usually replaces what the phone wrote earlier. From the phone, the night of the watch maker's own app is usually the one sent, unless it holds less than half of the longest night any app wrote.

A suspect short night. If the chosen night is under 60% of your usual night and another device measured the same date with sleep stages, and holds at least 75% of your usual night, we use that other device's night instead (of several, the one nearest your usual). It never swaps between the two doors of one device, and never picks a night without stages, because an unstaged night is just a window that counts the awake time.

Your own word. A night far from your usual is flagged on the Sleep tab. It is “much shorter than usual” when it is under 60% of your usual night, and “much longer than usual” when it is more than 3 hours over it. Your usual night is the median of your stored nights over the last year. The note reads, for example, “The night to 3/11 is much shorter than usual: … of sleep against your usual …” and then says “It is counted as it was measured.” You can press “Use the night from {device} ({duration})” when another device measured the date, or “Delete this night”, and you can take either back with “Undo”. A deleted night is kept aside whole, scores leave it out, and no later sync writes one back until you undo it. A choice you made holds against the rules above.

Steps, distance and energy#

Steps, distance, calories and active minutes are the day's volume. When two connected devices count them, a fixed order decides, the same for every account. It cannot know which device you wore that day, so a sports watch you wore for an hour can win a day it hardly saw while an all-day band counted far more. You are the only one who knows, so Settings asks.

In Settings, “Devices”, a card “Where your steps come from” appears once two of your connected devices have counted steps in the last 30 days. It reads: “More than one of your connected devices counts steps. Choose the one you wear all day.” The options are “Automatic” and the names of the devices. The chosen device supplies steps, distance, calories and active minutes on the days it measured them, and heart rate and sleep are not affected. After the choice the card says “Saved. We are recalculating the last 90 days, usually within a minute.” “Automatic” takes the choice back, and the card then notes that Automatic “follows a fixed order, the same for every account, not what you wore that day”.

If the choice's device is no longer connected, the card says the choice “still applies to the days it measured”. If only one connected device counts steps, there is nothing to choose between and the card says so.

The phone, and which devices count as worn. A connected service counts as worn on your account when it has measured your body in the last 30 days: a night, a resting heart rate or an HRV reading. A scale or an app that relays the phone's pedometer measures no night, so it is not worn. A watch that sends through your phone's Health Connect counts as worn when it is a maker whose apps carry only worn devices (Garmin, Fitbit, Polar, Oura, WHOOP, Suunto), or when the phone saw its app writing heart rate. A worn watch's count outranks an unworn service's count. On days a watch counted your steps through the phone, its steps come first, and the card then says it does not offer a device that does not measure your sleep or heart rate. Between two worn devices the connected service keeps the day, as it does against its own device arriving through the phone.

One reading, two providers#

When two providers publish the same daily reading, for example a watch and a ring both report a resting heart rate, the newest reading of the day wins, and the stored value says who wrote it. For weight, body composition and blood pressure, two providers can publish a reading at the same second because one copies the other. Then the maker of the instrument wins over a relayed copy, for example Withings for a Withings scale. For vascular age, a figure measured on a scale beats an estimate from a ring.

The phone and a connected service#

If a connected service and the phone both bring a value and they are the same device, we count it once. A Garmin watch, for instance, writes into Health Connect through the Garmin Connect app and also reaches us through its own link. The phone's copy of what that service already delivered is left out, value by value, and for the Garmin link it is judged by what really arrived that day. While a Fitbit link is connected, the phone's copies of the same Fitbit's steps, resting heart rate and weight are left out as a double count. The phone fills silences: a day or a signal the service did not deliver can still come from the phone. A history pass of the phone only fills gaps and never overwrites a richer source, except for a past value the phone itself wrote.

An app that records only one workout, such as Strava, never wins a whole day's steps, because twenty minutes of a run is not a day.

Who decides, in short#

Measured, estimated, entered#

Beside many numbers sits a small chip that says where the number came from.

• “measured · Oura” (Czech “měřeno · Oura”): a device or app measured it, and the chip names it. Phone apps read “Garmin Connect · via phone”. The tooltip gives the grade of that kind of source for that signal, as “top quality”, “good quality” or “basic quality”.
• “measured · Polar · from night” (“měřeno · Polar · z noci”): the device supplied the heartbeats and we worked the resting heart rate out of them, as the mean of the lowest tenth of the night's samples inside your measured sleep, instead of taking the maker's daily figure.
• “estimate” (“odhad”): MyBodyAI computes it from measured signals, and it is not a reading from a device.
• “your entry” (“Váš záznam”): you typed it.
• “measured · 2 devices”: on the Sleep tab's night card, when two devices wrote values for the same night.

When we do not know the origin, the chip is not shown. A number with no label is honest; a label that may be wrong is not. If your account has exactly one connected device, we name it, and the tooltip then adds that the source is “inferred from your only connected device”.

Separately, a small “Data quality” chip with a percentage appears beside the verdict or the coach line only when it is below 50%. It says how many input signals we have for the past week, not how accurate they are. A low number means data are missing, not that a score is wrong.

A missing night#

A night can be missing because your watch was not worn, because it has not synced yet, or because the data are on their way. For the day being lived and the day before, a night that is missing whole is scored with your usual night: the median of each night value over the last 7 days, but only for values you delivered on at least 4 of those 7 days. The card says “Provisional” and the day is scored again when the real night arrives. A watch that really stopped is not hidden this way, and running totals such as steps are never filled in. The details and the wording of the card are in Body Status, and what a missing night does to Sleep Debt is in Sleep need, debt and rhythm. A resting heart rate on its own is not a night.

On the Sleep tab a window with no night says “No night in this window yet.” If you delete a night, it is left out of every score.

Zero and no data#

A zero that a device reports is a measurement. Missing data are not zero. If a value is missing, scores and averages leave it out instead of counting it as nothing: the activity score, for instance, uses the share of steps and the share of active minutes that exist and leaves a missing one out. A day with no data for a signal shows no number for it, and when the signals behind a score are older than they stay valid for, the card “No current data” says “Not shown right now: …” and names the signals and the day they last measured. The rest of the overview runs on what did arrive.

Values that are refused#

A reading outside what is physically possible is thrown away and never replaced with a guess. The limits are wide enough for athletes and strict enough for sensor errors.

A night average of blood oxygen below 80% is not thrown away: it is kept aside, stays out of every score, and still reaches the Overview, because if it is real it is the one reading that matters. The safety alerts are described in Body Alert.

What you can do#

• If a number comes from the wrong device, check its chip, then use the steps card in Settings or the night choice on the Sleep tab.
• To see exactly what each source brings, open the Connect page and press “Show what we read”.
• If two devices disagree, the one you trust for that signal can be the only one that has it: you can disconnect the other.

Frequently asked questions#

I wear a watch and a ring. Which one is used?#

For each signal, the one that measured it. Both are kept, but the night is one night per date, steps follow the fixed order or your choice, and a single reading goes to the newest of the day. The chip beside a number names the source.

Why are my steps lower than in my band's app?#

Because the day's steps may be taken from another device. In Settings, “Devices”, choose the device you wear all day in “Where your steps come from”.

Does MyBodyAI average my two devices?#

No. Each value comes from one source and is stored with its name. We never blend two devices into a new number.

Why does the app say my night was short when I slept well?#

The chosen device may have recorded only part of the night. When the night is far from your usual, the Sleep tab flags it, and you can use another device's night or delete the night.

Why is there no chip next to a number?#

We do not know its origin, for example because several devices are connected and the day does not record which device wrote the value. An unlabelled number is shown rather than a possibly wrong label.

Does a missing value count as zero?#

No. A missing value is left out of scores and averages. Only a zero a device reported is stored as a zero.