Resting heart rate algorithm? flawed?

[Saturn007]

Does anyone know how the Apple Watch calculates the “resting heart rate”?

When I bring up that screen, it shows a dot plot of rates by time — with a bright red line near the bottom of the graph with a value in red. That number matches the “Resting Rate” given there in a big white number.

However, every time I've checked that screen, that red line and value correspond to the 3rd or 4th lowest dot.

Yet, the overwhelming bulk of my heart rates while resting are anywhere from 5-10 beats higher. They cluster noticeably above the red line.

It seems that the way the Watch calculates the resting rate is off, dramatically so.

Does anyone know how the calculation is actually made?

The only thing I’ve found simply states it gives the rate when resting, but doesn't explain how it is determined.

It ought to discard outliers and provide, say, the median value of the bottom quartile…

In my case, it's clearly wrong.

What's it like on yours?

 

[cubodado]

From what I’ve understood, resting heart rate is the average heart rate you have while resting. It is different from average daily heart rate. There is an algorithm that excludes the increase due to activity or recover even if you didn’t start a workout. That should be why it is usually lower than actual heart rate.

 

[Saturn007]

Cubodado, that's what I thought, too, but, alas, it's not!

What I've found is that my average resting heart rate is 5-10 beats higher than what the Watch reports it is!

The cluster of dots I referred to in my original post was for resting heart rates, not all the other ones.

I can be sitting in the couch, resting, check my HR several times and it could be 58, 60, 65, 57, 62, etc., yet the graph draws the line through one of the lowest outlier resting rates — e.g., a 52 or 54 — that I had earlier!

This happens consistently. Instead of it being an average of my resting heart rates — or, as I would have expected, the median of the bottom quartile of resting rates — it is invariably one of the lowest resting heart rates I’ve had that day!

 

[jz0309]

Does anyone know how the Apple Watch calculates the “resting heart rate”?

When I bring up that screen, it shows a dot plot of rates by time — with a bright red line near the bottom of the graph with a value in red. That number matches the “Resting Rate” given there in a big white number.

However, every time I've checked that screen, that red line and value correspond to the 3rd or 4th lowest dot.

Yet, the overwhelming bulk of my heart rates while resting are anywhere from 5-10 beats higher. They cluster noticeably above the red line.

It seems that the way the Watch calculates the resting rate is off, dramatically so.

Does anyone know how the calculation is actually made?

The only thing I’ve found simply states it gives the rate when resting, but doesn't explain how it is determined.

It ought to discard outliers and provide, say, the median value of the bottom quartile…

In my case, it's clearly wrong.

What's it like on yours?

"Resting heart rate ... is an estimation of the user’s lowest heart rate during periods of rest "
Source:

restingHeartRate | Apple Developer Documentation

A quantity sample type that measures the user’s resting heart rate.

developer.apple.com

 

[Regulus67]

My heart rate is also lower than I believe is correct. Range last week, 45-187 bpm.
When I tested rest mode with a Garmin watch, with chest heart monitor, it was at least 10 bpm higher.
I stopped paying attention to it, for this reason. But I find it useful during exercise, to have some idea if my workout is hard enough.

 

[cubodado]

Thank you @jz0309 for your explanation. Just wanted to add that some app (if you give permission) can make its own estimate of resting heart rate and results can differ. From what I saw in this case the displayed result for the day is an average.

 

[NoBoMac]

"Resting heart rate ... is an estimation of the user’s lowest heart rate during periods of rest "
Source:

restingHeartRate | Apple Developer Documentation

A quantity sample type that measures the user’s resting heart rate.

developer.apple.com

Also from the link:

Because the resting heart rate estimates become more accurate as the day progresses, the system may delete earlier samples and replace them with better estimates. Apple Watch replaces only the samples written by the watch for the current or previous day.

I wind up with one data point for each day in Health.

 

[Saturn007]

JZ, thanks for the link. In other words, the so-called “resting” heart rate Apple reports is NOT one! ❌

Instead, it's the *lowest* rate for the day, with lower rates dropped on some unknown basis… ❓❗️

Compounding this, it's oddly an “estimate”, not a determination or calculation. Worse, as Nobo's excerpt shows, the estimate can even involve heart rates from the *previous* day! 🙈

I wonder how cardiologists or cardiology associations define “resting” heart rate. I'm skeptical they consider it the *lowest* rate you experienced on the day rather than the typical rate when you're resting — (i.e., the median resting rate or, if focused on the low side, the median of the bottom quartile).

I've only explored this a little, but Apple's approach of using the lowest rate doesn't match what several leading health groups suggest. The AHA, e.g., states this.

“What is a resting heart rate?​

Your resting heart rate is the number of times your heart beats per minute when you’re at rest.”​

Target Heart Rates Chart

How do I find my pulse or heart rate? Now that you have a target.

www.heart.org

Or, the Cleveland Clinic.

“Why your resting heart rate matters​

Essentially, your heart rate is a gauge of how hard your heart is working to pump your blood.​

We’re talking here about your resting heart rate — as in, how fast your heart beats when you’re not exercising or engaging in serious physical activity.”​

Is Your Heart Rate Normal?

There’s a wide range of healthy heart rates. How does yours stack up? Find out from a cardiologist.

health.clevelandclinic.org

A medical blog from the Harvard Medical School concurs

​

”Measuring your resting heart rate (RHR) — the number of heart beats per minute while you're at rest…​

​

Repeat a few times to ensure an accurate reading”​

​

Your resting heart rate can reflect your current and future health - Harvard Health

...

www.health.harvard.edu

​

Although these are hardly definitive, they suggest resting HR is the *average* or typical resting rate, not the *lowest* one. They certainly don’t define it as the “lowest rate for the day”.

​

Yet, adding to the complexity, HMS adds:​

• Do not take your RHR within one to two hours after exercise or a stressful event. Your heart rate can stay elevated after strenuous activities.

Does Apple only use rates an hour or two after exercise? ❓

The HMS blog also tells us:​

• The American Heart Association recommends checking your resting heart rate first thing in the morning (but before you get out of bed).

Hmm… that's definitely not what Apple does. That could easily be an artificially low rate as rates are typically lower overnight.

My concern is that Apple's current approach is misleading, can sow concern or anxiety, and hampers its utility as a medical barometer.

The issue is that Apple ends up *underestimating* people's resting heart rates. That's problematic for those who have normally low rates as it could lead them to think they have bradycardia (excessively low HR).

OTOH, those who might be suffering from tachycardia (excessively high heart rate) could be induced to think there's not a problem as their supposed resting HR — the lowest on the day — is mistakenly reported as falling in the normal range. For sure, many or most of them should be caught by the high HR alert, but having an accurate resting HR would be helpful, too.

Bottom line: Apple should give us options as to how we or our doctors wish to define it. After all, they let us set the range for what's considered low and high heart rates, why not do the same for resting heart heart rates?! ✅ 💯

 

[jz0309]

JZ, thanks for the link. In other words, the so-called “resting” heart rate Apple reports is NOT one! ❌

Instead, it's the *lowest* rate for the day, with lower rates dropped on some unknown basis… ❓❗️

Compounding this, it's oddly an “estimate”, not a determination or calculation. Worse, as Nobo's excerpt shows, the estimate can even involve heart rates from the *previous* day! 🙈

I wonder how cardiologists or cardiology associations define “resting” heart rate. I'm skeptical they consider it the *lowest* rate you experienced on the day rather than the typical rate when you're resting — (i.e., the median resting rate or, if focused on the low side, the median of the bottom quartile).

I've only explored this a little, but Apple's approach of using the lowest rate doesn't match what several leading health groups suggest. The AHA, e.g., states this.

“What is a resting heart rate?​

Your resting heart rate is the number of times your heart beats per minute when you’re at rest.”​

Target Heart Rates Chart

How do I find my pulse or heart rate? Now that you have a target.

www.heart.org

Or, the Cleveland Clinic.

“Why your resting heart rate matters​

Essentially, your heart rate is a gauge of how hard your heart is working to pump your blood.​

We’re talking here about your resting heart rate — as in, how fast your heart beats when you’re not exercising or engaging in serious physical activity.”​

Is Your Heart Rate Normal?

There’s a wide range of healthy heart rates. How does yours stack up? Find out from a cardiologist.

health.clevelandclinic.org

A medical blog from the Harvard Medical School concurs

​

”Measuring your resting heart rate (RHR) — the number of heart beats per minute while you're at rest…​

​

Repeat a few times to ensure an accurate reading”​

​

Your resting heart rate can reflect your current and future health - Harvard Health

...

www.health.harvard.edu

​

Although these are hardly definitive, they suggest resting HR is the *average* or typical resting rate, not the *lowest* one. They certainly don’t define it as the “lowest rate for the day”.

​

Yet, adding to the complexity, HMS adds:​

• Do not take your RHR within one to two hours after exercise or a stressful event. Your heart rate can stay elevated after strenuous activities.

Does Apple only use rates an hour or two after exercise? ❓

The HMS blog also tells us:​

• The American Heart Association recommends checking your resting heart rate first thing in the morning (but before you get out of bed).

Hmm… that's definitely not what Apple does. That could easily be an artificially low rate as rates are typically lower overnight.

My concern is that Apple's current approach is misleading, can sow concern or anxiety, and hampers its utility as a medical barometer.

The issue is that Apple ends up *underestimating* people's resting heart rates. That's problematic for those who have normally low rates as it could lead them to think they have bradycardia (excessively low HR).

OTOH, those who might be suffering from tachycardia (excessively high heart rate) could be induced to think there's not a problem as their supposed resting HR — the lowest on the day — is mistakenly reported as falling in the normal range. For sure, many or most of them should be caught by the high HR alert, but having an accurate resting HR would be helpful, too.

Bottom line: Apple should give us options as to how we or our doctors wish to define it. After all, they let us set the range for what's considered low and high heart rates, why not do the same for resting heart heart rates?! ✅ 💯

I did a bit of searching and could not find a common definition of "resting heart rate", at least we know how Apple defines it (right or wrong).

Does Apple only use rates an hour or two after exercise? ❓
for today, my resting heart rate was taken ~ 1.5hrs before my workout, and it hasn't changed now ~3.5hrs after.

Apple should give us options as to how we or our doctors wish to define it.
that would be nice, just don't see it happening, they can't even make widgets optional

 

[Thomas Davie]

Does anyone know how the Apple Watch calculates the “resting heart rate”?

When I bring up that screen, it shows a dot plot of rates by time — with a bright red line near the bottom of the graph with a value in red. That number matches the “Resting Rate” given there in a big white number.

However, every time I've checked that screen, that red line and value correspond to the 3rd or 4th lowest dot.

Yet, the overwhelming bulk of my heart rates while resting are anywhere from 5-10 beats higher. They cluster noticeably above the red line.

It seems that the way the Watch calculates the resting rate is off, dramatically so.

Does anyone know how the calculation is actually made?

The only thing I’ve found simply states it gives the rate when resting, but doesn't explain how it is determined.

It ought to discard outliers and provide, say, the median value of the bottom quartile…

In my case, it's clearly wrong.

What's it like on yours?

During the 3 1/2 hours I’m in dialysis, I’m hooked up to the dialysis data station and having pulse/bp determined every 30 minutes (was first at every 15 minutes until I was deemed to be a stable patient). B/c, they allow me to use the data station as long I don’t go outside certain areas; I can access historical bp’s and pulses and the current session’s body hydration state. I sometimes copy a days worth of data 9-11 readings over 3.5 hours) and sometimes compare those to that of the Apple Watch using Heartwatch app. Pretty good coherence; the possible ‘but’ is that I am 100% i mobile except using Twitter/iPadPhone and my hands are fluttering all over - and that doesn’t represent my real world other than dialysis mobility state.

Hydration state - Is the rate at which fluid can be safely removed from the body. Typically it’s only used by the data station when using variable rate dialysis, which is when the data station constantly monitors the rate at which it is removing fluid and the body’s physiological response. This is as opposed to constant rate fluid removal, which will remove a set, specific ml fluid/minute. Variable rate will adjust up and down w/in certain parameters.

If too much fluid is removed, you can stop fluid removal (by dynamically adjusting the strength of the dialyzing solutions) and only pull off toxins.

Dialysis has come a long way since the old days, and if you understand the tech it can make the whole procedure go easier and you do goodlier 😁

Tom
(about 1/2 of the nurses are wearing Apple Watches; one has an AW & an Oura Ring)

 

[Saturn007]

Tom, appreciate your report on dialysis, and the watch's accuracy. I wish you well with it all.

I smiled over your observation that half the nurses are wearing Apple Watches!

JZ, appreciate your research foray and follow-up. Good points! It is weird that there isn't a standard, precise definition among the medicos.

By the way, is there a way on the Watch to see when the resting heart rate was taken? Or, can you only find that on the iPhone?

I had an unusual reading late this morning. My resting HR was 60 and my walking HR average was 58! Like to see Apple explain that one!

I think we're going to have ask our doctors, PAs, and nurses, no matter their specialty, what they consider a resting heart rate is.

 

[jz0309]

By the way, is there a way on the Watch to see when the resting heart rate was taken? Or, can you only find that on the iPhone?

I had an unusual reading late this morning. My resting HR was 60 and my walking HR average was 58! Like to see Apple explain that one!

I think we're going to have ask our doctors, PAs, and nurses, no matter their specialty, what they consider a resting heart rate is.

not that I am aware of, always have to go to the "data section" in the Health app on iPhone (show all data)

 

[Mackilroy]

Instead, it's the *lowest* rate for the day, with lower rates dropped on some unknown basis… ❓❗️

I don't believe this is the case. I've seen my resting heart rate at the end of the day be higher than the lowest rate that I noticed (whether or not it's an absolute minimum): e.g. I might see a rate of 64 BPM at one point, but my result at the end of the day will be 68.

 

[NYCValkyrie]

I had an unusual reading late this morning. My resting HR was 60 and my walking HR average was 58! Like to see Apple explain that one!

I think we're going to have ask our doctors, PAs, and nurses, no matter their specialty, what they consider a resting heart rate is.

Resting heart rate differs for everyone depending on your personal level of health, how active you are, etc. It should be an average of your heart rate while you are actually resting for an extended period of time and not doing anything like sitting on the sofa, at your desk, etc. but isn't necessarily your lowest heart rate.

My resting is anywhere between 55 - 65. When I'm sleeping, it is in the 45-55 range. When I do regular activities, it gets into the 70s-80s. When I'm working out it gets to over 100 as I am not in the best shape lol. If you are extremely fit, then your heart pumps more efficiently and doesn't need to beat as often in order to circulate oxygen in your body. That's why some athletes have an active heart rate in the 50s.

I was on some new supplements and it made my heart rate drop into the 30s when I would lay down/sleep and the AW would give me a warning buzz. But my resting was still in the high 50s/low 60s. I got off those supplements immediately and things went back to normal.

When I was sick (a cardiomyopathy form COVID), my resting was in the 70s and even just showering or walking to another room pushed it up well over 100. Things were bad but all better now

 

[Toonartist]

Just found this thread so a little behind the conversation.

Anyway, I feel that what Apple reports as resting heart rate is actually "Sedimentary sedimentary Heart Rate". This will be taken during the day while you are not exercising or carrying out other activities that may elevate the heart rate.

As a tool for monitoring physical fitness, a gauge to the bodies overall condition while at complete rest, resting heart rate should be taken at the point you have woken up before it's affected by physical exercise or movement. This way it can tell you your current condition. If you are coming down with a cold, over training or the body has been working hard overnight to deal with excess food or alcohol. These issues cause a RHR to increase by 5-10 heartbeats or so.

Apples measurements for RHR are taken during the day and when looking at the raw data via other heart rate tools, can often be categorised as "Resting" when in actual affect, I've been standing up painting, washing up etc etc. I've even had take measurements during the dog walk when I haven't been recording an activity as my heart rate during easy walks is normally around 70. My RHR taken at the time of waking each day will vary from 37-41 and once it hits 42 I know I'm probably fighting off a cold etc... or too much food / alcohol over Christmas 😂

The only way I have been able to gain a more accurate insight to my RHR is by wearing my watch at night but not enter it into sleep mode as Sleep mode will discount all data collected during the night. This is some of the most important data as between 12 - 3am your body is dealing with repairing the body and from 3am till you get up will then start to drop to its natural resting point. This will vary depending on health and fitness. A true RHR should not jump around like crazy during the day... but a sedimentary heart rate will.

Hopefully Apple's new "Vitals" monitoring will resolve this as it seems to suggest it will record the HR during your sleep which may give us a better insight as to actual true RHR that in turn can be used as an early warning system as to health issues. Apples current RHR metric isn't very useful if you use their sleep function.

 

[Mackilroy]

I think you mean sedentary, not sedimentary. Also, yours records RHRs at times mine never does. I only get recordings at night or if I haven’t moved for a while.

 

[Toonartist]

"sedentary" correct.

This morning it's updated twice so far. Once while I was sat at my dest and once while playing a game of tug with the dog. Compared to Garmin, Apple's RHR is poor. Most things work great.... ok, VO2 Max is another metric that isn't really fit for purpose but as a whole, I prefer AWU over Garmin as I use it for far more than just health stats.

Looking at the app HeartWatch, I can see today my RHR just before getting up was 40-41. Apple reported it as 49 and I know that will go up and down during the day... it shouldn't be taking readings during the day. Sedentary heart rate should as it's recording HR while not carrying out any physical exercise.

The American Heart Association recommends checking your RHR first thing in the morning before getting out of bed. This is viewed as best practice as it's unaffected by any additional stresses and activity. You would think they would just take a reading or 5 minute average 15 minutes or so before it detects you are up and about or exited "Sleep" mode.

I'd like to use sleep mode but it just ruins RHR with inconsistent results which makes RHR useless for gauging training progress.

Edit. Actually, looking at "All Recorded Data" for RHR, today it's first recording was taken at 9:45am some 3.5 hours after I got up?!?

 

[Mackilroy]

You can use third-party apps like Athlytic if you want to see something else. It takes a measurement not long before the user wakes up.

 

[Toonartist]

Thanks... I'll look into that!

 

[PaladinGuy]

I’ve always wished Apple would use the approach of Garmin and others and simply take the lowest heart rate reading before waking. Much more consistent and reliable in my opinion.

 

[Toonartist]

I’ve always wished Apple would use the approach of Garmin and others and simply take the lowest heart rate reading before waking. Much more consistent and reliable in my opinion.

Exactly... as soon as you start taking readings during the day, or adjusting them like Apple does, it adds too many variables for it to be a useful metric.

I was looking at the data for each day and it makes it look like one reading but when you click on it it provides two time stamps and the reading is based on the data between those two times. I have however found you can add / delete entries so you could check your heart rate data and add an entry for the reading taken just before you get up but it's a bit of a faff.

I'm trying that Athlytic app but it's £26 a year so not ideal. I'll see if it gives me anything else that HealthFit app provides, which I find really good.