How does Fitbit calculate Resting Heart Rate?

[BigHaole]

I'm finding this very frustrating to be sitting at my desk, and see my HR showing as 74, but my Resting HR being 80.  Clearly Fitbit is not using the conventional definition (from Wikipedia):

"The basal or resting heart rate (HRrest) is defined as the heart rate when a person is awake, in a neutrally temperate environment, and has not undergone any recent exertion or stimulation, such as stress or surprise."

This definition would lead me to expect my reported resting heart rate to be the low value reached in the early morning, or at least the low value I reach, during the day.  Instead, it's above both of these.  I would like to know how it is being calculated, so I can know if my Fitbit is reporting anything useful when this number goes up or down.  Over the recent new years holiday, I got more sleep and more exercise, with less stress, so I was expecting this to go down, but it has gone up and I do not understand why.

[rebecca.mc01]

Hi there,

Yes I understand that it is daily but the value should be relatively constant day to day should it not? Over time if fitness improves it should gradually lower but I don’t expect it to decrease by 10 over a week! Also, my Fitbit recorded cardio exercise while I was sitting on the sofa so I don’t think that it entirely accurate, I’m not sure what to take from this data as it does not seem accurate to me. Thanks for your help.

Thank you very much for your reply, that has really cleared things up for me! I did not think a decrease of 15 within 2 weeks was accurate which was what sparked my questions! I will now calculate averages over a longer period of time to see how more exercise affects my RHR.

Moderator edit: Merged replies

[Kagakusha]

Certainly in my experience it is not closely constant day to day.
It is clearly affected by how ‘well’ you sleep, by a lot of heavy exercise which can leave it slightly raised for hours, by alcohol, probably even emotional state.
Don’t worry about day to day, even week to week, variations. Look at long term trends, on months timescale.

Moderator edit: personal info removed

[rebecca.mc01]

I never said I was a professor or that it wasn’t useful to others? Just that I didn’t know what to use or when to use it, that is all. I posted a query on here because I wanted help with understanding how the data is collected, not in any way to tell others what to do. Thank you

[Kagakusha]

What you do or don’t do is entirely up to you.
I’m not telling anyone what to do.

But I am a career professional scientist.
It is quite clear that day to day variations in the reported resting heart rate have essentially no scientific value in terms of fitness.

You are welcome to use them as you like.
But that is simply a scientific fact.

Moderator edit: personal info removed

[Jamesk2]

It does have value, if only a little. If you know that on a particular day your heart rate is lower then average you can look at what you did that day. Did you sleep better, did you have a healthier diet, did you exercise the day before, did you meditate or do yoga? Similar questions can be asked if the RHR is higher than average. The daily resting heart rate is not very helpful in itself, but without the them you wouldn't have any data at all and science is about data so to say they have essentially no scientific value is false.

[Kagakusha]

The actual record of your heart rate during the day has value with respect to the things you list.
Fitbit’s ‘testing heart rate’ has essentially no value, because they do not reveal how the calculate it. No other definition of resting heart rate includes overnight values, and we do not know how Fitbit uses them.
So I agree *the actual record* tells you about those. But you simply don’t know *what* the resting value is telling you about them, if anything.
Averaged over long periods, it’s probably reasonable to say their ‘resting heart rate’ will give some indication of cardiovascular fitness, whatever ‘reasonable’ algorithm they use.
As a professional scientist of many years I can assure you none of us will use a measurement whose methods are undefined without extreme caution and scepticism. It is fundamentally unacceptable in science.

Moderator edit: personal info removed

[SunsetRunner]

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[FerdinandFitbit]

Hi everyone! Good to see you all in the Forums! 🙂

Thanks a lot for sharing your feedback and input on the matter. As I have explained before, you can find the official explanation of how Resting Heart rate is calculated here.

Anything else, I'm here to help!

[Kagakusha]

It *says* it answers the question, but it *does mot*.
It is extremely vague and general.
Without the actual algorithm we simply do not know what Fitbit’s ‘testing heart rate’ really means.

Moderator edit: personal info removed

[SantiR]

Hi @Kagakusha, I hope you're doing well! Thank you very much for taking the time to share your feedback regarding the information provided.

You can also check the All About Heart Rate article from the America Heart Association for more details on resting heart rate.

See you around! 

[Arjdad]

My first Fitbit calculated my resting heart rate while I was sleeping great. !!! My new Fitbit HR 2 even though I wear it to bed does not calculate resting heart rate until sometime mid morning. I would rather have it calculate at night is there a way to fix that? 

Moderator edit: personal info removed

[dlhnj]

I am wondering if Fitbit has changed the way it calculates resting heart rate over the past few years.  Mine has slowly crept up over the past 3 years and wonder if this is real of if the calculation is getting tweaked.  

[Nmd1950]

My resting heart rate is higher than when I start walking. I am currently sitting in my chair and my heart rate is 93.

[Jamesk2]

That sounds like a health problem, not a fitbit calculating RHR problem. I've check my pulse while I had my fitbit on and the difference between the two is within 4 bpm so it's not fitbit giving you incorrect data.

[HeydyF]

Hey guys! Thanks for participating in the Community! 

If you are not getting correct readings, or your resting heart rate is't not being tracked on your Charge 2 or your Charge HR, I'd like you to try the following: 

- Restart your Fitbit device

- Make sure that you are wearing it correctly

- Switch the heart rate monitor to OFF, then sync your tracker, then to ON, sync again and then to AUTO and sync it again. 

Also, please keep in mind that resting heart rate refers to the heart rate measured when you’re awake, calm, comfortable, and have not recently exerted yourself. We use your heart rate data from when you’re awake and asleep to estimate your resting heart rate. For best accuracy, wear your device to sleep. 

Your resting heart rate is usually higher than your heart rate while you are asleep, so don’t be surprised if your resting heart rate is higher than the lowest number that you see in your heart rate graphs.

Heart rate may be affected by any number of factors at a given moment. Movement, temperature, humidity, stress level, physical body position, caffeine intake, and medication use are just a few things that can affect your heart rate. Different medical conditions and medications can impact your heart rate. Consult your doctor before starting an exercise routine.

Let me know how it goes! 

[Nmd1950]

I disagree. I can assure you this isn’t a health issue. I just purchased this product and this is my 3rd day of use. So far, I am not very impressed.

Sent from my iPad

[HeydyF]

Hey @Nmd1950, thanks for your response! If you consider that none of the factors that I posted above have something to do with the inaccuracy of your resting heart rate readings, then let me ask you this, have you tried the other tips that I suggested, as the wearing tips or restarting your Charge 2? Let me know. 

I'll be around! 

[dlhnj]

The question was simple:  has the calculation of resting heart rate used by Fitbit changed over the past 3 years?  Any little tweaks to the formula, for example?

[cctennant]

I love my FitBit (Charge 2 and now Ionic), but I've struggled with the resting heart rate calculation.  It's something I check every morning as a proxy for my overall fitness/health, and it's often the case that when I look at the graph of my overnight heart rate, if I draw an imaginary line through the midpoint of that graph, the calculated resting heart rate is well above what I can see the average is.  And the difference isn't consistent -- sometimes the difference between the graph values and the RHR is larger than at other times.  It's pretty frustrating!

So I wrote an app to calculate my RHR directly so I could compare it to the FitBit values.  My default algorithm calculates the minimum average heart rate over any one-hour period during the day, and I've also experimented with shorter and longer periods for the average.

What I found is that the FitBit RHR is usually 4-6 beats higher than the minimum one-hour average.  There also appears to be a multi-day "damping" effect -- the FitBit algorithm won't respond quickly to changes in resting heart rate from one day to the next.  I have data going back over almost a year and a half, and it doesn't look like the FitBit RHR algorithm has changed dramatically during that time.

If you want to try out the app yourself you can.  To get access to the intraday HR data, you need to register the app as a "personal" app; there are instructions in the app.  I've tried to make the instructions on how to do this as simple and straightforward as possible.  It will work in a browser or on mobile.  

If you run into issues with the app, or have feedback, there's contact info in the app under "About" -- please feel free to send me an e-mail.

The app also helps you to download your raw HR data in CSV format if you want to look at the raw data yourself.

Here's a sample graph.  Orange is FitBit's RHR, blue is the minimum one-hour average.  Don't remember what caused the bit spike on 7/20 -- probably I got sick.  But you can see how the FitBit value 'lags' behind the changes in the underlying resting HR.

Thanks!

Moderator edit: Removed link

[FerdinandFitbit]

Hi there guys, good to see you around @dlhnj @cctennant!

@dlhnj, at the moment, we don't have that information or at least not an official public statement on this but you can rest assured that any change made to the algorithm has been made to improve the way it measures resting heart rate.

@cctennant, thanks a lot for sharing this!

Anything else, I'm always around!