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.

[UtrechtNL]

Exactly: mine should be much lower. Also mine can vary *a lot* from day to day, and their moving average stuff messes it up and makes it much harder to compare days to each other.

Anyway the battery life of my Charge 3 is slowly getting worse now (after 2 years more or less), so who knows next device will be a Garmin. They also supposedly can show you your info without an internet connection, e.g. when out camping in the wild. Fitbit app always needs a connection...

[Metsci]

My Fitbit tells me it needs an internet connection even when it tells me
it's connected to the internet.

[Danoxonuk]

I posted about the frustrations of the rolling averaging of the resting heart rate some weeks ago.

Despite being with Fitbit for 4 years, I have now abandoned the Charge 4 (with cracked screen) after just 2 months to try the Garmin Fenix. Two weeks with the Garmin and there will be no going back. RHR is accurate and believable. Larger screen with a brightness that I can adjust from 1 to 10. Instant connection to GPS. Exercise programmes I can download (with a click), which sync to Outlook and set-up the Garmin to give me in-exercise instructions, a screen that is clear, unlikely to crack and certainly won't burnish. A wealth of better data. The only "problem" is the shorter battery life but I can live with that opposite the many advantages, not least, that I believe the data.  

[UtrechtNL]

To be fair the Fenix is a totally different price range.

Btw when I got it my Charge 3 had about 10 days of battery life, it slowly dropped to about 7 now. Still pretty good after 2 years of continuous use.

I have the feeling it's a bit slower after the last software update. The screen is slower to turn on now.

[Restingrate]

I had a fitbit versa. It recorded resting heart rate typically of 62 when doing regular exercise . In periods when I did a lot of hiking such as being on vacation it would go down as low as 55. I got a new Fitbit Sense and lately have increased my exercise to the point where when I wake up at night it regularly reads between 56 and 58 yet for the last 5 days my resting pulse is recorded as 65. I do wear the Fitbit all the time except when charging it briefly. Why has my resting pulse hit a plateau with this new Fitbit sense when my exercise has increased and my pulse is clearly lower when I look at it during the night? Is this Fitbit sense broken or not functioning correctly?

[mpacker]

@Restingrate my RHR used to be in the low 50s or high 40s (48-53 would be normal for my resting HR) shortly after I got my sense it seemed to go up and recently no matter what I do it's reading 55-56 and even at night it rarely drops to 48 (normally i'd see 42-44 at night).  i'm strongly considering going back to my versa for a while and see if it makes a difference.   i'm really not sure if it's the sense or if fitbit has made some internal changes to how it calculates RHR.   If they did make changes and didn't tell us that is not good.   i'm fine with them making changes just tell us.   when you see you RHR go up 8-10% for no reason it makes me concerned.

[ElectricPics]

My Charge 4 tells me that my resting HR is around 61. On clinical BP monitors and pulse oximeters it's usually 54. Quite a difference if you're working to get your resting pulse down and decrease recovery time. 

[shipo]

It is my understanding the Fitbit model, which is, or at least was, a closely guarded secret, uses a much longer window of heart beat data compared to a pulse oximeter to calculate the RHR.  That said, while my heart beat rate sitting in the doctor's office is typically about 50, seemingly regardless of my level of conditioning; my Fitbit Ionic (and my Surge before that) typically shows me between 39 and 42 when I'm in good shape, 45 to 50 when I'm fair shape, and 50 to 55 when I'm out of shape.  Given I've been wearing a Fitbit tracker of some sort for six to seven years I've had my fitness level fall into the range of really good when I was running every day to what it was last year following a broken leg in 2019 and then COVID early last year, so I've pretty much had my Fitbit track it all.

[AlanFarr]

I'm sorry Fitbit moderator, but your "secret recipe" is reminding me of McDonald's "secret sauce" right now. My resting heart rate (RHR) as given by my Fitbit Charge 4 is 65 bpm. If I sit down for about 30 seconds, my heart rate is about 58 bpm. Even weirder, is that my Fitbit actually got this right when I first bought it about six weeks ago (about 62 bpm, which matched what I got when sitting still). I started exercising much more regularly (>500 zone min per week for six weeks) and my RHR has steadily increased to 65 bpm, but I'm down to 58 bpm when I sit still. At the same time my heart rate variability has increased by about 12 ms, which is actually going in the right direction. Soooooo, what?! My best guess is that my sleep has been more restless and it's throwing off your amazing secret recipe. Instead of your moderators coming onto these forums to tell everyone that your algorithms are flawless, you should be taking this feedback and updating your software to deal with these issues.

[shipo]

Ummm, what makes you say I'm a "Moderator"; quite the contrary, I am just a regular Fitbit user like you.

[AlanFarr]

I don't think *you* are a Fitbit moderator. My comment simply came after yours chronologically. I'm referring to the Fitbit moderator that explained in a previous post that they use a "secret recipe" to calculate RHR. Apologies for the confusion.

[Oregonmama]

Alan Farr - It could be sleep. I have seen significant variation based on my minimum heart rate when sleeping. I have also noticed that Fitbit's algorithm is thrown off if you don't do all of your exercise in one or two condensed bursts. Pre-pandemic I was active 8-10 hours a day and getting 12k+ steps most days at work. I was in better shape at that time than I was a few months later, when I had been mostly sedentary and eaten too much junk, but Fitbit showed an immediate drop in resting HR when I became sedentary and my heart rate didn't come back up until just recently when I started being more active all day.

[MartinJustMarti]

Sitting at my desk and fitbit has shown my heart rate as 50-54 BPM for the last ten minutes. Yet it says my resting heart rate is 65 bpm. I guess the answer is fitbit has a "secret" algorithm that it will not disclose so no one can copy or scrutinize. Obviously it is wrong or most kindly put an approximation.

[shipo]

Have you looked at your daily graph?  What kind of sleeping heart rate do you have?  I ask because my overnight heart rate seems to be very key to what my reported RHR is.  When my overnight heart rate is in the 35 to 37 range, my RHR is typically reported between 42 and 44 bpm, however, if my overnight rate is 40 or higher, my RHR is typically reported in the high 40s, or even in the low 50s.

[poem58]

I agree and  have seen the same thing.  However, RHR is exclusive from Sleeping Heart Rate.  So why does fitbit say we should wear the devices to bed?  The lack of transparency by fitbit on this issue is unfortunate.  I don't know why they don't just report the lowest recorded non sleeping heart rate during the day.   Nothing more annoying fitness wise than seeing my current actual heart rate 6-7 beats lower than my RHR.  Fitbit needs to be better on this.

[claudiu.cosar]

Madam... Really that's the best you can do???...

My garmin computed the rhr at 51/52... This fitbit s.. Charge 4 shows 61...

I m complete resting now at 57 bpm... 

This very simple algorithm doesn't need a distributed platform to be calculated.... And is so wrong... What the heck are you guys doing???

[shipo]

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@claudiu.cosar wrote:

Madam... Really that's the best you can do???...

My garmin computed the rhr at 51/52... This fitbit s.. Charge 4 shows 61...

I m complete resting now at 57 bpm... 

This very simple algorithm doesn't need a distributed platform to be calculated.... And is so wrong... What the heck are you guys doing???

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I'm not sure which post you are responding to, but I think you may be missing something in your understanding.  I have both Fitbit and Garmin trackers and there is rarely even a 1 bpm difference reported when I switch from one to the other.

[MartinJustMarti]

Has an issue ever been fixed by Fitbit based on feedback from the fitbit forum?

Claudiu, I've been through this. This forum is like a "help desk". It's designed to give the appearance of support from fitbit while doing nothing (reboot, reset.......). Fitbit appear to spend on marketing, new products, but never fixing issues with existing products/algorithms. 

The best you can use your fitbit RHM for is monitoring long term trends. Up/down/steady and not absolute values. Sucks but true. 

[af7567]

I came here to ask this same questions, but I guess there's no point 🙂

The only way to get the resting heart rate to actually show your resting heart rate is to do nothing at all all day long.

Mine has gone from 73 to 75 over the last couple of days just because I did exercise at lunch time. My sleeping heart rate has been 67 and 71 average for those days.

From looking at the fitbit app and my resting heart rate it seems that doing exercise is making me less healthy?

[shipo]

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@af7567 wrote:

I came here to ask this same questions, but I guess there's no point 🙂

The only way to get the resting heart rate to actually show your resting heart rate is to do nothing at all all day long.

Mine has gone from 73 to 75 over the last couple of days just because I did exercise at lunch time. My sleeping heart rate has been 67 and 71 average for those days.

From looking at the fitbit app and my resting heart rate it seems that doing exercise is making me less healthy?

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Far from it, you need to take into account when beginning an exercise program your heart rate will initially increase to help you recover from the unexpected exertion; then, as your body gets into better condition, your heart rate will decrease.