AF Association
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Heart Rate Part 4 Trending: The Fitbit

Generally speaking there are two forms of Atrial Fibrillation, paroxysmal and persistent. Paroxysmal is intermittent; persistent is constant. (I have persistent AF.)


Because paroxysmal AF does not happen all the time, it makes sense to take heart rate measurements manually or (as imperfect as these machines may be) using a cuff, pulse oximeter or other monitoring equipment that provides single-digit (or in some cases single-response) answers indicating either that one’s heart rate is a certain number of beats per minute (bpm) or that one’s heart is in atrial fibrillation. I imagine a reason a paroxysmal AF person might taking a heart rate knowing it might return the answer “in afib” might be to notice what is happening at the time and try to change one’s behavior to ensure more afib occurrences don’t happen as often.


Because persistent afib is happening all the time, it makes no sense to manually check one’s pulse or use a machine like a cuff or pulse oximeter (except to check blood pressure and blood oxidation levels respectively). Single digit answers (bpm = x) are, by (the) definition (of arrhythmia) simply irrelevant to AF.

However, for people in Persistent AF, a trend plot allows you to understand when your heart is running faster or slower than you’d like. Why might you want to know if your heart is running too fast or too slow?

a)To change your lifestyle so that you can better control your heart.

b)To independently check if the drugs you are taking or your pacemaker is successfully controlling your heart rate swings. (In my case, drugs control the highs and a pacemaker controls the lower limit.

THE FITBIT provides heart rate trends. (It is the only affordable commercial device I know that does this. The AliveCor Kardia unit also provides a heart rate trend but, because it can at most only track five minutes of activity and during that time effectively ‘handcuffs’ your hands. (More about this unit in Part 5 please.)

Fitbit trends include:

a)BPM RESTING RATE: A for-the-day heart rate trend accessed you click on the bpm (heart) icon.

b)WORKOUT: A more specific heart rate trend relating to time you specify to be a “workout”. (This is very useful because you can specify certain heart rate ranges to be “custom” and get a report indicating the amount of time your heart operated in your custom range.)

Fitbit problems include:

a)The Fitbit is certainly not the final word on heart rate measurement. Many (my cardiologist included) contend that Fitbit heart rate measurements are not accurate.

b)WORKOUT: The Fitbit does not always respect time you specify to be a “workout”. It assumes any workout will involve a heart rate increase. If it thinks your “workout” heart rate is too slow, it will automatically consider it to be sleep time. There are work arounds to get around this erroneous and annoying behavior.

I can go further, but would like to hear your comments regarding the Fitbit and its use within an afib environment. Most specifically I’m interested in how you feel about the fitbit’s heart rate accuracy. (I personally believe that, because it is recording a trend that even if it only gets it right one heartbeat out of ten it still provides a fairly accurate heart rate trend measurement.)

30 Replies

Are you a doctor of some sort to be making this statement, or is it a copy of something you've read or just your personal opinion?


This looks suspiciously like an advert to me.


Don't think it is if you read and followed parts 1 and 2.



No this is not an advertisement. I'm just trying to sort out:

1) what the relevance is of knowing my (persistent AF) heart rate as a single figure (none, so far as I've gathered from the great feedback this series of posts has provided)

2) What the relevance is of knowing my TRENDING heart rate figures. (Completely--in fact the only reading of any relevance when it comes to persistent AF)

3) What machines provide heart rate trends (Fitbit is the only one I know of--I'm currently wearing 2 (for 'experiments' sake') and, oh yes my partner's, on loan!)

4) Whether the data the Fitbit provides is of any use.


5)...whether my heart is running lower than my Pacemaker is set to.


Have I missed part 3 :(


No I double checked by going to their profile and looking at all their posts.

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Oops! Looks like I inadvertently numbered the thread (of threads) wrong. I overlooked "Part 3".


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I personally think that there is a major flaw and therefore does not work re trends simply because sometimes it could read high and sometimes low. This means what you think is a higher number that is supporting an upward trend could be a lower number and not supporting a trend or showing a downward trend.

I am not medically qualified. I have used my experience of using / being involved with electrical test equipment over the last 40+ years and also my heart rate measurements using my Kardia (AliveCor) and my Microlife WatchBPHome A where the patters results are sometimes spot on (or within a couple of beats) or sometimes low or sometimes high.

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I'd like to get into this more, because my reasons for thinking my Charge HR is accurate enough have more to do with understanding a bit about technology; a bit about logic; a bit about the scientific method... all skills you seem to very well up on.

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OK interestingly today I thought I would share my experience of my Fitbit HR. I received this in July from my son as a birthday present. I have found it so useful as I wanted to increase my overall fitness. This device is tuned into my phone it tells me when my Fitbit needs charging. Believe you me I am not Techno savvy couldn't set it up but I personally have found it useful. I have increased my fitness by trying to improve on how many steps I take each day I feel a tad disappointed if I haven't improved on the previous day so it's like having a good friend to go out with and up your game. I know how many times I climb up and down the stairs. How many calories I have burned through exercise and how many hours and minutes I havent been sedatory. More so it was important that I know how well or bad I have slept and it gives a graph of how I have slept which is averaged out and surprisingly I sleep longer than I thought. The fitbit has a watch too. I am sure it does much more but it certainly is something from a pure interest in improving exercise is a good thing for me. Of course it gives you your heart rate I have Paf. However I use to use my Samsung health app on my phone which probably does the same where you can record food and drink heart rate etc.. I also check what the fitbit records when I think my heart rate is up to my Samsung and it is definitely in sync. I am very happy with my birthday present and thought it was kind that my son wanted to buy me something to help me improve my health. I feel better because I am doing more so psychologically for me I think it is helping. The days I feel tired I can see clearly that I do less but that's OK learning to pace myself has been key to accepting that Paf has to be managed not just with meds but with the mind. Regards Chris


I thought, and still think, the Fitbit is fairly cool.

It’s encouraged me to:

- drink more water—essential to my health [very low blood pressure];

- take more steps ( I can’t count the number of times I’ve said: “I don’t need a ride, or to be picked up. This’ll give me the opportunity to get more steps (or staircases).”

- seek staircases (known as hills around here)

- Yes it’s a game, but a very effective one! (By the way, if you don’t particularly like water, try flavoring it with a water flavorer…no calories, only taste)

- To view my heartrate in very general terms (“When was it that my heart rate went up today, Ah yes, the walk; Ah yes, the argument; Ah yes, …stress…)

- To schedule workouts to take very careful measurements of what happened during them.

- Other features are more or less interesting to me. (Weight, for example. It’s exciting when I lose; Disappointing when nothing changes; Awful when I gain.)

- …and isn’t the “buzz” you get when you reach 10,000 steps, satisfying?


Hi Afibapnea

I am in persistent AF, and I borrowed a friend's fitbit for two days as I wanted to see how it worked and indeed if it worked.

All I can say is that for me it was almost completely inaccurate, and gave me some very strange readings both very high and very low but this was not the latest device which I understand is better called the "Charge HR" I think.

If the new one is better with AF, and that's an IF because I don't know, then for those exercising whilst in AF I can see the value of Fitbit, if however you want to use it to monitor your AF for health reasons, then I doubt it's efficacy, and would use Kardia.

However if you are thinking of Fitbit solely for for exercise reasons, I think the chest band devices with smart watches such as Polar would be more accurate than Fitbit.

Be well


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I never expected my Fitbit to accurately record all the body movements it records. Wearing two (three, if you count the 'dominant' side experiment) I notice that the figures are slightly off. But exact steps, exact staircases, are not what I expected from the Fitbit. I expected consistent approximations. Consistent enough that I would be able to know if I was doing better or worse each day.

But when it comes to heart rate.................................. That's where I hope, BECAUSE IT IS TREATING THE PHENOMENA AS A TREND and displaying it as a chart (which is by its very nature approximate) that I can get some fairly accurate indications when, and approximately where (during the workout; during the day) my heart beat is very rapid; normal; or VERY LOW.


Fitbit did come out as a "best buy" in this month's Which Report. For keeping a check on activity it seems to be good but I think we all know when our hearts are changing patterns.

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I may be mistaken, but I thought Fitbit was one they tested on "Trust me, I'm a doctor" if so, worth looking at programme on catch up

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I have the Fitbit Charge and it generally seems to accurately record my HR, but then into longer have AF. PS - I checked it against other recorders such as Kardia (AliveCor) and showed the same readings.

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Do you mean you no longer in AF?


I no longer have AF.


I also have a Charge FitBit and find it quite accurate and, like Chris, it has helped me to be more conscious of my steps and sleep patterns. I suspect the sleep results aren't totally accurate as I can frequently wake between 4 and 5 o'clock but if I don't get up and stay up, it records it as sleep but restless.

I also have PAF and I find being able to check my heart rate extremely useful. If you can afford one and you have a Smart phone, I would recommend buying one.



You say it is accurate.

What gave you cross checked it with to confirm accuracy?

What type of AF do you have?


Right; how can one possibly know if the reading is accurate unless it is checked against something else, e.g., manual pulse check.


My point exactly!!! That's why I asked NooNoo14 what she crossed against because she said it was accurate.

Look at other posts especially the current "series" called Heart Rate.

For someone in persistent or permanent AF you CANNOT accurately determine someone's pulse manually. The only way is by an electronic means such as a Kardia (AliveCor) or hospital one. In any case a reading has to be taken over a minimum of a minute ideally two or more to get a number that you can trend against. If you take a 15 second snapshots from a longer SAME reading of mine my HR could be low as circa 45to 50 at low end or 120 or so at high end!!!!


Good sales pitch lol

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Im a nurse and use fitbit hr mostly to help improve my fitness tracking. I have checked its accuracy with listening to my heart with a stethescope and found it to b accurate on heart rate when I am in sinus rhythm but not in a fib as heart beat isnt strong enough to create strong pulse for fitbit to detect. When I was on sotalol I was worried about how low my heart rate would drop at night and fitbit proved it never went below 55, which was comforting.


In response Peter, I have not checked it against anything other than my BP monitor but, to be honest, all I am interested in is peaks and troughs, which it shows. I have AF and, currently, a change in eating patterns and loss of weight + the meds (which I hate taking) appear to have stopped my AF events. I know that things could well change in the future but, for now, taking into account my additional health problems, I have postponed having an ablation.



I am on meds so same as you hopefully we both stay well Netty and enjoy our fitbit.



Fingers crossed Chris.


OK here’s the root problem I’m dealing with.

I do yoga—an hour meditation a day. Been doing it for over 30 years.

I am in chronic, persistent, asymptomatic (I cannot feel what my heart is doing! Some have told me it’s a blessing.) afib.

I have a Pacemaker, set to give my heart a ‘burst’ when my heart rate goes below the Pacemaker’s set value.

…I've noticed that, apparently, while doing meditation I am able to significantly slow my heart rate.

Here's the situation.

1) Previously, while monitoring my yoga workout, my Fitbit never reported a dip in my heart rate trend below 50, the rate my Pacemaker was set to ensure my heart would not go below.

2) Recently, I needed an MRI. (As you know MRI’s and Pacemakers don’t get along well.) The MRI went well. The procedure was accompanied by my cardiologist/surgeon who checked the Pacemaker out before and after the procedure and declared it in good shape.

3) Since my MRI, my Fitbit consistently reports dips in my heart rate trend that go below 50, into the 40s. I called the hospital. The cardiologist did an “interrogation” of the pacemaker. “The test reports everything is in order and the Pacemaker is doing just fine.”

was his report.

(I don’t trust that if a machine manufacturer test report indicates ‘all is copacetic’ that the machine is necessarily road worthy. I want independent verification.)

4) So I say to my doctor: “I’m kinda surprised I can control my heart rate, but I don’t think I can push it below 40. So would you please set my minimum heart rate to 60. If I can push that into the 40s that should indicate something.”

The minimum heartrate was set to 60 bpm.

(there’s more to the story, but this is enough for now)

I set my Fitbit “Custom” heart rate ‘zone’ for 60-30 bpm (rates my pacemaker should not be allowing my heart to go). It regularly reports 25-40% of my 60 minute ‘workout’ heart rates in my custom zone. (Incidentally, I bookend each of my workouts with a short walk—something to bring my heartrate up before, and after the yoga-- to check that all seems to be working well and that the low trend that will be occurring exists in a fairly consistent/healthy context.)


Since I'm trying to figure out how, or why, the Fitbit heart rate trend might be more accurate than many give it credit I may be posting a number of "RATIONALE" (reasons it might be true). Here's the first:

[ACCURACY RATIONALE #1] I can understand that the fitbit might make mistakes, but when, during an hour in which I'm trying to take my heart rate down, the fitbit reports 45% of that hour in the "Custom (bad) zone" mustn't SOME of that data be correct???


I’m aware of two reasons the Fitbit is not an adequate way to measure one’s trending heart rate.

1)My cardiologist says it isn’t.

2)The Fitbit does not work as advertised.

Reason #1: Unfortunately, this is an appeal to authority, a completely inadequate way to defend an argument, even if the authority may be correct. I have personal reasons I believe he is not COMPLETELY correct but, unless someone is interested, I’ll refrain from giving them.

Reason #2: The Fitbit advertises that it has a function called the “Workout’. It is enabled and begun by pressing the button on the side of the Charge HR (a stopwatch appears) and ended by pressing the button again (a checkered flag appears). The Fitbit should, over the duration of a Workout, chart one’s heartrate. After the Workout has ended, the Fitbit should display that heartrate as a trend, complete with highpoints/lowpoints, amount of time in heartrate zones, etc.

What actually happens is that IF the Fitbit detects that the workout heartrate falls into the area IT BELIEVES indicates sleep, the Fitbit will not log the time as a Workout but will instead consider it to be Sleep time and display it as such (no heart rate trend chart, etc…).

For people interested in tracking low heart rates or people involved in exercises that at times result in LOW heart rates (e.g., many types of yoga) this can be extremely disconcerting. I’ve repeatedly experienced this problem and brought it to Fitbit’s attention many times—I believe it is a simple programming mistake—but they have seen fit not to do anything about it.


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