Sense Heart rate accuracy

[Christopher1992]

Hi everyone new user here. My question is how accurate is the heart rate monitor on the Fitbit sense as I've seen a number of articles stating how inaccurate it is. Has this issue been fixed with software updates? Had the apple watch 6 previously but it's so bad that I had to send it back

Moderator edit: subject for clarity/label  

[WilsonFitbit]

Hello @Christopher1992. Welcome to the community forums! 

Thank you very much for the information and for your question about heart rate accuracy. At this time, I'd like to let you know that as with all heart-rate tracking technology, accuracy is affected by personal physiology, device location on your arm, and type of movement. Also, note that several factors can affect resting heart rate: stress, alcohol or caffeine intake, or fever usually raise resting heart rate, while regular exercise or meditation can lower it. Air temperature and certain medications can also affect resting heart rate.

For tips and recommendations about how to improve the heart rate accuracy, I recommend visiting the following help article: 

How do I track heart rate with my Fitbit device?

Lastly, regarding your question about if software updates have helped, I'd like to let you know that the latest Fitbit OS update included bug fixes and improvements. For more information, check: What's changed in the latest Fitbit OS update?

Hope this helps. 

[juostu]

Totally inaccurate while working out and Fitbit does nothing about it except useless copy/paste moderator posts. Check the forums.

[SonoItaliano]

FitBit Sense, which I have had for about a week now, is my third try with a smartwatch/fitness tracker.  Not sure why I keep trying...

In my case, the Sense hear rate measurement - when at rest - is pretty consistent with readings my chest strap device, a pulse oximeter, and an Android app that uses my Pixel 4XL's camera.  FWIW, my "sitting at my desk" heart rate is right around 60 bpm.

When I get up on a treadmill and walk at 3.5 mph, my chest strap device reports 80 - 85 bpm, as does the treadmill's own electrode-based measurement (hold both handles for about 30 seconds until it displays a reading).  If I pause long enough to use the camera-based app on my phone, I also get readings similar to the chest strap. But, the Sense is consistently 15 to 20 bpm high even under this light exercise, with readings of 98 to 105.  I wear the Sense snugly on my left (non-dominant) wrist; if I tightened it up by one notch on the strap I would never get it on and if I loosened it by one notch it would be flopping about.

I'm pretty frustrated with this state of affairs.  I mean, come on, 20 bpm high?  How does Fitbit justify that?  It makes all the collected data worthless, especially calorie burn.  And, we are talking about *walking* at 3.5 mph - not a lot of bouncing around like if I were jogging/running.

If I don't find a way to fix this, I will probably return the Sense.  It does not do me any god at all if the data it collects is so far off from reality.

[Sparky617]

I just upgraded from a Versa 1 to a Sense.  With the Versa my morning dog walk of 40 minutes (3+ mph) would regularly log 35+ minutes of active zone minutes.  On today's walk I didn't log a minute.  Per the Sense my max heart rate was 98, my zone starts at 99.  

[SonoItaliano]

I am convinced that the Sense simply cannot be trusted for any of it's major functions.  HR, way off.  HRV, highly suspect.  Breathing rate, highly suspect.  Step counter, tends to over count (I have taken as many as 572 "steps" before actually getting out of bed in the morning...), mileage based on steps (treadmill, for example), no matter how much I try to adjust stride length, I cannot get it "dialed in" closer than 80% of actual.

The data I get from the Sense does not even remotely agree with the data I get from other sources that I consider highly reliable.

[SunsetRunner]

@SonoItaliano 

curious as to what will be your next step or option having read all your posts...

I wonder if a lot of the other functions of the Sense rely on HR. If HR is inaccurate, will that affect all other functions that rely on HR? 

The source info (HR) should be accurate first, yes?

[Guy_]

It is known that the heart rate sensor is only of use when still for a minute or so, on a Sense or Versa 3, irrespective of firmware version. Verified by using SimpleClockPro in Always on mode, you can watch the rate frantically adjusting from some ridiculous figure to the correct one once you stop moving.

As a result, all calculations based on heart rate cannot be of any accurate value, though sleep, when one is mainly still, seems more reasonable.

Based on the perpetual official response being put down to a problem of how you wear the watch, rather than acknowledging the fault, it seems very unlikely the problem will ever be resolved. If it were recognised there might have been some hope. But nearly a year has gone by.

Combine this with the ridiculous floor counting which counts floors randomly all the time, calorie calculations are going to be way off [if it's used in doing the calculations, it should be].

Best solution, get an original Versa or Ionic instead, still the point of reference in this Fitbit range.

[Sparky617]

An update.  I went for a bike ride yesterday and compared my chest strap HR to my Sense HR numbers.  They were generally within 5 BPM of each other.  I have noticed that sometimes the delta between a Fitbit and my chest strap HR can be quite high.  Especially when I'm pushing peak HR on my rides.  At peak Fitbits tend to always be low.  This was true with my Versa and the Sense. 

On today's 30 minute walk I did get 9 minutes of Active Zone Minutes.  Looking at the HR while walking I see that I'm drifting up past 99 BPM but not staying there consistently.  The only thing that has changed is the Fitbit on my wrist.  The tempo of my walks, the distance, the terrain, and speed are all the same.

[SunsetRunner]

I do want to note that the Sense seems to notice "Increased Cardio Fitness" What I mean by that is.

2 weeks ago, I was able to get a 150 BMP HR doing HIIT on a Spinning bike (Sense was within 1-2 BPM of Spinning Bike HRM)

This morning at the same intensity I was only able to hit 124 (Spinning bike HRM matched with 1 BPM exactly for for the whole session)

I was also not as winded as previously, yet still dripping with sweat. As your heart gets stronger, it requires less BPM to push the same amount of blood. In this case a lower BPM is actually a good thing.

I have found Apple and Samsung don't take this into account while exercising and instead use algorithms based on studies from Harvard and others that estimate a person of x weight, at x intensity should have around an x heart rate and burn x amount of calories...there is a reason my sister has gained 20 pounds since switching from Fitbit to Apple watch, its HR, calories burned, and weight management features are over estimated by a large margin.

The Sense HR monitor will decrease your heart rate over time because your heart is getting stronger from all that walking you do. If you want more zone minutes, you gotta walk more or walk faster, your heart WILL grow stronger over time and that same walk you have been doing for a month will no longer put you in AZM anymore because your heart is stronger now, so you will have to push more, its just the human body works. At least Fitbit isn't lying about your heart rate.

[Sparky617]

A chest strap is always going to be more accurate than a wrist sensor that uses light to detect a heat beat.  I compare my Sense (and Versa and Surge) to my chest strap reading while riding and sometimes they agree, sometimes they're within a few BPM other times the Fitbit is way off.  Resting HR seems to agree more often than not.  

If you really want accuracy you need to use a chest strap.  Not something I want to wear 7x24.

[SonoItaliano]

I hear you, but still.

I know what my resting hear rate is and have at least half a dozen easy and convenient ways to check it if I so desire.  But, I find that the "exercising" heart rate is so far out of whack on the Sense as to be totally useless.  And, of course, that throws off everything - calories burned, HRV, and so on.

Speaking of HRV, 19 - 21 overnight?  Somehow, I doubt that is accurate.  And, if it is, I'm not convinced that HRV while asleep is all that meaningful, anyway.

And I still can't get power walking on a treadmill to give any sort of consistent measures.  Over 4 miles (according to professional grade treadmill), the Sense tells me anything from about 7,000 to about 9,000 steps and, believe me, I really go out of my way to keep my left arm free to swing normally.  Treadmill mileage?  All over the place, no matter how many times I try to "dial it in" to improve accuracy.

I've got another two weeks to return it to BestBuy.  Pretty certain that is exactly what I am going to do.

[SunsetRunner]

Hi!

I have some heart issues involving heart rate (HR), so this is something I've been very attentive to.

Most of the above posts have very helpful and useful infos, definitely to take into account. I'll try to contribute to this discussion with my personal experience.

I have tried before a Versa 2, which I had to return, much to my regret, due to a slight skin burn/overtan it was causing on my wrist.

Then I used a Xiaomi Miband 5.

Now I'm using a Sense since December. With the Sense:

- No problems with the wrist skin.

- Still not perfect on HR, but slightly more reliable then both previous ones. The best, so far.

All these watches/trackers rely on beams of light located at their bottom, in touch with the skin. To be more accurate, the lights should be stronger, but then they would burn the skin, besides draining the battery more quickly.

None of them is 100% accurate concerning heart rate, far from it. But the secret, I think, is firstly follow Fitbit instructions, as stated above by other user, secondly to explore, by trial and error, the tiny adjustments you can make both on the wrist positioning and the band tightness. In the beginning, check the heart rate shown on Sense with other instrument or just by counting your heart beats with your fingers. Untill you find your own best adjustment. But... even then, there will always be the occasions when it goes far off the right HR.

For me, Sense is the best, so far, in self adjusting and going back to the right HR values after a few minutes of wild values, if I can keep the wrist quiet enough for some time. When I just walk, HR are usually great if Sense is on the right wrist position with the right tightness, and... if I am not wearing any hard sleeves nor continuously touching the Sense.

There is one situation when Sense, or any other watch I tried before, NEVER gives me reliable HR, always showing values too high: when shaking the wrist, washing hands or hand washing something else (sharp movements). But having the wrist quiet, the HR always gives the right HR after 1 minute or so.

Having said that, in the end of the day:

- I could never totally rely or trust the calories shown on Sense or any other watch/tracker I tried. They just give me a rough idea, sometimes completely wrong. When this happens, I try to remember what sharp movements I did during the day that could explain unexpected high values. Tricky...

- The same with daily minutes in active zones.

And I think this will probably happen with any watch/tracker using the optical technology wrist watches/trackers, like Sense, use nowadays. That is why chest straps are more accurate: they use electrical measurements from your skin, not optical.

But, from the moment some upscale watches, like Sense, Apple and some Samsung, started using electrical sensors to get ECG, the technology is there. Why aren't they using it for HR? I don't know. It could be due to battery issues (do electrical sensors drain more battery than optical ones?) or just the software for it is not ready yet. Or the need of a more distant electrode, which doesn't fit in the watche's small size?

Finally, healthy people who do intense physical exercise (not my case) complain that Sense HR is lower than it shoud be near the highest HR during training. This makes me wonder: wouldn't it be better if Sense provided the possibility of individual adjustments made by the users to fit each individual situation? And... would that be possible or feasible or practical?

[Steveparadox]

The sense is so inaccurate, way way off. During HIIT workouts the bpm is recording so low, sometimes not even going into "fat burn zone" during very intense workouts. I noticed it recording under 100bpm during mountain climbers, jumping jacks, etc yesterday. The device is utter junk not capable of primary functions, let alone any "advance" features. 

[SunsetRunner]

Speaking about Sense before these firmware updates mess, I would say maybe Sense is not the best choice for everyone.

With my heart condition, Sense helped me a lot with its heart functions, even with their flaws and all, and more than 6 months later my heart health is better and I can see it and feel it, as is my peace of mind.

[MARKY_N]

Hi,

I had a heartbeat monitor and the fitbit sense working at the same time, they were very close to each other.   So I didn't have any concerns that the heartbeat wasn't being monitor accurately enough.

[Steveparadox]

@MARKY_N  what conditions did you test them in? Did you test them during workouts? what bpm ranges were recorded? Thanks

[SunsetRunner]

@MARKY_N and everybody, until several years ago I regularly used to run and cycle, but then I only had a chest strap, which seemed accurate enough to me.

I only started using Fitbit Versa 2 and later my current Sense after I started having heart problems. Since then I don't run or do cycling, but sometimes my real heart rate, HR, goes up to 130 for a couple of minutes just when going up several flights of stairs again and again, due to my current bad shape. Sense's heart rate values are always OK! But... this efforts happen slowly, almost step by step, and don't involve quick arm or wrist movements, certainly not the shakings you have when cycling or running. From other experiences, I would expect quite innacurate Sense HR values during some periods of hard training sessions.

Curious enough, now when I walk, while HR is 80 or so, now and then Sense HR values start rising for no apparent reason, sometimes reaching 140 while my heart keeps beating at 80-95 bpm. Many times I realized this happened after I was repeatedly touching the Sense, either browsing its menus while walking or just by wearing something with long hard sleeves whose end I had left just above the Sense, repeatedly touching it, instead of covering it. But even in these occasions, Sense HR usually ends coming down to the right values after several minutes. But not always.

Hope this helps.

[Guy_]

@SunsetRunnerIsn't the point of the Heart rate value to constantly show you your actual heart rate, regardless of what you are doing?

Besides a totally out of range heart rate measurement upsets all the other values, AZM, Cardio etc.

If you have to resort to other instruments, or taking your pulse by hand for 15 seconds and multiplying by 4, to get a real reading what is the point of the watch heart rate measurement ?

[SonoItaliano]

Exactly.