Does the Charge 4 calculate HRV accurately?

[Seanseaton]

I have been recently playing with new hrv update and after some benchmarks, research from experts and manual calculations it appears that hrv measures are inaccurate in general across all advanced watches and bands.  Is this the case for you as well?

Moderator Edit: Clarified subject

[Gr4ndp4]

Hi, this article addresses your question. Inevitably wrist-mounted sensors are not medical instruments.

 https://help.fitbit.com/articles/en_US/Help_article/1565.htm

Cheers

[Salted_caramel]

what HRV are you getting? Mine is super low (in the 20s) so it freaked me out. 

[MommaOfDwagons]

Same here! Im rather relieved to find out im not alone. Ive been looking at coughing up more money for dedicated HRV readers or chest straps after seeing my abysmal Fitbit metrics. Glad I came here first. Hrv 20 today. 

[Pegomas1]

I think the hrv is all over the place on fitbit. I was really looking forward to this feature because it was genuinely useful when I had it on a Garmin tracker. Fitbit state that the relax breathing app uses hrv to time the breathing rate. I think this shows it is inaccurate because its the only relaxation breathing app which accurately seems to want you to speed up your breathing 😂.

I meant actually not "accurately "

Moderator edit: merged reply

[Nicola_grec]

I don’t believe Fitbit is acurate , Fitbit gives me 130 heartrate variability, 

if I use polar heartstrap with an app for heartrate variability. It gives me 76 , 

I think the polar whit app is accurate , cause it’s ecg . 

[SunsetRunner]

Mine has been in the 20’s and today it's at 18. It's not accurate. I don't think any of the measurements are accurate on the Fitbit except for maybe heart rate when you are completely still. 

[Kgou]

Yes the HRV seems to be a bit on the low side as all the other metrics indicate I'm in fair health. In my experience, while the numbers are not exact, heart rate and sleep score generally reflect how I feel when I wake.  Maybe the HRV is a bit like the SpO2 and recorded changes are a more important indication than absolute levels. (Charge 3). 

[Nicola_grec]

Today I think it was good , 82 heartrate variability. 
it depends.  Some days good , other days not . 
charge 4 

 

[YiannisP]

I suspect you guys are jumping to conclusions. I mean of course no such device will be super accurate. Just got the Charge 4 recently and my first 4 readings have been 75, 60,70,68, which I guess sound reasonable (it's not supposed to be constant of course). Are you sure your devices fit properly while sleeping? That said this has piqued my curiosity...unfortunately I also just bought a Polar OH1 arm band, which is not compatible with HRV apps (well the one I found, EliteHRV). So I think I will get the Polar H10 as well to get accurate HRV and come back to you. That said, I would need to sleep with the strap but OK, I'll suffer for the wider knowledge:) Btw, looking at readings from the OH1 (which is supposed to be pretty accurate for HR at least) and my Charge 4, they seem to be quite well aligned, both when resting and running. Definitely much better when running than my Suunto 5 for example. Overall I find the Charge 4 to be quite satisfactory when it comes to HR and sleep monitoring, not so good when it comes to GPS (cuts corners a lot, the Suunto's GPS is better) an readability under sunlight. So for running I use the Suunto paired with the OH1 and for sleeping/HRV the fitbit...

[Nicola_grec]

I have done HRV , with my polar h10 and an app called , HRV + , it gives me around the 76/8 , Fitbit charge 4 is most of the time not good , gives me 120/150 , but if it registers it good then it’s also around te 70 , 

[YiannisP]

I see, thanks. But what do you mean by "if it registers it good"? Also, the fitbit only gives you the average while you're sleeping. Did you do the same with the H10 and the app?

[Nicola_grec]

No , I dit the app with polar h10 strap after waking in the morning, just a 1 min or 3 min . 
also with polar vantage or other watch you can do to same , but you must use your h10 strap and do the fit test . The Fitbit does it good , but sometimes for me it don’t works , caus I work in shifts , 1 week I sleep good , and other week I don’t . 

This is an image that I take from the app of my HRV . 

 

Moderator edit: merged reply

[YiannisP]

Hi Nico,

Well, just to be more correct we need to clearly define what we are comparing. From my brief research on the web, "HRV" numbers from different devices/apps may correspond to different definitions. From what I read (Fitbit engineers correct me if I'm wrong please), Fitbit's number comes from (is) the RMSSD calculation. So in comparing the HRV+ app and the Charge 4, the RMSSD quote must be used from the HRV+ app. (though it seems what they call "HRV and the RMSSD are very close, but just saying).

The other thing to take into account is that the Fitbit number is an average over the course of the sleep, while the HRV+ reading is "instantaneous" as of a few minutes after you wake up. Apparently (see https://www.myithlete.com/how-your-hrv-varies-throughout-the-day/) the RMSSD follows a pattern during the course of the 24h day cycle and is typically higher during the night and at its lowest in the morning. So, the Charge 4 averages the RMSSD over the period when it is highest and that's the number is gives you. So, that alone could explain why the Fitbit gives you a higher reading. 

I am not saying this is the explanation, especially because a reading of 150 that you mentioned seems to be abnormally high (and thus potentially wrong). Just sharing what I've found out about this.

[Kelly2002]

Me too it's done the same to me, cardio fitness is excellent and my hrv is 15 

[YiannisP]

Are you sure that when you're sleeping the sensor always touches your skin properly? Have you experimented with tightening it one notch, or putting further up the wrist if your wrist is thin? 

[Kgou]

I have changed the band fit, and the results didn't change. The HRV reading
has been fairly consistent. Maybe the reading is accurate and a low value
is not that unusual.

[YiannisP]

How low is it? If too low I would buy a Polar H10 and check accurately for my peace of mind...

[Kgou]

Not sure yet that it's worth checking out just yet. The reading is just a
surprise because the fitness score is 52-56 which I suspect is a bit
inflated as I don't really do much cardio; HRV so far is between 17 and 27,
but it has been enabled only for a short time here.
[image: Screenshot_20201016-080534.png]

[ShadowAndJeb]

You have reassured me. I have been getting off the scale measurements also