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

[Tjht]

Don't freak out! I think it isn't super accurate. I exercise daily and
think I am in decent shape, yet mine varies from 15 to 35 ...usually around
20.

[Clint88]

I find the Charge 4 HRV to be very consistent. I have been tracking mine in a spreadsheet since the first day it was available, and I think it is pretty good. Is it medically accurate? Probably not, but that's not really important since it is not a medical device.
The best way to use any of the FitBit Health Metrics is to get your personal baseline and watch for variances from there.

HRV is very sensitive to alcohol consumption. When I drink my HRV absolutely craters. It is also sensitive to intense training. If I put in a heavy workout, my HRV drops. A recovery day or two and it is right back in the normal range.

[Tjht]

Since I like red wine maybe that is why my hrv is so low 😆. I'll have to
test that !

Thanks!

[Clint88]

---

@Tjht wrote:
Since I like red wine maybe that is why my hrv is so low 😆. I'll have to
test that !

Thanks!

---

My personal results as an example of how detrimental drinking is to the HRV score ...

Drinking: 25 HRV average with a high of 29 and a low of 22

High Intensity Training: 43.85 HRV average with a high of 57 and a low of 36

All Other Days: 55.02 HRV average with a high of 86 and a low of 48

That is based on four months of tracking the score. I don't drink very often, but when I do my score craters.

[ChrisB1966]

Just an update to earlier posts I have made on this. I got a Polar H10 around 2 months ago and use that with Elite HRV app. putting the results in a spreadsheet that averages all the readings over time to give trends/limits. I still record the Charge 4 readings too, so here are some observations.

As a rough guide the C4 is not too bad if you have a regular routine and don't exercise hard in the evening, but the numbers seem to be generally low.

The C4/Health Metrics place too much reliance on resting heart rate overnight from the Restoration graph of the sleep analysis, for example I trained hard yesterday and finished around 3 hours before bed and the C4 indicates a low reading this morning (16) against a medium reading on Elite (42).

The C4 can be slow to spot changes because of this, recently I was away and did not get much sleep one night. Elite spotted that the next morning because its based on the live data but the C4 did not see it until the next morning.

I think that after we all lost data for a few days, some improvement was made to the analysis as my C4 readings came back on track after being noticable off for a few months.

I would be good to know when things are changed, never seen any release notes from Fitbit.

I have accepted the limitations of my C4 for the convenience of a wrist monitor, but I'm still disappointed with the performance at times. 

[skas]

I ended up here because my HRV ranges between 8 and 20 ms. 12 ms seems to be my baseline.

I'm in my late 20s, relatively fit, and at a healthy weight. I'm a bit concerned because most other "low" HRVs are 20 ms and above, whereas I rarely get above 20.

[YiannisP]

And an update from me too since I finally bought the Polar H10 strap and been using it with the Elite-HRV app for the last 35 days together with the Fitbit. Fitbit of course measures some time (times?) during sleep, I measured with the strap just before getting out of bed for 2.5 mins.

Surprisingly, as it turns out at least in my case the Fitbit and the "proper" HRV measurement with the ECG HR monitor are in pretty close agreement on the average over these 35 days: 61 RMSSD for the H10-EliteHRV to 58 RMSSD for the Fitbit. The daily variation is another thing though, the Fitbit seems less variable, but that would be logical if it represents an average over more than 2.5 mins during the night. Their daily reading correlation was 45%, so no great agreement there. But at least the overall HRV levels are pretty much agreeing.

Does that mean the Charge 4 is generally accurate for the other people here? Maybe not. On the other hand I've read that some people can have naturally low HRV without this being a "bad thing".

Moderator Edit: Formatting

[SunsetRunner]

I agree that it is very inaccurate. The highest number I ever got was 33.  Today was 19, sleep score & stress management scores in high 80s.  Makes no sense to me

[Zests]

Hi

For me over the last week the polar with the Elite app has been giving me scores of between 30 and 40 ms. The Fitbit all around 20ms so a pretty major difference. Maybe the Fitbit wrist measurement is more accurate depending on characteristics related to closeness of Fitbit to vein or something? I imagine that might vary a lot from person to person.

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[rayhal]

My Charge 4 shows an HRV reading of 15. Elite HRV paired with a Wahoo Tickr chest strap shows 67.

Looking at tests of the Charge 4 against lab and medical equipment it appears the Fitbit is quite good at recording sleep and SPo2 compared to other similar devices.. This is why I bought the device. Many other things are quite poor. For example I went for a 1.5 hours bike ride and set the activity as 'bike' on the Fitbit. When I got back the Fitbit had recorded 8,000 steps and 22 flights of stairs!

When sitting still HR is spot on (against chest strap) when exercising it's way off, typically +25%.

Basically I think this type of device is ok for measuring trends but should not be used for absolute numbers.

[ShanP1]

I am also 45 years old. My Charge 4 has shown between 28 and 37 ms for the first 7 nights I have worn it. I don't think it's accurate.

[MJM76]

My HRV has been between 14 and 25. I was freaking out too until I came upon these posts. I am 63 and in really good shape. My heart rate is ~65. After using my Charge 4 for 16 months now, the trend is most important. When I work out heavily it's 14 -18. When I take a few days off, it reaches 22-25. So from rayhal's post on 9.24.21 a 15 score on my Charge 4 is possibly a 67 on more accurate readers. This makes more sense based on how I feel. So determine your personal baseline on the Charge 4, and then follow the trend which seems to be accurate. Thank you for all your posts.

[caffeinejolt]

when measured using a polar h10 which can accurately measure hrv, i am around 50 - the charge 4 usually measures me at around 25

so at least in my case it is off by about half... which in my view makes it utterly useless for this purpose.  the charge 4, unless i am at complete rest, is mostly useless for accurate bpm as well so i guess it is not a surprise that it is inaccurate for tracking hrv which requires much greater precision

[BobSaccamenco]

Just as a reminder that the Fitbit measures the RMSSD value of the HRV.

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

The range seems to be in the 21 to 53 range, depending on age. If you are in your 60s a reading of 25 is actually well on the good side.

https://www.sciencedirect.com/science/article/pii/S0735109797005548

As a 35 year old male I have a HRV of around 20 +- 5 and also freaking out because it sometimes it says on the net that a healthy value is > 100.

So, yeah, the fitbit seems to be off in general but also make sure not to compare apples with oranges.

[KL33]

My HRV is low as well. I am 74 runs 5 km a day. HRV between 25 and 40 but mainly around 29. Dont know if my Charge 4 is accurate. KL

[rayhal]

Don't take any notice of the HRV values in Fitbit or any other watch with optical heart rate sensor. This type of sensor cannot measure heart rate exactly. My Fitbit 4 is not hugely inaccurate and is usually within 3% to 5% of my Polar H10 chest strap, but this is not accurate enough to measure HRV in milliseconds.

According to Fitbit my HRV is around 17, using the Polar H10 and Elite HRV app it is usually around 65 to 68.

[rayhal]

I should have pointed out that Elite HRV gives an average HRV number but doesn't say what that number represents. Checking all data an average HRV of 67 equates to 56ms (rMSSD)

[dz1234]

I don't think it is accurate, but the numbers I get are much more reasonable than they were when fitbit first started tracking. I'm a 52 y.o. male and it was giving me numbers over 100, which would be several standard deviations above the norm. Now it seems to vary in the 40 to 80 range, which is probably more realistic, but there is no real sense to the readings. It doesn't change in a noticeable pattern with excess exercise or drinking or sleep patterns. I don't trust it.  

[HayleyLou77]

I have been freaking out about a consistent score in the 20's! So happy I've found this thread....this is not long following another period of anxiety about my spO² levels which incidentally was another Fitbit error. They need to remove these measurements if they can't make the tech work. It's ridiculous. No way would I pay for Premium in future and (after being an avid Fitbit user for 10+ years) will probably try another brand when my charge HR 5 dies. It seems to think I'm on the brink of death myself!