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What changed with HRV measurement in software 27.00 for Fenix 6?

Was there a change to how HRV is calculated on Fenix 6 Pro with software 27.00?

All year my HRV readings, on my Fenix 6 Pro Solar, were mostly in the Balanced range, with some brief dips into Unbalanced.

The last 5 weeks, Oct 31 - Dec 4, the HRV readings have been consistently in the Low category, with a few days in Unbalanced. This doesn't match my training load, which has been reduced drastically, compared to the rest of the year. Something has changed and I believe it is with the HRV measurement. This is very frustrating. I don't have any specific life or medical changes that would cause this. I am believing the HRV measurement is broken, and not worth reviewing.

Thanks for your response.

Mike

0 trux 7 months ago

HRV changes seasonally, so that's a more probable reason than a change in measuring. We see this kind of posts regularly twice a year, here on the forum. See a similar post, and a more detailed explanation for example here: https://forums.garmin.com/outdoor-recreation/outdoor-recreation/f/instinct-2-series/396880/hrv-constantly-low-since-one-month-instinct-2s-surf/1868018

0 5463366 7 months ago in reply to trux

Trux,

Thx for your reply. Reviewing my HRV data for the last 2 yrs, I do not see any support for dips from seasonal changes. There are occasional drops for a 3-8 days, into unbalance, which are more likely from training loads. There are no extended periods of multi week unbalanced and very few low reading. This current issue is 5 weeks long and is mostly low readings. This is drastically different from the previous 24 months.

How does the Fenix 6 measure HRV? Could there be an issue with the sensor? My HR readings seem to be OK, so if HRV and HR share the same sensor, that would be unlikely. Any other reasons?

0 trux 7 months ago in reply to 5463366

5463366 said:
How does the Fenix 6 measure HRV?

It is the variation of the heart rate, so called R-R interval variation. See for example the article What are R-R intervals? - Elite HRV Knowledge Base for more details.

No separate sensor is needed, but you have to stay still, otherwise the optical sensor may not be capable to detect accurately the HR peaks. Chest strap HRMs are much more accurate.

0 JAbbate13 6 months ago

I have the exact same issues. My HRV is reading 10ms lower on average. And it's getting annoying. I have changed my cardio load, but still int he gym regularly. Reviewed two years of data and have always been about 10ms higher in average. Even through very stressful periods at work. It all changed mid September/October ish.

0 JAbbate13 6 months ago

I have had the same issue since mid September. HRV is down by 10ms on average. Reviewed two years worth of history and it's never been like this. Cardio load has decreased and lifting weight have increased. But that's the only change. My HRV is lower now and I have had significantly higher periods of stress over the past two years and it was still higher.

It's getting annoying now as I try to alter things to get it back up. And it's causing a mild amount of paranoia. Lol

0 trux 6 months ago in reply to JAbbate13

JAbbate13 said:
I have had the same issue since mid September. HRV is down by 10ms on average.

Besides the seasonal changes, fatigue, overtraining, stress, food, alcohol, disease, and other influences, HRV also changes with age, so do not expect that your HRV will be always identical.

From Are Changes in Heart Rate Variability in Middle‐Aged and Older People Normative or Caused by Pathological Conditions? Findings From a Large Population‐Based Longitudinal Cohort Study - PMC

Longitudinally, HRV measures decreased significantly with aging in both sexes, with faster decline in younger age groups.

0 5463366 6 months ago in reply to JAbbate13

After 8 wks of literally red-lining, with almost no variation, my HRV reading have moved back into green. I can find no trigger, from any of the potential influences on HRV, to start the extend low, or to come out of it. Compared to the previous 2 yrs of data, this low period seems to be an aberration. I will not be using HRV readings from my Fenix watch as any health indicator.

0 2326790 6 months ago in reply to 5463366

Me too. I have been getting sleep scores of >90 as well as personal bests in my running and cycling power plus no signs of illness so i would not expect to have Low or even unbalanced HRV.