This resource has everything to get you started: https://www.hrv4training.com/quickstart-guide.html

I can't comment on how the Fenix defines unbalanced, but you generally want stable, but steadily increasing HRV as you work through your training plan.

https://simplifaster.com/...s-hrv-training-data/


the hrv number on its own is nearly meaningless.. higher than usual HRV could mean well-rested and ready for a hard day, or exhausted and the body is frantically trying to recover from unusual stress.. have to look at the history and other indicators as well. The Fenix scores are the result of a black box algorithm and I wouldn't pay any attention to them.

https://medium.com/...-part-2-323a38213fbc

It's saying something else. Garmin's definition of unbalanced is that your 7-day HRV average is outside of your personal baseline. It is unrelated to other people as far as I understand it. Here's an explanation of how Garmin handles HRV and what "unbalanced" means:

https://www.garmin.com/...urements/hrv-status/

The Garmin implementation is only comparing you to yourself.

So you've got an initial 19 night calibration period. During that timeframe you won't get any color-coded scoring (e.g. High/Balanced/etc...). You will see your nightly trends and historical trends.

Once you clear the 19 night calibration period, then you'll start to see the balanced/etc. In the case of Whoop, the Recovery score it gives you each morning is straight-up that last night score. This makes it a bit less useful, because it's super variable. Whereas Garmin gives your HRV value, but the actual Balanced/etc is trended over a number of days (thus one night of drinking won't kill your score).

The Garmin implementation will take that 19 days and expand it up to the last 90 days of HRV data, as a rolling calibration period.

In any event, where you can get into challenges with any HRV baselining is if you've done something significantly different during that initial calibration period. For example, one person I know got COVID the same day they got their HRV-capable device. So they basically calibrated with a crazy-low HRV value baseline, which...while geeky...slaughtered their baseline for quite some time, since they deal with low HRV values for a few weeks.

Inversely, if you were to baseline while sitting on a tropical island drinking alchohol free umbrella drinks for two weeks, you'd be baselined very high/relaxed.

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My tiny little slice of the internets: dcrainmaker.com

Thanks for all the answers and pointers to additional articles.

I've had my F7 for several months, so it should be looking back to whatever the max number of days are.

What confuses me is that the HRV says "unbalanced" (is higher than my normal), but the readiness says "peaking". My HRV trend is upward.

I have an Oly a week from Saturday and because of my schedule this year, this is a B+ or A- race for me (not really an "A" race, but close). So I do want to be peaking or max ready for the race. I have a cycling event this Saturday. If this HRV "unbalanced"/"peaking" means I shouldn't go for a full 80 or 100 miles, I'll stick to something like 50 at z2 with a sprinkle of z3. But if 80 actually helps me, I'll do a z2+ 80.

If the weather is good, my goal is to break three hours at the Oly, which will be a PR for me. That's why I now have this interest in understanding HRV better.

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Not a coach. Not a FOP Tri/swimmer/biker/runner. Barely a MOP AGer.
But I'm learning and making progress.

I've been surprised with how my measured HRV on my recent-gen Garmin 255 (has the upgraded HRM sensor that the older models don't have) corresponds to training fatigue and load.

I originally ignored the data for 2 months as it was mostly the same, but then I've been doing blocks of significantly harder training with a lot more volume, and have been amazed at how the HRV responds exactly as the papers say they should - dips downwards with acute stress, then comes black slowly with recovery days.

Importantly, at least for me, it seems to correlate with how 'energetic' or 'ready to train' I feel for the day. I wouldn't say it's a big surprise of a result, as I know I'm feeling tired already and don't necessarily need a number to tell me that again, but it's encouraging that my HRV numbers don't seem to be wacky at all, and actually seem really consistent.

I now check my HRV every day, I just use it as an additional piece of info to help influence my daily plan decisions. I was going to do an extra swim workout this morning since my schedule permits, but since it's my pullback week, and I'll feeling quite 'blah' from high weekend volume, I checked my HRV and it's still 'low' per Garmin (red), so I opted to just go with how I felt and skipped the swim workout. We'll see how this pans out long term, but given that I tend to overtrain rather than undertrain, I suspect I'll be seeing similar or better results with less wasted workouts.

Not me. I start climbing the walls at those kind of "vacations."

More seriously, does anyone have a quantitative or qualitative assessment of Garmin v. Whoop w.r.t. HRV? I gave two serious attempts at Whoop, once with the older generation, and then with the newer. I gave up both times.

I have a fenix 6x pro (945/245 equivalent). I've tracked hrv on various devices periodically for many years. I find nearly zero correlation between hrv values, and training state. That's for both magnitude and direction of change. I have numerous personal examples of hrv moving higher in response to a stimulus one week, and moving the opposite direction (to the same workout) the next week.

Further, I find no relationship between how I feel on any given day and my hrv status.

A perfect example... For the last 28 days my hrv has ranged from 21ms to 36ms, averaging 26ms. At the end of that block (last Thursday) my last workout was 1:30 with 45min of hill sprints. My hrv Friday morning at 28ms. I rested Fri, sat, sun.. With hrv of 23, 27, 25ms respectively. Yesterday, I ran 45m (short) easy (first run in 4 days).... Today my hrv was 48ms...highest it has been this year.

It is not nearly so simple to interpret.

Yeah, same thing with my Whoop. I found this quantitative comparison, and don't hold a ton of hope given it indicates Whoop 3.0 is quite good compared to competitors, yet I couldn't find value in it.

I wonder if your Fenix 6 (wikipedia says released 2019) doesn't have the most recent updated optical built-in HRM.

That could definitely account for your meaningless HRV numbers.

I wrote about this before, but I've been super impressed with the built-in optical HRM on my current-gen Garmin 255 (released June 2022, has an upgraded HRM that's shared in modern models.)

On my Garmin 945 which I was using right before I upgraded, the optical HRM was almost trash. It was ONLY useful at rest, and barely if that. I always used a scosche+ for run workouts and strap for bike. It didn't have the HRV stat when I got it, but if they added it in as a software update, I'm almost sure it would be useless given how unreliable that sensor was.

In comparison, I've never worn my scosche since getting the 255 since the built-in actually is BETTER than my scosche, with less errors on the initial phase. I strongly suspect having this modern-gen HRM is really key for getting good, reliable HRV data.

It's actually shocking to me how strongly and reliably my HRV correlates to training load and 'beat-down feeling' I get.

I have tracked hrv with chest straps for all the years before I got the f6. I've used garmin connect iq apps, and hrv4training on a phone both paired with a chest strap. The results were always very similar to my f6 ohr.

So, perhaps the f6 ohr isn't great, I'm not a huge fan of hrv using ohr anyway. I find the rmssd values to be very low compared to what I have gotten with a chest strap previously---somewhat expected given the blunted qrs from optical pulse rate.

Regardless, the random directional trends with respect to stimulus has been very typical for me for many years.

I think you have to try the new device. It's unlikely that guys like Dan Plews (who posts a bunch of his data in one of the articles linked above) is getting inconsistent results like yours - my results look a lot like his, with big drops after big days and slow recovery to normal when I'm recovering.

Doesn't sound like it'll work with your current equipment, but def don't forget to take a look at it again if you get a recent-gen Garmin; I suspect you'll be surprised with the results.

The gold standard for HRV is electrical (ecg) measurement of the r-r intervals between successive qrs waves. Not any optical device measuring pulse intervals, at all. I would be quite suspicious of any ohr device that showed data differently than an electrical measurement.

I'm aware that it works for some people... My point is it doesn't work for all. My autonomic system seems to react differently than yours. However, I've had similar conversations with other reputable individuals who know how to take controlled data under repeatable conditions---eith observations similar to mine.

I see your point, but unless you have done the ECG-measurement yourself, I don't think you can rule yourself out as an HRV-nonresponder.'

Similarly, the optical sensor in the current-gen Garmin seems to be giving me and others very plausible readings. Sure, I haven't gold-standard ECG'd it, but it's certainly correlating well with strain and recovery thus far - really well.

That's what a quality chest strap provides. You don't need multi-lead ecg for hrv measurement. You just need a precisely measured qrs peak.


Strain (and recovery) is just a transformed version of hrv trend analysis. So, it would be weird for it to NOT be correlated...regardless of any relationship to the real world.

The new Garmins measure HRV during sleep, overnight. It takes a lot of readings across the entire night and plots the entire timeline overnight.

Are you wearing your HRM overnight and having your device take HRV measurements across the evening? Upon looking at my data again, it does seem that if you focus only on small 1-hr segments, the info can seem random, but by using the whole overnight average, it smoothes out to consistent daily patterns.

This is a sample screenshot of someone's HRV page (not mine) that was posted on Reddit so you can see the 'nightly timeline'

Taking more data that varies even more wildly and then averaging it down does not, in and of itself give you "better", more meaningful data.

Yes, I have done all kinds of various measurements over the years. Yes, I wear my fenix6 24/7. Yes, I have the same nightly graph as any other garmin forerunner/fenix user. I've done the same overnight measurements with a chest strap. I've done 5m and 1m measurements under controlled conditions... To compare with overnight samples.

I never found anything actionable in hrv... Ie, it would have prevented me (correctly) from doing something I otherwise would have done. And it was wrong at least as often as it was right.

I really did want it to provide me with useful data and I spent a LOT of time trying to make sense of it and relate it to something physical. It wasn't even as useful as simple rhr for me. The only meaningful use I found was that generally hrv trends up with fitness. So, you can see fitness trends in a long term increase in average hrv. But, you know.... I can see that in run pace, too.

It WILL tell you when you are about to be deathly ill. Every time I have gotten the flu, my hrv drops out the floor (eg, by like half).

Well, I guess it sounds like it doesn't work for you, unfortunately. If you get a new Garmin device, try it again - I suspect you'll be surprised with the results, if you'd get anything similar to what I'm getting.

Throw away the overnight measurements, unlikely to be useful.

As Alan Couzens says in the article I mentioned above,



I use the app HRV4Training and have found it reliable, it has kept me out of the bigger training/exhaustion holes since I started using it.
The author has a PhD in data science and MSc in sport science, says,

Quote:

always measure at same time after waking up in morning.
measurements taken at other times can still be interesting, but for a different purpose

I would disagree with the overnight being useless at least with the new garmin. It’s amazing how mine tracks with load and recovery, you can see my weekly training load just by looking at the graph over time.

Yep. I've read all of Alan's posts years ago when I first started trying to use hrv. I have a great deal of respect for Alan's work. Overnight measurements are too much noise to signal to be much use.

My own anecdotal results mirror Alan's from a consistency of method perspective. What I found most consistent over a week of quiescent measurements was a 5 minute measurement first thing in the morning.

1. Get up and urinate.
2. Sit quietly in a chair for 2 minutes to relax, feet on the floor.
3. Start 5 minute measurement.
4. Remain relaxed and still. Breath normal.

Its the same basic process as for RHR and morning BP readings.

The 1min measurement wasn't much worse.

I also tried configuring my watch to take a 5min measurement at 0430 every day while I was asleep. This was junk as it was dramatically influenced by sleep stage at the time of measurement. Numbers were all over the place. So I settled on the 5min measurement.

Nevertheless, once I began rolling workout stress on top of baseline there was never any consistency. It was a crap shoot whether any one workout would cause a high or low reading compared to baseline on any given day. Applied stress (in makeup and volume) did not result in a consistent response. Even ignoring the sign of the delta there was no usable info in simply the magnitude.

At best it mirrored rhr, and self-evaluation,and ultimately how the days workout would go. At worst it didn't match up at all. At 54, I still find self-evaluation to be the most reliable indicator or weather I over did it 24-48 hrs ago.

If I feel good and I perform well for the day, but hrv says "whoa buddy... Take it easy" and I feel fine again tomorrow, and can maintain the pattern for weeks/months/years in the face of unstable hrv readings..... Which should I believe? Results or a metric?

That's why I gave up on HRV4Training. My first attempt at HRV, particularly since it was free.

I don't get up at the same time every day due to the obligations of that day. Even on weekdays. And I'm not going to pick the earliest time I wake up regularly, then wake up at that time every day just to take a reading, then go back to bed. That'd be around 4AM. The loss of sleep from doing is not a cost I'm willing to pay. Conditions are also not the same. This might be good for someone with the luxury of having a perfectly consistent routine. Life gets in the way of that for me.

I'd much rather pay a premium to have some device record all the time then figure out for me which periods should be sampled to get the best data.

I can't say I've tried to be super scientific about how I take my measurements, but I'll agree with previous posters that I don't find much useful information from it. Didn't sleep well that night, don't feel awesome in the morning, yup hrv says I'm tired. Doesn't actually mean I can't perform that day though. Also had a surprising number of times it says I'm tired yet I had a fantastic night's sleep and I crush whatever I'm doing the next day. Also had it say I'm super recovered after a terrible night's sleep and I perform badly. All in all, yeah not worth the effort IMO.

Again, I suspect the measurement device is at fault. You can't make a conclusion about it properly if you don't have a device or even a protocol that can at first seem validated on obvious states of conditions.

Try again in the future if you get a current-gen Garmin with the upgraded optical HRM sensor (I think all the ones from this year on have it) - it's a huge upgrade from prior models. There may be some methodology in Garmin's algos as well that are baked in - but whatever it is, it's quite good (to my amazement) in my hands. I really thought it would either suck, or at give me some really off results, but my results from the last 2 months including 2 abnormally high training weeks and even the abnormally high training days, get reflected in the HRV that evening.

I have a polar, which have tended to be the class leaders in HRM sensors.

In general, it tracks with how I feel. Yes, there are outliers which i mentioned in my other post, but yeah, the trends make sense. That's the problem though. It has never told me something I wasn't able to figure out by sitting in bed for a minute and checking in with myself. There's nothing actionable about the information in my opinion. That's great that you enjoy it though.

I suspect there's a difference between the new sensor on the garmin's and 'just another HRM. I've used like so many kinds of HRMs in the past (Polar included) - they worked great for straight HR sensing, but they weren't designed with continuous HRV monitoring overnight in mind. Polar has made HRMs for a long time but I haven't seen anything from Polar re:HRV optimization (I could be wrong about this though, I don't research Polar closely.)

I don't really need a device to tell me I'm tired after a big session or block of training. What its key intended use though is for people to back off their training when HRV is showing they are fatigued.

To do this though irrespective of how you feel would take immense discipline. Can't imagine many would choose to have an easy day because of a HRV number if they are otherwise feeling great...

What I have seen though is my resting HR (not HRV) definitely spikes if I'm about to get sick. A few times I've had a illness and looking back at my HR you can see a spike leading up to the symptoms presenting. For this reason resting HR is a better metric for me than HRV.

I don't think you understand what hrv is. Garmin has no algorithm for measuring hrv. That's very well defined, as the root mean square of successive differences (r-r intervals). You simply take each rr square them and sum all up and take the square root. Nothing magic.

The algorithm and sensor technology is all about finding the pulse wave, and finding the "peak" in the pulse wave (measured as change in reflectance of a specific wavelength of light). The pulse wave is much more "rounded" than the electrical pulses measured by chest straps and ecg. As such, peak detection is a bit more tricky (and susceptible to error). In addition, they need methods for filtering out normal variation from watch movement, etc. In some cases they may have to discard invalid samples, and again the "trick" comes in deciding what to discard, and what to replace it with (nothing? Average of prev and next sample? Etc).

All of this is about minimizing the effects of erroneous measurements. Electrical systems suffer almost none of these issues, as they are much much smaller in magnitude and impact. As a result, bluetooth straps to phone apps can just use the rmssd formula above. Most of these systems don't even bother to handle dropped samples. They just report if it apps to any significant measure and say "try again".

I'll take your word for it; I'm sure Garmin does have some sensor-specific things they've done like you mentioned to try and get the optical sensor to more closely match an electric signal.

But whatever it is, it's working extremely well for me thus far. I find it hard to believe it's all just garbage and noise like you and others claim, as I havent had a single day yet where it's gone opposite of what my training load and sensation of readiness has been (which is amazing to me, as I've said several times.) If it's work so well for me with the current-gen device, it's hard for me to believe it's giving useless data for others if they were using a similar device.

Even this week, which is my pullback week, eveyr single overnight average has increased from 70ms (low for me) all the way up to 104ms today (normal). The 7-day average is still slightly low, but will be essentially back to normal by the end of the week. I now trust my own data enough to be actionable, which is crucial as well - my HRV was still in the low 80s last night, so even though I had the time, I didn't do my typical doubled swim then bike or run, and just did the single workout, but I'll go back to doubles instead today with the normal HRV. (I did feel more fatigued yesterday than today particularly in the AM, but by the end of the day I felt like I should be rolling!)

My last 3 months of data haven't had a single glitched week where there was a mismatch between my training load/feel vs the HRV, meaning no weeks (I can't even note a single day really) where HRV said "you're tired, rest!" but my fatigue said "nope feel great!" or vice versa. It's remarkable how my curves dip with the big training weeks and then come right back up to green as I decrease load.

If you want to try and get the best out of the HRV data, you need to sleep with a strap. I don't think the optical sensor is sensitive enough to provide sufficiently nuanced results. That said I do wear my 955 24/7 and look at HRV. I've found it's good at indicating "stress" or sickness but the number in and of itself isn't super meaningful.

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-Of course it's 'effing hard, it's IRONMAN!
Team ZOOT
ZOOT, QR, Garmin, HED Wheels, Zealios, FormSwim, Precision Hydration, Rudy Project

The study I posted above indicates some are quite good when compared with the "gold standard" of lab-grade PSG. In particular the Whoop 3.0 is dead on. Caveat that the Garmin data isn't from the newest generation of Garmin HRV. These graphs are showing the deviation from PSG, so a horizontal line would be perfect agreement.

Edit: Important context with the graph that the Whoop 3.0 was the only device that provided raw R-R intervals. For the rest the study had to use the output of proprietary black box systems. So it's not apples-to-apples, and the underlying sensors may not be primary source of error. E.g. the authors speculate that the Garmin may have done relatively poorly because it was mixing in waking HRV with sleeping.


In separate sections of the same study, they're also fairly good at estimating broad sleep metrics. Less good at identifying specific phases of sleep.

Interesting. Do you have a link to the original study?

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Post 10 in this thread.

for amateurs like us, the stress load of a workout is negligible compared to the stress of getting up at 4am to make a living etc.. so I don't expect to see correlation between workouts and HRV, and seldom do. Exceptions obviously for major races and similar.

If your RPE and self-evaluation is reliable, you don't need HRV. But most of us can't reliably evaluate our stress levels and ability to absorb training. I started with HRV after getting old and becoming unable to do that anymore, found myself repeatedly overreaching and needing weeks to recover. My secret is I'm tired all the time ;-) and the HRV helps me not to overload.

I'm awful at it. I'm 49, and have been an endurance athlete since age 13-14 on cross-country teams.

I've driven myself into deep, deep holes regularly across every decade. I do not get smarter. I respond great to training and feel awesome after tough races or training weeks. Until I suddenly don't and I'm already at the bottom of a deep well.

oh yes, did that repeatedly as a young man.. then with kids and a job, didn't have time to train enough to get really broken ;-) then getting old, it doesn't take much anymore to fall into the hole..

the HRV as I say does seem to be helpful, it gives me external validation for easy days which otherwise I don't want to take..

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"It is a good feeling for old men who have begun to fear failure, any sort of failure, to set a schedule for exercise and stick to it. If an aging man can run a distance of three miles, for instance, he knows that whatever his other failures may be, he is not completely wasted away." Romain Gary, SI interview

Dammit.
You made me check mine.
I’m clinically dead very soon.

I agree with the above.

Just these past 8 days, I belatedly found I had a very low-grade virus. Felt really low-energy for 2-3 days despite it being a pullback week, and for the 1st 2 days I was thinking "WTF?" as I know I typically feel really good on pullback weeks after 2 days. I did have a brief cough for a morning, but I didn't even consider it to be significant at the time.

But my HRV continued to not improve during those 2-3 days, and even went down a little on the 2nd day despite me doing very low exercise. On the 3rd day, I decided to just pull the plug and rest, and by then it was very clear that I was under a bug since there was no possible other explanation for my dragginess (good sleep hrs, low to no training).

Started feeling better very quickly, and in the ensuing days, HRV has gone back up to almost-normal. It may not be a perfect metric, but it's something I'm definitely paying attention to now as an additional data point - I'll start to really consider life stressors, illness, or other things, and if my general feeling of malaise and HRV are suggesting I take it easy - I'm not going to gut out the workouts like I've typically done in the past. (Prolonging illness when you do that.)

Update on my HRV monitoring over the past nearly half year - HRV for me seems to correlate very well with my general fatigue and readiness to absorb training. If I posted pictures of my HRV, it's amazing how well for me it correlates with going into 'the red zone' when I'm pushing my limits in volume and intensity, comes back up to 'strained' when I'm gradually acclimating to it, and recently, has gone nearly in a straight line back into the green 'good' zone after a mild pullback week and adaptation to the higher training load. Per my Garmin HRV graphs, I pushed into the 'red' zone in early March, and it took me until this past pullback week to get back to normal, which seems about right as I ramped up my training in prep for June races.

Subjectively, I think it has a lot of potential value in integrating non-workout stresses, as my whole family got hit with a mild cold for a few days at one point when I was in a pullback week, and even with cutting a few sessions out completely due to excess fatigue and sleepiness (we all had it, with some sniffles), HRV didn't come up and stayed strained.

I still think you have to pay attention though and not just autopilot HRV, as I suspect it's a better measure of 'global' fatigue and not so good for muscle-specific fatigue. So for example, if I went out and did a lot of super hard run sprints that toasted my legs, but was still overall low volume, I suspect my HRV wouldn't go down a lot. At least that's what I think based on when I've done some super hard swim sets that weren't big in volume.