Heart Rate inaccurately low during almost all exercise

I have the same problem here, after upgrading from 15.07 to 15.08, the problem persists with 16.10

From my experience so far, all on 16.10, in the passive 24/7 HR monitoring, watch is good enough for sedentary life. The moment HR raises moderately it is a hit and miss and extremely unreliable above that. These are observations by simply glancing at the watch, without starting an activity and comparing to a HR strap or Fitbit.

This trend has been noted by countless users on the forums, and appears to be an expected behaviour and a battery saving feature rather than a bug. Moral of the story is if you want reliable HR data, you MUST start recording an activity.

HR has been mostly accurate once you start recording an activity with the biggest HR anomaly noted during a benchmark run where HR was 20+bpm lower than on the repeat. A few momentary dips in the HR on other activities have been noted but largely positive experience otherwise.

These momentary drops in HR during recorded activities could be a bug as just about all reviews generally have the HR accurate, often perfectly matching the HR strap. Other part could be the known limitation of the wrist HR monitors. For me, it's HR strap cycling but do expect reasonably accurate HR data from the wrist while running.

doctordarko said:

From my experience so far, all on 16.10, in the passive 24/7 HR monitoring, watch is good enough for sedentary life. The moment HR raises moderately it is a hit and miss and extremely unreliable above that. These are observations by simply glancing at the watch, without starting an activity and comparing to a HR strap or Fitbit.

This trend has been noted by countless users on the forums

I know there are people who have problems with the optical sensor, but I do not know what percentage of the total number the "countless users" represent. However, it is definitely not the case how it works with me.

I did some tests many times with several watches, but to be sure I just did it again right now with my I2, in case something has changed recently. I've put my HRM chest strap on, opened the Strava app to see the real-time reading from it, and in the same time I looked at my I2 display watching the HR.  I did not start any activity on the watch, and the strap was not connected to the watch! The values on both the watch, and from the strap were at 79 and 80 respectively when starting. I begun doing quick squats, and the HR value started rising immediately (within 5 seconds), going to 90 bpm, and then continuing far over 100 without any considerable differences between the two (I'd tell under 5 bpm most of the time).

I can repeat the test on another day, record the data and post it here, though it won't help anyone having problems with the HR readings anyway. I am just posting this to deny that the watch is not designed to read high HR in non-activity mode. It is, and it does work (for some at least).

... BTW. something else, of course, is the all-day HR graph, which does not show the life data from the HR sensor. It only shows the averages over 2 minute intervals. And there you won't see any short bursts of the high HR, of course. It in no way means, the sensor did not detect it.

trux said:

I looked at my I2 display watching the HR.  I did not start any activity on the watch

trux said:

I can repeat the test on another day, record the data and post it here

Thank you! Make sure that you read the HR from the watchface and do NOT call up the HR widget.

trux said:

I know there are people who have problems with the optical sensor, but I do not know what percentage of the total number the "countless users" represent. However, it is definitely not the case how it works with me.

There is several of us at least in this thread with an issue and if you search "HR low" you will find many more users over the years, across just about every watch model with unreliable HR data, both with recorded and passive modes. I didn't count, hence countless.

trux said:

It only shows the averages over 2 minute intervals.

In this case (2nd set of screenshots), sensor did not detect it, full stop. Can see smoothed data (over 2,5,whatever minutes)  for the second half matches well but first half doesn't even remotely match the HR strap.

Unreliable HR data

trux said:

I am just posting this to deny that the watch is not designed to read high HR in non-activity mode. It is, and it does work (for some at least).

That is what this forum allows us to do, give feedback to Garmin on what is working and what is not. The fact there are algorithms calculating HR, means there is always room for improvement so HR can hopefully work well for everyone.

trux said:

the all-day HR graph, which does not show the life data from the HR sensor. It only shows the averages over 2 minute intervals.

How Does Heart Rate Data Display in Garmin Connect?

….“Garmin Connect averages out the heart rate values at 2-minute intervals while watches average out the heart rate values at 15-second intervals.“….

https://support.garmin.com/en-US/?faq=dLag82HPPk0l4T2tRELSgA 

doctordarko said:

That is what this forum allows us to do, give feedback to Garmin on what is working and what is not.

This forum is a uses-user forum. It's possible that a Garmin employee is reading here, but I wouldn't expect it.
If you want to report problems to Garmin, you should contact Garmin Product Support.

doctordarko said:

There is several of us at least in this thread with an issue and if you search "HR low" you will find many more users over the years, across just about every watch model with unreliable HR data, both with recorded and passive modes. I didn't count, hence countless.

Yes, there are several threads on the forums, but I see mostly the same people posting on them. And considering the millions of users who do not complain, I wonder whether the "countless" users represent 0.1 ppm, 1‰, 1%, 10% or more.

bluefish said:

“Garmin Connect averages out the heart rate values at 2-minute intervals while watches average out the heart rate values at 15-second intervals.“

This is actually an outdated information. The 2 minutes averages in GC are correct, and exactly what I wrote, but most of the recent models (including I2) no more sample each 15s. They now sample continuously. You can check it by looking under the watch. While still about a year ago the sensor only flashed each 15s, now it flickers continuously all the time, during the sleep mode including. And the displayed value also changes in real-time every second (if the HR changes). Weather the displayed value is a floating 15s average or not is a question, and it is quite possible, but the watch is still capable of detecting high HR even in non-activity mode.

bluefish said:

Make sure that you read the HR from the watchface and do NOT call up the HR widget.

Makes little sense to watch the continuous real-time HR on the watchface, because the watchface updates ony once a minute, unless you wake it up with the wrist gesture, or by pressing a button. But if you wish I can do that, though I will have to wake it up each ~20s. 

trux said:

They now sample continuously. You can check it by looking under the watch.

Sounds a bit like Schrodinger’s cat. You’re not sure what’s actually happening until you look. But when you look you can’t be sure what was happening before you looked because the very act of looking changed things…or did it?