Heart rate unstable read during activity

I have updated the software to version 9.20. Why is this still happening?
The heart rate reading does not match the actual condition.
It can be seen from the drastic increase in heart rate in the middle of an activity.
I have tried changing the position of the watch, tightening or loosening it but there is no change.
Suddenly in the middle of an activity it increases drastically.
This is not normal, I hate it. Please fix it!!

here my heart rate graphic during activity

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0 Jonathan 3 months ago

I have a similar experience.
Instinct 3 Amoled 9.21

While doing legs exercises (weights) I felt my heart rate going higher, but the watch showed under what I felt. after few minutes it went up .
While running in the treadmill, the heart rate in the treadmill showed me 156 bpm while the watch was in 125.
Then then treadmill was in 175 and the watch 156 or so. Eventually it catched up

There is an issue somewhere there for sure

0 V2007 3 months ago in reply to Jonathan

I have a similar problem, about ten minutes into running there is always a sharp jump in heart rate (+20).

0 V2007 3 months ago

I have a similar problem, about ten minutes into running there is always a sharp jump in heart rate (+20).

0 Vizi 3 months ago

That is known issue from beginning of 2024. Before that, HR did not have such issues. The issue affects range of Garmin watches, many people complained, Garmin reluctanlty acknowledged the issue but did nothing to fix it. You can report it to Garmin support but they will not have solution for the problem.

0 Banteng 2 months ago

Garmin, when u goin to fix this bugs? Happening often recently

0 trux 2 months ago in reply to Banteng

Strangely, I did not experience this bug yet, despite doing three activities per day in average. And when I wear an external HRM, and then compare the data with the wrist HR sensor, the curves are almost always identical, not showing any unexpected changes like in the case shown in the OP. The graph below shows my today's run comparing the wrist HR (red curve) and the external chest strap HRM 600 (blue). There are only very tiny, barely visible differences, and the abrupt changes come due to pauses we did (running in a group, waiting for the slower runners frequently).

I have access to several other I3s among my running club fellows, and I have yet to see such case as described here.

So based on that experience, it does not look to me like a general bug. Perhaps your watch is malfunctioning, or you have some specific physiological condition making it difficult for the watch to read your HR correctly (tattoos, high tan, thick epidermis, low hemoglobin level, peripheral vasoconstriction, heart rhythm irregularities, ...). In your place I would probably ask Garmin to exchange the watch, in order to see whether it does not simply come from a defect sensor. If that does not help, then using an external HRM may be a good workaround.

0 JayHenMac 2 months ago

There are several items being discussed in this thread. Both are common to optical heart rate monitors. The sensor detects heart rate by shining light onto the surface of the skin and detecting changes in the reflection of that light caused by blood flow. It combines that data with inputs from the accelerometer and attempts to interpret heart rate, pace, movement, and other items.

The original post looks to be an issue called "Cadence Lock". The issue is the sudden increase of reported HR. It's when the wearable misinterprets your pace/cadence as your heart rate. This is an issue all optical heart rate sensors must overcome, not just Garmin products. As you swing your arms while running blood pumps into your extremities. The watch is challenged with determining if the blood flow change is caused by the movement of your body (pace/cadence) or if it due to a heartbeat. When your heart is beating slowly, it is easy to separate the two actions. As your heart rate increases, or more accurately, as your heart rate approaches the rate of your body movements, the watch has difficulty differentiating and sometimes locks onto your pace/cadence instead of your HR.

There are some ways to prevent this, but none are perfect. Especially in extreme temperatures. For example, here in the southeast US, it is very hot. Blood flow to the skin surface is greatly impacted by environment temperatures. The same problem happens when it is cold and there is less blood flow to the skin. A way to help prevent cadence lock is to ensure the watch is securely fastened and making contact with your skin. In some cases, doing a separate warm up activity prior to starting the main activity helps. I find that when I am cold, and I include a warmup in the same workout as my main workout, I experience cadence lock. When I start a warmup activity, then stop the activity and start a new workout activity, the occurrence is much less likely.

The second issue discussed in this thread relates to a delay between HR reported by the watch, and a treadmill or a chest heart rate monitor. This is because, again, the watch uses an optical heart rate sensor, and a treadmill typically uses a sensor that detects the electrical activity produced when the heart beats. It does this via the metal sensors on the handles. Chest strap HRMs also use electrical activity to detect heart rate. These devices are generally more accurate. They are not impacted by blood flow or movement of your arms. As such, they are able to detect changes in the heart rate much quicker. The watch will have a delay in detecting because the flow of blood to the skin is not an instant reaction as the heart slows down or speeds up. The watch must recognize the pattern change and then report the newly calculated number.

Both issues are common to Optical sensors.

0 Vizi 2 months ago in reply to JayHenMac

You omitted very important fact - this issue occurs much more often after 2024. Optical HR sensors did not change, software algorithm did.

You also omitted the fact that Garmin acknowledged the issue and said would fix it but later did nothing about it.

forums.garmin.com/.../garmin-965-heart-rate-inaccuracy

There are many more posts but this is enough to clearly illustrate the point that elevate 4 (and 5) watches have this issue, thus Instinct 3 also has it.

0 JayHenMac 2 months ago in reply to Vizi

Good to know! Knowledge is power!

0 7299199 2 months ago

I have similar problem with my FR255.

Mostly during the start of an activity, the heart rate isn't correct. Sometimes it works to pause the activity, select "Resume later", wait a moment and then resume the activity. But in most times nothing works.....

See below the issue: