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Heartrate doubling (e.g. actual: 40bpm, measured: 80bpm)

I just started using a new 935 and I have noticed that the oHR (not during activity) is not that significantly better than my 235 or 735xt.

More specifically, my actual HR when sitting is usually around 35-45 bpm and when I walk lightly around 60bpm. Unfortunately, when I switch over to the HR Widget, I notice that the 935 measures pretty much double the HR at 70-90 sitting and 120 in light walking. As a side note, during actual activities I am using an HRM-Run so I don't have anything weird to report there.

a) Has anyone else noticed that HR-doubling (which is not caused by cadence lock since it's not during activity)
b) Is there a way to "bias" the HR monitor by indicating that my natural HR state is much lower than other people?

PS
My guess is that Garmin's algorithm does some sort of Fourier analysis on the periodicity of the HR and somehow it gets "stuck" on the 1st harmonic rather than picking out the fundamental.

0 Dr Phil over 7 years ago

It could be cadence lock because you are still moving even though you might not have an activity being recorded. However, here have been some other posts about WHR issues and the HR widget that I think might be specific to the most recent upgrade.

Can't find them just now so not sure If I'm remembering things correctly.

0 Steve.E over 7 years ago

Mine is also between 37 and 45 usually. Depending on how much training I?m doing and I haven?t noticed this issue. Seems fine. Is there something non typical about your heart beat? - but that wouldn?t make sense because you would?ve noticed it on your previous watches. Maybe there?s just something wrong with your actual watch? Do you have a friend with a 935 you can try?

0 kalamarios over 7 years ago

It could be cadence lock because you are still moving even though you might not have an activity being recorded. However, here have been some other posts about WHR issues and the HR widget that I think might be specific to the most recent upgrade.

Hmm, I guess it could be cadence lock.

I did the following simple test. From rest (35-45bpm), I got up and walked lightly from one room to the next and looked at the HR through:
a) the HR widget
b) starting a Run activity with an HR datafield

If I look at the measured HR in case a) I get something in the ~100-120bpm as I reported in the OP.

If I look at the measured HR in case b) I get the actual ~60bpm HR.

This makes me feel that the HR reading is less accurate in the low-power 24/7 mode (even while walking around) but if the sensor gets in the high-power, exercise mode then the accuracy is better?

WRT to cadence lock, unfortunately I cannot get an accurate estimate of my cadence while I am looking that HR Widget.

0 kalamarios over 7 years ago

Mine is also between 37 and 45 usually. Depending on how much training I?m doing and I haven?t noticed this issue. Seems fine. Is there something non typical about your heart beat? - but that wouldn?t make sense because you would?ve noticed it on your previous watches. Maybe there?s just something wrong with your actual watch? Do you have a friend with a 935 you can try?

So you actually get readings in the high 30s with the HR Widget?

I can regularly get readings in the 30s while sitting but only if I am on Run Mode looking at an HR datafield. When I look at the HR Widget, it very rarely falls under 40bpm.

I have a friend with a 935 and I can verify it with his. Lastly, I hope my heartbeat is OK but I don't have a heart condition as far as I know :)

0 kalamarios over 7 years ago

Man, I really don't know about this. The bottom line is that I have very low HR and the 935 does not detect it, period!

Everytime I switch over the HR widget, it reports anything between 60-100 bpm, and by simply taking my own pulse I know I am at between 30-40. The moment I start an activity, the measured BPM drops to sub 40.

I don't think I am going to be keeping my 935. I was really hoping that by now Garmin would have solved the OHR problems for endurance athletes with ultra-low HR :(

I don't think I want to start "debugging" a $500 watch to see if it's the algo, my arm, a bug or whatnot. At this price-point I simply expect it work.

0 jminar over 7 years ago

Have you tried changing the position of the watch to see if the problem persists? Inside instead of outside, other wrist etc.?

0 kalamarios over 7 years ago

Have you tried changing the position of the watch to see if the problem persists? Inside instead of outside, other wrist etc.?

Yes I have moved the watch up/down my wrist and I experimented with different tightness for the strap. At this point I have verified beyond doubt that when the OHR is in High-Power mode (like during activities) my measured HR while walking around is just fine, but in the Low-Power mode (24/7 measurement) the measured HR is all over the place.

I haven't tried wearing it on my right arm as I only wear watches on the left.

0 bbdcl over 7 years ago

I had the same problem with my Forerunner 235 in the past in that often the recorded OHR was roughly double the correct value e.g. 45 vs 85. It seemed to appear with a firmware update and I never got to the bottom of it. It was only intermittent though and didn't happen once true HR got up to a certain value e.g. about 60 or so. I also experienced it with a wahoo tickr x but found that was down to a poor electrical connection and so when I spent time massaging in a lot of electrode gel it would read correctly. My pulse was always reasonably regular and I have had various cardiac investigations done which show no electrical abnormalities. Never had an issue with 935.

0 kitenski over 7 years ago

I've started seeing this exact behaviour since 6.0, I've not noticed it previously. Was sat down and it's reading 139! I took the watch off and it continued to display a high HR.

0 kitenski over 7 years ago

I think this maybe a bug, when I last saw today it there is a definite "gap" in the 24x7 HR measuring where it was reading > 130 at rest. I only took it off my wrist for 30 seconds or so