Garmin Fenix 6 Pro HR sensor false detection and error accumulation issues

I bought Fenix 6Pro since last Nov. to replace my old Garmin 235 due to the short battery life time, and I was very happy to start to run with new fenix 6 PRO, but the trouble was stared, the fenix 6 PRO HR is not accurate at all comparing with my old Garmin forerunner 235, it seems HR detection error is keeping accumulate during running, after around 45 min. and 5 miles easy run at pace 9:30~10:00, the HR reading became 180. if i wear forerunner 235 to run the same route and same pace, the HR is only about 125~135. I also did following tests with external Garmin HR strap, hold the fenix 6 pro, and wore on long sleeve running shirt. all Runnings had warmup.

1). Test#1: Tried to run 1 mile with Fenix 6 pro and external Garmin HR strap, running pace was around 10:00~8:16min. HR range was around 176~187, and cadence range was around 176~189. fenix 6 pro did not detect the heart rate pulses from the external HR strap, it detected and synced up with the cadence.

2). Test#2: Ran 2miles on the 0.25miles track, and hold fenix 6 pro with the large gap between optical HR sensor and the fingers on the hand, no any skin was touched with optical HR sensor, HR strap was removed. Fenix 6 pro detected the cadence for HR again during running. the running pace was around 8:47~7:29Min., HR range was around 168~190, and the cadence range was 183~196.

3). Test#3: Ran other 2 miles on the track to test Fenix 6 Pro HR sensor with long sleeve running shirt, wore loosely the fenix 6 on the top of long sleeve at the wrist, no skin was directly touched with optical HR sensor, the HR rate reading shown the cadence again, It seems Fenix 6 Pro HR sensor is fake, and HR data is calculated using ACCELEROMETER data or just used cadence directedly as HR. the running pace was around 9:00~8:16min., HR range was 169~186, and cadence was 180~194.

4). Test#4: Ran 1mile, and put Fenix 6pro in the short pocket, HR sensor did not detected any, and HR optical sensor automatically turned off, after running around 0.2 miles, put the watch back on the top of long sleeve again, it started to turn on optical HR sensor, and it slowly detected some things and synced up to the cadence again, it seems the watch optical HR sensor runs himself for HR no matter what you are running.

The test firmware version for Fenix 6 pro is V15.20. there are also a lot of small problems on the watch, i just do not want to go over it since HR issue is the most important, and is the essential data for my marathon training.

Hopefully, Fenix 6 pro development team can fix this problems ASAP!

Thanks a lot!

0 Dr Phil over 4 years ago

https://forums.garmin.com/outdoor-recreation/outdoor-recreation/f/fenix-6-series/195729/anyone-still-having-heart-rate-accuracy-issues-with-their-fenix-6

Read this. All covered already in one form or another.

0 mcalista over 4 years ago

What you are describing is known as "cadence lock" where the watch moves on your wrist and light enters the OHR sensor in a rhythmic way with each step. The sensor picks up on this rather than your heart rate. As a larger and heavier watch than your old 235, the F6 is more prone to moving on the wrist than what you may be used to. The solution is to wear the band tighter (personally, I find I have to have the band on my F6 1-2 notches tighter for accurate HR while running than I do for 24/7 monitoring), and also positioned on the fleshy part of the wrist, well away from the wrist bone - this ensures a better "seal" against external light.

In terms of the long-sleeve shirt, the Power Manager includes a "Jacket Mode" specifically to disable the HR sensor in situations like this.

0 RichardB over 4 years ago

From what I can understand of the problems you have there seem to be two:

Your wearing the F6 on top of your sleeve and expect it to be able to detect your heart rate.
Your F6 isn't connected to your HR strap.

Is that correct?

0 William5473 over 4 years ago in reply to RichardB

Thanks RichardB!

#1, i was wearing the f6 on the top of my long sleeve was not trying to expect it can detect my heart rate, i thought it should be shut off HR sensor since there is no skin was touched by sensor, but the sensor was not shut off, it was still continuously show your HR reading, and like the sensor was still detecting your HR thru your skin, and HR reading gradually increased to reach, thru, and over your cadence. it seems that HR sensor run itself along as long as you are running, not sure what sensor was detecting.

#2, my f6 has paired to my HR strap, but it just locked to the cadence when i start to run. i guess the cadence might be calculated from accelerometer sensor in Garmin f6, there is some coupling between accelerometer sensor and HR sensor either in DSP input or some firmware code, this coupling messed up HR calculation. hopefully, the F6 engineering team can test it, and find the root cause of the issue to fix it.

0 5135968 over 4 years ago in reply to William5473

William5473 said:
#1, i was wearing the f6 on the top of my long sleeve was not trying to expect it can detect my heart rate

Some HR sensors can be fooled into giving HR readings when not in contact with your skin:

https://www.wareable.com/fitness-trackers/why-heart-rate-monitor-work-on-toilet-rolls-6606

In that scenario, I'm not really totally surprised you might get a cadence lock.

For your second scenario, I would think that a cadence lock when using an external chest belt is very very unusual.

I'm not trying to dismiss your points or to say your F6 Pro isn't as good as your previous watch - reports of inaccuracy are common, I am just not convinced by your testing and methodology which appear flawed to me.

0 bluefish over 4 years ago in reply to William5473

William5473 said:
i was wearing the f6 on the top of my long sleeve was not trying to expect it can detect my heart rate,

forums.garmin.com/.../my-garmin-fenix-6-and-table-heart-rate

0 William5473 over 4 years ago in reply to 5135968

for my second scenario, i was trying to practice running 185 cadence with external HR strap, somehow it start to synced up to my rhythm right away.

0 William5473 over 4 years ago in reply to bluefish

Thanks bluefish for the link!

0 5135968 over 4 years ago in reply to William5473

William5473 said:
for my second scenario, i was trying to practice running 185 cadence with external HR strap, somehow it start to synced up to my rhythm right away.

Can I suggest what I think is a better way to test this?

Install on your watch a CIQ datafield called Auxillary Heart Rate

apps.garmin.com/.../a461bc0d-828d-47c8-a4a5-8d014b5fedc9

this will keep the optical sensor active while also recording from your ANT HR strap (you must make sure the ANT strap is NOT paired to the device directly, only paired via Auxillary Heart Rate ), if you still have access to your Forerunner 235 install it to that device too.

Run with a device on each wrist. - you should see an identical ANT stream on both devices, which I think will rule out your second scenario. I would expect variance in wrist HR between devices.

Compare your wrist HR to the ANT HR, and also compare wrist HR between both watches.

I am quite sure you are not seeing a cadence lock using an HR belt.

William5473 said:
for my second scenario, i was trying to practice running 185 cadence with external HR strap, somehow it start to synced up to my rhythm right away.

0 William5473 over 4 years ago in reply to 5135968

Thanks 5135968 for suggestion!

My current F6 pro has been paired with Garmin external HRM, just try to double confirm, do you mean i need to remove this pair before installing Auxillary HR?

Many thanks!