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Optical HRM reading low, but only in activities

Former Member over 7 years ago

Upgraded to Fenix 5+ Titanium last week, running 4.20. Optical HRM seems to be working well for basic tracking, RHR, sleep, etc. However, when used in an activity, the measured heart rate seems to be stuck in the 70-90 bpm range. The watch is snug on my wrist. So far I’ve seen this behavior on both a rowing machine (ie, back-and-forth motion) and on a stationary bike. I’ll note that I am broadcasting to an iPhone and have had the same drop others have seen after ~2 min. I’ve attached 2 photos to illustrate:

1) 1000m warm-up row this morning, where HR gets stuck in low range
2) Similar 1000m row from 2 weeks ago using an HRM-RUN with Fenix 3

Following the warm-up row, I saw the same behavior during a 36 minute sandbag workout, so I switched from optical HRM to HRM-RUN at ~15 minutes, and the measured HR jumped from 80-100 bpm to 140-160 bpm.

Any ideas or confirming experiences would be appreciated. Thanks ciq.forums.garmin.com/.../1401908.jpg ciq.forums.garmin.com/.../1401909.jpg

0 Dr Phil over 7 years ago

Lots of ideas and confirmation dotted throughout any number of threads on all the devices with OHR. Won't take you too long to find the information you seek after a brief search.

0 SAHO over 7 years ago

Nothing wrong with your specific watch/sensor - it's the current technological capability of OHR in certain (most?) activities that simply isn't there.

Solution? It's a no-brainer: Use your chest strap when exercising.

0 esselite over 7 years ago

There is nothing you can do. OHR will show you inaccurate measurements. It react slow and does not give you correct value. use chest strap like colleagues just said.

0 Former Member over 7 years ago

Thank you for your responses. I’ll have a look at some threads on other devices and continue to experiment to see how performance varies across different activities. Maybe there are some where it’s good enough to give the chest strap a break.

0 SAHO over 7 years ago

In any case rowing is certainly not among those activities since you are constantly flexing your arm/wrist muscles.

0 nmyeti over 7 years ago

As per above, I wouldn't expect much from an activity where you are flexing your wrists. I tried the sensor while rock climbing at the local gym (don't think I'd risk the watch on one of the local crags) and found the HR to only measure close to reality after i'd stopped climbing no matter how i wore the device. The HRM run works well enough while climbing, but the data derived was less useful than i thought it might be so I gave up trying to track gym sessions with the watch.