Fenix 5 Plus HR very inconsistent

I've had my 5 Plus for a little over a week. I use it a lot as a HR strap in conjunction with my Edge 1030. The first week, the HR rates seemed consistent with what my strap had been reporting based on effort. The last 2 days, it's been all over the place, telling me my HR is 105 on an all out sprint. Even on a hill climb, I could not get it to read above 157 when I knew i was much higher.

When I got home, I threw on my HR strap and fed it into the Edge and left the Fenix broadcasting. I did about 5 mins of jumping jacks; enough to get my HR up. Strap read linear and based on effort; Fenix stayed about 30bpm below and not reactive.

I tried rebooting it; changing wrists, flipping it to my wrist. Nothing changed.

Do I have a bad unit or did the most recent update bork it?

0 Former Member over 6 years ago

I was an early adopter of wrest HR with the MIO alpha watch. This was great and responsive in spin classes, the only down side that at start-up it sometimes reported half the heart rate. Once the watch resolved this with some steady pedalling from me it was fine. I upgraded to the 5S plus and was disappointed with the responsiveness of the wrest HR, so much so I now use a chest strap, not really the upgrade I was looking for. How about Garmin look at the MIO processing algorithms and purchase the IP. Then give us a feature to switch between improved accuracy / longer averaging and interval/sprint mode for faster updates, at the expense of a little accuracy.
Bottom line just recreate the performance of my old MIO alpha!

0 _hernan over 6 years ago

Just to add to this: I made a comparison by wearing both my F5 and my F5+. If I start from a sitting position (still and relaxed), both watches will be at about 55-60bpm. But if I stand up and start walking slowly, the F5 will show 65-70 bpm (which is correct) while the F5+ very often spikes to like 100 or even 110bpm. The F5+ will eventually go down and find an HR lock at a correct value, but that sometimes takes a couple of minutes, skewing all calorie calculations etc in the meantime. And those spikes happen so frequently that I would say my watch spends around 50% of the time showing values that are totally incorrect.

All this doesn't happen on my F5, and I remember I noticed the accuracy of it becoming better at some point with a certain update. My F5+ is still on software 4.20 (it's APAC), so my only hope is that software 5.10 and the new OHR firmware improves the situation. Has anybody seen any improvements through this update?

0 joriqqq over 6 years ago

My watch measures very low number during and after burpies or man makers -100 instead of 150 bpm. And walking - 95 instead of 115 bpm. It does look like the issue is happening after 5.10 update. I emailed to support and waiting for help. I think the more people contact support, the more chances the issue will be addressed.
Let's make Garmin aware of this issue

0 Former Member over 6 years ago

I have noticed a slightly different problem with my Fenix 5s+ OHR during runs.
For the first few (summer) months that I wore the watch, the OHR during running seemed spot on. Contrast this to my Fenix 5s, which often had trouble warming up and could take up to 1 mile to give the correct heart rate, and then would have random spikes in HR.

Over the last few weeks, I have noticed similar behavior in the 5s+ in which the HR will spike up to 160s and 170s, when it should be in the 150s. This can occur when going downhill, but also on flat ground, although usually is correct on uphill. Stopping and trying to reposition the watch usually does not work. Stopping will temporarily lower the HR, but then the minute I start the run it will jump back up to 170. Eventually it usually corrects, but this can sometimes take a few minutes, and then my run is screwed in terms of recovery time and such because the watch thinks I've been all out exerting myself.

I thought this might be due to cooler weather, but I suppose it could be related to the recent firmware? (I am running 5.53) I always wear my watch the same way so I have no other reason to explain why it suddenly is so much worse when it used to work really well.

0 c1rclez over 6 years ago

I have recently acquired a F5+. Coming from 5X and Apple Watch Series 4.

The OHR is laughably bad. Indoor bike trainer activities take 12 minutes to acquire a reasonable heart rate. I’m talking it’s easing 70-80 bpm when Apple Watch on the other wrist is reading 150. I spent $800 on a multi sport watch and I would expect it to at least be in the same ball park as my heart rate. It’s ddfinitely being returned.

I understand the limitations of wrist heart rate, but this is unacceptable on a device marketed as a premium training device. On a stationary bike there is no excuse for heart rate being so far off.

And yes before I’m lectured on how to wear the device I understand it needs to be snug on the wrist and not move during exercise.

0 GavRace over 6 years ago

I concur with a few on here.

I went from a Foreunner 645M to a fenix 5 Plus, because I'm doing more and more triathlon stuff. The 645M OHRM seemed to work really well and matched up what I'd expect and my HR strap.

With the fenix 5 Plus, it's consistently elevated when exercising. It's about 20-30bpm over what it should be. The trend line *looks* OK but it's out. I did a slower warm-up run the other day over 2 miles and it showed an average of 158bpm. I then did a 4.5 mile run at 2mins per mile faster than the warm-up and the average HR reading was actually less. This is clearly not right.

If I wasn't doing triathlons, I definitely revert back to the 645M.

I've taken to wearing the strap where I can but I don't find it comfortable running it. It's OK if I wear a compression top but tends to slip down under a normal t-shirt when I breathe heavy.

I don't need the HR to be *exact* but I do want it to be in the right area so I can at least gauge intensity etc. At the moment, it's next to useless when exercising. How can the OHRM from two similar watches be so different? I get there are slight size differences but the sensors and clever bits must be very similar under the hood.

0 Dr Phil over 6 years ago

might be due to cooler weather,

In cooler weather boiled vessels get smaller and go deeper making it harder for the blood flow to be detected.

I keep looking to see if OHR is ready for 'active' activities but each time I go back to the strap.
If it

tends to slip down under a normal t-shirt when I breathe heavy

then I suggest it might not be tight enough.

Garmin, and all the other manufacturers of devices with optical heart rate are well aware of the limitations with trying to detect heart rate using optical methods during activity. And for completeness, I to have an AW4. On the occasions I have used it for an activity, it's been no better than any of the Garmin devices I have.

I'm sure we would all love to ditch the strap. Unfortunately, I do not think that's going to be an option for a wee while yet, if ever.