Heart rate readings too high screws up Garmin Coach

Mingar 5 months ago

I recently got a Fenix 7s Pro and noticed unrealistic heart rate readings and erratic jumps. I'm fit, light-skinned, not particularly hairy and wear it tight, but not too tight. Often the watch reports too high readings. Two examples.

Here I'm biking on a flat oval track at near constant speed - no incline, no wind, no change in effort. Suddenly, the watch thinks my pulse jumped up:

Here is the heart rate vs speed of the same activity in detail, the speed units on the right are in km/h:

It spiked up right when I actually slowed down a bit. Makes no sense. Believing the watch at first, I tried to bring my pulse back down by going slower to no avail. It stayed up.

This is very frustrating when I'm trying to use Garmin Coach that assigns activities where I have to stay within a certain pulse range. Here is one such cycling workout where I was supposed to stay at 105 bpm +/-7, so 98 to 112 is acceptable for the watch. When you go outside of it, you get marked down with a bad execution score.

My pulse measure fluctuated wildly between 100 and 140, way above 112 most of the time. I desperately tried to get it down. Look at my speed! Again, it's in km, not miles, per hour. 5 km/h is basically walking speed! This is a 1.1 km loop around a lake, completely flat. People were looking why that dork was riding his bike around the lake slower than a mommy pushes her baby stroller. I even had a jogger lapping me! Biking at that speed is near effortless, more coasting than biking.

At some point, the watch jumped my heart rate to 151, and I got so frustrated, I stopped (see speed = 0 section) and took my pulse by feeling it manually twice, once on my wrist, once on my neck - 78 and 80 bpm. Yes, that's about how I felt too, but the Fenix insisted my pulse was 126. A ~60% error margin! Ridiculous.

A Garmin Coach workout like that is useless, a complete waste of time. Not only does it have no training effect towards my goal, but since the watch thinks I'm exerting myself by biking walking speed it adjusts the training plan as if I had just started fat camp.

Is this a hardware issue? Software? Something I can do?

0 JayD 5 months ago

What you can do is using a heart rate belt.

Optical heart rate sensors are terribly bad for training because of their tendency to get locked on physical vibrations (e.g. cadence lock when running). Personally using a wrist sensor when cycling is even worse cause your hand will absorb all the vibrations from the handlebar. So again: get a HR chest strap. You can find some good one for not much money! If you do not care about Garmin metrics, go with Polar or Wahoo.

No wrist sensor is good for training. I had a Suunto 9 some years back and the reliability was much worse than Garmin.

Also Garmin Coach is not really a high-level trainer, but this is another story

0 2892955 5 months ago in reply to JayD

It used to be pretty accurate, than they released F8 and started to break whatever they can for F7 series.

0 JayD 5 months ago in reply to 2892955

I can give you that it is accurate if you run with a cadence which is outside what makes the wrist sensor going crazy. Kinda like a lucky match between your bio-mechanics and the HR technology.

But using wrist sensors for cycling is a very optimistic choice in my opinion!

I never had problem with SW on my Fenix 7X despite minor hiccups but I was probably lucky.

But this does not change the fact that serious training cannot be done on wrist sensors. At least an optical monitor on the upper arm if you do not want to go with a chest belt

0 meuhbat 4 months ago

The optical hr sensor on the wrist doesn't work properly for biking activities, because you grip the handlebar, and you get vibrations too.

If you want to train seriously with precise HR data, you need a HR belt (can be any brand ant+ or bluetooth, I use a polar H10, you can get a garmin one if you want to use the internal memory).