Heart rate measurement during workout

This matches very closely what I just experienced. Training indoors, my training App was reading 130bpm via my HR strap, but the F7s was reading 85. If I started an activity on the FR7s though, it seemed to get closer. I also wondered if it's a battery save thing when not tracking an activity - may it's just not pollingHR very often. Mine did not improve much when I used the HR glance, although I maybe needed to leave it on that screen longer

It has been posted on several occasions in other watch forums, and acknowledged by Garmin, that the WHR polls less frequently when an activity is not being used. This is primarily because the heart rate changes less and beats slower than when active. Also noted by Garmin in their support document is that heart rate is calculated differently for different exercises. WHR Iis not actually measuring the heart rate, it’s deducing it from colour changes as blood flows beneath the skin.  

Long story short, if you want to track your heart rate during an activity you need to select an activity on the watch. 

support.garmin.com/.../

www.garmin.com/.../

I noticed something similar today. I did a kettlebell workout, haven't done this in ages and HR went up big time. But the 7s didn't measure much more than 103. Checked on an oximeter afterwards and got into the 130s. Once my HR went down to about 100 the fenix was in line with the oximeter again. It's like the watch trying to prevent sudden HR spikes because my whole evening is full of similar-sized spikes (not feeling well) I doubt my HR really stopped at around 100 every time I did something this afternoon, really.

HR data is very much in line with my OH-1 optical sensor that I'm using with my phone when out running for comparisons sake at the moment. So I guess I'll start an actual strength workout on the watch tomorrow evening and see what happens.

I just want to verify I'm understanding the issue being reported.

If you happen to have the HR as a field on the watch, say in a watchface or something, that's when it doesn't report the HR accurately, right?

What I've experimented with, and it works normally, is if I go into an activity like "Run" for example, but don't press the start/stop button to actually start the activity, I get HR tracking that's accurate, even though the activity isn't technically "running". Then if I start the activity, the HR continues working accurately.

Its not clear to me in the two quotes below exactly what mode you had the watch in when the HR readings weren't correct, can you clarify.

ROBW999 said:

Training indoors, my training App was reading 130bpm via my HR strap, but the F7s was reading 85. If I started an activity on the FR7s though, it seemed to get closer.

LiviuNastasa said:

if I'm not using actively the Fenix during an workout (bike indoor)

24 7 mode a bike to work, it seems to be showing my heart rate a a fenix7 which is lighter than fenix x

You are right, for Garmin the WHR during 24/7 wear is designed to give you some idea about the HR, but is investing less energy in the accuracy of the measurement protecting the battery - it's a balanced somehow for a longer battery life. And that's clear for me, since my Polar Vantage V2 is more accurate when measuring the wrist heart rate even when I have not started "formally" an activity, but the 24/7 monitoring is taking a bigger toll on battery life than on the FR945 for example. I understand the compromise and I can accept it.

What I can't really understand is the fact that Garmin doesn't correlate two (or more) sources of information for better overall reporting of HR values. So, let's say that I'm using an external HR monitor (chest or arm strap) during an activity I record with for example my Edge 530 - that is reflected in my Garmin Connect account (and mobile app) - and the HR goes in the 160-170bpm area for a period of time. Because I didn't start my activity on my Fenix, the collected WHR is in the lower range of up to 110 bpm, favouring the battery life. When you look in Connect (web or mobile) your max HR over the day will be reported as 110bpm instead of 170bpm and the HR evolution during the day is the one provided by the Fenix which is not correct since you had an more intense activity which was registered by Garmin in Connect but not "merged" into the daily recordings. 

My expectation would be that, if Garmin accepts an activity with HR measurement and "knows" that the measurement during the activity is more accurate (usually) than the "passive" 24/7 measurement, for overall HR evolution during the day to report for the activity period the registered HR from that activity and not the passive WHR measurement.

Brief, I'd love to see that WHR 24/7 measurement being more accurate, but I can understand and accept the compromise favouring the battery life - but I'd also like to see that for overall reporting we are favouring accuracy regardless of the source, it doesn't have to be the watch WHR especially if it is in the more passive measurement mode.

So far (and my 7s is new) exactly that - the HR shown on watch face, and the Glances page when not in an activity is way low typically and never seems to go much over 100. I haven't done enough activities yet to be sure on accuracy when riding say - but as mentioned here, if I go into the Bike page but don't hit Start, the HR does seem to track more accurately. I need to do more experimentation, but the "not in activity" HR tracking seems way out compared to the FR645M I replaced with the 7s.

Fortunately, I don't have that problem

Holy cow! Thank you... I recorded my first indoor ride on my F7 today, having lent my Edge to a friend doing a race this morning. 171 ave and 191 max seemed about spot on... Using a Wahoo HRM for what it's worth. And yes, it obviously matches my Zwift ride rather closely. 

OP - Have you actually paired your external HRM to your watch? Wrist based HR is notoriously off on esp cycling. Good enough on running, but somehow cycling does not work. 

I've done everything with these garmin watches and so far this fenix 7 solar is extremely good compared to 6x
And I always have a hrm-pro on my workouts