Heart Rate Readings whilst using Zwift

Did you open the HR widget and take a look at the last 4 hour chart. I find the the watch face and first page of the widget show a low value but the last 4hr chart shows the correct value along with a correct recorded history.

There are already a handful of topics on this. @p_cook I presume the watch was not in workout mode? Then your HR will not be accurate at all.

@mcbit interesting, this is the first time I read this on the forum. I always got the answer that it is normal that the HR is not accurate when not in workout mode. I do not find this normal for a 1k watch. If the underlaying stats are correct, that would be a relief. I have to check this.

Yeah, that was my first point of call.

My assumption was that for it to record accurately, it would need to be in workout mode but then it questions how reliable it is when not working out and picking up potential heart rate issues

The watch HR sensor operates in a low power state when not recording an activity. This is suitable for recording resting heart rate, sitting, strolling etc..

For more intense activity to be recorded correctly you need to start *recording* the activity. Since you already have, and use, a chest strap it will give you the best result and additional data benefits to pair the strap and record on the watch.

This will give the watch more data from which to calculate VO2max, training load, performance condition etc etc..

If you currently sync Zwift data to Garmin I would review this practice. Lots of physiological and performance data will be lost by going this route.

Perhaps you don't care and prefer to have the Zwift metrics for speed, distance, elevation gain instead of accurate and complete physical metrics. I don't care to sacrifice relevant training data. I want it all.

My Zwift metrics get synced to Strava, not Garmin, and my Garmin watch records all the data about ME. In other words, I dual record my Zwift activities, but, rather than duplicating data, I keep two separate sets of data which record different aspects of my ride (or run).

I understand why it is more accurate when in workout mode. But when using the watch 24/7 you would expect that it picks up when your HR is 150 for 20 minutes? I am not talking about how fast it picks it up or anything. But a 1000k watch that can't pick up my HR more than doubling for 20 minutes is mind boggling. What about auto detecting an acitvity, what about notifications for elevated heart rate? 

The HR in workout mode is impeccable, really good. So mayby it is inaccurate in normal mode to save battery? I don't know.

I have a Polar, a Wahoo and a WIthings watch. They can all pick this up.

Only acceptable explanation for me is what mcbit is stating.

eezytiger said:

The watch HR sensor operates in a low power state when not recording an activity. This is suitable for recording resting heart rate, sitting, strolling etc..

This is what Garmin says and what I observe:

My watch WHR gives the same HR (out of activity) as my external HRM does (in activity), and I have checked this frequently..

I do not understand competely. So the issue we are having might be related to the specific wokrout (indoor cycling) we are doing and our upper body is sitting relatively at rest? So the watch is not aware it should take more accurate readings?

I do see a spike in HR when I am running up the stairs, being not in workout mode. So the watch is picking that up.

I am talking about indoor cycling when using Zwift, I check my watch on occasion to confirm the externa HRM and that's when I discovered that I had to open the WHR 4 hour chart to display the actual reading.

I confess I have not performed actual tests with my Epix Pro, but this was the behaviour with my Fenix 6X Pro Solar.

To be honest I will always use a chest strap for any activity more strenuous than walking (or possibly hiking, which for me is simply walking off paved surfaces). For Zwift, outdoor runs/rides, gym etc a chest strap is standard operating procedure, so the issue simply does not arise.

Is the watch HR accurate for walking? No, not always, especially in the first several minutes, but that's no big deal. When I'm out of Z1 then I want proper HR data. I only trust a chest strap to give me that, plus it gives me HRV too.

Today I did try a test with Zwift, albeit on the treadmill. I used my Fenix 6X to record my run and left my Epix on my wrist displaying the watch face.

After a bit of heel dragging for the first minute or so the Epix matched my chest strap within +/-2 BPM for the majority of the run, all the way up to 184 BPM max from the chest strap. This is all very encouraging.

However, during my warm down the watch lagged with my decreasing heart rate by around 10-11 BPM for much of the time. i.e. true HR of perhaps 133 BPM, watch showing 144 BPM.

As I just walked out my final few steps with my arm raised (not swinging) to observe the HR on the watch face it plummeted to as low as 90 BPM while my chest strap was still showing figures in the 130s. So that was a complete (if not terribly important) failure. Sorry about the woeful photography, but here's an example when I stopped to take the photo and the watch shows 93 BPM while my true HR is 143 BPM. i.e. the watch is not measuring correctly at all.

On syncing and reviewing the data it seems that Move IQ identified the treadmill effort, which resulted in the good tracking of heart rate. Once my movements did not correspond with "running" (no arm swing) it looks like it lost the plot. I would imagine that inddor cycling makes it rather difficult to identify that there is a recognisable activity taking place, due to limited movement of the wrist and no road shock etc..

EDIT :  The sharp eyed amongst you might note that the Zwift screen is for a ride, not a run. This is because I prefer running to cycling as an activity, but riding on Zwift is way more enjoyable than running. So I use Stryd as my power meter - "Ride with Stryd".