Instinct Solar, HRM Pro Plus and Intensity Minutes

My setup is as follows..

HRM-Pro Plus Strap
Garmin Instinct 2 Solar

I connect my HRM strap to the device Zwift App is running on. I wear my watch but do NOT record activity on it. The activity is only recorded on Zwift using metric from my trainer and HRM Pro Plus.

Usually, this results in my intensity minutes increasing but yesterday that did not happen despite the session having a training load of 238 (and I had an average Heart Rate of 144 for the session with a max heart rate of 170).

I just hopped on the trainer again. On Zwift I can see my Heart Rate being connected to the HRM Pro Plus and I when I check my watch I can see that it is connected to the HRM Pro Plus. However, I noticed that once I revert back to my normal watch face, the Heart Rate value was showing around 70.. even though on Zwift it is showing about 130. I tried with the watch off my wrist to see what happened. In this instance the Heart Rate value disappeared from the watch (Which I thought was odd as I thought it would display the Heart Rate from the HRM).

As a final test, I started an activity on my watch.. just a cardio activity.. The cardio session screen then started showing the correct heart rate.. matched to what I was seeing on Zwift.

I don't understand how Zwift can show a value of 139 from my strap but the watch shows 72 even though it says it's connected to the HRM strap?

I do notice when I go into the Garmin App on my phone, if I go to devices when wearing the HRM strap, it briefly says a synch failed before reverting to displaying 'connected' status on it.

Any tips or advice or anyone know what has changed to prevent the watch from accessing the correct heart rate value and using it to calculate the correct intensity minutes?

Top Replies

trux 6 months ago +1 suggested

mikem2208 said:
I don't understand how Zwift can show a value of 139 from my strap but the watch shows 72 even though it says it's connected to the HRM strap?

When not recording any activity with…

All Replies

0 trux 6 months ago

mikem2208 said:
I don't understand how Zwift can show a value of 139 from my strap but the watch shows 72 even though it says it's connected to the HRM strap?

When not recording any activity with the watch, it does not use the strap. It uses its internal optical sensor, and it does it in the low-power mode, with a slow sampling rate.

mikem2208 said:
Any tips or advice or anyone know what has changed to prevent the watch from accessing the correct heart rate value and using it to calculate the correct intensity minutes?

Record the activity with your watch. Only then it will use the HR data from the strap, and the Intensity Minutes will be calculated accordingly. Personally I would not bother about linking Zwift with Garmin Connect, and I would just record the activities with the watch, but if you prefer importing the data from Zwift, discard the activity on the watch at the end, instead of saving it.

0 mikem2208 6 months ago in reply to trux

trux said:
When not recording any activity with the watch, it does not use the strap. It uses its internal optical sensor, and it does it in the low-power mode, with a slow sampling rate.

Thanks for the clarification.... But something has changed in the last week as my setup hasn't altered but over the last two zwift sessions the heart rate on the watch is miles off the heart rate from the strap.. less than half and obviously inaccurate. So not sure why the watch is suddenly behaving like this when I'm on the turbo.

This never used to be the case up until this week. I noticed there was a firmware update the other week, wondering if that has anything to do with it. I'll give it another go over the weekend but maybe disconnect the watch from the HRM strap.. leaving the watch optical sensor to figure heart rate on it's own (for intensity, which is all I want the watch to do when on the turbo) and leaving the HRM strap connected to Zwift. See if that addresses the problem.

If I did use your suggested approach though of recording the activity but then discarding it, I assume that won't impact the intensity minutes that have been calculated as a result of recording the activity on the watch?

0 trux 6 months ago in reply to mikem2208

mikem2208 said:
I noticed there was a firmware update the other week, wondering if that has anything to do with it.

If you mean a firmware update on the watch, then it cannot have any impact on the HR recorded by Zwift, unless you feed Zwift by broadcasting the HR from the watch, and do not have Zwift connected directly to the strap.

If Zwift records incorrect HR, then the issue may be with the strap - for example dry electrodes, weak battery, or a damaged hardware.

mikem2208 said:
If I did use your suggested approach though of recording the activity but then discarding it, I assume that won't impact the intensity minutes that have been calculated as a result of recording the activity on the watch?

Intensity Minutes are processed in real-time by the watch, so it does not matter whether you keep or discard the activity.