heart rate tracking during intervals

[RickyBee]

I have a Versa 2 and am frustrated by inaccuracy during interval training. I have tried all the suggestions I have found like rebooting the device and wearing it at different positions on my arm but the problem persists so I am looking for other ideas.

I run intervals on a treadmill, alternating between running and walking. The length of the intervals is NOT always the same. I use the Treadmill program on my Versa 2, not an interval timer since I adjust intervals manually on the fly using the treadmill controls.

I start walking for about 1:30, then go into a run interval for about 3:30 duration where heart rate rises fast and levels off at maybe 125-130. I then repeat this sequence.

For the first 15-20 minutes of my workout, heart rate is wildly inaccurate, typically 20-30 beats higher than actual (as measured with a Polar HR10 chest strap, which is very accurate). Actual might be 125-130 but the Versa will display 150! Eventually it settles down and from maybe 20 minutes in to the end of my workout, heart rate becomes much more accurate, typically within 5 beats of the Polar.

This behavior reminds of of a poorly tuned PID controller that is self-tuning and finding better tune parameters. It's like the Versa is not only monitoring, but also extrapolating to try to predict where my heart rate is going. It overshoots! Eventually it tunes successfully and does give correct heart rate data. But the first 20 minutes is just crazy and worthless. It doesn't remember the better tuning and starts from scratch every time. 

I wonder if there is a better program on the Versa 2 for this type of training that won't overshoot in measuring heart rate.

Other ideas? Have others had this exact problem?

[MrMarv]

@RickyBee -

I agree that the Treadmill exercise app has HR issues, though my observations always seem to show a major under-reporting of HR with an occasional over-reporting.

What does anyone think the odds are of my heart rate actually dropping from 109 bpm to 56 bpm in 28 seconds? BTW 104 bpm 90 seconds later.

And I am a 68-year old male with a viral attacked heart from 2017 that only pumps out 25% of the blood from my heart each beat instead of the normal 75%. 

And what is not shown are two instances where my heart rate display went blank and the iOS app heart rate panel showed resting heart rate.

While irritating, especially since I reported this flaw over six months ago and the same flaw in the Charge 3 over a year ago, this is not a show-stopper for me. Even the Apple Watch Series 5, routinely rated as having the most accurate heart rate recognition, has documented issues with the heart rate algorithms when in "exercise mode".

Like I said, just irritating.