Polar A360 vs Garmin HRM-RUN – HR Accuracy In A Controlled Environment

I updated the A360 today with the new firmware v1.128. Even though HR improvements are not listed as part of the firmware release, I hoped for the best. I hoped to shed some light on a few tests I’ve been doing over the last couple of weeks.

This test was on a turbo trainer. Cooled room with a fan to keep me cool. A controlled environment. Controlled position with me not moving about too much although I was alternating from hoods to aerobars

Session: warmup: 10 mins Z3, 10 mins Z4, 5 mins Z5, 10 mins Z4, 10 mins Z3. Zero rest, so it’s quite hard.

I hate this session.

Today wasn’t too bad though as I seem to have got fitter and the session was actually do-able for once. Although I was 10w off on the Z5 which helped.


Clickable. Blue Polar, Red HRM-RUN

You can see how the HR goes up gradually despite the step changes in power. You can see how the HR stays relatively high after the Z5 power effort even though the power has dropped down a fair bit.

There were two and a bit dropouts from the Polar at the start at low levels. I was faffing about here doing one legged drills. OK the Polar was on my wrist and not my ankle but I’m not too fussed about these dropouts. I’ve seen them on several other devices.

As the session started I glanced fairly frequently at the Polar. All looked AWESOME. A bot out here and there. No probs.

BUT as soon as the Z5 effort starts (35 minutes) you can see it all goes pear-shaped and never recovers.

I should point out that the HRM-RUN reported 4% error which is HIGH-NORMAL but even with that the track of the red line/HRM-RUN is still a fair reflection on reality.

The ONLY simple explanation I can think of for this is sweat and/or the cooling effect of evaporating sweat around the wrist area. I have poor peripheral circulation, Reynauds, and evaporating sweat would reduce bloodflow to my forearms and hands. Nothing else in the environment could have caused it – such as motion artefacts as, essentially, there wasn’t any motion. Changes in position could not account for it as they were the same on the increasing effort as well as the decreasing effort.

It’s not simply the level of the HR either. Compare this to an earlier SWIM where the device handled higher heart rates well. there are no dropouts here at all and the HR track does reflect the trend of reality during the exercise.


Swim HR Data

It could also be an algorithmic problem – I’ve no idea about that.

It’s probably my funny bloodflow then. That might make sense as that is what it is measuring changes in essentially!

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looks not very pleasant for Polar on such performance, surprised to see this from on of their devices as they hold normally HR accuracy quite high, did you had chance to take a look in Firstbeat how what was error percentage there for the FIT file recorded?