Polar H7 vs H10 erratic readings

mikeymo
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Polar H7 vs H10 erratic readings

Postby mikeymo » 27 Apr 2020, 6:40pm

Today my heart rate went from 215 to 0, according the the Polar H7, connected to a M400. I'm pretty sure they aren't true readings! At least, I don't remember being dead at any point on the ride.

I'm pretty sure I know the reason, I was going downhill, at a decent speed, and my shirt is a bit flappy, and synthetic. So I'm guessing it's a static thing.

I suppose it's no big deal, once I was on level ground it settled down. Still, it would be nice if it didn't do that. I'd wetted the electrodes before I went out. And the strap was as tight as I want it to be.

Any tips? I quite like the shirts I wear and though it's a cycling shirt it's not super tight, which I like. Has anybody moved from an H7 to an H10, or maybe the new H9, and found them better?

Thanks.
Last edited by mikeymo on 16 May 2020, 5:40pm, edited 2 times in total.

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Paulatic
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Re: Polar H7 erratic readings

Postby Paulatic » 27 Apr 2020, 6:46pm

Sounds like the opposite to my Wahoo. I can max out at 120 bpm up a hill and then if it’s cold on the descent I can reach 180 bpm. All comes good when I reach the warmer flat bits.
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RickH
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Re: Polar H7 erratic readings

Postby RickH » 28 Apr 2020, 12:40am

The two main things that can easily affect this type of monitor that is using electrical signals are

1) The strap is not tight enough & the contacts lose their connection to the skin if the strap is being buffeted around by bumps or wind.

&/Or 2) The contacts get too dry if you aren't exerting yourself for a while, particularly in cooler conditions & the electrical contact becomes erratic.

rjb
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Re: Polar H7 erratic readings

Postby rjb » 28 Apr 2020, 8:32am

One of our club members started a discussion about erratic heart rate monitor readings in the pre lockdown cafe. Someone suggested he spoke to his GP. On his next visit the GP got him into hospital and he had a pacemaker fitted within the week.
Stay safe.
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mikeymo
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Re: Polar H7 erratic readings

Postby mikeymo » 28 Apr 2020, 9:26am

rjb wrote:One of our club members started a discussion about erratic heart rate monitor readings in the pre lockdown cafe. Someone suggested he spoke to his GP. On his next visit the GP got him into hospital and he had a pacemaker fitted within the week.
Stay safe.


Thanks for your concern.

I'm pretty sure that the actual heart is OK, but that this is related to the device itself. Partly because I check my blood pressure frequently, and the BP monitor also detects aFib. But mainly because when I was up for a drugs trial a while ago I was given a very comprehensive examination, including a 12 lead ECG and auscultation, full blood count etc. etc. The consultant, 20 years younger than me, declared that "I wish I had your blood pressure", and confirmed that my heart was behaving exactly as it should, no echoes or unusual sounds. Obviously that wasn't an exercise stress test though.

The unusual readings, which I've had before, are usually on the same stretch, which is downhill, and fairly early on in the ride. So I suspect it's flappy shirt syndrome. Yesterday they varied between 215 and 0, within seconds. And I wasn't trying that hard, often coasting on that section. Whereas on slower uphills the heart rate was very steady. I'm assuming (hoping?) that if it was anything to worry about, medically, the problem would exhibit itself under stress.

But it would be good to know it's accurate. Partly because I'd like to establish my true maximum heart rate, using the cycle-up-a-tough-hill-4-times method.

https://www.cyclingweekly.com/fitness/training/training-zones-what-are-they-and-why-do-they-matter-180110

I once measured 182 (not as part of a test, just an ordinary ride), up what felt like a very hard hill, which seems very high for somebody of 62, but the 220-age calculation is, apparently, only the vaguest of guides.

Mainly I was wondering if the H10 was better. Reading round though it seems the H10 is more accurate, but not because of the actual H10, but because of the strap that comes with it, which has more electrodes and somehow is more immune to interference. And the strap can be bought separately and will work with the H7 I've got, apparently. So maybe that's the way forward if I'm bothered.

backnotes
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Re: Polar H7 erratic readings

Postby backnotes » 28 Apr 2020, 12:14pm

I had a many, many generations ago Polar HRM that sometimes had a funny turn when you rode under power lines (and also near to the radar station at RAF Portreath....). Does it happen on any route after a while or in exactly the same place on one particular route? If the latter, have you considered and discarded the idea of some kind of external interference at that point?

You could test the flappy shirt / static hypothesis by wearing a less flappy (or maybe cotton) shirt and seeing if that makes a difference?

Or as above it may just be that you have a long downhill early in the ride, and the contact gets worse until you have started to work again.

mikeymo
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Re: Polar H7 erratic readings

Postby mikeymo » 28 Apr 2020, 12:49pm

backnotes wrote:I had a many, many generations ago Polar HRM that sometimes had a funny turn when you rode under power lines (and also near to the radar station at RAF Portreath....). Does it happen on any route after a while or in exactly the same place on one particular route? If the latter, have you considered and discarded the idea of some kind of external interference at that point?

You could test the flappy shirt / static hypothesis by wearing a less flappy (or maybe cotton) shirt and seeing if that makes a difference?

Or as above it may just be that you have a long downhill early in the ride, and the contact gets worse until you have started to work again.


Yes, I suppose I should use my other shirt, which isn't at all flappy. In fact it's a bit too tight, it must have shrunk in the wash. :wink: Actually, quite a lot of my clothes have shrunk in the wash, even 10 year old jackets that have never been in the wash. I can't imagine how that's happened.

It's no big deal. I'm reasonably confident that it's accurate when it matters, sweating up hills. But it would be nice if the graph on the Polar Flow site looked a bit less like the outline of the Himalayas. I bought it used, so the strap has got a bit of give in it. Also presumably the previous owner's, er, "residue". Eww! Maybe I will just buy a new strap.

I think the Polar chest straps are reckoned to be pretty accurate, I think somebody did a test against a proper ECG machine and they were way more accurate than any wrist HRM, to within 1% or something. And after all I only want to make sure I'm in the various exercise bands.

backnotes
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Re: Polar H7 erratic readings

Postby backnotes » 28 Apr 2020, 1:02pm

That's a co-incidence - I find a lot of my clothes have shrunk over time all by themselves too - maybe we use the same detergent?

I found this paper https://bjcardio.co.uk/2017/10/heart-ra ... nd-or-foe/ which sort of sits on the fence, saying that while some heart rhythm issues can be picked up for the first time when people use HRMs, the data they gather isn't always reliable and you can also end up with a lot of "worried well" people thinking they have problems when they don't.

But as above, better to get checked out rather than not if worried, but sounds like you already had the full works and they found nothing to worry about.

mikeymo
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Re: Polar H7 erratic readings

Postby mikeymo » 28 Apr 2020, 1:13pm

backnotes wrote:That's a co-incidence - I find a lot of my clothes have shrunk over time all by themselves too - maybe we use the same detergent?

I found this paper https://bjcardio.co.uk/2017/10/heart-ra ... nd-or-foe/ which sort of sits on the fence, saying that while some heart rhythm issues can be picked up for the first time when people use HRMs, the data they gather isn't always reliable and you can also end up with a lot of "worried well" people thinking they have problems when they don't.

But as above, better to get checked out rather than not if worried, but sounds like you already had the full works and they found nothing to worry about.


Yes, I'm as sure as I can be that my heart is OK. Oh, I had a several chest x-rays too, lungs clear, heart normal size. Also BMI is normal. I don't smoke, drink or take recreational drugs. If it wasn't for the swingers' parties I'd have no fun at all. Also the condition I had, hyperthyroidism, involved other tests too.

Yes, I'm sure that cheap and cheerful HRMs like the one I've got aren't a replacement for an exam by a cardiologist, but I'm pretty sure that if I went to the GP they wouldn't refer me. Well, I did, and they didn't.

Just watch, I'll drop down dead with a heart attack tomorrow. And serve me right for being smug.

mikeymo
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Re: Polar H7 erratic readings

Postby mikeymo » 28 Apr 2020, 5:17pm

backnotes wrote:That's a co-incidence - I find a lot of my clothes have shrunk over time all by themselves too - maybe we use the same detergent?

I found this paper https://bjcardio.co.uk/2017/10/heart-ra ... nd-or-foe/ which sort of sits on the fence, saying that while some heart rhythm issues can be picked up for the first time when people use HRMs, the data they gather isn't always reliable and you can also end up with a lot of "worried well" people thinking they have problems when they don't.

But as above, better to get checked out rather than not if worried, but sounds like you already had the full works and they found nothing to worry about.


Thanks very much for providing a link to that article, which I've now had time to read. It's interesting. The conclusion is, as you say, that for heart problems, the sort of HRM that fitness/sports people use have some, but not complete, value, in a medical sense. The article is slightly out of date, AliveCor have now released a 6 lead version of their ECG, and as it's been cleared for medical use, we will have to assume it works well enough for doctors to give it a thumbs up, with whatever caveats they apply:

https://www.alivecor.com/kardiamobile6l

The phrase "worried well" is, I think, unnecessarily loaded. I remember talking to a doctor, in a social setting, who said he loathed the phrase, as it had the effect of making people who took their health seriously think they were being silly or wasting doctors' time. As he said, he would rather have a whole stream of "worried well" attending his clinic, finding out they were OK, and going home after having cost the NHS hardly anything. Instead of the "fat b******s" he usually dealt with. Yes, I too thought that was rather unprofessional language to use about his patients, but he was a diabetes specialist. And I think, like many people, he thought that the fact that a full 10%, about £11 billion, of the NHS budget is spent on one single disease, type 2 Diabetes, that is almost entirely caused by lifestyle and diet choices, is, frankly, a disgrace. It's not as though we haven't been told what obesity does. Would that more people were "worried well", than smashing their heart and arteries with tobacco, fat, salt and alcohol.

"Whether clinicians like it or not, wearable monitors that provide HR and activity data will become increasingly common. " These days clinicians actually give patients portable ECG machines sometimes, don't they? I imagine that as "consumer" devices become more sophisticated they will gradually become accepted by the profession, as the AliveCor devices already have been. It's astonishing really that £150 now buys you an ECG that doctors will believe. I think that it is possible to get more detailed info out of Polar stuff, but as the article says, manufacturers need to open up about how their devices work. Presumably that is what is partly stopping them gaining medical accreditation. And perhaps AliveCor has opened up its devices to inspection.

I think some of the heart conditions, like atrial fibrillation, are sporadic. So perhaps undetectable on the once a year one visits a doctor, but if reliably detectable by a wearable device, would be found and therefore worthy of further investigation. My BP monitor is capable of detecting it, but hasn't yet. Mind you, once it confirmed that my BP is smack in the middle of ideal, the novelty wore off, so I've not used it that much recently.

Fig. 3 in the article, "Doris" (I love the way she's labelled the cafe and pub stops) has a similar spikey appearance to mine, though mine is over a far shorter time, and the y axis on mine went all the way from 0 to 215, whereas hers is only from 60 to 200. Also, I want to know why the sudden jump in heart rate when she got home from the pub, eh?

mikeymo
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Re: Polar H7 erratic readings

Postby mikeymo » 2 May 2020, 8:56pm

Did the same ride today in a 100% cotton T-shirt. There was plenty of speed and wind on the down hill section, and the shirt was loose enough to flap as much as the synthetic cycling shirt. No spikes or drop outs on the heart rate. So it looks like static from artificial fibres might be the reason.

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cycleruk
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Re: Polar H7 erratic readings

Postby cycleruk » 3 May 2020, 2:39pm

When my HR monitor (Garmin) has not indicated it has just been a bad contact with my skin. My old monitor's instructions said to wet it before use. A bit of saliva usually gets things going again.
You'll never know if you don't try it.

mikeymo
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Re: Polar H7 erratic readings

Postby mikeymo » 3 May 2020, 3:27pm

This consistently reproducible spike/dropout thing has been relatively recent. I didn't pay that much attention to the condition of the strap when I first got it (I bought it used), but I think the strap has gradually deteriorated. The elastic bit at one end has gone non-elastic and sort of corrugated. That end is very near one of the electrodes. So if there's wind, movement or whatever, if that part of the strap is losing grip slightly, that may well account for this, and the fact that it's got worse. I bought some actual medical grade gel, designed for electrodes. Which had no discernible effect, compared to water. But does leave a not so pleasant residue.

Anyway, I've ordered a Polar H10. Once it arrives I'll do some testing. I thought about just getting the Polar Pro strap that comes with the H10, as it's the actual strap that makes the difference, allegedly. But then the H10 has a few other advantages, and it might be hard to get the H10 unit without the strap, if I wanted to later. Plus buying the whole thing means I've got two complete units, strap and monitor, for other family members.

I'll report on the H10/strap when it arrives.

mikeymo
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Re: Polar H7 vs H10 erratic readings

Postby mikeymo » 16 May 2020, 5:43pm

So however hard I try, I can't get the H10 to give me the same spikes and troughs that the H7 did. I went out today, took it very gently till I got to my downhill, then fast, in the drops, with the top of my (synthetic) shirt open to increase flappage. Heart rate in Polar Flow smooth as anything.

Conclusion. The H10 is better than the H7. Probably down to the strap.