Pixel watch didn't capture my heart rythm while I was swimming

[Steveblock]

None of my apps, swim.com, Fitbit, or cardiogram tracked my heartbeat while I was swimming. Is this a known issue and is there a way around it? Was on a pixel watch. Was told to ask here over at the pixel watch forum.

Moderator edit: Subject for clarity.

[t.parker]

I believe it works same as for all Fitbit watches - HR isn't tracked during swimming.

[alexthecat]

@Steveblock The optical sensor does not record data when the device is in swim mode because refractions from the water can impact the heart rate reading. This is true for Fitbit devices, as well as the Pixel Watch. 

[Steveblock]

Ah that's frustrating as that's what I got it for. Is there a way of strapping it to my arm such that that does not happen or bypassing it so it does capture?

[t.parker]

@Steveblock you probably need to ask on Pixel Watch community forum but assuming that Fitbit is main activity tracking engine on Pixel Watch there is nothing you can do (swimming doesn't capture HR, there is no HR metric for swimming in the Fitbit app). You may try to use thirdparty apps for WearOS like GoSporty! which can use external HR sensor like chest strap but I don't know whether it would work on Pixel Watch. It does work on Galaxy Watch (but Galaxy Watch captures HR when swimming anyway).

If you got Pixel Watch for swimming then know it's more limited in that matter than Fitbit devices (for example it doesn't recognize strokes). Also, on the screen you can only see timer when swimming.

Answering your question, it isn't a flaw. It's done by design. That sounds like Pixel Watch is a poor choice for swimmer.

[RodrigoMFitbit]

@t.parker Thanks for your input and recommendations.

@alexthecat Thanks for the explanation. That is exactly why. 

@Steveblock Welcome to the forums. thanks for taking the time to share your current situation with the Google Pixel Watch.

I want to confirm that this is now a flaw. As Alexthecat explained, since the PurePulse technology uses light to capture the hear rate, light travels slower in water than in air. Therefore an underwater reading will be completely different. That is the reason there is no heart rate stat for this particular training. I concur that it is not the best choice for a swimmer. If that is the main reason you got the Pixel watch for, I would consider another device to record your swim session.

[t.parker]

@RodrigoMFitbit how another Fitbit device is going to solve the problem of not reading HR?

[Steveblock]

Yeah I guess to me the answer doesn't make sense and isn't well publicised. The watch is tight to my wrist so the amount of water between my skin and the sensor is minimal to none. So how do I tell my watch to capture my heartbeat? If I can't do that it's a flaw regardless of whether by design or not. Still, life goes on. Thank you to everyone who replied. I am not in the fortunate position of being able to buy another device, the watch was a birthday present that sadly turns out not to be fit for purpose.

[matteo2191]

Hi Rodrigo, Thanks for the explanation. Now it is clear to me why the heart rate monitoring function is deactivated.

However, I would like to add a few considerations: first of all, when I swim, the adherence of the watch prevents a lot of water from entering between the wrist and the watch itself. This should be enough to get an accurate reading. If this is not the case then tracking any other sport with arm sweat should also not work properly.

Apart from this consideration, why then does Fitbit not allow the use of external sensors for monitoring the heart rate? I can't explain this.

Thanks

[TaoDoggy]

The Fitbit "Swim" workout won't track HR.  I use the "Aerobics" workout when swimming and my Pixel watch tracks my HR perfectly.  Remember to tighten the strap before swimming because it has to be tight against the skin or it won't be accurate.  Light travels differently in the water, so tighten it so that water isn't able to flow through.  It doesn't have to be so tight that it's uncomfortable, just make sure that it's snug enough not to slide around while swimming.

[RodrigoMFitbit]

Hello everyone!

@TaoDoggy Thank you very much for your own experience and advice. I guess that would work. However, Fitbit cannot guarantee proper heart rate reading while swimming. That is the reason it was not implemented. Thanks again. 

[TaoDoggy]

That is correct.  However, HR monitoring accuracy is device dependent, not app dependent.  So if your Pixel watch can accurately calculate your HR, it will provide the correct information to the app, whether the app is developed by Fitbit or another company.  My (recently purchased) Pixel watch is build number RWDA.230114.013 running Wear OS 3.5. Good luck!  I hope you can get this working with your device, even if the "Swim" app won't access the information, so you can use a different app. 

[RodrigoMFitbit]

@TaoDoggy Makes sense. If heart rate measurement during the swim session is the most important thing of the training, I guess this would be a way to get that information, sacrificing the other stats of course. Thank again for sharing and taking the time to explain. Hope you are having a great day!

[t.parker]

@RodrigoMFitbit Pixel Watch users can get Swim.com app for WearOS that does a lot more than Fitbit's swim tracking. Fitbit users unfortunately are out of luck and stuck with half-baked feature. Although there isn't much to sacrifice when implemented swim tracking is pretty much useless for swimmer (no relevant metrics, no real-time in-watch data) so as well users might get HR instead of nothing.

@TaoDoggy if you compare HR captured during swimming from wrist with chest strap you'll see that it's far from perfect. Garmin tried to improve wrist tracking in the water and the cost of that is power consumption higher than when using GPS (LEDs become brighter in the water and more power hungry algorthm is involved to remove errors). Still, despite it follows correct trends it's far from data from chest strap. I tried Sense and Sense 2 (using different types of activities) and results were just horrible. If HR is important to somebody durint swimming then there is only one solution - watch that supports chest strap sensor and that sensor usually must be of the same brand as watch due to caching algorithms (BT/ANT+ disconnect in the water). This bit annoys me most (why companies can't introduce some standard protocol?) as I had to get strap just for swimming despite having all-purpose one.

@TaoDoggy I don't own Pixel Watch but had a chance today to use one and it only confirms my theory that HR won't really be "perfect" and not even close to accurate (I tracked it as generic workout):

Pixel Watch tracked my HR way lower than the HR monitor and, as you can see, it does not correspond with intervals of my workout. Even if you wear (any) watch tight it will still let water under the sensor due to the pressure (imagine that any swim watch can break under the water pressure so snug/tight fit is not an obstacle for moving water). Pixel Watch has some holes in the data when the sensor couldn't read HR at all. I can get a comparison for my Garmin watch using its optical sensor (I can use two sensors and afterwards I can override wrist OHR with HRM data) and that will be better but not good enough. The best optical sensor I've seen that works in the water is Polar Verity Sense but it's more powerful (high sampling frequency, very bright 6 LED lights) and must be worn on goggles (ideally, goggles under a swimming cap and covering the sensor). This gives quite decent results (but there are caveats).

[RodrigoMFitbit]

@t.parker Thank you very much for your input and explanation. I really appreciate you taking the time to show the results of your training. That should be the reason then, that  heart rate measurement is not available for swimming sessions. This will surely help other users with the same doubts. Thanks again!

[t.parker]

@RodrigoMFitbit that isn't exactly true. Most of the watches indeed don't bother with tracking HR as it requires some updates of algorithms and, in some cases - hardware. However, giving the option to turn on HR while swimming wouldn't hurt anyone considering showing a disclaimer informing about lower accuracy. Said that today I forgot my chest strap and had to rely on my wrist HR. As much as I don't think it's 100% accurate when it comes to swimming I take that into account and look more at trends of HR rather than absolute values. If you look at my today's workout breakdown using the wrist HR of a dedicated watch (some dedicated improvements for HR reading in the water):

You can see that trends are matching pretty well. Each interval can be seen. I'm quite sure that the 400m intervals would be a lot smoother at the top if I used a chest strap but this output is acceptable for me as a swimmer. There is still a cost I mentioned before - it ate 10% of my battery within a 1-hour workout. This is more than GPS eats (GPS on that watch is 3%-4% per hour). So as an "emergency," I do use optical HR, just not on Fitbit because I'm not being given a choice. This happens maybe once every few months as usually I keep my swimming chest strap in my swim bag 🙂 What I'm trying to say is nice to have a fallback (and choice even if it means shooting your own foot).

Another thing is how the AZM is calculated when HR is turned off. Zone minutes require heart rate yet swimming grants them based on... what?

[RodrigoMFitbit]

@t.parker Hello there. Thank you very much for taking the time to share this with us. This is great information and you make a very good point. It is indeed possible to take a look at the trends and not focus on the value of the measurement. I am glad it works for you as an alternative in case of "emergency". It does mean sacrificing accuracy, but you can still get the heart rate trends troughout the swimming session. I find that very helpful, thanks again. 

Regarding the Active Zone Minute, I honestly do not know how the algorithm to calculate them works. It is true that AZM are based on the heart rate zones. I do not swim, so I had not noticed that AZM are credited for a swimming session. I will have to try it out and check out my results to make my own assumptions. However, I will indeed ask internally and let you know once I get more information. Thank you again for taking the time to share this with us.