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Wrist heart rate very inaccurate in cold weather

Former Member
Former Member over 6 years ago
Hi all,

First cold weather since having my Garmin 935 and my heart rate measured via the wrist sensor is very far off, it registers very high heart rates. Instead of an average around 140 I'm facing 160 bpm and more.

I remember when the wrist hr sensor concept was introduced the inaccuracy was one of the cons of this kind of HR measuring when operating in cold weather.
I was one of the early adaptors of this kind of technology when having the Adidas Smart Run based on Mio technology in 2014.
However I'm a little bit disappointed the technology integrated in the 935 anno 2018 is far worse.

As I use the 935 for steering my training programma based on my measured HR and the watch predictions on how and when to run I'm a little bit lost and very disappointed to say it friendly.
I don't think there is a hardware fault or scratches on the sensor...

Anyone else experiencing this malfunctioning of the watch when running in cold weather?

I also noticed that the speed of variation (heart rate increase/drop when changing running intensity) is far less accurate than when measuring with the classic heart rate strap.

I wondering if the latest Polar Vantage having 4 leds instead of 3 on the Garmin makes better measurements.

The wrist heart rate is a very nice feature (user friendly to wear) if it works fine, but I doubt this strongly.

Best regards,
Frank
  • 0 over 6 years ago
    Hi Frank,

    I experienced similar issues with OHR.
    See attached pictures and blue-marked areas with abnormal measurement of HR.
    The first picture illustrate HR during repeatable uphills - the same uphill factor, the same pace, but HR...
    The second picture shows HR during my marathon race. See some places of HR graph where my HR seems to be quite inaccurate.
    It was the reason that I started using chest strap HR.
    Now, my FR935 is sent to RMA, because of battery drain during activity with chest HRM (about 20% battery / hour).


    ciq.forums.garmin.com/.../1419053.jpg
  • Former Member
    0 Former Member over 6 years ago
    No issue on my side, same HR and never experienced any true issue in any conditions.

    I would rather say it depends on your skin.
  • Former Member
    0 Former Member over 6 years ago
    Hi,

    That seems indeed very abnormal as heart rate change is not in relation to your effort when running uphill.

    In my case (average) heart rate is overall too high compared to the same run (distance intensity) when temperatures were higher.

    Yesterday it was only around 7 degrees C. Before this run temperatures were still between 14 and 20. I have the watch since beginning of October.

    With the HR strap I don't see anomalies nor in the power consumption, at least I didn't notice it yet.
    I will follow up and report back.

    I hope your problem can be fixed soon!
    Br,
    Frank
  • Former Member
    0 Former Member over 6 years ago
    I would rather say it depends on your skin.


    Humm could be, I know that the color of the skin and some other characteristics can influence, but as far as I know my skin is still the same as 4 years ago when wearing the Adidas wrist heart rate sport watches (Fit Smart and Smart Run).
    At that time I ran with 2 watches monitoring hr measuring based one on the wrist sensor and the other one on the strap, the heart rate averages were usually the same, but the heart rate variation slope when effort changes (speeding up or slowing down fast) is less good than when measured with a classical HR strap.
    Also it is advisable to do some warming-up before starting to measure when using the wrist sensor.

    Thanks for the feedback...
    Maybe it was a one in a time spiky run. I will follow up nevertheless currently it ruines my watch based advice for recovery and other stuff.

    br,
    Frank
  • 0 over 6 years ago
    https://fellrnr.com/wiki/Optical_Heart_Rate_Monitoring

    Simply put, surface blood flow can be restricted due to a cold climate. Also if you don't know this, ALL optical heart rate monitors read blood flow under the skin. Not actual beats, not your pulse, they are at best guessing a tertiary system which is why it gets tricky (some would say unreliable).
  • 0 over 6 years ago
    Yeah, this is something that happens to me as well as soon as winter arrives. It obviously depends on many other parameters such as body temperature and therefore varies from person to person.

    A couple of tricks that help for me (not always) are: first, warming up inside for 10-15 mins, and this helps your workout anyway, and second, switch wrists. If i wear the 935 on my right wrist, measurements tend to be better. Purely speculating but, I'm right handed and my right arm is therefore stronger and that may help the sensor pick up blood flow better.
  • 0 over 6 years ago
    When the optical sensor is getting a weak reading from the blood flow in your wrists, like when it's cold out, it's not uncommon for it to see your footfall as your pulse often referred to as cadence lock.

    The thing I found that is most helpful to me in preventing cadence lock when running in cold weather while using optical HRM is keeping my hands warm is more important than keeping your arms warm. It may seem counter intuitive but I've run in similar conditions with a long sleeve shirt and no gloves, and a short sleeve shirt with gloves and got much better results with the latter.
  • Former Member
    0 Former Member over 6 years ago
    Thanks for the feedback guys.
    So probably back to the old reliable stuff, the HR strap.

    Best regards,
    Frank
  • Former Member
    0 Former Member over 6 years ago
    I have a Fenix 5s+ but I have noticed very similar behavior as yours with OHR. I got the watch in July and the OHR worked flawlessly for the summer months. Probably in the last month or so, just as it has started to get colder, I will get random spikes in HR up to 160s-170s when my HR is actually in the 150s. There is nothing different about the placement of the watch during these runs, and since the OHR worked so well previously, I think it must be related to the cold weather.
  • Former Member
    0 Former Member over 6 years ago
    Hello Margcp626

    Thanks for confirming that you are experiencing "unfortunately" the same issue in cold weather.
    So it seems I have to rely on my strap in the winter time at least if temperatures are very low.

    Best regards,
    Frank