Heart Rate inaccuracy-Runner cardio — TomTom Community

Heart Rate inaccuracy-Runner cardio

GordiniGordini Posts: 6 [Apprentice Traveler]
edited January 2019 in Runner & Multi-Sport
Is it possible that my H.R. can go from 80 bpm to 148bpm within the first 680 mts of a brisk walk.
I am 68 years old and do an average of 80 kms. per month and have not seen this occur before.
After about a further 500mts. my H.r. settles down to between 125 - 135 depending on the effort I am exerting.

Any thoughts would be appreciated.


Ron heiden


  • tfarabaughtfarabaugh Posts: 15,907 Superusers
    This is very common with wrist based HR sensors. Spikes in HR are generally from poor blood flow producing weak pulse strength, so the watch reads cadence instead. This is most common in running and is particularly apparent early in a workout or during a non-intense workout when you are not warmed up. You have to think of the optical heart rate as an algorithm that is attempting to track a signal in a set frequency range (30-230 or whatever it uses). If the pulse signal is weak it latches onto the next strongest rhythmic signal, which is your cadence in running and the vibrations of the bike in cycling. For most people who experience this while running it spikes to around 180-200 bpm which is also the average cadence people run at. Additionally, each person has a different HR signal ‘strength’, depending on a range of factors, so some are prone to get it more than others. But usually their signal strength is lower for the first 5-10 minutes until they warm up properly. So in that time, it is prone to latching onto cadence, which is a common fault with all optical HRs, unfortunately. If you notice it while it happening you can try moving the watch a bit or briefly pausing your run so it loses the cadence reading and latches back onto HR, which I find usually corrects it. I generally pause the watch, stand still for 20-30 seconds and will see it immediately start to drop. Once it gets into a more reasonable range and the pulse reading stops dithering (dithering is when it is not getting a good signal and it is a lighter grey in color) I start up again and it stays true for the rest of the run. You can also try switching wrists and the position on the wrist. I find I got better readings on my right wrist over my left and some people find they get better readings if the watch is on the inside of the wrist rather than the outside. It also helps if you warm up a bit to get your blood moving and your HR up so it is producing a strong signal. Play around with it and see if any of this helps you. The challenge for the manufacturers of optical HRs (and this is a common issue with all brands, my Scosche also does it) is to figure out how to factor out the other "noise" that is overriding the pulse signal without also factoring out other important data.

    When worn properly the watch should be very accurate for most people (some physiologies will be less accurate - skin tone, arm hair, tattoos, etc. all play a factor). The watch also needs to be worn rather tight (but not to the point of uncomfortable) and needs to be worn much higher up the wrist than a regular watch (about 1" above the wrist bone). Any light seeping under the band will cause interference. You also need to let it settle down before using. When you first go to an activity screen you will notice the HR pop up, but it will be light gray. Once it has established a strong signal it will get bolder, which is an indication it is ready to go.

    I hope this helped answer your question. If so, please mark it as a solution so others can look for it if they have the same question.
  • GordiniGordini Posts: 6 [Apprentice Traveler]
    Thanks a lot, that really helps and I will try out your suggestions.
  • tfarabaughtfarabaugh Posts: 15,907 Superusers
    Glad I could help. When you get a chance please mark my response as a solution so others with the same question can look for it.
  • GordiniGordini Posts: 6 [Apprentice Traveler]
    Hi There.
    Please excuse my ignorance but not sure how to mark as a solution.
  • tfarabaughtfarabaugh Posts: 15,907 Superusers
    Gordini wrote:
    Hi There.
    Please excuse my ignorance but not sure how to mark as a solution.
    If you go to my response there should be a button fro Mark As Solution at the bottom, but it will not work from mobile. One of the moderators can take care of it.
  • Jarhead_SAJarhead_SA Posts: 5 [Master Traveler]
    I have a slightly different issue. When I use the Gym mode the readings are completely off e.g. it will show my Heart Rate to be 55 while in fact its is 140 (I check on the treadmill). However, when I change over to Run r=then the Heart Rate reads correctly.

    Surely, this is a issue with the way the watch is programmed.
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