Heart rate spiking to high levels / not reading consistently

ultramega Registered Users Posts: 2
Apprentice Traveler
edited January 24 in TomTom Sports
I've been using my Spark, primarily for running, for a couple years. I purchased it expressly because the heart accuracy was considered above average for a wrist device. I've been satisfied until recently.

Two weeks ago I ran a marathon and I noted unusually high heart rate readings (above 200) well into the run (past mile 13). The same issue happened again today on a shorter recovery run. In the screenshot, note my heart rate spiking, and then eventually not reading at all, while my pace remains consistent.

I haven't changed anything about how I wear the device, which wrist it is on, etc. Nor does this issue happen every time I use the device. Thus, I'm wondering if there is an issue with the sensor or the device itself.

Has anyone else seen this issue? Is there a fix?



  • tfarabaugh
    tfarabaugh Posts: 16,948
    You generally get spikes in HR due to the watch either losing the pulse signal and locking onto another signal, like cadence, or the cadence simply overpowering the pulse signal. 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 or when you are doing sprints with very high effort. 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, not just TomTom unfortunately. Optical HR also can tend to lag in measurements, so if you are doing intervals it can take a but to catch up so it shows high HR during the rest periods. 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.

    In your case it is odd that it lasted so long and then stopped altogether. You may want to call Customer Support to ask them about it, but I would try a factory reset first in case it is just an issue in your firmware install. To do a factory reset, make sure the Connect software is running and dock the device to your computer. The Connect window will open; press the gear at the top right and select factory reset from the next screen. Follow the steps provided and when prompted to register or sign in to MySports, select sign in and use your existing account credentials. It is fairly straightforward and should take less than 5 minutes.

    To get the number for Customer Support, choose Contact Us at the bottom of this page, select the service required and the product name and click Contact Customer Care and then Phone Us. It will give you the phone number for the country your account is registered under (this can be changed by clicking the flag icon in the bottom right corner of the screen).

    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.
  • pugwash94
    pugwash94 Registered Users Posts: 3
    Neophyte Traveler
    I have found this on occasions too but put it down to sweat. I have cured it each time by either moving the watch or tightening it. Works every time.
  • ultramega
    ultramega Registered Users Posts: 2
    Apprentice Traveler
    I did a factory reset shortly after @tfarabaugh posted the suggestion above. The issues I was seeing haven't returned over the last several months, so I'd say this is definitely the first thing to try. Thanks!