Spark- Heart rate very low — TomTom Community

Spark- Heart rate very low

jesuscjesusc Posts: 4 [Apprentice Traveler]
Sometimes when the heart rate should be very high (170-180bpm), it falls to very low levels
(100-120bpm). I wear my watch firmly fit in my wirst. I don't understand such a high measurement error.

There is a bug in the last update?
Current version 1.3.27


Thanks.

Comments

  • tfarabaughtfarabaugh Posts: 15,918 Superusers
    jesusc wrote:
    Sometimes when the heart rate should be very high (170-180bpm), it falls to very low levels
    (100-120bpm). I wear my watch firmly fit in my wirst. I don't understand such a high measurement error.

    There is a bug in the last update?
    Current version 1.3.27


    Thanks.

    During what type of activity are you seeing this behavior? It is hit or miss with weightlifting and other gym activities, as are most optical HR units, due to forearm flexing and tension. When you life weights you are constantly tensing and flexing your forearms, which is squeezing the blood vessels the watch is reading, so it sees this as a reduced pulse. You may also see it during rowing and even cycling (when the rider is leaning forward putting all their weight on the wrists). There is not a lot to do about it other than be aware of it and try to stay loose, but that is not always possible. Hopefully TT can refine the algorithms a bit to better detect this and compensate for it a bit, but this is the case with every wrist based HR I have tried.

    On the other hand, prolonged spikes in HR like that are generally from poor blood flow producing weak pulse strength, so the watch reads cadence instead. This 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 getter 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. 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 quite tightly (almost 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 (that is why there is a special band for the cardio models with more rubber under it to shield the sensors from light). 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. Also make sure both LEDs are lit at the underside of the watch when it turns on, if one is out it is a defect and will impact accuracy.

    I hope this helps, please let me know if this answered your question. If it did, please mark it as a solution so others can look for it if they have the same question.
  • jesuscjesusc Posts: 4 [Apprentice Traveler]
    Thanks for your answer so extensive.

    The activity is mountain biking. It happens on steep climbs. I have to leave a lot of weight on my arms.
  • tfarabaughtfarabaugh Posts: 15,918 Superusers
    jesusc wrote:
    Thanks for your answer so extensive.

    The activity is mountain biking. It happens on steep climbs. I have to leave a lot of weight on my arms.

    That is likely at least partially the cause. The weight bearing is tensing the forearms and squeezing the muscles and blood vessels that the watch is reading, which is interpreted as a lower pulse (as there is less blood flowing through those veins). There is not much that can be done about it, it is a function of the technology. All my optical HRs (even from other brands) perform the same way.
  • FerryammerlaanFerryammerlaan Posts: 1 [Apprentice Traveler]
    So if I get it right: I bought myself a sportswatch to keep track of my heartrate, with a modus for cycling; but beacause I have to hold on to my steering wheel and thus put tension on my wrist, the watch doesn't work ....

    Were can I leave a complaint?
    regards Ferry
  • SimiaSimia Posts: 20 [Outstanding Wayfarer]
    I'd guess you should just return your watch as failing to provide what was promised/advertised. Alternatively you could try with customer support.
  • ep013ep013 Posts: 15 [Outstanding Explorer]
    I think it hasn't been mentioned yet that cold weather and sweat can also interfere with the normal functioning of the HRM.
  • anguus24anguus24 Posts: 32 [Outstanding Wayfarer]
    ep013 wrote:
    I think it hasn't been mentioned yet that cold weather and sweat can also interfere with the normal functioning of the HRM.
    In cold weather its merely imposible being accurate the HRM.
  • Mike WMike W Posts: 1 [Apprentice Traveler]
    tfarabaugh wrote:
    Also make sure both LEDs are lit at the underside of the watch when it turns on, if one is out it is a defect and will impact accuracy.
    I also have big problems with the Spark 3 reading hiking cadence instead of heart rate. On the underside there are 3 very small green LED emitters in line. Is that right, or should there be more?
    Mike
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