Problem Spark HR readings with HR Monitor Strap

highstream
highstream Registered Users Posts: 30
Master Traveler
edited January 24 in TomTom Sports
Been using the HR strap with my Spark HR/GPS for several months. I've found since early on that at some point during a 5.5 mile outdoors pole hike/jog I do from time to time, the HR showing on the watch is well off for several minutes or more, at least once. Most of the time it does this, and it occurs well after starting, the watch shows a very high HR, e.g., 215 bpm when it should be at 120-130 or so, or very low, 110s-120s when it should be in the 140s-150s. The odd thing is, though, that the uploaded readout never shows these absolutely very high readings. OTOH, it's common for the readout at some point to show a jump to, say, 140 bpm, when I was in the 110s and the watch never showed the jump - and there was no reason for it in the terrain or my effort.

Before each of these sessions, I wet the sensors with water and then add some saliva, which I found over the years with Polar HRMs makes for a better connection (it does with the Spark too). And after every use, I wash the whole band with dish soap and warm water. I got the strap because I was tired of false readings with the wrist sensor - that technology has a long way to go - so it's been disconcerting to see the same kind of thing happen with the strap. Anyone else run into this?

Comments

  • WimdeHek
    WimdeHek Registered Users Posts: 1
    Apprentice Traveler
    Hi, I have the exact the same problems. Extremely high HR and often lost connection. Also I have to replace batteries after 2 of 3 sessions which is an expensive thing. I really hope to get a solution for this.
  • tfarabaugh
    tfarabaugh Posts: 16,943
     Superuser
    The battery issues in the strap have nothing to do with the watch and actually indicate a fault with the strap which may be causing the other issues you mentioned. I would look at the strap and see if that is the problem, perhaps try a different strap and see if the problem persists.
  • highstream
    highstream Registered Users Posts: 30
    Master Traveler
    I hope the thread will remained focused on the discrepancy between reality and what's showing on the watch with the TomTom HR strap.

    Correction: On further look back through my activities, I need to correct what I said about the watch and readout on upload. I found two readouts from last fall that did in fact show the 190+ bpm reading, on one of them there were three spikes up, from 195 to 219 bpm; two lasted nearly three minutes and the other lasted seven. I'm a 70 year old male, so those are impossible short of heart disease, for which there's no evidence. I also found another upload where the HR jumped from 120 to 150 and then back for no good reason. So it's the ultra high or way too low readings that's the issue, not what's uploaded.
  • tfarabaugh
    tfarabaugh Posts: 16,943
     Superuser
    Spikes in HR 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 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.
  • highstream
    highstream Registered Users Posts: 30
    Master Traveler
    Thanks for the explanation! I'll play with your suggestion. I've found the leap up can occur at any point and usually is after I'm well warmed up. In fact, the highest I've seen is 219 on a easy downhill. My jogging cadence is typically in the 170s to low 180s (I now run with short steps like an ultra marathoner). The jump in HR does make more sense relative to cadence when I'm walking. I do have a very short myocardial bridge, maybe 30 mm, but systolic pressure is about the same on both ends, so I doubt that would account for it. Probably just natural variation in blood flow, as you suugest. Although I'm not sure how that would account for a long period of 20-30 bpm low readings. I've been doing this, training on and off with an HRM that is, for about 20 years, so have a good sense of what to expect and a good sense of feeling vs. HR.
  • tfarabaugh
    tfarabaugh Posts: 16,943
     Superuser
    I have seen the spikes when going downhill as well on occasion. I am not sure the cause but I attribute it to more arms movement throwing off the sensor and causing it to grab cadence instead, but that is just my guess.