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Another faulty HR-measurement issue

DaKo
13 days ago

Hi all,

It has pasted the forum a few times already, but I still want to share my experience with you and ask for your insights.I am having troubles with an increasing HR, while there is no reason for it. I use a Garmin HRM Dual for measuring HR, and it is connected to my Garmin FR955 Solar.

Today's run was an Easy run, around 10km/h for 1 hour. Based on my stats from past years, I am pretty sure the HR should be between 140 and 150 bpm, towards the end slightly above.This is zone2.

If you look at the graph below, you see some interesting point in the red HR-line:

  • at the start it is increasing as it normally does
  • after 7 minutes, HR starts to increase to 165 at a pace below 10km/h. Way to high. Notice my efforts to slow down to stay in zone2.
  • at 10 min you see a sharp descend. It is the moment I disconnected the HR module, and reconnect it. It did reset the HR back to just below 140 bpm. Perfect!
  • from minute 13 it starts raising again to 160+. I disconnect the module again, and let the OHR take over after 2 minutes. That is shown as a gap in the chart.
  • OHR registration after that is fine, around 150 or just below. As expected.
  • negative spike at min 40 is me re-attaching the HR module again to the strap, after a few seconds, the watch uses the external HR data again, and it is fine until the end.

<sorry, it seems the pasting of an image is not allowed. Maybe later>

This kind of behaviour is not new to you guys. It is written all over the forum. But I an trying to figure out what could cause this.

  1. Is it really hardware  FR955?
  2. Could it be the HR-strap/module?
  3. Can it be an unhappy marriage/combo between strap and watch?
  4. Is it the software, as suggested on this forum.

The most important finding in my opinion is that OHR is giving right data (it is a relief that my actual HR was not increasing like it seem), and the External sensor takes over the right data after disconnecting for a while.

BTW, yesterday I ran a 10k timed race. I was expecting HR around 170bpm (and it felt like that), but the whole race it was above 180bpm (188 max). Normally I cannot keep up the tempo at that kind of HR, unless it is a short distance.

  • 0 11 days ago in reply to DaKo

    Todays run, right in the middle I disconnect the strap and waited for the OHR to take over. You see a drop from above 180bpm to just below 170bpm. I had a scheduled run in zone 3 for 45 minutes. My tempo at 4:50 should just be fine to start at about 160bpm, and end with 168-170 bpm. So again, I suspect the combo FR955/HRM Dual to register values that are to high. It used to be OK, I use the strap for 1,5 year now. hardly ever had weird readings.

  • 0 2 days ago

    As a test, I did a softreset yesterday before I started my Interval workout with strap. My warming up HR seemed fine, as expected. My first three intervlsl were also in the expected bandwidth. But my third interval suddenly dropped my HR by 30-40bpm, in a descending line while I ran my 4min interval. The 5th interval was again as expected. Soft reset did something, but not the whole thing. Next run I will look at it again, and if the issue is still there, I will change battery in the strap.

  • 0 2 days ago in reply to DaKo

    What do you mean by "soft reset"? Do you mean the watchdog reboot caused by holding in the Light button?

    I would suggest changing the battery in the HR strap. They can behave intermittently when the battery is getting low. Also, not all Lithium coin batteries are equal. I've had problems with Lidl branded 2032 cells, but never a problem with branded Panasonic cells.