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HRM-Tri - Download Heart Rate - why does it change TE etc?

alexpez
over 7 years ago
Hi, I've posted a little about some behaviour that I don't understand over in a thread about continuous monitoring by the HRM-Tri strap, but I'd like to open a new thread regarding this behaviour as its separate from continuous monitoring when outside of an activity, and either a bug or some setup option that I have missed.

I have previously trained and competed wearing a Forerunner 610 with an accompanying chest heart rate strap.

I purchased the 935 Tri bundle two weeks ago and started running using the packaged HRM-Tri strap. When I put the HRM-Tri on, I get notification from the watch that it is connected, and the watch itself is set to automatically set my upper HR (currently at around 193), and resting is using average of 50bpm. I have been keeping the watch on the HR screen so I can see what my HR is during the run.

I noticed that upon long run completion, the TE values were often 5.0 and 0.0, so scrolling around the menus post race I noticed the DOWNLOAD HEART RATE option. I selected that and the watch seemed to pull data from the HRM-Tri and then processed them. The TE values generally changed quite dramatically, along with other metrics (the TE was the one that caught my eye).

It has been suggested to me that perhaps my watch was losing the connection with the HRM-Tri mid run, and using the OHR instead, so DOWNLOAD HEART RATE was feeding the watch with more accurate data post run. Today I decided to test that out.

I ran 15km or so today, with the Wrist Heart Rate sensor disabled (Settings/Sensors & Accessories/Wrist Heart Rate/Status -> OFF). I put the HRM-Tri on, and the watch said it was connected, I waited for a GPS signal, and started my Run activity. The screen was set to display HR so I could see whether it was reading from the HRM-Tri, and at no point during the run did I see a blank value on this screen.

Upon completion, I saved the run and checked out the TE values:

5.0 aerobic
0.0 anaerobic

Thought that was a bit strange, so I clicked on DOWNLOAD HEART RATE to see what it would do (note that the Wrist Heart Rate sensor was disabled, so the watch has only used HRM-Tri data to calculate that TE value). The watch showed me the DOWNLOADING STORED HR DATA screen, then the PROCESSING DOWNLOADED HR DATA screen, then HR DATA DOWNLOAD SUCCESSFUL. I then checked the TE values:

2.9 aerobic
2.0 anaerobic

Can anyone explain why this is happening? Are people who are not selecting DOWNLOAD HEART RATE following a run activity when they are using an HRM-Tri getting inaccurate data? Is there some setting burried somewhere that I've missed or incorrectly configured?

Why are the values take pre and post DOWNLOAD HEART RATE so different if the watch has only used the HRM-Tri during a run?
  • 0 over 7 years ago
    I have done a test with the last run I did and I have the same issue.
    The original TE values were: 3.6 aerobic, 2.1 anaerobic.
    After downloading the Hr data from the HRM-Tri my TE values become: 2.2 aerobic, 2.5 anaerobic.
    Moreover, as the previous version on the run was already uploaded on Garmin connect, now I have two different versions of the same run on Garmin Connect!!

    I think there's something wrong with that...
  • Former Member
    0 Former Member over 7 years ago
    I asked Garmin Support about the "Download Heart Rate" menu item and waited over one week for a reply.
    The reply was useless boilerplate text explaining how I should go about solving an issue with my watch and phone them.
    All I want Garmin to do is explain this menu item and put it in the User Manual where it should be.

    I tried a run this morning with Optical HR disabled (I usually leave it enabled) and using my Tri strap.
    On saving the activity I noticed there was again a change to the Run details after executing "Download Heart Rate"; it affected Calories used, TE values and there was a small variation to either Max or Average heart rate values (can't recall details but it is unusual for a variation to HR values).
    Generally I find after executing this option Aerobic TE reduces and Anaerobic TE increases.

    Based on this and other anomalies my guess is that the Watch system is buggy probably because of poor design.
    Probably the developer that added the "Download Hear Rate" menu item left the team and didn't tell anyone he added it.
    OK I am stirring but I am getting sick of the lack of information.
  • 0 over 7 years ago
    I agree that the TE value change is hard to understand. I suspect the Firtsbeat algorithm responsible for calculating TE does not take into account a scenario involving live HR data and then downloading it again from the strap.

    But I do not understand why you think that the "Download Heart Rate" option is there by mistake. There are cases when it could be of use.
  • 0 over 7 years ago
    Seems like that's was a bug, it's supposed to be fixed in next update.
    Please see discussion in related thread: https://forums.garmin.com/forum/into...60#post1279360
    Anyway, that's frustrating, when you've been run a half of an year relying on wrong TE/TS numbers that comes from wrong place.
  • Former Member
    0 Former Member over 7 years ago
    I think the download HR option is a mistake when you Save and activity and you have had a Tri strap connected for the whole activity.
    The option should not be necessary unless there is additional data to download (I believe that this is not the case).
    What additional "Heart Rate" data could there be?
    If a strap was connected for the whole activity and the option is selected (after Save) the watch should indicated HR data is already downloaded (not reprocess the strap data and change the activity details).
    In fact the option should be disabled in this case.

    If the watch and strap are physically separated during an activity (or there is a disconnect) then the option is fair enough.
  • 0 over 7 years ago
    Ok, I see your point now. I think the option is there just to make things simpler for the sake of implementation. Otherwise the watch would have to keep information about the source of HR data and would have to decide if the data is complete or not - which might not be that easy, since due to the specifics of ANT+ the watch does not keep a constant connection to the sensor - it just receives periodic packets of data. Deciding whether all packets have been received or if some have been missed would be cumbersome.
  • 0 over 7 years ago
    Clearly something odd going on here but bit hard to comment without seeing any data. Do you have GC links "before and after"?

    Does your HR data seem to be materially changing after the download - e.g. average HR and time in zones somewhat different?

    Are you using Smart or every second recording?

    Is your max HR consistent between your 935, GCM app and GC website?
  • 0 over 7 years ago
    Seems like that's was a bug, it's supposed to be fixed in next update.
    Please see discussion in related thread: https://forums.garmin.com/forum/into...60#post1279360
    Anyway, that's frustrating, when you've been run a half of an year relying on wrong TE/TS numbers that comes from wrong place.


    I thought that was just related to swimming. Anyway in your use case you appear to be "replacing" data you should already have from the HRM-Tri with the same data. But, as I mentioned, above is this actually the case? Bit different with swimming when before the "download" you would be unlikely to have much or indeed any HR data already saved into the activity.
  • 0 over 7 years ago
    Well I contacted support, and they advised a hard reset to clear all data from the watch.

    i did that, and then switched off the weist based HR monitor, put on the HRM-Tri, paired it and had it connected, and went for a small test run (2k).

    During the run I left the watch on the HR screen, and as far as I can tell it didn't lose the connection at any point.

    Upon completion of the run activity, I saved it and checked out the TE values: 2.4 and 0.0.

    About 5 mins later I chose DOWNLOAD HEART RATE to see what would happen.

    same thing happened: the watch start downloading data from the HRM-Tri, and then processes it, giving wildly different (generally lower) TE values: 1.2 and 0.0

    Can everyone with a 935 and HRM-Tri test this? I think this is a nasty bug that renders TE pretty useless (possible some config is wrong, happy to check it all out).
  • 0 over 7 years ago
    Similar problem with my Fenix 5 and HRM-Tri. Sometimes after an activity, it downloads "stored hr data" automatically and if it happens the calories burned are dramatically raised.
    I was sure, the hrm tri was connected all the time, because the watch showed me the current hr and it was not on my wrist...
    Though I have never tried to manually download the stored activity (only after a swim, a couple of times, for months ago)

    I will try it next week with the 6.83 fw to see if the bug was fixed.