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Switching from chest to wrist HR during triathlon

Former Member
Former Member

Hi, all.

  • I have the 935, and get really good HR data from my wrist. I also have a chest strap which I sometimes use for biking/rowing, but don't wear it running because I just can't get it stable and it actually gives worse data.
  • I'm doing an Ironman soon, and because of the age of the watch and my time, I want to "top off" my battery toward the end of the bike, necessitating me taking it off (because of the charger placement). Thus I'll obviously lose wrist HR capability during this time.
  • So my plan is to wear my chest strap during the bike, at mile 70 take off the watch and charge it to the end of the bike ride, and in T2 put the watch back on, take off the chest strap, and go on my marathon.
  • My concern is: will the watch know to switch to wrist HR once I take off my chest belt to which it had been paired in the same ongoing activity?
  • So today I did a test on my bike: I wore my chest strap, at the halfway point I took off my watch and charged it in my bento box, at about the 75% mark I put the watch back on and put my chest HR strap in the bento box. From here on I got HR data, but it was very weird (much too high). Previous rides my HR is nearly even the whole ride (it's pretty flat here). This is my ride if you want to see the HR data: https://connect.garmin.com/modern/activity/5429126815

Any thoughts what might be going on? Was the chest strap sending bad data from the bento box? Does the watch not "calibrate" or something if it switches HR source mid-activity? Other? I still have time to do other tests. And honestly, I could do without HR data on the bike (I pace by power) but I REALLY need good HR data on the run. I could forgo the chest strap entirely, but would still need to know that I can take my watch off and put it back on during the event and the HR will resume picking up accurately.

  • Former Member
    0 Former Member

    If you need good HR data on the run I would stay with chest strap, either for bike and run or only for the marathon. From my experience the quality of OHR is often very poor for running.

  • Former Member
    0 Former Member

    hi,

    nice test, you now need to know from which source the hr data came

    • you can use Fit File Repair Tool, it shows the source for every logged data record
    • you can try it your self or with your consent we can have a look at your fit file
    • post it here or send it via pm (zip the fit file and drag & drop it on your post)
    Was the chest strap sending bad data from the bento box?

    could be the case

    Does the watch not "calibrate" or something if it switches HR source mid-activity?

    yes it does

    from belt to ohr it starts with around 70 beats, from there it start measuring again and should move to the real hr value

    fyi

    the connect activity you need to set it to public, at the moment it is locked for viewing

    happy & safe sporting

  • Former Member
    0 Former Member in reply to Former Member

    For me, I have always gotten really good HR data from the wrist - maybe the watch just fits right for me. On the run, no matter what I do the chest belt slips and slides and I get nothing, or it picks up my cadence, ... I have tried making it tighter, looser, etc.

    I'm going to try what OnlyTwo has suggested and I'll post back

  • Former Member
    0 Former Member in reply to Former Member

    Wow, this is a really cool app. I've loaded it up, but I can't find where it tells the source of the HR data?

  • Former Member
    0 Former Member in reply to Former Member

    Oh, and I made the ride public - thanks for reminding me!

  • Former Member
    0 Former Member in reply to Former Member

    hi,

    in tab "records" select sources and it shows you a number after the value

    that number corresponds with the sensor you will find in tab "devices file info"

    happy & safe sporting

  • Former Member
    0 Former Member in reply to Former Member

    I assume that's only in the paid version? It's greyed out for me. If that's the case, I'm willing to buy because this is so cool!

  • Former Member
    0 Former Member in reply to Former Member
    I'm willing to buy because this is so cool!

    indeed, the funny thing is, it works Slight smile

    • checked your sensors from connect

    you use the garmin dual sensor ? and one unknown, unnamed sensor

    happy & safe sporting

  • Former Member
    0 Former Member in reply to Former Member

    Beside the 935 itself what was connected to it were my phone, my chest HR, a Garmin Varia radar, my Powertap P1 pedals, and my Di2 electronic shifting. I think that's it (LOL)!

  • Former Member
    0 Former Member in reply to Former Member

    thank you for the feedback

    happy & safe sporting