Chest strap inaccuracy

Former Member
Former Member
I've got an HRM4 paired with my 5x and it's generally pretty well-behaved. The exception is when I'm on the treadmill doing intervals. My watch is consistently within 2 or 3 BPM of the HRM on the treadmill while I'm walking, then when I start to run the Fenix jumps to 250, give or take, and stays there. Even when I slow back to a walk it stays at 247-250. The HRM on the treadmill shows me back down around 135 but my 5x is still showing 250 for the remainder of the run. I've adjusted the strap to make sure it's damp underneath and I'm religious about rinsing it daily and taking it into the shower with soap every few days. Thoughts?
  • I've experienced similar issue (heart rate at 240-250 bpm) when my chest strap was too loose.
  • Former Member
    0 Former Member over 6 years ago
    Thanks but I don't think I can get it much tighter. When I pull it away from my skin it snaps back pretty forcefully. Contact with the skin is excellent. I've tried water and aloe vera and sweat as a conductor and nothing does the trick.
  • I wonder if there could be some electrical disturbance in your body when you are on the treadmill, causing your HRM to pick up the disturbance and confuse it with actual heartbeats.

    How does your treadmill measure your heart rate? Could that device somehow induce a weak electrical signal to your body?

    (I am really only guessing here.)
  • I wonder if there could be some electrical disturbance in your body when you are on the treadmill, causing your HRM to pick up the disturbance and confuse it with actual heartbeats.
    (I am really only guessing here.)


    Static electricity from the treadmill belt would be prime suspect here.

    Perhaps see if you get the same reading with the OHR sensor? (Take the chest strap off to activate this).

  • Former Member
    0 Former Member over 6 years ago
    You might also want to try replacing the battery in the HRM, if you haven't already tried this. Sometimes when the battery is low you can start to see some unusual readings.
  • Is this is the older button-snap style HRM-RUN with the little dude and the replaceable strap?

    If so it's dying. Mine did the same thing -- it started the same way, but it would eventually cut it out after 20-30 minutes into a workout. Then it did it routinely and every time. I tossed it eventually and bought a new one -- problem disappeared.

    It's NOT the battery -- I replaced mine with a known good, brand new battery -- no change.

    These things fail in this sort of way and when they do they screw up your data for a *long* time too, as that bad data is in Connect and there's no way to get rid of it that I know of.
  • These straps do benefit from some tender loving care. And that begins with following the care instructions. If you have been diligent with that then, as noted above, chances are the strap's conductivity has been compromised. You're in luck if yours is the one with the snap-on module as the bands are readily available and cheap. If not, then it's a costly replacement.
  • It's not the strap part -- and yes, I do know what the care instructions say and I did and do follow same.

    They have a habit of failing in exactly this fashion where they read impossibly high heart rates; it starts as an intermittent problem which leads you to believe it's the strap or battery (even though they do monitor for and report a low battery) but replacement doesn't resolve it. Eventually the fault becomes permanent, but long before then the data they return -- not just the heart rate itself -- has corrupted your profile in Connect and, if you keep playing around with trying different things the pollution in your Connect profile and data such as Lactate Threshold will be severe enough that it will be months before it returns to normal once you replace the strap -- and I know of no way to clear that bad data out either.
  • Former Member
    0 Former Member over 6 years ago
    I wonder if there could be some electrical disturbance in your body when you are on the treadmill, causing your HRM to pick up the disturbance and confuse it with actual heartbeats.

    How does your treadmill measure your heart rate? Could that device somehow induce a weak electrical signal to your body?

    (I am really only guessing here.)


    Hand grip. I'm just not clear on why it would be fine until I start to run for the first time and then it never goes down. Nonetheless, I think this is a good one to explore. When it goes south again I'll transition to the rowing machine and see if the problem persists. I'm somewhere very very hot and there's no option but to run inside, so checking it by running outside is not an option.
  • Former Member
    0 Former Member over 6 years ago
    It's not the strap part -- and yes, I do know what the care instructions say and I did and do follow same.

    They have a habit of failing in exactly this fashion where they read impossibly high heart rates; it starts as an intermittent problem which leads you to believe it's the strap or battery (even though they do monitor for and report a low battery) but replacement doesn't resolve it. Eventually the fault becomes permanent, but long before then the data they return -- not just the heart rate itself -- has corrupted your profile in Connect and, if you keep playing around with trying different things the pollution in your Connect profile and data such as Lactate Threshold will be severe enough that it will be months before it returns to normal once you replace the strap -- and I know of no way to clear that bad data out either.


    That's pretty grim. Sounds like me and my ex wife...