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What is a good upgrade for a 645M?

dcaccount
over 4 years ago

Hello,

I would like to replace my 645M with another one with a more accurate HR.

What model would you suggest considering?

Thanks,

Dan

  • 0 over 4 years ago

    745 or 945 if you want navigation maps.

  • 0 over 4 years ago

    I'm not sure there's an upgrade to get more accurate best rate. Wrist-based HR is known to struggle for accuracy during activity. Perhaps getting a chest strap ( if you're not using one) would provide the accuracy your looking for.
    That said, I recently moved from the FR645 to the FR945. That decision was to pick up the added features of the FR945 not to correct accuracy deficiencies of my FR645.

  • 0 over 4 years ago

    If you're not satisfied with the HR on the 645, you're not likely to be satisfied with another wrist-worn optical heart rate monitor (oHRM). The lighter watches tend to perform better because they bounce less, and you can't get much lighter than the 645. The 245/745/945 may have slightly newer technology, but I haven't heard any reports of substantial improvement. Make sure your watch band is snug enough. Failing that, get an upper-arm oHRM (e.g., Scosche Rhythm+) or a chest strap.

  • 0 over 4 years ago

    If you dislike chest strap hrm, then get upper arm Polar OH1+ to pair with your 645M.

    You will not be disappointed with the accuracy.

  • 0 over 4 years ago in reply to pelototin

    Thanks for the suggestion, what is the most accurate upper arm available? Can it be paired with the 645? 
    And I am curious, why these upper arm bands are more accurate of the HR monitor of the watches, the technology looks like the same.

    Thanks for helping,

    Dan

  • 0 over 4 years ago in reply to dcaccount

    AFAIK, polar OH1+ is the most accurate optical hrm. It supports both BLE and ANT+ communication.

    My assumption, the upper arm is more ideal location for optical hrm because it does not swing as much as wrist, and the ohrm is more securely strapped there.

    You can check the review at dcrainmaker website, it have much more detail on the specification and test.

  • 0 over 4 years ago in reply to pelototin

    Just out of interest, what's the point of an upper arm sensor given that it will still be much less accurate than a chest strap and probably more noticeable when you wear it? 

  • 0 over 4 years ago

    I managed to get a good deal on a 945 (less than the 745 RRP at the time) so went with that. Already had a chest strap HRM so using that with the new watch as well. The 745 has started being discounted as I see it now available for €445  so that's also an option.

  • 0 over 4 years ago in reply to George

    I've never used an upper arm sensor, though from what I understand, they're more accurate and responsive than wrist sensors, and they avoid some pitfalls of a chest sensor. A chest strap needs the right amount of conduction; too little moisture or too much caked electrolytes and it can be wildly inaccurate. The strap can also lose contact in wind (or water) - I've had that happen going downhill on a bike with an otherwise adequately tight strap. Other than that, it's mainly preference. Not everyone likes something around their chest or can fit one under a sports bra.

  • 0 over 4 years ago in reply to George

    there are a few upper arm optical hrm that are having accuracy very close to chest strap, virtually identical, if u don't need HRV measurement.

    and polar OH1+ are having a benefit of onboard memory, so it can stored your session without watch or phone, works underwater, unlike older FR645. (except that the data cannot be aggregated in garmin connect for swim session, u need polar app to save swim hrm data, unfortunately)