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Lactate Threshold HR and Pace divergence

Nunokrav
over 4 years ago

Hello Everyone,

I'm getting back to sports after a few years, and I have been running with my new fenix 6 since 25 November (so don't expecto good times yet), always with a chest strap, and with Heart rate zones based on Manual entry of my estimated Lactate threshold of 175 bpm. Last week, without the watch detecting my threshold, I decided to do the guided test, and It detected 174 bpm with a pace of 6:31 (I'm 41 years old and my maximum detected HR is at 192 bpm, so maby it is a bit higher if I test it right). Three days later, I ran 10Km with an average of 174 bpm, and the average pace was 5:45 min/km. Should I disregard the 6:31 threshold pace given by the test? I have my data synced with training peaks, and after I uploaded this run, training peaks notified me of a new pace threshold of 5:43 min/km.

Most of the time I am relying on my HR zones, and I am happy with the results for now. In this five weeks of training, with the same heart rate while base training, I am about one minute faster per Km, but I would like to know wich threshold pace is the correct one. For now I will keep training relying on HR zones based on the 174 bpm lactate threshold. Do you agree this is the option you would use?

Thank you.

  • 0 over 4 years ago

    I’ve been using pulse zones based on LTHR for a couple of years now, and my experience is the same as yours (although with a Fenix 5 Plus): Detected LTHR seems quite spot on, while estimated LT pace tends to be 0:30 - 1:00 min/km too slow.

  • 0 over 4 years ago in reply to SAHO
    SAHO said:
    LT pace tends to be 0:30 - 1:00 min/km too slow

    May be the reason for that is that instant pace on Fenix 6 seems to be too slow in general, especially when the GPS signal strength is less than ideal. According to the customer support, Garmin is aware of the issue.

  • 0 over 4 years ago in reply to silentvoyager

    Might be, allthough I use the Fenix 5 Plus w/ Stryd for pace/distance. That said, I suspect Garmin uses GPS data «under the hood» for the FirstBeat metrics no matter what source is set for pace/distance by the user. I’ve tested a couple of times to disable  GPS, but then I don’t get any FB metrics even if I have «perfect» pace input from the Stryd (and HR data from chest strap). This might be the case for pace input for LT estimate as well.

  • 0 over 4 years ago

    Your LTHR is 90.6% of maxHR, which is right in line with what you would expect (90-92% for a regular runner).

    I too find the pace a bit conservative. But I also find the same thing with the guided FTP test for cycling, where the recommended FTP is considerably (15-20W) under what I can achieve on a 20 minute test.

    My guess is just the algorithm is generally conservative, rather than an issue with GPS pace.

  • 0 over 4 years ago

    In my experience both LTHR and associated pace seem spot on.

    my LTHR is 178 and pace fluctuates between 4.09-4.18.

    It does depend on whether you train at that pace or not. I suspect that for a new user, as s/he gains fitness, the pace will lower while the LTHR (~90 max HR) will increase at a lower speed.