Is LT a function of pace or HR?

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  • #10787

    Hi all!

    I’m new to the forum after reading 80/20 Running and a few other running books. I’m a beginner and have been running in Z2 for most of the last 8 months. I’ve seen improvements and I started adding speed work, which is more fun!

    I like data and I’m confused about the intensity I should train to improve LT and VO2max.

    My question is about LT. I read what it is (Training for the Uphill Athlete offers a very comprehensive explanation) and I’m still uncertain whether using a LTHR is a good proxy to determining training zones. It does not seem that the accumulation of lactate depends on HR. It seems to be more about ATP requirements, hence power output.

    Should we then just scrap LTHR and only use pace/power when determining intensity zones for LT and VO2max workouts? And let the HR react to it according to whatever other factors are at play that very day?

    I have read in the forum that HR is not considered a good proxy. Nonetheless, it seems that the LTHR is still used as a gold standard for training zones.

    Please help! 🙂


    Matt Fitzgerald

    Hi Luigi,

    Welcome to the forums! Our testing/zone system actually makes no attempt to identify the physiological lactate threshold. Rather, it determines/is anchored to a functional threshold of 1-hour maximum sustainable HR/pace/power. For this reason and others, I actually find performance metrics–namely intensity and power–more useful than HR.

    The exception is our Talk Test option, which identifies the first ventilatory threshold, which in my view is of greater practical importance than LT.

    If I Only Had Room in My Suitcase for either the Lactate Threshold or the Ventilatory Threshold, I Would Pack the Ventilatory Threshold: Here’s Why

    Coach Matt


    Dear Coach Matt.

    Thank you very much for your prompt reply. I had not read your article, and I found it very spot-on. It mentions the same doubts about the “lab determination” of the LT that had begun to form in my head. Awesome!

    I’m sold on the importance of training below VT, and I’m probably doing it on the conservative side (MAF formula or Z2 based on max HR). My pace at smoothness at the same HR got much better over the last 8 months.

    I will follow your advice about speed work: when I train above VT I will relax my anxiety to hit HR zones and focus on pace (I may try power on my Coros, although I run in pancake-flat Singapore) and RPE. I’m experimenting with different workouts and I will probably be able to draw some empirical conclusions. Two days ago I learned what a too-intense interval session looks like at my current level of fitness: the extra pace was small (5 s/km) but it killed me.



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