AeT heart rate, intuition, and nose breathing?

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  • #25505
    DrewThayer
    Participant

    I recently picked up Steve and Scott’s new book (amazing!) and am trying to get a decent estimate of my AeT heart rate for the first time. Brief Hx: 31 years old, ~15 years casual consistent varied endurance activities (HS cross-country, alpinism, cycling, recently ski mountaineering and skimo races), generally a slow-twitch kinda guy. All my running and skiing is above 5400 ft in CO (sometimes above 10k ft).

    My primary question is: can an athlete with decent self-knowledge and observation tell their AeT and LT efforts by intuition? Is the AeT basically what you settle into as ‘2nd gear’ and the LT as ‘3rd gear’?

    Also, it fair to say that these rates don’t correlate much with the ability to breathe through the nose?

    Anecdotally, I’ve noticed that my ‘2nd gear’ heart rate, e.g. consistent uphill effort I can sustain for hours, but never ‘fun-hard’ pushing, is 156-162 BPM, and my ‘fun-hard’, pushing up a hill but will burn out in an hour HR is ~ 170 BPM (or 168).

    On nose breathing: recently, paying attention to an HR monitor, I’ve realized I can reliably run uphill for an hour+ with a HR around 162, and calmly breathe through my nose the whole time. On steep rocky sections if I keep the same speed my HR will jump to 170 and I can STILL breath through my nose, but surely my AeT is not in the high 160s… right?

    If I can do a long, hilly run and always feel in ‘2nd gear’ (never grindingly slow but never trying to go fast), and my HR is within 156-162 the whole time except for brief uphill rock-gardens, my intuition tells me I am near the top of my Aerobic zone. HOWEVER I want to make sure I’m not ‘black-hole training’ in zone 3 and just have bad intuition. (An AeT of 162 would also be really high according to the Maffetone formula — I’m just a rec athlete)

    Note: I’ve been trying to do the HR drift test comparing 1st and 2nd halves of a long run (the method that looks for aerobic/anerobic system decoupling) but I don’t think I’ve done it on flat enough terrain (getting inconsistent results).

  • Keymaster
    Scott Johnston on #25522

    In my years of coaching XC skiers who were very well aerobically trained I noticed that blood lactate levels of 2mMol/L (one definition of AeT) corresponded very closely (<+/-5%) of the nose breathing limit. So we preached that in our first book. Since then I have worked with many not so well aerobically trained athletes and discovered that for them this ventilatory threshold (nose breathing) did not correspond well with AeT. So we now propose the HR drift test. I suggest doing the test on a treadmill for much better control. We've seen much higher correlation between the HR drift test determined AeT and gas test AeT. It is worth taking the time to find this point as it will inform much of your training. Scott

    Participant
    Jan on #25559

    Maybe this thread with a very similar question (but a bit different answer) is interesting for you:
    Zone 2 training – better to go by heart rate or by respiration ease?

    Moderator
    Scott Semple on #25564

    …can an athlete with decent self-knowledge and observation tell their AeT and LT efforts by intuition? Is the AeT basically what you settle into as ‘2nd gear’ and the LT as ‘3rd gear’?

    Yes, but only after having measured it accurately for years. What feels like the right pace for most people is actually zone 3 (a misnomer, but often called “the black hole”). Based on your description, your “second gear” sounds like zone 3, and “third gear” sounds like zone 4.

    If you really want to know for sure, it’s best to get a gas exchange test at a lab that understands the difference between the aerobic and anaerobic thresholds. (Not all labs do.)

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