Difficulty staying under AeT

  • Creator
  • #26820

    Hey everyone I’ve really fallen in love with alpine rock climbing and alpinism in general over the last year, and recently set out to revamp my training accordingly. I’ve been digging into the website and TFTNA recently, and just did my first aerobic threshold treadmill test on Tuesday using the nasal breathing method. I ended up with an AeT of about 149. Today I set out to attempt a 5 mile Z2 run. I live in New Orleans, where it both very flat and very, very hot and humid (today it’ll be in the high 80s and humidity will probably top 85%, this is typical for a lot of the summer). For reference, I did a 4 mile run in similar conditions last week and held about an 8:19 pace throughout, but I was definitely way out of Z2 for pretty much all of it. By the last mile I’d rate my exertion around a 7 out of 10.
    Anyway today I went out with an HR monitor on, trying to keep my HR in the 140s throughout the run. I was able to do so for the first half, albeit at what felt like a very slow pace (11:00-12:00 miles). On the second half my HR climbed up into the high 150s, and I couldn’t get it down without slowing almost to a walk. By the last mile I had slowed to a pace near or at 13:00/mile, and still my HR would not drop even into the low 150s. If I stopped completely, my HR would drop down into the 140s pretty quickly, but then as soon as I resumed the slowest jog it would start climbing again. Oddly, my exertion throughout felt very low, and I was able to maintain nasal breathing pretty consistently. My question is, in short, what gives?? Do I just need to commit to a lot of very, very slow runs around 13:00 until my AeT and pace start to build? Am I missing something? Do I need to re-do my AeT test using the HR drift method? Thanks for any advice in advance.

  • Participant
    briguy on #26822

    I’ll let the experts chime in, but I think your post said it – you live in New Orleans. Hot/humid conditions are well known for driving up HR in significantly different rates compared to pace/Level-of-effort/etc.

    jsmith85 on #26823

    Makes sense. So then, should my approach be to slow my pace down even further (almost to a walk) so as to keep my HR below the AeT number I got from the nasal breathing treadmill test, and just focus on putting in the hours to get that threshold and pace to move up?

    jsmith85 on #26824

    Also I should probably add that from what I’ve read I fit the model for ADS- long history of Crossfit style glycolitic work between my personal life and my former job (military), in which I did “longer efforts” (i.e. 30-60 minutes) pretty regularly, but at way higher intensity than the Z2 focus I’ve learned from reading TFTNA. So I can hike 12 miles with a 40-50 lb pack and maintain sub-15:00 miles, but will feel like shit afterwards and the next day.

    briguy on #26826

    It’s not unusual for those just getting introduced to this type of training (be it Maffetone or that proposed in the Uphill Athlete books) to be somewhat shocked at just “how slow” you have to go to keep the HR under threshold.

    Fortunately it seems to respond fairly quickly and you’ll notice your paces at those low HRs drop fairly quickly too. Below is an example of mine when I was recently returning to running from injury. All paces at below my “MAF” heartrate which is kinda/sorta similar to Z1/Z2 work espoused in TFTUA book. Each reading was about 1 month apart:


    Considering I am an older athlete, I was pretty happy with this progress!

    Compounding your situation though is that you’re trying to do your work outside in extreme heat/humidity. Maybe try a treadmill just to rule out the environmental factors.

    Anonymous on #26832


    briguy is right on all counts. Running in the heat and humidity will bump HR 10-15 beats easily. That’s because your body is shunting a lot of blood to the skin to shed heat. That’s blood that’s not available for the leg muscles. So the heart has to work extra hard to supply enough blood/O2. The slowing in the second half of the run is typical when over heating is happening.

    With regards to ADS: Your perception of exertion is low because the pace is slow, the muscles are not making much power so it can feel silly easy, even when you are not overheating. There is only one way to correct ADS that is with a high volume of low intensity training. If you have a long history of HIIT training like Crossfit then you can’t use nose breathing to find AeT. Not sure why but I’ve seen this many times. You need to use one of the other tests, the sijplst being the HR Drift test described in the article by that name.


    jsmith85 on #26833

    Scott and Briguy-
    Thanks a ton. So when I’m running in the heat (this will be unavoidable for a big chunk of the year), should I slow as much as is necessary to get my HR below my AeT (once I find that number with the HR drift test), or should I use a pace that I know would put me around my AeT in cooler weather and ignore the 10-15bpm increase that’s attributed to the heat?

    briguy on #26866

    Scott should definitely confirm but my understanding is that when training ADS you should keep HR under your prescribed threshold, no matter the conditions.

    One other effect you’ll notice is you’ll begin to acclimatize to the heat/humidity as well but even at 100% acclimatization it will have an adverse effect on HR bpm.

    Cosmic Hillbilly on #26889

    I wondered the same. Here is a link to a good article that gives a convincing answer to your question:

    spantik on #26990


    I have a question regarding ME training under hot and humid weather: I am about to do the Z3 Weighted Climb (from the 24-week Big Mountain Plan) and I was wondering if it’s OK to have my HR above Z2 under such condition?


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