Aerobic Threshold Testing

  • Creator
  • #74516
    Bob Taylor

    Is there a protocol for choosing a heart rate when performing or repeating a heart rate drift test to determine aerobic threshold (AeT)? I have read “Training for the New Alpinism” and “Training for the Uphill Athlete” and have listened to the your podcast on aerobic threshold testing. If this is addressed, I am missing it.

    Expressing my question by example (as am using silly numbers on purpose):

    If I choose to walk at 2 mph and my heart is 90 and does not drift 5% over an hour, I know my AeT is greater than or equal to a heart rate of 90.
    If I choose to run at 15 mph and my heart rate is 160, rises, and I cannot complete an hour, I know my AeT is less than a heart rate of 160.
    If these silly examples were true, what heart rate or running speed would I use when I repeat the test to determine how much my AeT is above 90 beats/min.

    How do you make a first guess at AeT heart rate? Brief nose breathing or talking/reading test? Maffetone’s maximum aerobic function formula?


    Bob Taylor

  • Keymaster
    Jane Mackay on #74600

    Hi Bob,

    That’s a good question. First, your AeT for running will likely be different from your AeT for hiking. So that’s the first thing to take into account when choosing the HR to start at.

    Do you already have some data from hikes or runs using a chest strap monitor to record your HR? If you do, and you even casually monitor your HR during the outing, you likely have a sense of the point at which the workout starts to feel hard — once it goes beyond the “all-day” pace. That would be the HR to start with.

    It does take a bit of trial and error, but the good news is that you only have to play this guessing game the first time. Once you’ve established your AeT you then have a baseline.

    Does that help?

    Bob Taylor on #74601

    I understand that different activities might yield different values for AeT. For the sake of this discussion, change the words in my silly example above from “walk at 2 mph” to “run at 2 mph”.

    Please allow me to paraphrase your answer:

    1. Determine the level of exertion for your first attempt at measuring AeT with the heart rate drift test by guessing. Uphill Athlete does not have a specific protocol. Interestingly in my case, my intuitive guess is about the same value given by the Maffetone formula.

    2. If I can maintain my first guess at the level of exertion that represents my AeT for one hour without heart rate drift, Uphill Athlete does not have a protocol for determining whether this first result is correct or too low. I know you did not say that but the absence of this information in the books, podcasts, and your answer cause me to draw this conclusion.

    I was hoping there was a more rigorous, scientific approach. I realize this is part art and part science.

    Thanks for answering my question. Uphill Athlete is great.

    Bob Taylor

    Jane Mackay on #74603

    Hi Bob,

    Paraphrase 1 is correct. Paraphrase two is incorrect. This video explains how to analyse a heart rate drift test, using real-life tests as examples. Please let us know if you have more questions after watching it:

    How to Administer and Analyze a Heart Rate Drift Test

    You’re absolutely right that it’s part art and part science, to the point that each person’s individual AeT will drift around from day to day and even within each day, depending on physiological factors.

    Bob Taylor on #74606

    That podcast was very helpful. It answered my second question. As I understand it, if I do the test and get a heart rate drift of about 3-5%, then that level of exertion approximates my AeT.

    The source of my confusion was the “Fundamentals of Mountaineering Part 2: Aerobic Threshold Testing” podcast with House, Robitalille, and Clark. I went back and looked at the transcript. At 32:35 Chantelle says “…So you’ll see I talked about this before you’ll see the heart rate to pace ratio or rather the pace to heart rate ratio and you’ll want to see that’s within 5%. If it’s higher, then maybe you started a little higher than you should have and you’ll want to redo the test but no big deal. If it’s lower, you may have started a little bit too low.” This left me wondering what if the drift is 0% or 4% or anything less than 5%. The “How to Administer and Analyze a Heart Rate Drift Test” podcast that you recommended and that I had not seen before, makes the answer to this question clear.

    Thanks for you patience in answering my questions.

    Have a great day.

    Bob Taylor

    Jane Mackay on #74608

    Hi Bob,

    I’m glad that confusion has been cleared up. The podcast with Chantelle that you listened to was more off the cuff than the video I linked, so the explanation was not as clear as it could have been.

    So, yes, if the drift is within 3-5% then you can take your starting heart rate as your AeT. If it’s a fair bit higher than 5% (say, 7% or more), it’s probably a good idea to retest, targeting a lower HR. If it’s not too far above 5%, you can estimate. E.g. if your target HR was 134 and the drift was 6%, you could estimate your AeT at around 132 or 131. Again, the number is never going to be 100% precise because human physiology is imprecise. In that situation, I prefer to estimate low, because then I’m less likely to drift into Z3 (through inattention or poor self-control) when the intention of my training is to stay below AeT.

    If the drift is less than 3%, either retest at a higher HR or estimate. If the drift is negative, then retest at a higher target HR.


    slowandsteady on #74613

    Nose breathing or easy pace did not correlate closely at all with my actual Aet. I tested mine in a lab, but I can nose breathe and run for quite a while like 30bpm higher than my lab aet.

    So I’d recommend getting a lab test

    Bob Taylor on #74616

    You seem to be an example of why Uphill Athlete (I am not speaking for them. I am just reporting what I have read in their books, podcasts) recommends using the Heart Rate Drift test which is the topic of my questions. Certainly a lab test is great but I do not have that available where I live. I realize I could buy a lactate measuring device but Uphill Athlete seems to think the HR Drift test works fairly well for AeT estimation and I can do that for free.

    Determining my anaerobic threshold aka lactate threshold aka VT2 is a whole different can of worms. I would love to have that measured with a gas exchange lab test if I was readily available to me.

    Participant on #75133

    Last year, my drift test put me at an AeT of 142 with a drift rate of around 4%. After my running season ended, I switched immediately to base building starting at a self-imposed heart rate cap of 130 and then raising that cap by 1 bpm per week. And I also decided to do drift tests each week right at my cap just as an experiment. Here’s what was interesting:

    1. I was clearly under 3.5% drift at 130 up to about 133 bpm.
    2. But at 134, my drift started to exceed 5% which confused me. Nevertheless, I pushed on and…
    3. At about 138, my drift dropped back below 5%.
    4. At 139 to about 143, my drift continue to drop. In fact, at 143, it’s at only 2.1%!

    I know the 2.1% is not an anomaly because I was below 3% from about 140 to 142 as well. So that’s four drift tests all in the 2-3% range using a Polar chest strap. Plus, I was able to run pretty comfortably at 143 for the entire 1.25 hours needed to complete the test. Probably could have gone another 30 minutes to an hour.

    I don’t know how to explain this seeming inverted U shaped curve in my drift rate as a function of my HR. I’ve seen lactate measurement tests on this site that also seems to show an increase in lactate and then a decrease as HR goes higher over certain ranges. So my drift test seems consistent with this. If anyone has any insights about what’s going on, I’d appreciate it!

    Bob Taylor on #75134

    That is interesting. My understanding is there may substantial day-to-day variation depending on physical state such as recent training, recovery, hydration, etc., but perhaps you are seeing a real, but unexplainable trend rather than day-to-day noise. I am interested to hear what the experts have to say.

    Participant on #75161

    Another possibility is that my AeT had eroded from a season of racing and hard intervals sessions and then I gradually built it back up during the base phase with fairly easy running. I had nearly 3 months of base under my belt (early Nov) by the time I did my 143bpm test (late Jan). I think the lesson for me here is that your AeT is far from fixed and you have to test a lot to know where you are at any given time.

    Run_JMH on #75422

    I just did my AeT test. Avg HR was 135 for my run. But my Pa:HR was -.78%. Not sure how to read this data.

    I have been training a fair bit (likely overtraining) with insufficient Zone 2 work.

    Happy to re-run the test but I would still appreciate clarity on what this number is telling me.

    Many thanks.


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