AeT Test Results I Just Can’t Believe

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  • #32355

    I performed the DIY Treadmill AeT test just 2 days ago with an initial HR of 162. The first half to second half average HR increased by only 1.2%, which indicates 162 is below my actual AeT. However, I was literally near exhaustion by the end of the 1hr test – an indication of *Anaerobic* threshold. I also performed one 12 days ago with an initial HR of 160, with a half to half increase of 3.1% (also with great difficulty at the end). With two tests giving similar answers, this should mean my AeT is greater than the low 160’s.
    I am having trouble believing my AeT could be this high, due to the near exhaustion felt at the end, due to my training history, plus noticing what other folks report as their AeT on this forum (I know, that’s not always a good thing to do).
    My questions are: Does this seem realistic? If not, what could I be doing wrong? If this AeT test result is indeed valid, can one’s AeT be so close to their AnT that it’s impossible to separate one from the other? (that situation sounds like it takes YEARS of careful training, which is not me)

    Training History / Info:
    – Before January 2019: sporadic to regular Crossfit for the prior 2 years, running (probably mostly zone 3 as this was before I discovered TFTNA / UphillAthlete), never considered myself an athlete nor performed structured training of any kind.
    – February 2019: Began the “24 Week Expeditionary Mountaineering Training Plan” following it quite closely for the goal of climbing Mt. Rainier. LOVED the training BTW, and found the climb to be surprisingly easy physically (classic Muir route).
    – August 2019 to present: Almost exclusively Zone 2 trail running/jogging, not very regular and not structured.
    – I am 45 years old.

    Prior AeT Tests Results:
    – 2-2-2019: >142
    – 3-16-2019: >149
    – 6-4-2019: >150
    – 11-8-2019: >160
    – 11-18-2019: >162
    (Note I have never done an AeT test which resulted in me seeing >5% increase in avg HR)

    AeT Treadmill Test Methodology:
    – Fasted for >2 hrs
    – 20 minute warm up
    – Set the treadmill speed/incline and didn’t change it for the entire test duration
    – Recorded HR with high quality HR chest strap

  • Participant
    depeyster on #32356

    I too never had much drift (age 64, always used chest strap). I stopped testing after averaging 152 and then 156 in successive stages, during my most recent test in October. These were clearly way higher than I could endure regularly, so I realized that I am one of those for whom the HR drift test, as conventionally performed, does not provide a meaningful reading of AeT.

    Do you have a special diet? I ask because I eat very low carb. I do not do it for athletic performance reasons, so I am not proselytizing. I just believe that a lot of the measurement norms that work for most trainees, seem not to work for the few people on this site who drastically restrict carbs.

    Dane on #32357

    To me it sounds like you were at your AnT. I’ve seen it explained in a different post that since there isn’t much room for your HR to increase above your AnT (the spread from top of Z3 to Max HR is pretty small), you won’t see it budge much if you’re doing an hour at max effort so the % drift will be low. Regardless of where your AeT is, working at that threshold should still feel relatively easy compared to being at your AnT. I’ll let someone with more knowledge weight in but if it were me I’d redo the test at a lower intensity (conversational effort/still able to speak in sentences) and see what it looks like. If you’re at ~5% drift at an easier intensity that’s probably closer to where your AeT is.

    For what it’s worth, I started with the TftNA plan in Jan of this year for Rainier with zero endurance background besides hiking/backpacking and I initially over estimated my AeT because where it actually was felt frustratingly easy/slow (I didn’t use drift, just nose breathing pace). For my current training cycle I’m using a lactate monitor to find AeT since my neighborhood is hilly enough to make Pa:HR difficult to rely on. I’m getting better at feeling it out now and almost without exception the minute my breathing starts getting a little labored in a run my HR will hit my AeT.

    OwenFW on #32359

    Rodney, I’m 42 with a very similar history of prior training, a similar experience with UA training, and similar results in the field. My AeT test results on the treadmill from two days ago are similar to yours–maintaining the speed that gives me what I think is my AeT for an hour is unpleasant even if my breathing seems to confirm my HR drift results. FWIW, these results also line up with a gas exchange test I had done earlier in the summer. Then my AeT clocked in at 159 (up from maybe 144 when I started training with ADS) and now it seems like I’ve edged up to the low 160s, with an AnT of around 180 and maxHR of 196, which seems high for my age. While these numbers still technically indicate ADS, it is greatly reduced and I’m in the best shape of my life, loving my time on the trail.

    I interpret the results you describe and which I’ve experiencing in terms of the “black hole” of Zone 2 training that TftNA warned against. Maybe I’m relying more on fat metabolism at these higher heart rates, but running faster is still harder and still takes more recovery time than running slower, even if the faster speed isn’t as *much* harder as it used to be. I think I’m quickly approaching the level at which I need to back off on Z2 training to avoid excess fatigue.

    Anonymous on #32364


    Thanks for writing in to us and for the kind words. It seems you’ve made really big gains in improving you aerobic base. Congratulations. I find that running an hour at me AeT is very tiring. All athletes with a good aerobic base will find the same thing. That’s because (in my case) AeT and AnT are only about 10 bpm apart.

    I suspect that your AeT has moved close to your AnT. This is why when when this occurs we recommend cutting Z2 training and polarizing your training in Z1 and recovery runs with some Z3-4 hard workouts. This is when the Z2 can become a black hole.

    I hope this helps.

    Anonymous on #32730

    In addition to the gap closing between your AnT and AeT HRs, your pace has been increasing. The increase in pace (I think) is what makes AeT work so much more fatiguing now. So although the metabolic cost is low, the neuromuscular cost is high. That’s where the fatigue comes from.

    So as Scott said, you’ll need to back off of Zone 2 training. It’s too fatiguing, and now you don’t really need much of it. You can maintain that high AeT in an interval type-format, and by supporting it with a lot of Zone 1 (or easier) training. The athletes I coach that have highly developed AeTs do most of their training in “Zone 0”.

    Flatlander on #33164

    Scott J. and Scott S.,

    This post raises a similar question I posed on another recent post regarding my treadmill cardiac drift test results (Validity of Heart Rate Drift Test): How valid or reliable is this test for setting the AeT we will use in our UA training programs? In my case, others have suggested that I start my Uphill Athlete 8-week Basic Mountaineering Plan at a much lower HR than determined by this test. You seem to suggest that Rodney also train at a lower HR level than determined by his test.

    I chose to start with the AeT determined by the test so that I can have a relatively consistent method of measuring my progress. I’m just not confident I made the right decision…

    Anonymous on #33228

    @davidbrush: The thing to be careful of is that you don’t inadvertently test at your anaerobic threshold because that will behave in a similar fashion.

    The big difference is that with an AeT drift test, your average HR could rise further but it doesn’t. At AnT, your average HR can’t rise further because of the mix of intensity and duration.

    I was skeptical of the drift test too, but I have more faith in it after comparing it to gas exchange tests. Here are some examples from athletes that I coach:

    * Athlete H did a drift test that suggested an AeT HR of ~150. He later did a gas exchange test that suggested the mid-140s. The test was not our protocol, and his AnT HR is much higher, so we continue to use ~150;

    * Athlete V did a drift test that suggested an AeT HR of ~130. A later gas exchange test that was done according to our protocol suggested ~135. His AnT / AeT gap is huge and training at ~135 is not very taxing, so we started using 135.

    Done properly, the drift test will give you a reliable heart rate to base your training off of.

    In the post that you linked to, I think you’re trying to be precise with something that can never be. Heart rate is a reflection of global stress, so unless all of the other stresses in your life are static, you’re splitting hairs to try and determine the difference between say, 135 and 140. Within five, perhaps even ten beats, it just doesn’t matter. For example, a ten-beat difference on 140 bpm is ~7%. So if you train ten beats too low, you’re getting 93% of the benefit. Close enough!

    Only when AnT / AeT equals <= 1.1 can small changes in heart rate reflect significant changes in load. (And at that point it makes sense to use something that can be precise like pace or power.)

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