Interpreting AeT drift test

  • Creator
  • #48685


    I was hoping to get some advice in interpreting my results for my drift tests to determine my AeT.

    Some background:
    – 30 y/o female, running regularly for past 3-4 years most days of the week; have been on/off with various recreational sports since childhood.
    – This year was my biggest training year: 600+ hours with focus on mountainous ultras, 100,000m annual vertical accumulation. I’ve done most of my training with nasal breathing, usually in a fasted state, with a few bouts of higher intensity sessions throughout. I find I’m able to keep my mouth closed for extended periods usually <=175bpm, although I’ve noticed I’ve gone higher sometimes but haven’t tested much above. I’m not sure how likely ADS is for me since I’ve spent a lot of time at seemingly low intensities.
    – I did a lactate threshold field test using the Joe Friel method end of October where I ran on the treadmill for 30 mins at a constant pace @ 1% incline and determined my AnT was 195 using that method (although I find it hard to reach this HR outside and think it may actually be closer to 190 where it begins to feel very difficult):

    Recent drift tests with their starting HRs (I’ve performed all of these on the treadmill for 1hr after at least a 15min warmup at a constant 3% incline & speed. My foot pod was not calibrated well, so paces are not all accurate and should be be constant as I didn’t change treadmill settings):
    – 160: 1.8% (
    – 170: <1% (
    – 177: 2.2% (
    – 180: HRM chest strap failed during the last portion, but was getting very low drift before this happened (

    I’ve been unable to get close to 5% so far and am unsure of how to test further. For my last test starting at 180 I felt it was moderate intensity and got tiring near the end, although didn’t feel any obvious lingering fatigue after the test. I’m unsure if above that is reasonable to test as it seems quite high for how zone 2 is typically defined.

  • Participant
    Reed on #48831

    Summarizing the workouts you linked to, I see:

    • ~30 minute anaerobic test suggests AnT at ~192bpm, 7:46/mi pace
    • 1hr aerobic workout, 164bpm, 10:11/mi pace, 2.67% drift
    • 1hr aerobic workout, 170bpm, 9:32/mi pace, -0.74% drift
    • 1hr aerobic workout, 183bpm, 9:18/mi pace, 1.22% drift

    I’m guessing that you may have had slightly higher drift at 185bpm (i.e. your last workout where the chest strap cut out), and that you could conservatively consider your AnT to be 190bpm, AeT to be 180bpm.

    You might consider making Z4 to be >190bpm, Z3 180-190bpm, Z2 165-180bpm, Z1 140-165bpm, and target spending more time in Z1 than anything else.

    With 600 yearly hours of training, it seems like you might have opportunity to increase strength / force production and increase both your AnT and AeT speed, depending on your training goals. If your AeT speed on a relatively flat treadmill increased to an 8:00/mi or 7:30/mi pace, that training might also get you closer to 4mph or 5mph for an ultra.

    rita on #48838

    Thanks Reed! That’d be awesome if I could get to those speeds. I’m currently focusing on Lake Sonoma 50 this April that I would like to improve for. Those zone ranges sound great and my perceived efforts at those zones match up to the intensity descriptions in the TftUA book. A huge portion of my training has been under 165 or so, so I will stick to that as my primary zone, and it sounds like then I should also add some Z3-4 sessions to help improve my aerobic speed, perhaps once weekly starting with Z3 to help build up more muscular endurance.

    For my AnT calculation, I arrived at 195 since Joe Friel’s method requires you take the average of the last 20mins (perhaps to account for cardiac lag), but the average of the entire 30mins (192) that you took seems like a better approximation as that’s when I usually feel I’m at my capacity when running outside, although I will round down to 190 as you suggested to be conservative.

    For my drift tests, I calculated the drifts by taking the averages of the two halves instead of the Pa:Hr shown (since my footpod seemed to have thrown out some inaccurate pace changes), and I considered the starting heart rate where it stabilized as the test AeT, instead of the average HR of the entire hour, as described in the article. I also just recently conducted a nasal breathing test outside where I gradually ramped up and concluded with spending several minutes around 185 (sustainable, but I wouldn’t say comfortable). Using 180 as a ballpark sounds good though so that my Z3 training range is not too narrow to target.

    I’m not sure of the significance of 3% incline that was suggested in the article for the treadmill drift test, but I am thinking to do a new test for my current aerobic speed at around 180 on a 1% grade (that may translate better to outdoor speed on flat), to set as a benchmark for myself, after some better footpod calibration. I think it should be currently somewhere between 8:00-8:30/mi.

    Thanks again!

    Reed on #48893

    That’d be interesting to see – if your pace info in TrainingPeaks is accurate (maybe it’s not?), your AeT pace at a 3% grade was something like 9:15/mi pace at ~183bpm. I’m curious how much impact that grade has vs. a 1% grade or a run outside on flat.

    If you’re looking for another way to triangulate, a lactate meter might be a useful tool. Not cheap ($300 or so plus maybe $10-20 of strips per test), but a useful tool. I purchased mine from Nova (

    And if you haven’t already, maybe try out Scott’s Killer Core workout two or three times a week for the next six months. Every time I’ve checked my ego at the door and scaled an exercise back to an easier version, it’s still been super hard but has led to more improvements. I still can’t to an L-sit, though. 🙂

    rita on #48901

    Hmm, seems like this forum spam filter doesn’t like the full TP links, my response didn’t go through:

    I’m not sure what my pace on the treadmill for those tests was set to (wish I recorded, but was only concerned for HR data at the time), but I suspect the footpod was not that accurate. I will follow-up with my results for a new test with hopefully more accurate data. But for some comparison, here are the TP workouts for a couple runs I did outside where I averaged around 8:55ish or so at 163-167bpm: &

    Thanks for the lactate meter link. Did you find these drift tests to give you high correspondence to the lactate tests (or GET/MET)? Not sure how confident I should be of my results. Seems like the meter would be useful for the benchmark pace tests since HR fluctuates so much if I wanted more accuracy & tracking.

    I’ve saved Scott’s Killer core workout after I discovered it yesterday and intend to try it out, looks good 🙂 My current strength training routine is mostly climbing (usually hiking up steep grades, running down) which I’ve found to be very effective for lower body, and some bar work for upper body (incline push-ups, hanging leg raises and such), although I cannot do Scott’s full leg raise version and have much room for improvement 🙂

    Reed on #48910

    Gotcha – for those two workouts you linked, after 15-20 minutes of warmup, you did ~7 miles in the next hour (~9:00/mi pace) at ~165 with minimal drift. Looks to me like you should be pretty confident in your results. Erring on the conservative side, you could consider a wide Z2 (15bpm wide, roughly 165-180bpm) and spend more time in Z1 even if it means a 9:30 pace for a while.

    I’m not anywhere near your level of 600hrs/year, yet I did have some success at speeding up my AeT running speed from ~9 min/mi to ~8 min/mi. See

    If you’re a data junkie like me, the lactate meter is great. But it’s not necessary.

    I finished a few ultras (slowly). I trained decently well, but was pretty beat up afterwards. Years of intermittent strength training in the form of squats and deadlifts gave me some strength, but not enough all-around toughness and certainly not very much deep abdominal strength. It took months and months, and picking easier forms of the exercises, but Scott’s routine was hugely helpful. Highly recommended. Be patient and consistent with it.

    By the way – there’s some great discussion elsewhere on this forum about fasted training, and some of the differences between men and women. Might be worth taking a look. Runs longer than 90 minutes might be more useful to fuel for, either beforehand or starting at 60-90 minutes in to the run.

    rita on #48917

    Sounds good! Most of my runs are much slower than those two runs I posted, so having to train at a mostly 9:30 pace (even considerably slower than that) is not a problem for me – I’ve become so accustomed to these zen-like runs that I really enjoy them and prefer them so much 🙂 On the trails I’ve been mixing in a lot of hiking, usually for uphills to ensure the intensity is low, and generally focusing on more time on feet above else. During the last year I’ve noticed I’ve become a lot more fatigue resistant, recovering faster and needing less food which has been great! But I wish I had known about UA and these drift tests earlier on as it would’ve been interesting to see the data on the progress like you have. Those are some great results for that training load and such short time! It’d be interesting to see how much that’d improve if you added more volume.

    Thanks for the forum suggestions, lots of great stuff here. I’ll be sure to add Scott’s routine 🙂 I’ve been getting some lower back pain during extended steep climbing sessions that I suspect may have something to do with core strength/posture, so think this could really help with that too.

    rita on #49032

    Just following up with my benchmark test for ~180 without drift:

    This was done on a 1% incline and treadmill was set to constant 7:55 pace (footpod’s paces shown still not super accurate). Felt pretty amazing and a comfortable moderate effort! I think outside this may be slower.

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