3rd Time’s the Charm – Drift Test, my path to figuring it out

  • Creator
  • #71473

    Hey girls and boys,

    I report back finally with some sort of sensible results, and thought my process of figuring this out might be helpful for someone else. Yesterday I completed my 3rd drift test and got a steady and sure 4.2% drift that looked right on analyzing, AND also felt right.

    Test 1: 12.5% @ 2.6mph
    In early Sept I did a test and, assuming I am not fit, targeted 120bpm. I figured if I undershot, it’d be a clear no-drift. Completed on a treadmill, I analyzed and saw a 3.4% drift. I thought “OK, so I am in bad cardio shape for my age, this must be my AeT”. Over Sept I did a lot of “Z2” work based on that number (so like…110bpm), and I noticed that I basically never felt stressed in any way, and it always felt very easy. I could probably sing the whole time without missing a beat. Hmm.

    Test 2: 13.5% @ 2.8mph
    On our assigned drift test day first week of Oct, I did another drift test, this time targeting 125 “just to see”. To my surprise, I had 0% drift…maybe even slightly negative, and it still felt very easy. Bizarre, and Mark Postle said ‘do it again higher’. He suggested 130, but I had done a couple things there and it all felt easy, so I figured “lets try to surpass my threshold and get a very clear drift above 5%”

    Test 3: 15% @ 3 mph
    Yesterday I repeated the test, but targeted 140bpm. ALRIGHT, finally, it felt like I was doing work, but not too hard, and I would not please an audience with any singing. Total effort was 1h25m after a good warmup toying with speed. I had a 5bpm drift over the test, starting HR of 140, first half ~143, second half ~149, so 4.2% drift. 140bpm for my 35 year old age also happens to be must closer to where I “should be”.

    I haven’t done extended treadmill anything ever, so I think my first test’s drift was just modality newness and my body’s surprise. The key with test one and two is they did not feel like I was working, and should have heeded that more. The last test was definitely at my “nose breathing boundary”. I realize I should have just followed the “180-35” guideline and started at 145, that would have gotten me real close up front. Alas, I’m scared of overtraining and figured there would be no harm to undershooting at first.

    Happy Tuesday to you all from Jacksonville, FL!


  • Participant
    Jeremy on #71476

    Great that it finally worked out. A takeaway I got from the first zoom call that I didn’t know before:

    When doing the test outside I was so concerned with keeping the speed constant. But in the call learned that when doing the test with a GPS watch and loading into Training Peaks, the algorithm will take changes in speed and distance into account and calculate an accurate drift.

    Is this correct?

    FYI I agree with your post above just thought was a useful note.


    Nanook on #71488

    This is a super timely post for me as I was laid out all last week with a cold so ended up deferring the program by a week & am working though the drift test just now.

    For me I did the drift test over about 1:30 outside & at about 140bpm average for the test proper (targeting 142bpm) I noticed that I had about 1.38% drift.

    My takeaway is to redo the test targeting 148-150bpm & see what the result is.

    Has anyone else had trouble keeping the drift test pace? I find that if I run my HR goes to about 167-175bpm, but I’m having to power walk to get to the 142bpm range that the math says I should be targeting.

    Any tips on pacing for the drift test? I think I just need to learn to run slower… but that’s a skill I still need to learn…

    advaitdreamon on #71491

    I have a tendency to get impatient or self- critical if i dont crack somthing at the first go.
    Hence I needed to hear that things take time. Trial and error is necessary to arrive at any level of accuracy.


    TLoftus on #71495

    Nanook, Sounds like you have a good target HR for your next test. Have you considered using a treadmill? I found it difficult to manage a target HR/pace outside for this one and it became so much easier on the treadmill. I just get psyched and do it and then go back outside. Regards, Tom

    aaronnorlund on #71497


    Yes! In the most recent call Mark put up, in the middle of it, he walks through analyzing somebody’s outdoor run and explains exactly how to do it. You can load that video from the membership area and it will show you exactly how.


    I have the same problem. I’m just not a runner, so even a slow jog spikes my heart rate. I’m having to use the treadmill at a very steep incline to get my heart rate about where I need it.

    Anonymous on #71500

    @Jeremy in general, you are right; however, you should take care of your HR and not about your speed or pace, which means if you target 140 bpm you just check and keep this HR during the whole test (the speed and pace might vary), this is the case if you are doing the test outside (GPS based). At the and you just check Pa:Hr, and the algorithm will do the rest… If you are doing the test on a treadmil, you can and must “only” fix the speed (pace), and you will see inmediatly the HR drift as your HR increases (ideally 🙂 ) during the workout. To calculate the drift (in cas eof the treadmill test), you use a different method: first half Hr average (after WU) vs. second half Hr average. I hope this helps.

    Anonymous on #71508

    Jeremy, This is correct. Pa:hr will account for changes in HR and/or pace if you have good GPS data

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