Learning to trust the drift test

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  • #44997

    Fellow trainees,

    I’ve been trying to nail down my AeT for uphill hiking (my primary activity) and indoor cycling (secondary/backup/alternate activity).

    I’ve been ramping up level of effort (slope/speed on treadmill, targeted power output on exercise bike) and looking for cardiac drift. What I think I’m finding is that in order to achieve cardiac drift of ~5+% on a one hour effort, I’m putting out an effort that violates all of the subjective measures of being within AeT (breathing intensity, perceived effort, indefinite endurance). If I achieve a small cardiac drift, I’m usually completely spent at the end of the hour test, I’m definitely not able to nose breathe, and my heart rate is typically 80-85% of what I think my max heart rate is.

    I think from my reading that Cardiac Drift should be a more reliable measure than the subjective metrics, but I thought I’d ask here. Do someone people just not cardiac drift until further over Aerobic Threshold?

    I am not a well trained athlete – I am new to endurance training.

    I have significant data that I can post, just not sure what would be helpful yet.

  • Inactive
    Anonymous on #44999

    What are you using to collect HR data? This is the first time I have herd of this situation. It is usually the opposite; folks can’t believe how slowly the musy move to stay under AeT.

    Let me know.

    danspam on #45000


    Many thanks for responding.

    I am using a Polar HR10 to measure HR. Collecting data with a garmin watch for treadmill, and my watch (transitioning to a garmin Edge once I got power meters) for the bike.

    I’m using a Assioma Favero Duo to measure power on the bike.

    For power output control, I’m using a constant slope/speed on the treadmill, and a constant resistance + a metronome on the bike. I’m also watching the power meter output as a sanity check (it’s been stable).

    I just saw your response in the thread about training in heat and it sparked a thought. I sweat voluminously while doing these workouts. I stay hydrated, and the workouts are indoors, usually around 78F with a beefy fan on me, but I wonder if my physiology is such that it’s devoting a lot of energy to cooling. My power output to get these HRs and some cardiac drift is not very high.

    I am a 47YO male, I weigh about 170 pounds. Never very athletic, but I enjoy climbing, so I’ve transitioned from 5 miles of flat walking per day to programmed endurance training over the last 3 months or so. Sitting HR is usually in the upper 60s, overnight resting around 60. I’ve always had lowish blood pressure. Just in case my background sheds any additional light.

    I do have a bunch of workouts recorded on Trainingpeaks. Most are not dedicated AeT test workouts, but most are 60-90 minutes long and have solid HR data.

    Anonymous on #45007


    I’m not sure what the HR10 is but I am guessing you meant H10 chest strap?? I was just checking to be sure you were using a chest strap as wrist monitors are not useful for zone training despite what the manufacturers try to tell us.

    Heat will have a profound affect on your perceived exertion. For the time being (till you can train in cooler temps) I suggest you switch to using the MAF formula for AeT determination. For you this means 180-47= 133. Since you do not have much aerobic training history this will get you in the ball park and should not crush you for these aerobic base workouts. Give that a try and report back.


    danspam on #45008

    Yes, my bad, I meant polar H10 chest strap. I have seen first hand what you mean about wrist monitors being unuseful. In my last workout, my watch lost pairing with chest strap near the end, and reverted to its internal optical meter, yielding results 50bpm lower than the chest meter.

    Since my workouts are inside my house, I can set the temperature whatever I like. I usually live in the 76F-78F range. Can you suggest a range I should target for testing?

    I’ve done a about 3 months of workouts at effort levels that yield in the 120s and 130s, and those feel absolutely fine and as though I could sustain for several hours. The power output at those HR are about 125W for biking and around 175W for incline treadmill walking. I can continue at those levels for sure.

    The thing that confused me was that I never got a cardiac drift unless I upped my effort to the point where my HR was in the high 150s or 160s, I struggled to maintain nose-breathing, and I felt absolutely spent at the end of an hour.

    Again, thank you for your input, and also for all the work you’ve put in learning and communicating these systems to us.

    Anonymous on #45014


    Sorry, but I can’t tell you why you do not get a HR drift unless you are going so hard that you are really tired by the end. I have never seen this before in 20 some years of using this method. But I can say that if you are not recovering from these aerobic workouts in 24 hours so that you could do it again, and again and again, day after day then the effort/pace is too hard. That’s as good a way to figure out if you are going too hard.

    As for temps; If you are sweating that heavily your body is overheating. Try for a temp that allows light sweating.


    danspam on #45018

    Thank you. I posted a reply that includes links to a couple of recent treadmill tests on TP, but it’s not showing up here – perhaps spam protection which I would understand.

    Anonymous on #45271


    I could be wrong, but it sounds to me like you’re testing your anaerobic threshold, not your aerobic. Because the anaerobic threshold is at the limit of aerobic endurance, it naturally puts a ceiling on heart rate drift.

    * At the anaerobic threshold, drift doesn’t happen because it can’t;
    * At the aerobic threshold, drift could happen but doesn’t.

    If 150 bpm is hard for an hour, try a drift test at 120 and see what the drift is there. (I know you said you’ve done sessions there, but I’d be curious to see the drift.) Post a link to the workout file in TP and we can take a look.

    (There weren’t any links in this thread; none caught by spam. Can you repost?)

    Scott S.

    danspam on #45275

    Scott S.,

    Thank you for additional comments. I’ll try a drift test at 120 today and post results.

    The weather outside has gotten cooler this week, making it feasible for me to do my indoor tests at temperatures in the lower 70s which seems to be lowering heart rates. This is pleasant for me but makes proper experimentation a little trickier as there is one more independent variable.

    I’ll try to post some TP workouts in a subsequent followup post (so that this one doesn’t get squashed)

    danspam on #45277

    I alternate incline treadmill walking with exercise biking. Here are a few recent treadmill walks. I believe that 9/14 was the first of these where I was actively trying to get the air temperature a bit lower.

    (When I posted this with links, the post just never shows up in the thread.
    Trying now with just the workout IDs – the part at the very end of the URLs)

    CXP5O7FWKSL2JTI4FEYTRMETSU – Walking 9/20/20 2.6mph @ 15%
    TXKJHORZ54YBPTI4FEYTRMETSU – Walking 9/14/20 3.0mph @ 15%
    BDW4Z3SH2H7EPTI4FEYTRMETSU – Walking 9/12/20 3.0mph @ 15% (Note – Watch lost connection to Polar HRM around minute 70, and fell back to inaccurate wrist-based meter, hence the big drop)
    7ZZG65YAEGNL3TI4FEYTRMETSU – Walking 9/10 3.0mph @ 15%
    76INHWXIJN6BHTI4FEYTRMETSU – Walking 9/7/20 2.8mph @ 15%

    If this posts, I’ll put bike workouts next

    danspam on #45280

    Some recent bike tests:

    danspam on #45009

    Two recent treadmill tests on TP to illustrate are linked below. Both have some flaws but hopefully the lack of cardiac drift is evident.

    Both tests were done at 3.0mph, 15% incline. The first test is a little bit short (I underestimated warm up time) and the second one, my recorder lost pairing with chest HRM and reverted to wrist near the end, but there is still nearly an hour of good data.


    danspam on #45015

    Thank you. It may be a mental aspect…what I perceive as difficult or exhausting may just be way lower than most of your trained athletes. Or maybe I just have an outlier physiology. Or it could be the heat. I appreciate your insights. I will continue to explore.

    a couple of recent treadmill tests @ 15% / 3.0 mph for illustration:

    September 12
    September 10

    danspam on #45402

    Today’s test targeting 130 bpm.

    Anonymous on #45478

    Interesting. I looked at the last three, and no drift in any of them.

    One thing though: What are you measuring these with? Near the end of the September 12th test, HR dropped 80 beats in ~40 seconds, from ~160 to ~80. That’s very unusual and makes me wonder about the recording.

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