Drift tests all over the place. What do I do next?

  • Creator
  • #44747

    I am having difficulty discovering my aerobic threshold to start the transition period training. I hope that the wisdom of the forum will help guide me.

    I use a Polar chest HR monitor that links to my watch.
    I use a treadmill to set the incline and speed.
    My warm up is at least 15 mins until the initial target HR is stable. I then do the test for 60 mins and get the ave HR for the first and second 30 mins. I have repeated the tests around the same time of the day. After each drift test attempt, I adjusted the incline/speed at the beginning of the next test based on previous drift result and HR target.

    My tests and results have been all over the place.

    Test 1. 10% incline at 4.1 kph. HR 117 increased to 121. Drift 3.4%.
    Test 2. 9% incline at 4.1 kph. HR 121 increased to 124. Drift 2.5%.
    Test 3. 10% incline at 4.3 kph. HR 127 increased to 131. Drift 3.1%.
    Test 4. 12% incline at 4.5 kph. HR 123 increased to 127. Drift 3.25%
    Test 5. 13% incline at 4.5 kph. HR 130 increased to 136. Drift 4.6%.

    Tests 1 and 5 are close to the drift range 3.5 to 5% but the heart rates and effort to get those drifts are very different. What would you consider to be my aerobic threshold? What would you do next?

    I am female, 63 yrs of age.


  • Participant
    willplayforfood on #44765


    (just another student of these arts here so take with a grain of salt)

    Honestly, these all look like good/useful tests. If it were me I would probably set my AeT at 125 (or maybe 130) and proceed from there and retest in 6-8 weeks.

    I think you may just be falling in to a common error of what I think the coaches have labeled ‘false precision’ in previous forum conversations. You have done all the rights things – yay you! (warmup, controlled environment, consistent time of day, etc) But even after we control for all those things the reality is respiration and heart rate are still imperfect tools and a complex output of not only our workout but also other life/environment factors.

    For example, in my own training I routinely notice easily a 10+ bpm variation for a variety of hard to control for factors (time of day, poor sleep, life stress, heat/humidity, excess fatigue from prior days, dehydration).

    I have come to accept this imprecision and thus try to error a little on the conservative side, hence why I might target 125 vs 130 bpm in your case even thought both are probably fine. Also knowing my own nature I tend to push too hard so a conservative boundary gives a buffer.

    As a cross check you could also gauge next day fatigue for a normal length AeT workout. I think the general rule of thumb is you should feel reasonably fresh the next day (like you could repeat the same workout) and if this is consistently not the case then you might benefit from dropping your AeT target (try 5 bpm). Note: this might not be a reasonable gauge the day after your ‘long hike/run’ of the week at AeT simply because this longer hike/run is designed to drive higher fatigue.

    Curious to hear what others think and good luck,


    trudyw on #44769

    Thanks Nick for your detailed reply. I will start with 125 bpm and cross check next day fatigue etc as you have suggested.

    Play safe and stay well wherever you are


    Anonymous on #44961

    Nick is correct. Your method is a good one, and these are all good tests. You’re trying to be too precise with something that can’t be.

    The only difference I would suggest is to use 130 instead of 125. It’s not a significant difference, but the first-half average in the last test was 130 and the drift was less than 5%. So that’s the number to use.

    trudyw on #44969

    Thanks Scott and Nick. Good feedback. I am going to do the alpine combine test today so will start the transition period training next week.
    thanks again

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