Trying to maintain power even if fatigued

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    Hi all. I got a question.
    Let’s say I’m doing a Cycling foundation workout and I’m supposed to ride 1hr @ Z2 power. (70- 83% FTP).
    Normally I would aim to stay at around 75-77% FTP and my HR also stays pretty consistent at Z2.
    But I’m not feeling that great and I see my HR starting to creep into ZoneX. So I lower my power to the Z2 minimum (70% FTP). But still my HR keeps trying to go into Zone X.

    Should I:
    a) Reduce power even further even if it means going into Zone 1, to prevent my HR from going into Zone X, or,

    b) Maintain Z2 power even if my HR sets up camp in Zone X?

    Your thoughts are much appreciated

    David Warden


    First, you would only want to measure both Power and HR zones at the same time if the underlying threshold test for both was done at the same time. If the two were done in different tests (and therefore different environments) they really can’t be compared. Choose one or the other to use until you test them both in the same test.

    If they were done at the same time, I would still ignore HR and use just power until your HR crossed into Zone 3. In other words, until HR jumps a full zone over, it’s not worth making an adjustment.

    Not all coaches would agree with me on this. Some coaches see HR as the arbiter of intensity. I see HR as the chameleon of intensity. Yes, an elevated HR is a sign that maybe something else is happening. But the issue is that most of the time it is a completely benign thing that is elevating HR, and not worth modifying training for.

    Other coaches would say that an elevated HR is *always* bad. I disagree. If it is one day, ignore it. Two days, take note of it, 3 days there is an underlying issue.



    Thanks a lot David. I’ll keep that in mind


    I had a similar issue germandelarosa today. Thanks for making your post.

    I did full FTP test last week, taking the average 30 mins power, and average last 20 mins HR. Doing CF9 today, I was quite suprised by two things. 1) I thought CF9 would be a breeze, but the Zone 2 power actually felt a little more difficult that I expected. And about halfway through the workout, I looks at my HR, looked up my HR zones and noticed that while my power was at the center of Zone 2 (by design because it was being handled by ERG with my Wahoo Kickr and Garmin Edge 830), my Heart Rate was not only above Zone 2, it was past Zone X and in Zone 3, and for a short bit got int Zone 4 before I brought my power down. I wasn’t ever able to get both my HR and my power in the same zone today during the remainder of the workout. My HR didn’t come back down to Zone 2 until I had brought my back down to Zone 1.

    Possible explanations that occur to me:
    -Yesterday was a rest day for me, I didn’t run or bike. But I did do a hard and long lower body weight training routine (mentioned elsewhere in a forum post) late in the day yesterday.
    -Waking up today my Garmin Body Battery showed a high score at wake time of 67 (out of 100), which seems a bit low for the morning after a recovery day and a full night of sleep.
    -Could my lower body strength training yesterday afternoon have messed up my HR zones for this ride this AM?
    -Or is it possible that in the FTP test that I did my average HR was abnormally low, throwing off my zones? In the recent past, I have had a calculated (auto-generated by Garmin and TrainingPeaks) threshold HR of about 15 bpm higher than what I calculated in my actual FTP test ride last week.

    @David Am I missing anything – explanations or tips? I hear you on the idea to focus only on the power metric, make a note this elevated HR happened today and see what happens in the next couple of bike workouts.
    One a related note, do you guys do anything with recovery metrics like HRV, Garmin Body Battery, or resting heart rate to monitor and quantify recovery – an adjust training to the data feedback?

    David Warden


    This is unusual. Having HR span one zone is somewhat common, spanning two rare, and I’ve never heard of HR spanning 3 zones relative to Power.

    Additionally, short-term muscular fatigue usually manifests itself in the opposite way, where HR is very difficult to elevate. If your fatigue rooted in is the nervous system, not the muscles, this can lead to elevated HR. But, nervous system fatigue is chronic, not acute like muscular fatigue, and you would be experiencing this elevated HR in all other areas (resting and waking HR).

    None of the other factors resonate with me. At face value, it’s a puzzle. The difference between high Zone 2 and low Zone 4 is 20bpm! To have kind of swing in less than a week is a first.

    Any chance you can share with me both workouts (FTP and the Zone 2 ride) in TP so that I can take a look?


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Retired Mexican Navy Aviation Officer. Age Group Triathlete. 80/20 Endurance Certified Coach and Brand Ambassador. Lvl 1 Certified TrainingPeaks Coach. Stryd Certified Coach. ONTargetEndurance head coach.