Decreasing Intervals | 80/20 Endurance

Decreasing Intervals

Viewing 4 posts - 1 through 4 (of 4 total)
  • Author
  • #8381

    I read Matt’s article with much interest. It goes directly to the heart (pun intended) of a nagging question I have had with 80/20 running…

    I rarely reach my zone IV heart rate when doing VO2 interval with the 80/20 protocols whether pace or heart-rate program. The allotted times are simply too short.

    With the caveat that I know absolutely nothing about the physiology of this stuff, my intuition is that I am not getting the best results from VO2 workouts and I might be better served stepping away from a duration based workout and moving to a less structured workout that takes me into the VO2 heart-rate zone for a prescribed period of time. That appears to me to be the cause for the conclusion of the investigators in the referenced article.

    As I indicted in my other posts, I am currently treating this COVID period as a prep phase and experimenting with workouts, machines, and protocols within the framework of the 80/20 Maintenance Plan. So, my question is this: Does it make sense for me to convert the Zone IV workouts in the Maintenance Plan such that I reach and sustain the heart rate at zone IV for the prescribed times in the plan?

    David Warden


    Your question represents one of the most interesting and misunderstood components of training. Heart Rate does not represent output. HR is a lagging indicator of how your body is responding to intensity. VO2max is based on ventilation, not HR stroke rate. If you are processing 5 liters of O2 per minute, and your VO2max is 5 liters of O2 per minute, you are at VO2max, regardless of HR.

    Yes, blood carries oxygen to the muscles, but the lungs carry oxygen to the blood. That is VO2.

    The only accurate method of measuring VO2 is by ventilation. Since that is not practical for training, we use the proxy of threshold pace, power or HR, and HR will always be the weakest method for short intervals.

    So, perform those VO2 workouts with confidence. Even if your HR does not get up to Zone 4+, if you are at an intensity that you can only sustain for 5 minutes at a time, you are at or near VO2max, independent of HR.




    Thank you. Now it all makes sense.

    Applying what you are saying I will continue to use pace in the structured workouts.

    Reading into your answer, I assume in practice that RPE (breathing rate) would be a good check that I am indeed executing at the prescribed intensity and have everything dialed in properly. Correct?


    David Warden

    Hmmmmm, I don’t have enough expertise on breathing rate to make a recommendation here. I would not know how to measure it. RPE? Yes, for sure, but I could not put values around breathing at this time. Power works really well for these short intervals, as you have about a 3 second lag compared to a 10 second lag for GPS (Pace).


Viewing 4 posts - 1 through 4 (of 4 total)
  • You must be logged in to reply to this topic.

$ubscribe and $ave!

  • Access to over 600 plans
  • Library of 5,000+ workouts
  • TrainingPeaks Premium
  • An 80/20 Endurance Book


30 day money back guarentee

For as little as $2.32 USD per week, 80/20 Endurance Subscribers receive:

  • 30-day Money Back Guarantee