Morning vs afternoon HR drift?

  • Creator
  • #18716

    Hi all,

    My main low-intensity cardio is running, and my ADS is still solid enough that I can complete my shorter Z1/Z2 runs fasted, which I have been doing. The easiest time for me to do this is in the morning (running to work), with the secondary timing being afternoon (running home from work, with no snacking past lunch). These runs are about 1 hour, after a 10-15min warmup.

    I have noticed that I must run at a slower pace (around 1min/km) in the morning to keep my HR at AeT, which from what I read online is the opposite of most people’s experience. A look at my running history in TP shows this to be very consistent, and independent of temperature – runs in the summer heat or cold winter (77F down to 10F) show the same trend of faster pace in the afternoon for the same AeT. My short runs are on the same route to/from work, so that is not a variable here.

    Does anyone else experience this? Any ideas why this happens? Does this indicate some problem? Thanks in advance!

  • Participant
    snkaban on #18742

    Whoops I should clarify that my pace isn’t 1min/km, but 1min/km slower in the morning compared to the afternoon.

    Anonymous on #18773

    What’s the difference in your perception of effort between AM and PM runs?

    I do not have a ready explanation for what you are seeing. It’s an interesting point though. I just have not seen it before.

    If you recover well from the PM runs at the faster pace then try doing the AM runs that fast and see how that affects your ability to recover overnight.


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