Wednesday: Slow HM with High HR

It’s workouts like today that really spark my curiosity about exercise physiology.

I’ve been having a great string of workouts, and I’ve been feeling pretty sharp.

I will admit that I was feeling tired when I got up this morning, but I got a good night’s sleep.  But I was looking forward to a nice long, easy cruise.

The plan called for a 2×45’/4′ rest.  I decided to substitute a half marathon at the same power just to change it up a bit.

What happened in the workout was very strange.  My HR started low, and just kept going up.  I didn’t feel like I was working extra hard, but my HR just never plateaued.


Just look at the difference between this and the 2×45′ session I did on Sunday.

  • Same power
  • Same Stroke Rate
  • Wildly different HR

So, what’s going on?  A few theories

  • Accumulated fatigue?
  • Warmer today than Sunday
  • Fasted vs not fasted
  • Morning vs Afternoon

I’d love to understand this stuff better.

2 thoughts on “Wednesday: Slow HM with High HR

  1. sanderroosendaal says:

    Would be interesting to have lactate values for the two workouts. I am not an expert, but at the physical level the body must have been doing very similar things. Same power. Same muscle groups. Same energy flow. Same oxygen requirement. Let’s assume same energy pathways.
    So, in my simple world that would mean that on your workout with the higher heart rate less oxygen was “pumped” to your muscles at each heart beat. So were you dehydrated, or perhaps the heart as a muscle was more fatigued and decided to pump less volume per beat? Or some other process in the body required more oxygen? Fasted vs fed?
    I agree, very interesting.

    Liked by 1 person

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