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.
Quantified Rowing 
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.
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My theory is that this is related to the energy system hysteresis effect that I posted about before.
https://quantifiedrowing.wordpress.com/2016/07/16/friday-3-x-20-130-rest-w-lactate/
At least for me, there are days where my fat vs CHO crossover point is much lower and fat metabolism gets shut down. It could have something to do with time of day, nutrition state, or something else.
The real question is, what’s the right strategy to manage it when it happens? Slow down or press on? I suspect slow down is the answer.
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