Ahhh, this makes a lot of sense. "Whole body response" is why these moves FEEL like so much fun for me. It is a qualitatively different feeling from simple exercises like repetitive weight lifting. I am bad at it, so every little thing calls for a lot of brain power, too. I can't jump and talk at the same time, for example. It's also scary, so yeah, flight or fight.
This is a separate episode of my noob parkour adventures I just wanted to write down. I am not sure yet how it relates :-)
When I tried the monkey vault for the first time, I stood in front of old tires I stacked for the purpose. I tried them for stability, stretched a bit, and jumped. Instantly, I found myself flat on my face, without any idea whatsoever of how I got there. I did not get hurt other than minor scratches. I lay on the grass for a while, feeling rather helpless cognitively. I did not know what I did wrong. I did not know what steps to take to even start figuring out what I did wrong! I thought my dog, who came over to observe, was laughing at me. I laughed too.
This was a luxurous feeling because it was so new. I've been analyzing learning for as long as I can remember, for the last 20 years professionally. And I don't even remember when I felt that total lack of learning opportunities, steps, ideas - the total pedagogical vacuum, experienced very directly through the whole body.
This is how many students must feel about mathematics.