[mountain_peak]

Not claiming that the science is settled, but I when I entered keto over 10 years ago (TL:DR daily 10K+ 'performance' runner, neuropathy from glucose intolerance - genetic, avoid all drugs), I wanted to be sure that I could run without ingesting carbs (since everyone said you couldn't).

Read "The Art and Science of Low Carbohydrate Performance" and can absolutely say that after an initial horrible period that lasted for months, I was eventually able to run further and just as fast as I used to when I was carbo-loading. I can honestly say that running is more difficult now - my legs are generally sore and I don't feel like I'm 'flying along', but I've always tracked my times with Garmin, then Apple, and the stats belie how I feel.

From the book: "[Keto-adaptation] allows even a very lean (10% body fat) athlete access to more than 40,000 kcal from body fat, rather than starting a prolonged event depending primarily on ~2000 kcal of glycogen."

I think the studies you quoted would back-up the authors, but I also wanted to lend my long-term personal experience. I can't recall where I read it, but thought adaption also occurred in leg muscles where they found a massive increase in the number of mitochondria for athletes on keto.

I tested myself daily for years until I found a combination of diet and exercise that worked. My body definitely adapted and became much more efficient at burning fat - there's no performance 'wall' anymore, but I think the experience is different for everyone.