The amount of wear and tear on a human body, especially voluntary wear through exercise, simply requires ample nutrients for adequate recovery – and that means amino acids.
Aren't branched-chain amino acids a subset of amino acids, of which we only require a relatively small amount as essential?
My memory may be failing me here, but ISTR the "Sugar: the bitter truth" dude Robert Lustig mentioning BCAA as something problematic WRT cancer and corn-fed beef, as cause to consume grass-fed instead.
Disclaimer: I know nothing.
Edit: it seems I'm not senile yet, the talk I'm recalling:
Inflammation (read: the mitigation of) also plays a significant role in health.
And, of course, there's the gut and gut microbes.
We survived and evolved and that was more than a story about amino acids. Or at least that's my current interpretation of the process to date.
https://scholar.harvard.edu/exercised/home
https://www.amazon.com/Burn-Research-Really-Calories-Healthy...