Do we know the biological mechanism to cause OTS, though? That would open up avenues for treatment and more precise prevention besides "rest more" (not that that's a bad preventative).

Yes, a lot of them. Non exaustive list:

- bone microfractures

- nervous system depletion

- tendon "microlesions" (not so sure about this term though)

- immune system blunting due to stress

- raised cortisol levels

- (possible) nutritional deficiencies given the increased exertion (or just metabolic bottlenecks)

A lot of it is anorexia by another name. There is a subspecies that involves compulsive exercise. Doing lots of athletics without proper nourishment is a good recipe for low performance and injury.

That particular issue is known as RED-S: https://en.wikipedia.org/wiki/Relative_energy_deficiency_in_...

But over-training can happen even with sufficient nutrition (even if it is less likely, as nutrition is a major part of post-exercise recovery).

Also anorexia by another name in many cases, alas.

> A lot of it is anorexia by another name.

Literally my first thought after reading this training log excerpt:

> 10/4/2012: I’m really trying to be conscious right now about losing some worthless snack weight… Need to be more diligent, take action, get fucking after it, and restore the body and the mind!

"worthless snack weight" sounds very similar to epithets that anorexic people often use.

What's fatigue? Is there a fatigue molecule?

Lactic acid?

Nope. Lactate and lactic acids are by-products of fatigue, not causal agents. Far from being toxic, elite athletes are even intentionally ingesting lactate as fuel these days.

Correct. Related to that, accumulation of free hydrogen ions is associated with acute fatigue (although not necessarily related to chronic conditions like OTS). This is why some endurance athletes are now taking sodium bicarbonate supplements.

I'd say ask ChatGPT because the list is loooong

Yeah, I mean these days, apparently it consists of melanin.