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)