In my experience the pain of riding hard isn't like the pain of an injured back. A hurt back seems to me far worse than a quad burning from a hard sprint, say. It's an ache that makes you feel like you are just going to cave in. Horrible.
There's more. The pain of riding hard is...well, J. S. Mill the philosopher referrd to pains that produced pleasures later. The pain of riding hard seems to be that kind: even when its bad, you can sort of try to put up with because something might come of it later. Whereas, when your back hurts because it's injured, it just (which J. S. Mill did not say) f---ing hurts. Allowing the pain to continue doesn't help some pleasure happen later.
I'm not trying to make light of anyone's pain issues and I hope it doesn't look like I am. Just being conversational.