They have the ability to turn off their pain entirely so it’s less of a miracle than if they were experiencing it.
Or you are drugged with something strong enough. A much simpler explanation that doesn't require to believe in guys developing supernatural superpowers.
One can build up a lot of tolerance.
Some vascular problems can be fixed with surgery and some nerve damages can repair itself, even if is a frustrating slow process. Hope you the best in your recovery. Stay connected here if you need to talk.
And even if there was a drug that would let you tolerate this level of pain, you would expect that it would make you super drowsy or at least not be able to stand still like they do. I don’t know, maybe you’re right though