I hope I'm not reading, in places throughout this thread, that Christianity is being blamed for being out-of-touch with what is really real, or possible, or present, in and with the human soul?
Jesus said that if we had faith the size of a mustard seed, we could say to a mountain 'throw yourself into the sea' and it would do it.
The unbendable arm, as an exercise, doesn't have a Christian equivalent since the mountain-into-the-sea thing can't be 'done' just to test God (expressly forbidden, that is), but the human part of the action is present in both--faith, ki, it has other names too.
I feel completely certain that once I've trained and learned, I will be able to toss an attacker around a bit and say, 'jump in a lake, mate' and it will happen.
Depending on how much ki I can put with my mustard seed, of course!