Yo Mistah Bags,
Not entirely true on the stone. Real-life martial artists can break rocks with their hands. And not just the cement blocks -- I mean actual rocks.
Yes, I'm a martial artist. No, I can't do it myself. But my buddy showed me how he did it. It's a skill, just like anything else. You find the weak points, you learn how to strike at the right angle, and you practice pummeling things until you can do it without hurting yourself.
We're not talking about straight-on punches. Most of the time, you'd be doing hammer-strikes, which subject your hand to a lot less punishment and still deliver the appropriate force.
Again, not saying it's easy, and doing it is a lot less glamorous than stepping back and doing a massive kiai and then chopping the rock, or however people are imagining it, but with proper training, it can be done.
And if it can be done, in that limimted way, by a good martial artist who trains in it for a long time (and builds up a nasty callous on the heel lf his hand), I find it not implausible to imagine the Strong Hero, who is presumably going to be using a melee weapon and not just his bare hands, doing the same thing.
The ability isn't about mystical powers. It's about learning how to spot the weak stress points and strike them at the right angle to do the most damage. It's training, just like anything else.
-Tacky