Old school, Chinese KF folklore stuff. Fong Sai Yuk (played by Jet Li in The Legend) was supposed to be trained in "Iron Shirt", exaggeration is that those who train this is impervious knife attacks. It's still out and about today across other Eastern MA, but mostly for the mystical bits. Muay Thai and the infamous bottle/bar rolling across the shins. I remember as a kid, punching and eagle clawing sand bags. "To harden and toughen my fingers and knuckles". We would also do a lot of forearm clashing. Kinda light taps, but enough to cause bruising at the end. it's just....conditioning, but the idea being ramped up into magic tricks. Saying that, will never understand the idea of smashing concrete with a headbutt.
Here's a very good (or bad rather) example There was a lot more to this. The guy was on something, and he had quite a few Officers on top of him and he was unfazed by baton strikes and even taser. The baton strike was to his hand with the knife, which apparently broke the hand but he was still able to grasp the knife and stab away.
This happened in america. Why one cop carries 145 rounds of ammo on the job So what is the consensus? Can practicing iron body make a person baton impact resistant?
Uhh....yes and no? Conditioning in general goes a long way. Again you got the outlyers and the "tricks". People who are able to ram fingers into melons, chop coconuts, baseball bats to the shin/foot/thigh/head/shoulder. But if Iron shirt really works...then everyone would be doing it.
Also if you are: Prepared for the strike Know where the strike is going to Aren't actually fighting. Seems that it's a demo trick more than anything else. Remember when yi long did this? Yi Long KO
We used to do destruction in the KF club I trained at. Concrete blocks and roof tiles. After nearly breaking my wrist on a 2 block break (I broke the top one), I found out later that the blocks should be dried out so they are brittle. (I left mine out on a cold wet winter night). Lots of tweaks to make the display look more than it is.
From what I understand. Strike Once, Strike Hard. Easier to argue reasonable force if you go for the 1 effective hit.