Dear Tabby, One of my teachers, William CC Chen, learned an iron shirt nei kung set from Prof Zheng. William now discusses this publicly but won’t teach it, won’t describe it. Nigel Sutton and his students in the UK and Southeast Asia claim to teach it. I have been fascinated by it for decades. Do you have any idea what it is? Apparently it came from a master named Zuo Lai Feng.
This questioner probably knows more about this subject than I do, but here's my lousy few cents. First some background. I don't really hold with the whole iron shirt thing. It sounds like a great idea, but I've done a lot of catch-as-catch-can stealth training in Filipino kali/escrima type of stuff over the decades and one thing many of them say that kind of stuck with me (so to speak) is every hand a knife.
So depends what the effect of the Iron Shirt is supposed to be. If it's mainly to toughen against punches and kicks, that doesn't ring my bell because, well... 'every hand a knife'. A knife is so easy for an experienced guy to conceal and instantly deploy. There's no percentage in training a mindset of taking a punch (or having somebody hop down on your stomach from a chair!?) only to find yourself sliced to ribbons by the first shank that comes along.
Be water my friend! Water doesn't try to be a macho tough guy and "take it". Just yields, deforms and reforms, evades and survives to fight another day, as will be beautifully exemplified in forthcoming great training film from my friend Vladimir Vasiliev "KNIFE IN A FIGHT". Watch for that.
In the meantime though obviously I don't hold with Iron Shirt, I will say I've seen the punch version demonstrated many times in Russia (though they don't call it Iron Shirt). Mikhail has tons of guys who can take any kind of punch from hardass fighters who are UFC type MMA champs in their own homelands They showed this easily and casually many times.
Of course, there's also the 'hard qi gong' schools which have guys bending bars over their arms and spear points into their throats and so on. I don't know if that fits the definition of Iron Shirt or not but I doubt its a very practical skill. It seems like in these demos everything needs to be set up and positioned just so for it to work though I do admit this kind of thing if real would be closer to my idea of Iron Shirt which needs to address that 'every hand a knife' thing.
Prof. Zheng also had a student, a real old scrawny guy, who could take any kind of punch from anybody. There's a photo of Robert W. Smith punching that guy published somewhere. But my teacher told me that one day te Prof himself saw the guy doing that and sternly admonished him to cut it out because someday he''d meet up with somebody who really knew how to hit and it'd be game over. Prof then demonstrated with a light finger poke that instantly put the guy down on his knees.
Anyway William Chen was originally very close to Prof, but later not so much. My teacher on the other hand was always absolutely close stuck like glue to Prof and never deviated one hair from his teaachings. As one of the Prof's very first Taiwan students, I tend to believe my teacher when he tells us that all this endlessly whispered Zuo Laifeng stuff is totally irrelevant, and that there never was any secret nei gong held off the market by Prof.