Hard Qigong is a secret method of strengthening the body with chi energy. A bit less physical than fake martial arts and more with bogus claims and pretense on some spiritual and self-development path. They claim to develop Qi to a level that allows performing "supernatural feats." Immediately using it as proof to a gullible and ignorant audience that their teaching is authentic because it gives real superpowers. They often devalue actual spiritual teachings and methods as fake, as they don't bring such incredible demonstrations of abilities. They often say that things they perform are deadly and dangerous, and I have seen one "Enlightened Qigong Master" say that he can bend a sharp spear with his throat, but his Teacher, who had trained for 50 years, can twist the knife with his eye. It is a blatant scam, and anyone selling this is either a mentally crippled being with IQ below the floor level or an impious devil incarnate who is intentionally lying and scamming people to gain financial profits and media recognition.
Iron Shirt Qigong followers are numerous and not exclusive to any particular tradition. You can find the same tricks being shown all over the world. Let's debunk them one by one.
Bending sharp objects by the throat - they are not piercing their throats. Humans have a very sturdy collarbone there at the base of the throat, and this is a thing anyone can do with no training, even someone's grandmother. No mastery over internal energy is required to perform this trick. Bending a knife or sword by eye works with the same principle as the trick above. "Grandmaster" pushes the blade against the skull eye socket instead of directly pushing it into the eye's middle.
Breaking bricks on the head, by Hammer, or any body part is not dangerous. Hitting the head with a hammer without bricks would be lethal, but having multiple bricks shielding and spreading out impact force not. This scam aims at people who don't have even the most basic physics knowledge.
Walking, sleeping, or standing on nails - ordinary people use it as a massage tool. Scamgong artists claim it is a superpower ability worth decades of training and extraordinary talent. If it were one sharp needle, yes, that would be dangerous.
Breaking stones by hands or fingers - the trick here is that an impact with another stone damages the fragile rock; even a 6-year-old child can do that; if you watch the videos closely, you will see that moment of a lifting.
Bending spoons is a 100% scam based on physics and friction. Otherwise, miracle metal benders would bend any metal, not just a spoon. Spoons and forks have a weak point, overheating under physical pressure until it becomes moldable.
Firewalking - is a useless activity. Anyone can do this. Prepared coals and feet soles poorly conduct heat. Walking on broken glass - big chunks of glass from bottles are not even remotely dangerous. The tiny needle-like particles you might find at home can make you bleed a lot and be painful.
Pyrokinesis - many salts and chemical liquids can cause fire after exposure to air or friction. While any demo can be faked this way, the one where "Master" puts his hand inside a pile of rubbish and moves it is the more obvious scam.
GrandMaster Wolf, a known charlatan, and scammer used a heat machine and cut out the soundtrack from the video to hide it.
Electrokinesis - several devices you can buy relatively cheaply that can produce lightning bolts (discharges) from fingers in certain conditions. Roughly a $20 device can turn a nobody into a John Chang and make it possible to scam fools out of their money.
Telekinesis - one funny case I can mention is that I have seen a "Master" who trained in meditation for 25 years, and he was showing how he moves with his hand a match stick on a thread inside a plastic bottle. This demonstration was a purely static electricity feat; anyone could do it without training or meditation. In many cases, telekinesis is a wind or heat movement.
Magnetism - is a superpower that works with things and physical objects, getting stuck on dirty and sweaty skin. It utilizes the supernatural law of friction, which is unknown to all who claim this ability.
Despite all the debates around it, Breatharianism - another superpower many scamgong masters from Yogi and Ancient Chinese claim to have, is the easiest to prove and debunk. Anyone who claims this ability is a scammer with no morals or principles. Sometimes people unknowingly delude themselves into thinking they have an ability or superpower. They truly believe it because they want to and have lost touch with reality. It is also a sign of weak cognitive function and Dunning-Kruger syndrome. If "Master" engages in scamgong activities knowingly and willingly, it is a big red flag. You are not dealing with anything even remotely spiritual here.
The whole thing about chasing abilities instead of developing spiritually and developing self is an egomaniac approach; those people rarely get further than half step in cultivation. It is understandable why this happens. Developing superpowers over a weekend seminar sells very well, jerking off Egos is profitable business, and those seeking to gain these feats are the prime consumers and enablers of scamgong. You don't want to learn real martial arts or spar with real opponents; you want to become Goku without sweating. You find any of the numerous fake martial arts masters out there to satisfy your needs and primitive urges.