When microfractures occur, bone is remodeled by cells called osteoclasts and osteoblasts. The osteoclasts remove bone, and then the osteoblasts come in and deposit the building blocks for a stronger bone. When the bone has been damaged, the osteoblasts deposit a dense, honeycomb structure which will be stronger than before. However, if the bone is not given an opportunity to heal, the osteoblasts cannot heal the bone fast enough and the microfractures will be a point of weakness. This delicate balance is the key to Iron Hand.
Iron Hand can be used to develop any hand strike, but if we take the example of a normal punch, the bones in the knuckles will harden and the skin covering them will thicken. The nerves of the knuckles will also become desensitized, allowing for harder hits without as much pain.
If this is done incorrectly, a larger fracture in the knuckles or a buildup of scar tissue may occur, disfiguring the hand or limiting knuckle mobility. In fact, Shaolin Kung Fu Academy says in their manual that, “If there is any blood on your hands you fail and take 100 days break. If you lose a fingernail or even break a finger your training is over.” By practicing Iron Hand, you are gradually strengthening your body, not looking to scar yourself.
There are a few variations of Iron Fist, but they are all based on the same principle. You start by hitting a softer material and gradually build up to a very hard material such as rocks or iron pellets. If you can repeatedly hit the hardest material without damaging your hands, you have achieved Iron Fist. However, continual practice is still required to maintain this level throughout your life, and more repetitions are required for higher levels of Iron Fist.
Shaolin Kung Fu Academy uses five containers progressing from hot water to beans, soft sand, course sand, and finally rocks. Even before using the containers, a student is required to be proficient in several exercises, which are to be used as a warm up for the task. These include meditation, bag work, and hitting a sand pillow.
The traditional method is more difficult, but in the modern method, a student will hit each container 100 times in 100 Chinese seconds (slightly longer than Western seconds) with 100 seconds break in between. This achieves level 1. The highest level requires hitting each container 1000 times in 1050 seconds.
Not only are speed and endurance required to reach this level, but the manual again warns that “any visible damage, blood, skin scrape or such immediately stops the exercise, and you are not allowed to resume until the damage is totally healed without visible damage or scarring!”
This technique is called Iron Hand because it can be used with any striking configuration: punches, fists, open hand, fingers, or claws. However, some configurations, like scraping fists, are not recommended. Many practitioners choose an open hand called Iron Palm because it is less likely to cause long-term damage and stop the training.
For Iron Fist as we imagine it in the West, a student would use a normal punch with the thumb curled under the fist. To avoid breaking the wrist, the inside bone of the arm (the radius) should be lined up with the index and middle finger, and those two knuckles should be the striking area (what we call the “ram’s head”). Since the knuckles of the index and middle finger are the main points of contact, a lot of force is concentrated on a small area. This makes the possibility of injury higher, so anyone attempting this method should be very careful of scarring or broken knuckles.