When iron palm training is done correctly there should be no loss of sensitivity in the hands. A common misconception is that the constant training and hitting of the iron palm bag damages the nerves in the hand. Some martial artists do train in this manner, but it isn’t healthy, nor is it correct iron palm.
The object of iron palm training is not to turn the hands into clubs. Proper iron palm training allows the hands to maintain full sensitivity. Even someone who has been practicing for 20 years should still be able to feel the slightest sensation, such as that of a tiny bug walking across his palm or fingers.
Remember that iron palm training is not just hitting the iron palm bag as hard as you can. In most cases the hands are “dropped” onto the bag. Proper training also involves qigong (chi kung) and dit da jow (external liniment) which helps to not only protect the hands but also help repair any damage that may have occurred during that day’s training session.
The rule holds true for any form of “iron” kung fu training. Iron body practitioners who do iron forearm training, for example, should still be able to feel the softest sensation on their forearms even tho they are now also able to block and absorb powerful strikes on their forearms without experiencing pain.
In fact, this concept can be used as a gauge by which to evaluate a potential iron palm instructor’s credentials. For example, if your teacher tells you that you must sacrifice the sensation in your hands in order to develop iron palm, you might want to think about looking elsewhere for instruction.
It is this which makes iron body and iron palm training unique: as a result of the training, the body is able to both absorb more damage and deliver more damage, but sensitivity is not lost.