Seiken
Before one can punch, one must learn to make a seiken (literally: “proper-fist”). You will break your hand if you do not learn this. Often, when new students are asked to made a fist, they do something like this:
[a view of a bad fist, with the thumb inside the fist, from the palm side]
Punching someone like this is guaranteed to break your thumb, and probably a few other fingers too. To make a seiken, curl your fingers individually, from smallest to largest, and then wrap the thumb around the outside of the fingers. Twist the wrist slightly, so that the first two knuckles are perfectly in-line with the forearm. When punching, the only allow the front of the first two knuckles makes contact with the target, as this is the hardest and most robust part of the hand.
[Photos of a proper fist from seiken from bottom, front, side, top]
Curling the smaller fingers first results in a tighter fist that helps protect the many small bones in your hands. In addition, it pulls the smaller fingers farther down the hand, so that the third and fourth knuckles will not make contact at all. Punching with the smaller knuckles of the ring and little fingers is to be avoided at all costs. The wrist and forearm offer no support behind these knuckles, leading to boxer’s fracture, a break of the third and fourth metacarpals.
It is not possible to form a seiken with long fingernails; their length will prevent you from clenching your hand tightly. Though long fingernails can be used to scratch an attacker, gaining the ability to deal superficial scratches is a poor trade for losing the stopping power of karate techniques. It is in your best interest to keep your nails neatly trimmed.
The back of the hand should be parallel with the forearm. Beginners for some reason, either twist their wrists up or down when punching, causing a painful (and entirely preventable) jamming of the wrist. Keeping the forearm and the fist straight and level with respect to each other will keep you safe.
[photo illustrating proper and improper wrist orientations (from the side)]
