When people think about what they would need to do if they ever had to defend themselves, punching their attacker is usually at the top of the list. Unfortunately, unless you have a lot of training and experience, you're more than likely to be hurt more than the person you're defending yourself against.
There are several reasons for this. First and foremost, most people aren't trained or experienced at throwing a punch in general, and punching a hard surface in particular. Without this training and experience, most people will instinctively try to punch their attacker in the face/head. With training and conditioning, this isn't that bad of an idea. A head strike can slow down, stun, deter, and even possibly knock out the "bad guy". Where the problem comes in is a result of not having that training and conditioning.
The main problem with a punch in general comes down to knowing how to make a tight fist and making sure your wrist is locked at the moment of impact. Bruce Lee said it best when he stated, "There are no wrists in boxing." If you've ever seen a boxer before they put their gloves on, you'll see that they have their hands and wrists taped. This isn't for show. It's to allow the boxer to hit their opponent as hard as they can without causing damage to their fists and to keep from tweaking and/or breaking their wrist if they hit their opponent wrong.
If you don't lock your wrist when you punch a surface, you run the risk of having your wrist buckle from the force of impact. This buckling can cause either temporary or permanent damage to the wrist joint due to stressing the joint beyond it's operating range. Whether the surface you're striking is hard or soft is irrelevant. The act of striking is what's relevant.
Where the hardness of the surface makes a difference is how conditioned your hands/fists are. If you haven't done any type of conditioning exercises to toughen up your fists/knuckles, then striking a hard surface has the risk of breaking your knuckles. I've done that at least once in the past myself. At one time, I could punch through 2 inches of pine boards without a problem due to the conditioning I was doing on a regular basis. How I broke my knuckle was that it had been several years since I had been doing the proper conditioning exercises and on a whim, I decided to try and break a board by punching it. Didn't work out so well for me. It took around 2 months for my hand to completely stop hurting. If I had been called upon to defend myself during that period of time, I would have been at a severe disadvantage.
With all that being said, in my opinion, for almost any self defense situation, a palm strike is usually the better option to go with. There are a lot of reasons for this. First off, you take your wrist right out of the equation. With a proper palm strike, you have no wrist involvement at all. What I mean by this is that the striking surface is the meaty portion of your hand where the bones in the forearm basically terminate at the hand. Now obviously I'm leaving out some of the finer structure of the hand/wrist/forearm out of the equation, but in a very general way, what I'm saying is accurate. There's a lot more structural integrity when hitting a surface with your palm. There's also a higher level of pain resistance and toughness involved with this type of strike.
One example that I've seen used repeatedly is the question of which would you rather do, punch a brick wall or hit it with your palm. You can more comfortably hit a target with more power using your palm over using a fist. You're also much less likely to hurt yourself, allowing you the ability to strike more times if needed. Another benefit of a palm strike is you have more options with your striking. With a punch, if your forearm and fist aren't in direct alignment with the angle of attack, you can't apply as much force behind the attack. With a palm strike, you don't have to be quite as picky.
I'm not saying that a punch should never be used. It works great against soft targets like the stomach, bladder, or kidneys. It's just that without practice, you're more likely to hurt yourself and leave yourself without the use of some of your natural weapons. With a palm strike, it's very unlikely that you're going to hurt yourself, even if you don' t have a lot of practice under your belt. You'll also have a higher level of relaxation when using a palm because of the structural dynamics of the strike. With a punch, you normally have to have your forearm, wrist, and fist tight when striking. This introduces a higher level of tension in your arm. With a palm strike, almost none of that tension exists. The only tension that's produced at the point of impact is bending your hand far enough back so you don't hit with your fingers.
One final benefit of using a palm strike over a punch again comes back to training. With little or no training, you're more likely to "pull your punch" when actually punching because you unconsciously trying to keep from hurting yourself since this isn't a normal way you use your hand. In other words, because of the lack of familiarity with punching, your sub-conscious mind is going to prevent you from apply your full force behind the strike. On the other hand, since most people have experience with hitting stuff with the palm of their hand, i.e. slapping something, pounding on something with their palm, etc., their sub-conscious knows what to expect and has a better idea of how hard an impact you can apply before you cause injury to yourself.
So if you're ever in a situation where you have to defend yourself, you are better off using a palm strike instead of a punch. Let's just hope that you're never called upon to make that kind of choice.
