After more than twenty years of martial arts training, I can confidently say that I've learned some highly effective self-defense techniques.
My favorite: run away from trouble. Second best: walk away from trouble. Third choice: defuse trouble from where you are.
These approaches, of course, aren't what most people are looking for when they join a martial arts class. Punching, kicking, grappling, throwing, submission holds -- that's what sells in the worlds of karate, aikido, judo, tae kwon do, jui-jitsu, boxing, and such.
What's most effective, though, in the real world?
Not the dojo (training hall), boxing ring, wrestling mat, or wherever, but the parking lot, sidewalk, bar, walking path, or other locations where ordinary people are most likely to get into a confrontation with somebody who could do them harm.
Sam Harris, he of "The End of Faith" fame, has quite a bit of martial arts experience. On his web site, Harris has posted some interesting articles. The Truth About Violence discusses three principles of self-defense that make a lot of sense.
Principle #1: Avoid dangerous people and dangerous places.
The primary goal of self-defense is to avoid becoming the victim of violence. The best way to do this is to not be where violence is likely to occur. Of course, that’s not always possible—but without question, it is your first and best line of defense. If you visit dangerous neighborhoods at night, or hike alone and unarmed on trails near a big city, or frequent places where drunken young men gather, you are running some obvious risks.
...Principle #2: Do not defend your property.
Whatever your training, you should view any invitation to violence as an opportunity to die—or to be sent to prison for killing another human being. Violence must truly be the last resort. Thus, if someone sticks a gun in your face and demands your wallet, you should hand it over without hesitation—and run.
If you look out your kitchen window and see a group of youths destroying your car, you should remain inside and call the police. It doesn’t matter if you happen to be a Navy Seal who keeps a loaded shotgun by the front door.
...Principle #3: Respond immediately and escape.
If you have principles 1 and 2 firmly installed in your brain, any violence that finds you is, by definition, unavoidable. There is a tremendous power in knowing this: When you find yourself without other options, you are free to respond with full commitment.
This is the core principle of self-defense: Do whatever you can to avoid a physical confrontation, but the moment avoidance fails, attack explosively for the purposes of escape—not to mete out justice, or to teach a bully a lesson, or to apprehend a criminal. Your goal is to get away with minimum trauma (to you), while harming your attacker in any way that seems necessary to ensure your escape.
Notice: no mention of dramatic fighting techniques.
Not even Brazilian jui-jitsu is going to do you much good if you're attacked by more than one person and end up doing your submission hold thing on the ground while the guy's buddys hit you over the head with a baseball bat, then steal your wallet.
(See Harris' favorable, yet cautionary, take on jui-jitsu here.)
This is one reason why I've come to enjoy Tai Chi so much. After thirteen years of "hard style" martial arts training, I switched to Tai Chi about seven years ago. No regrets. Tai Chi can be a kick-ass martial art, or a great way to promote health through body-friendly graceful movement.
The flowing and circular moves of Tai Chi resonate wonderfully with Sam Harris' third principle: respond immediately and escape. In a Tai Chi class students learn how to meet aggressive force with receptive emptiness, deflecting and defusing an attack by moving flexibly with an opponent's energy.
Push away, then head in the opposite direction. Throw off balance, then run. Pull past, then head for a safer spot.
These techniques are simple; easy to remember; suitable for almost everybody. If attacked, don't fight. Run like hell. After throwing your wallet or purse behind you. This won't get you a role in a martial arts movie, or gain you cage fighting fame.
But it could save your life, which is a lot more important.
(Here's a knowledgeable and well-written examination of Tai Chi's martial roots, Supreme Ultimate Boxing: Considering Tai Chi Chuan In Its Original Martial Context.)