One of the questions you get as a karate instructor is does this really work? It is a strange question because you spend a lot of time teaching a student the basics, how to kick, punch, stay out of striking range until they are ready to strike and then they pounce! What do you mean does this really work? I should say it is a strange question to me because I have had the experience of it really working.
A bit of back ground is in order. As a fledgling karate student (before much formal training) I use to break boards, read books, watch TV shows and movies and tried all of the stuff… most of it worked but I had no idea of how to pull it off in a confrontation. I got lucky a lot – stuff that should not have worked – did because I was a young – fast – strong buck.
So the question is more how one teaches the techniques and if taught correctly – can the students pull it off. Here is a funny satire on self-defense moves that in my opinion should not work (at least the way they are demonstrated). Enjoy this and will dive into this subject. 
This video was humorous and the people probably thought they were doing good showing women a few moves. I would argue that the context is horrible. Although elbows and hammer fists are good strikes – one needs a bit more preparation to pull it off.
The style of kenpo karate I teach has 240 self defense techniques (a lot more if you include variations). While I cannot speak for other martial arts styles I have to believe like mine – done properly the techniques really work. I come from a back ground after sparring in the school, fighting at tournaments and fighting while working as a bouncer – this is not a question of if it works – but rather a question of proper training and confidence.
Techniques are created to show students some common was of countering or escaping attacks. They do not change physics however. In karate a bigger, stronger man with equal training will almost always beat a smaller, weaker man. There is no political correctness in fighting – only the best man, woman, or child wins.
So why bother teaching techniques to smaller men, women, and children? Because martial arts are not all sport matches where there are rules and judges with weigh-ins to assure a fair fight. There are no rules in self defense! That means acting, deception, use of weapons, running, and such are all effective strategies in some instances. When someone attacks you – you do not owe him/her fairness!
So when I teach women and children self defense techniques (understand I teach a martial art – not short-term “self defense” classes), I stress all of the stuff that a student has to learn first such as stance transitions for power, proper striking positions, how to cover up and situational awareness. You see a 90 pound girl will not best a 200 pound man in a “fair” fight but rather faking fight and exploding with her moves when she sees an opportune moment!
But that will not even work if she does not know how to throw a elbow or hammer fist with speed and power! It also will not work with pretend attacks where the bad guys lets her off easy. That only perpetuates a false sense of security. That does no good to anyone.
So forgetting about the size difference critique one hears – the other thing I hear is the techniques are so complex they would never work – who could remember what to do if attacked? This is always the what if questions that makes even less sense then the PC I am woman critique.
If someone has ever wrestled – they know the moves are practiced. If someone tries for a certain grab – the experienced wrestler goes for a counter move. He may have a bunch of options but he may favor certain defenses or he body length might work better for certain defenses. Karate is the same thing – you learn examples of ways to counter moves – but when you have to practice – you have a starting point – that you can combine however it make sense.
I remember a cop asking me what I used to knock people out with? I answered whatever he was open for – hand – foot – either side – it did not matter. You see I did not have a pre-conceived plan before I started. I had practiced so much that my body knew how to throw kicks, punches, blocks, various strikes and escapes – I just went into automatic and my eyes saw openings.
So when you get the “what if” questions from students – tell them to practice their basics, learn the mechanics of the move, learn to do them fluidly (at least the ones they like) and let the rest just happen.
I should say the “do techniques really work” question is more properly a question for a short-term self defense instructor because you cannot become good at fighting in a short term class… I guess it is better than nothing though.
I hope you enjoyed my take on self defense techniques! Now I’m going to practice my Aerobic Self-Defense. (just kidding).