Sometimes ago I read a very interesting book called The Gift of Fear by violence prevention professional Gavin de Becker. A bestseller by the way. In addition to other interesting materials Gavin talked about the inadequacy of common martial art training in learning self-defense for the average citizen. Self-dense here means staying unharmed from violent attackers, rather then having (and winning) a fight with someone in a bar! For those who can't stand the vigor of Muay Thai like tournament fights (meaning most of us), the best option seems to be training in a dojo or gym context, i.e. common martial art training. Gavin has some good advice.
Gavin's view is that in a training situation, the trainees are trained not to harm instead of harming his opponent(s). His advice is for a common citizen to learn self-defense under special courses in simulated real-life situation with protected gears. The final test is a unexpected attack by faked assailants with hidden protective gears!
Fair to say, common martial art training can tune up one's body ready for fight. But that is not enough. Apart from Gavin's valid point stated above, there is the case of assailant(s) surprised attack, or ambush. In all sports where speed is important (like ping pong, tennis, and of course ring fights), the contestants will move constantly (usually left and right). In a real life attack situation, there is simply no time or chance for the victim to move about! It is where benefit of some chi-kung training can come into play.
The Grandmaster of I-style Wang Xiangzhai used to say something like "Try attack me by surprise, and you'll know the power of my martial art". And the famous Bruce Lee liked to demonstrate his surprise attack from a motionless state with his opponent frustrated not being able to intercept his attacking arm. Both had been trained in chi-kung and internal martial art. Their training (of course they were among the very best) allowed them to move speedily from a motionless state. With some proficiency in chi-kung training, a practitioner can get that split second advantage that may allow him to avoid danger that comes its way by surprise, and hopefully may allow him to see an opening in his assailant that he can take advantage of. Needless to say, some professional training along the line suggested by Gavin will be essential for successful application. According to Gavin, there is also an essential element of fear that one needs to overcome, and one should also use it as a stepping stone to turn one into a fierce counter-attack (aiming at the attacker's most vulnerable spots).