Twisting Your Technique
The martial arts are called martial arts because they are just that, AN ART. Correct Taekwondo technique has nothing to do with muscular ability. This means that a 12 year old girl should be devastating if she practices the martial art correctly.
The art of Taekwondo boils down to excellent technique. One of the key areas of having excellent technique is remembering only to twist your weapon and reaction force arm at the last second. This is where the damage of your technique is caused.
Students who just swing their delivery arm from A to B without any real thought of technique are basically using brute strength and pushing instead of blocking correctly. By twisting your wrist or knife hand just before the moment of impact you automatically deflect the power of the attackers movement so there is no need for you to take your own technique past the intended target thus keeping your vital areas protected.
Remember: The most important thing to get right is your preparation position before you execute your technique. If you are confused about where your technique should start remember that it has to twist at the end so your starting position should be the opposite way round. See the downloads on help and advice on getting correct technique.