I guess this could have gone in quite a few of the different topics as it is concerned with any movement or any form
I was watching a clip of someone doing what we call in TKD as 'san Magki" or "w-shaped block" i have seen a similar movement in Karate kata, basicly you are in a horse stance with your hands out to the side of you kind of like you are holding a barbell and preparing to do a squat.
the movement can be seen during this form
so in the TKD forms (sorry but i am not sure of the kata movement) there is a big180 degree step, from one horse stance to another and the arms move at the same time. when the instuctor was demonstarting the application he broke the movement and had his arms moving independantly of each other in a block and forearm strike technique, apart form the obvious problem of body mechanics i.e. the hips became disconnected with the movement, he had changed the principle of the movement to something that maybe he thought was easier to apply.
i accept that sometimes because you are applying a movement to a person rather than to the air there might be some changes and some fo the kata/pattern movemts have changed over time and sometimes we change them back one example of this would be high kicks. but how much can we change the movements of the forms to apply them? if we find ourselves changing them too much surely then it is a different technique, or have some movements been changed and formailised so much that is has to be changed to apply it.