Yang Cheng-fu changed the original Yang Lu-ch'an form that he received from his Father the most that it could have been changed without losing the original essence. In fact, Cheng-fu, in one of his books (written by Chen Wei-ming, as Yang was illiterate), he stated that to change the form any more than he changed it was to bring disaster! Students of Yang Cheng-fu who weren't particularly good students, then came after him and did exactly what Yang had said not to! They changed his form so that we Westerners could do Tai Chi in the park while eating our hamburgers in our lunch break! The Chinese Government went even further and had an old friend of mine, Wang Xin-wu invent even more shortened forms so that Tai Chi could be put into tournaments and be standardised!
So Yang Cheng-fu's words were never heeded and indeed much of Tai Chi today has gone down the "disaster path" just as Cheng-fu had predicted.
I hear from so many who have been practicing shortened forms of Tai Chi for many years who are beginning to get ill for no apparent reason. Then when I tell them about shortened forms and why they shouldn't do them, they begin one of the original longer forms and hey ho, they get well again.
So why does this happen? Aren't we only doing a set of exercise movements? No, of course we aren't, we are not only doing simple movement, we are also activating and enhancing the energy (Qi) flow in the body through the 12 main and 8 extra acupuncture/dim-mak meridians. This doesn't happen of course if you are only beginning as you are only doing a set of exercise movements. however, when you begin to get more advanced and the energy kicks in, this is when people who do shortened forms get into trouble health wise.
The reason is that the Tai Chi movements have been developed by family generations of genius in the field of body energy and movement. These Masters knew about how the Qi flowed through the body because of their TCM (Traditional Chinese Medicine) background. They invented a series of movements that would work on the exact same flow of energy that is activated during a 24 hour period when the Qi flows around the body every and is activated in each meridian each 2 hour period. Each movement was meticulously placed in the set of movements to represent each organ in the body and which of those organs were activated by the Qi in a 24 hour period one after the other. So when we practice our Tai Chi ch'uan form, we are actually causing the Qi to become activated in those meridians an extra 3 times! The amazing thing is that when we finish the Tai Chi form or set of movements, where our Qi flow and activation should have been at that time of the day, is exactly where it should be with nothing out of place! This is why Tai Chi is so good for health, not because of the exercise, but rather what it does for the whole body energy system.
So if someone was to perhaps change the set of movements, placing "Single Whip" posture for instance in a different place and coming after a different posture, this upsets the natural flow of energy. If we were to then leave out certain groups of movements in order to shorten the form, such as "Grasping Swallow's Tail" because that set is repeated 8 times during the form, we also upset the natural flow.
The main aim in our Tai Chi practice is to try to emulate the internal flow of energy with a set of natural movements. So we do a posture that works upon the Colon, then we do a movement that works upon the Lung etc. So if we change these postures around, and our movement is linked to our internal Qi/energy, we will upset that balance because our movement is no longer flowing from one organ to the next. And we then become ill over time, allowing external pathogens into the body because we no longer have protections.
The main excuse for doing shortened forms is that we haven't got the time. What? We can't find 20 or 30 minutes in the morning or afternoon? However, what we weren't told is that each third of the original Tai Chi set of movements represents a complete round of Qi/energy through each of the 12 main meridians! So, it is perfectly OK to stop after we complete the first, 2nd or 3rd third. The first third only takes between 3 and 5 minutes, so we have a perfectly balanced and health-giving short set of movements right there in the first third of the form! Or if we want a slightly longer work out, we could do the 2nd third only, or the final third. Much better of course to do all 3 thirds, but if you haven't got the time, this is the only safe way to go. No excuse for learning or teaching a shortened form such as Peking 24 or 48 or any of the Cheng Man-ching short forms. Go for an original long form and you will be much better off in the long run.