Wudang Taiji and Taiyi concepts include the principle of “Qi” or energy transformation. Qi is a power we can all use with our intentions. The mastery is about the efficiency of the Qi transmission.
I will try to explain it in the most practical way with ordinary bicycle gears:
From the inner movement
Like a bike we need a lower gear to get a feeling for faster movements or else it will be over in an instant. This internal mechanic is the reason why Taiji is performed more slowly than Gongfu. The correct speed comes from the control and mastery of each inner movement. However, we do have few fundamental principles about how slow and how fast we can be:
Breathing according to movements
Breathing generates power which we can use for our actions, and we cannot move slower or faster than we create power through our breathing technique. This process is also why Qigong mastery is essential for the understanding of advanced Qi transformation.
Relation of movements
We learn that all energy comes from the Dantian (energy center). Through our intention, we can control Qi from the Dantian to our movements. Energy (Qi) is always divided between Yin and Yang. Therefore every movement has the opposite Yin -> Yang, Yang -> Yin. To control Yin, we also need to manage Yang and to control Yang we also need to focus on Yin. This relation is the foundation of Qi transmission. However since Yin and Yang can never be the same value, it is the opposite. The inner movement can therefore never be in the same speed/power relation. Like the connecting chain in the bicycle gears, we generate more power over smaller gear wheels than with larger ones. Ignoring the relationship of the gears and the connection of the chain can break the inner movement and make the energy transmission inefficient. The speed and execution of Taiji, therefore, is slow and interconnects with the relation of internal and external actions.
The principle of energy transformation can be applied to everything. Taiji simply is one of the most standard practice for further understanding. In Gongfu, for example, we can use more power more quickly. Like the picture above shows us the use of the same power and the amount of achieved distance.
Now it should be more clear why “internal” masters practice Taiji very slow and execute Gongfu explosively fast. These principles are essential for Wudang and any other internal martial arts. Often you see fancy Taiji and Gongfu performances. While there is a lot of interpretation freedom, the principle of energy transformation cannot be skipped, and it does show the mastery level of power and control.