Fascia provides a connective network between each and every part of our body, from muscle to tendon to ligament to bone to nerve and so on. The recent researches indicate that fascia is able to actively contract and may thereby influence musculoskeletal dynamics (Fascia Is Able to Actively Contract and May Thereby Influence Musculoskeletal Dynamics: A Histochemical and Mechanographic Investigation, Robert Schleip, etc. Frontiers in Physiology, April 2, 2019). Chinese understood this secret few hundred years ago. It is a well known secret in Chinese Martial Arts practitioners that the fascia is the source of power. The following diagrams illustrate the four different ways to utilize the myofibers (muscles) and fascia in combination.
YJJ exercises were designed to use the fascia to actively lead the movements. Take a look the videos I posted for the 11 different YJJ movements. Each move was initiated by the tail bone, rocking the pelvis, swing through the spine, and eventually delivered the energy to the palms, feet, and head. All the YJJ movements follow the Item D: Actively loaded stretch, as illustrated in the above diagrams.
The beginners usually move the arms and hands too much, but with less engagement in the fascia and core muscles. It is because we are used to use our skeletal muscles to work, as illustrated in Item B: Usual muscle works. Extensive training is required to use the fascia to lead the movements because the fascia is not part of the somatic (voluntary) nervous system.
Let me know how you sense the progress in learning the YJJ movements.