The Art of Reversal

[Yeung]

Kai-he (open and close) are two separate movements with separate sets of muscles. Unless you mean stretch one set of muscles and return to the original state, and continuity in open and close is another issue that you might come across as well.

[robert]

Or think a little more abstractly. If the jin (muscle-tendon/soft tissue of the body) is connected it becomes one. The jin is the substance and opening and closing are functions. In stillness it is one, in movement yin and yang separate. Just an idea ...