Questions about Rotation (video)

A fantastic demonstration of and discussion of Rotation by Per Tengstrand, Håvard Gimse and Romuald Sztern from Helsingborg Piano Festival 2007

Some quotes:

"The movement originates in the two bones of the forearm" (radius and ulna)...."

"... the degree of ... using the fingers is ... personal. If you see five pianists doing a really good tremelo they will use the fingers (a different amount). You have to find your own way (by experiment)."

"There are elements of this movement in all kinds of passages ... as soon as there is alternation between two parts of the hand..."