You try standing in this position . . . for this long . . . on a rotating platform . . . without moving. Makes you appreciate art models!
The first part of the video shows the little adjustments that are made to the pose while the director tries to get the pose the way she wants it. Then Ana has to hold the pose through a spin. At the end of the video--this may be the most interesting part--she works out the stiffness from holding the pose.