Normally inside the body of the doll, there's skeleton to support  to avoid body twisted and falling down.  The skeleton determines the durability and weight tolerance of the body. Different skeleton designs determine the movements of the doll.
please see the below pic to show the skeleton how it work.

     We offer two kinds of skeleton with difference cost. The main difference is one can shrug and another  one can not.Please see below the difference.

   When you try to  move the doll,need to be noticed that there's movement limit.