Changing the position of MIRD Human phantom

Dear Geant4 users,

I am newbie to Geant4

I am working with the MIRD human phantom provided by the Advanced examples of Geant4 to calculate the the deposited energy and equivalent dose of human being in a room within radioactive source

Any way, my question is : How could I play with initial position of the human by changing his situation of sitting …
Thanks in advance