Figure 1.
When a person stands while leaning forward, referent body orientation (RO) differs from the actual body orientation (AO). This leads to the generation of active moment of force (MACT) counteracts the moment (MG) produced by the gravity force (FG). A voluntary body sway is produced by a gradual shift of RO (shown with gray arrows). This scheme leads to several nontrivial predictions (see text).
