Posture and Equilibrium How should posture be defined? What are its behav ioral goals? Posture is essentially the relative position of the various parts of the body with respect to one an- other(the egocentric coardinate system) and to the envi- ronment(the exocentric coordinate system). A third frame of reference is that of the gravitational field(the geocen- tric coordinate system). The orientation of a body part can