Postural changes accompanying voluntary movements. Normal and pathological aspects.

Voluntary movements are the source of a perturbation of posture and equilibrium. They are accompanied by postural adjustments which show three main characteristics: they are "anticipatory" with respect to movement and minimize the perturbation of posture and equilibrium due to the movement; they are "adaptable" to the conditions in which the movement is executed, they are influenced by the instructions given to the subject concerning the task to be performed. The central organization of the postural adjustments associated with movement is still largely unknown. The possibility is examined that a "repertoire" of postural adjustments exists; the possible sites of the repertoire are discussed as well as the level at which the parallel or "sequential" control of posture and movement might be organized.