Postural control can be defined as the control of the body’s position in space for the purposes of balance and orientation. A definition of balance is the ability to maintain or return the body's center of gravity within the limits of stability that are determined by the base of support (i.e., the area of the feet) .while spatial orientation defines our natural ability to maintain our body orientation in relation to the surrounding environment, in static and dynamic conditions. Maintaining balance encompasses the acts of preserving, achieving or restoring the body center of mass relative to the limits of stability that are given by the base of support ,which implies the control of posture in preventing falling. Then, in order to modify motor responses on the basis of sensory input, the appropriate responses to any external or internal perturbation have to be chosen/Nevertheless, to maintain stability, all movements that affect the static and dynamic position of the center of mass of the body must be preceded or accompanied by adjustments of other segments. During upright stance, balance corrections appear to be triggered by signals presumably located within the lower trunk or pelvis and sensory feedback is required from vestibular, visual and somatosensory origin. A bipedal stance position that provides good stability is maintained mainly by efferent ankle mechanisms; to minimize the effect of perturbations when segmental oscillation is allowed, hip mechanisms are used. Locations of the center of gravity at the borders of the limits of stability correspond to the region where balance cannot be maintained without moving the feet
