To maintain stable body balance in daily activities, the ability to respond to external perturbations is an essential factor. Such capacity is limited in pathological conditions, such as in stroke, in which postural control is impaired due to lesions to the central nervous system. Impairment to postural control increases body sway during upright posture and leads to augmented frequency of falls. In this sense, the identification of mechanisms involved in body balance disorders after stroke is particularly important in situations of postural perturbation. The purpose of this project is to evaluate reactive postural responses to unpredictable external perturbations, analyzing postural dysfunctions caused by lesion to different brain areas as a result of stroke, and test principles of dynamic body balance rehabilitation.

Inclusion Criteria:

• Inclusion criteria are as follows. Healthy participants: absence of detectable neurological or physical malfunction which might affect postural control, no use of drugs affecting body balance and preserved mental capacity. Stroke patients: capacity to sustain independently orthostatic posture for at least 5 min. and preserved mental capacity.

Exclusion Criteria:

• Exclusion Criteria are: no orthopedic malfunction, no clinical instability associated with systemic disease, no use of drugs affecting body balance and presence of "pusher syndrome".