For several years, the postural disorders assessment in hemiplegic patients was conducted through force plate, using the center of plantar pressure displacement in a static position.

These are widely used in physical therapy both for assessment and rehabilitation of patients with balance disorders.

For hemiplegic patients, an asymmetric distribution support on each foot and an increased surface area of postural sways (more marked on the medio lateral axis) are observed.

These studies, based on the study of plantar pressure ,are not enough to providea full description of the spatio-temporal organization of postural components in hemiplegic patients.

Indeed, postural stabilometric evaluation is based on a simplification of the human skeleton by considering it as a simple inverted pendulum swinging on his ankles.

This simplified model can't be used in dynamic assessment because of the simultaneous contributions of several joints during movement. This restricts its clinical interest because patients are more exposed to imbalances and falls in dynamic situations. Thus, the hip angular movement results in a center plantar pressure displacementwhich is impossible to discriminate from the ankle axis movement using stabilometric signal only.

Thus, it seemed interesting to study another variable valid in dynamic conditions : the displacement of center of mass during a dynamic balancing task. This variable is obtained through 3D motion capture of the different segments of the human body. The dynamic test is a dynamic postural assessment following ball avoidance from three different directions. The center of mass displacement will be compared with a functional test known to be representative of dynamic balance of the individual capacities: The Timed Up and Go test (TUG).

All of this data aims to improve the hemiplegic postural assessment for physical therapy and to help develop new rehabilitative approaches.

Inclusion Criteria:

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For hemiplegic patients:

• Aged between 18-80 years of age, men and women
• Left or right hemispheric sustentoriel stroke :

oIschemic or hemorragic oFirst symptomatic episode or TIA without consequences oBetween one month and one year since the stroke

• Balance standing > 30 sec without assistance in closed eyes condition
• FAC score included between 3 and 7
• Triceps Spasticity strictly less than 3 on the Modified Ashworth Scale with heel on the ground and an adductor spasticity up to 3 on the same scale.
• Free, informed and written consent signed by the investigator and by the patient or one of his/her relatives (in the case of a patient able to understand the information and to express his/her consent but with motor difficulties resulting in the inability to sign)

For healthy volunteers :

• Aged between 18-85 years of age, men or women, age-matched ( +/- 5 years ) with stroke patients
• Without a balance disorder
• Affiliated to social security
• Free, informed and written consent

Exclusion Criteria:

For hemiplegic patients:

• History of event affecting postural balance (orthopedic, rheumatological, neurological, ENT ...) before the stroke
• Pregnant women
• Patient with tiredness incompatible with the tests and instrumental assessments
• Patients under legal protection (according to French law) and detainees.
• Patients physically or mentally unable of giving informed consent

For healthy volunteers :

• History of event affecting postural balance (orthopedic, rheumatological, neurological, ENT ...)
• Receiving a psychotropic treatment (antidepressant, antipsychotic, anxiolytic)
• Pregnant women
• Within the period of exclusion in the French national register of persons suitable for biomedical research
• Patients under legal protection (according to French law) and detainees.