Inclusion Criteria:  Acute stroke group, subacute stroke group, and control group:  Age 50 to 80 years Affiliated with a social security plan Able to walk 20 meters unassisted  Acute Stroke and Subacute Stroke Group:  Stroke onset less than 14 days (for the acute stroke group) or between 14 days and 6 months (for the subacute stroke group) Stroke located in the left or right middle cerebral artery.  Exclusion Criteria:  Acute stroke group, subacute stroke group, and control group:  Person under guardianship or curatorship Refusal to sign informed consent Known rheumatologic or cardiologic history Medication that alters the vigilance and may affect walking (high dose psychotropic drugs, antispastic drugs).  Acute stroke group and subacute stroke group:  History of symptomatic stroke Previous neurological disease limiting gait, aphasia or impaired cognitive function (mild cognitive dementia, Alzheimer's or Parkinson's disease) Ambulatory functional category < 3 Control group: neurological medical history