Schizophrenia (SZ) patients with metabolic syndrome, patients with vestibular syndrome, and patients with borderline personality disorder, would benefit from physical activity (PA). Yet patient adherence to PA is low, at least in the case of SZ. the investigators work and the literature lead the investigators to consider that, in addition to motivational aspects, disorders of the bodily sense of self could play a role in this lack of adherence. Simply walking involves visual movements related to the self, which must be distinguished from movements in the environment. This means a distinction between self and not-self. Furthermore, these movements are all the more difficult to distinguish as they may also result from the fact that hidden objects become visible as a result of our own movement. In all sense-of-self disorders can themselves affect physical training, and the investigators will measure them in the first stage. In the second stage, the investigators will apply a standard, risk-free PA protocol by walking (3x3 sessions of 30 min). the investigators will test the impact of physical training on the sense of self under different conditions, with one environment minimizing self-related movement, vs. 2 environments with a variable level of enrichment (i.e. hidden objects inducing more or less self-related movement).

At the end of the protocol, the investigators will offer participants who wish to take part in an ancillary study, i.e. a walking session with mixed-reality goggles. These will superimpose a luminous flux on the periphery of the visual field. According to results obtained in the laboratory, this flux could restore sensory mechanisms impaired in schizophrenia. the investigators will use these glasses in the most difficult condition for the patient, and verify their impact.

Inclusion Criteria:

• Criteria common to all participants:
• Men or women aged 18 to 60 inclusive
• Subject affiliated to a health insurance scheme, beneficiary or beneficiary's beneficiary
• Able to understand the aims and risks of the research, and to give informed consent
• Visual acuity > 0.7 on the Freiburg Vision Test (Bach 1996) due to the use of visual equipment
• BMI (body mass index) < 40 (due to cardiovascular risk).

Patient-specific criteria:

• With schizophrenia: criteria for schizophrenia as defined in the DSMV (American Psychiatric Association, 2015)
• With borderline personality disorder: criteria for borderline personality disorder as defined in the DSMV (American Psychiatric Association, 2015)
• With vestibular disorders: peripheral vestibular disorders established after otolaryngological examination

Exclusion Criteria:

• Criteria common to all participants:
• Serious or unstabilized somatic pathology (including cardiovascular)
• History likely to affect cerebral anatomy or to be linked to an abnormality (neonatal suffering, neurosurgical operation, comitiality, stroke...)
• Presence of joint pain, likely to worsen after exercise
• - Substance use disorders (as defined by DSM-IV TR)
• 3D vision disorders as measured by the Wirt stereotest (depth perception at a disparity of at least 80'' arc)
• Movement perception disorders (correct movement discrimination in less than 75% of trials (cf. § V-2.2)
• History of general anaesthesia in the 3 months preceding the study
• History of neurological disease
• Impossibility of giving the subject informed information (subject in emergency situation)
• Pregnancy declared by patient
• Breast-feeding
• Subject in exclusion period (determined by a previous or current study)
• Subject hospitalized
• Subject under court protection

Exclusion criteria specific to control subjects or patients with vestibular syndrome:

History of major psychiatric pathology with current psychotropic medication (i.e., antidepressant, thymoregulator, antipsychotic)