The scientific goal of this experiment is to evaluate changes in balance control in response to microgravity during reactive balance tasks. For that purpose, kinematic and neuromuscular parameters under microgravity are compared to normal gravity conditions. To induce postural responses among the test subjects, an electromagnetic maneuverable postural platform will be used in order to randomly elicit perturbations. Postural reactions will be quantified by means of mechanical and electromyographic data. In Addition, peripheral nerve stimulation will be used to assess the spinal excitability by means of H-reflex recordings. H-reflex measurements were chosen as they allow reliable information about inhibitory and facilitatory mechanisms taking place at the spinal level.

Inclusion Criteria:

• Healthy volunteers (men or women)
• Aged from 21 to 65
• Affiliated to a Social Security system and, for non-French resident, holding a European Health Insurance Card (EHIC)
• Who accepted to take part in the study
• Who have given their written stated consent
• Who has passed a medical examination similar to a standard aviation medical examination for private pilot aptitude. There will be no additional test performed for subject selection.

Exclusion Criteria:

• Person who took part in a previous biomedical research protocol, of which exclusion period is not terminated
• Person with medical history of neurological disorders
• Person with medical history of musculoskeletal disorders of the lower limbs, especially of the ankle and knee joint.
• Pregnant women