The regulation of the cardiovascular respiratory system after changing environmental conditions or changes in work rates are essential for cognitive as well as physical functioning. For decades, it is known that high level of headward acceleration (+Gz) impairs cardiovascular function that may cause loss of consciousness. Some "anti-g" maneuvers, such as muscle contraction of the lower extremities and buttocks or intermittent exhalation on exertion (i.e., exhalation against a closed airway) have been proved to increase tolerance to high +Gz.

Main objective of this experiment is to investigate the effects of anti-g maneuvers on cardiovascular and respiratory tolerance to the push-pull-effect.

Cardiovascular and respiratory functions will be evaluated with the following parameters: heart rate, stroke volume, cardiac output, blood pressure, oxygen uptake, carbon dioxide output, ventilation, breathing frequency, body core temperature.

Electromyography (EMG) will not be a judgment criteria but will be used to check the quality of 'muscle contraction' anti-g maneuver.

The main hypothesis is that anti-g maneuvers will increase cardiovascular and respiratory tolerance to the push-pull effect, especially when they are combined.

Inclusion Criteria:

• Healthy volunteers (men or women)
• Aged from 20 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 (JAR FCL3 Class 2 medical examination). There will be no additional test performed for subject selection.

Subjects will be staff member of the team or of other teams participating in the parabolic flight campaign.

Exclusion Criteria:

• Person who took part in a previous biomedical research protocol, of which exclusion period is not terminated
• Treated or non-treated arterial hypertension
• Smoker
• Asthma
• Respiratory bacterial or viral infection
• Pregnant women