Subject Criteria

Note: These are the general screening criteria. Certain campaigns may invoke additional screening criteria.

Subject Recruitment Criteria

Subjects will be healthy adults, aged 25 to 55 years. Both males and females will be recruited with the specific requirement that a sufficient number of female subjects are recruited to allow potential gender-specific differences in bed rest responses to be statistically analyzed.

Subjects will be excluded from the study who:

1. Require medication that may interfere with the interpretation of the results
2. Have a recent sub-standard nutritional status
3. Have a history of thyroid dysfunction, renal stones, mental illness, or smoking within 6 months prior to the start of the study
4. Have a family history of thrombosis
5. Are using hormonal contraceptives
6. Are menopausal
7. Cannot clear a criminal background check
8. Currently on bisphosphonate therapy
9. Have a positive pregnancy test (females)
10. Have a history of gastroesophageal reflux disease

Potential subjects also will be screened to match the following physiologic characteristics to those of the U.S. astronaut corps. Subjects will be required to pass a modified Air Force Class III Physical examination, or equivalent, within 1 year before the study starts, and each must be capable of giving informed consent. The tests to be performed include: vital signs, 12-lead ECG, vision and audiometry, urine analysis, full physical exam, electrolyte panel, complete blood count with differential, test of liver function, drug screen, TB skin test, lipid panel, chest X-ray, HIV/hepatitis screen, and high sensitivity C-reactive protein. All subjects will be tested and interviewed by a psychologist to ensure they have the mental fitness necessary to complete all aspects of the bed rest studies. In addition to these criteria, individual investigators also have additional subject selection recruitment criteria.