The upcoming study, which will begin in January 2002, will require that volunteers lie in beds tilted head-down at a six-degree angle for 30 days, 24 hours a day. Bed rest in the six-degree head-down tilt position is considered the best Earth model to simulate the effects of prolonged microgravity on the human body.

"Head-down bed rest simulates weightlessness and induces many of the physiological changes similar to those seen with space flight," said Fritz Moore, Ames' project manager for the Countermeasures Evaluation and Validation Project (CEVP).

"These effects include cardiovascular deconditioning, muscle atrophy, decreased bone strength, and shifts in fluid and electrolyte balance," he explained.

The goal of the project, which is managed by NASA's Johnson Space Center in Houston, is to sponsor space flight and ground-based analog campaigns that facilitate evaluation of promising countermeasures for future flight validation.

A countermeasure is a drug, exercise or other intervention that minimizes the changes that occur during space flight and that impede normal functioning after people return to Earth. Ames manages the facility where the bed rest studies are carried out.

Male and female volunteers between the ages of 25 and 55 are needed for the study. Candidates must be non-smokers in good health and not participating in a highly competitive or rigorous exercise program. They should have no history of cardiovascular or musculoskeletal disease or hernia. Female volunteers must not be pregnant.

Participants will be housed in Ames' Human Research Facility for 45 days. They will lie in bed for 30 of those days. In addition to bed rest, these studies will involve a standardized battery of integrated physiological and cognitive tests called the Integrated Testing Regimen (ITR).

These tests measure changes in physical and mental performance before, during and after bed rest. Currently many of these tests are performed on astronauts before and after space flight to measure the changes caused by extended space travel.

"This regimen tests many physiological systems and will be used to evaluate the efficacy of medical interventions for specific problems that occur during space flight," said Moore. The majority of the tests will be conducted in Ames' Human Research Facility and Human Exercise Laboratory using both traditional and special physiological test equipment.

Most of the changes that occur during space flight are a normal acclimatization to the space environment, Moore explained. A successful countermeasure limits this acclimatization, so the astronauts can return to Earth without any persistent physiological or psychological impairments.

The first countermeasure to be tested is a regimen of resistance exercises performed with a machine called the interim Resistive Exercise Device (iRED).

The iRED exercise regimen will be compared with a no-exercise regimen to determine which is more effective at preventing losses in muscle volume and strength, as well as losses in bone mineral density that occur during bed rest. Testing will occur both before, during and after volunteers have undergone 30 days of bed rest at the six-degree downward tilt.

Participants, who will be employed as part-time, temporary employees of a NASA contractor, will be required to refrain from alcohol and caffeine consumption for the duration of the study. Limited overnight fasting also will be required at times. Certified personnel will draw blood samples. A medical monitor will be present, along with certified equipment and test operators, during maximal exertion testing. A thorough medical examination will be provided to verify the health status of all selected volunteers.

This study has been reviewed and approved by the institutional review boards at Ames and at the Johnson Space Center.

For more information about becoming part of this space station-related study, contact Heather Wilson at (650) 604-5551, or e-mail: [email protected]

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