— While NASA builds the hardware required for its return to the Moon by 2020, doctors and scientists are trying to model the effects such a mission will have on the human body.

‘s Houston-based Flight Analogs Project has been running continuous 90-day bed-rest studies at the
Texas Medical Branch
since 2005 to monitor cardiovascular changes, bone density loss and muscle atrophy experienced by astronauts in microgravity environments.

The facility now is testing another bed for a shorter duration test that will simulate the physiological reactions expected in the lunar environment.

Physicists have concluded that a bed with the head elevated at a 10 degree angle will mimic the lunar environment, said Joe Neigut, NASA flight analogs project manager at
. Once the six-day bed-rest study is under way, the facility will begin a pilot program in early 2009 for a longer duration test, but it will not be as easy to recreate unfamiliar territory, Neigut said.

“There’s no direct measure of the effects [of the lunar environment],” he said. “It’s hard to prove.”

Since the testing program began three years ago, NASA has put about 60 people through long-duration bed-rest studies on six beds that were designed to tilt participants’ heads down at a 6 degree angle.

Doctors have learned through trial and error that the 6 degree angle achieves the same effect on the human cardiovascular system as a microgravity environment like the one experienced by crews aboard the international space station, said Dr. Ronita Cromwell, a Universities Space Research Association employee and project scientist for the bed-rest studies.

In the first few days of the test, body fluids shift toward the participants’ heads, making them uncomfortable – and creating the puffy faces commonly seen on astronauts during spaceflight. The puffiness occurs as their body fluid is redistributed due to the relative absence of gravity, Cromwell said.

The cardiovascular effects are minimal, however, and fluid distribution returns to normal post-spaceflight and within two weeks of completing the test, she said.

The study could help with new technologies to minimize the effects of space flight, such as bone density loss. The bed- rest studies have shown a density loss of 1 percent to 1.5 percent per month, especially in load-bearing bones such as the pelvis and heels, Cromwell said. Astronauts and study participants have opportunities to use and exercise their upper extremities, which minimizes bone density loss and muscle atrophy. To counteract those effects, Cromwell plans to introduce a vertical treadmill that can be used while lying down.

NASA recruits volunteers for bed-rest studies through advertising with the hope of attracting people with a strong interest in space who want to advance medical research for astronauts.

During the 90-day study, participants can telecommute if their jobs allow, learn a new language or take a class. They are paid a stipend that amounts to about $17,000 and receive checkups six months and one year after the study is completed, Neigut said. “They can do most anything you can do at a desk, they just have to do it at a different angle,” he said.

The experiment imposes some discomforts on the participants. For one thing their heads must remain lower than their feet for the entire 90 days, with the exception of an occasional medical test that requires them to sit up, Cromwell said. That means that for the most part they have to stay in bed lying down either on their stomachs or backs with their heads tilted downward.

Daily hygiene is somewhat elaborate. Participants take trips on what is known as a shower gurney to a facility that can accommodate a shower while the participant is still lying down. To avoid having participants get up and go to the bathroom during the test, they are required to use bed pans.

The facility plans to test at least 20 to 25 people each year, and increase that number when the two additional beds simulating the lunar environment come on line.

The next mission will be to develop another bed for future Mars missions, Cromwell said, adding that those beds are likely to be set at a 20 to 30 degree incline to simulate the effect of that planet’s three-eighths gravity on humans.