The 'Bed Rest Study' being conducted by the US space agency is designed to study the effects of prolonged exposure to microgravity and requires participants to remain horizontal for a period of 70 days.
Conducted by the agency's Flight Analogs Project Team at the Johnson Space Center, the 'Bed Rest Study' is an ongoing effort to improve conditions for astronauts working in a weightless environment.
Since large-scale studies are unfeasible in orbit, the effects of microgravity must be simulated on the ground.
Head-down bed rest, it turns out, offers an excellent alternative to space flight, 'Medical Daily' reported.
"This study will show how much your body, tilted down slightly with head down and feet up, for 70 days, 24-hours a day, without getting out of bed, except for limited times for specific tests, is like an astronaut's body during the weightlessness of space flight," according to NASA.
"Watching you will help scientists learn how an astronaut's body will change in weightlessness during space flight in the future," the agency said on its website.
The programme divides participants into exercising subjects and non-exercising subjects.
Exercising subjects will spend 105 days and non-exercising subjects will spend 97 days living at the
University of Texas Medical Branch in Galveston.
The programme has three segments. First is the 'Ambulatory Period' in which both groups will be free to move around inside the bed rest facility and do normal things.
Next comes the 'Bed Rest Period', in which participants will spend 70 days lying in bed, with their body
slightly tilted downward (head down, feet up).
The last is the 'Recovery Period' during the final 14 days of the study. The groups will again be free to move about within the facility. Because of deconditioning that takes place during bed rest, volunteers will slowly begin normal everyday activity.
During all phases of the study, participants will take part in tests of their bone, muscle, heart and circulatory systems, and nervous systems, as well as their nutritional condition and their ability to fight off infections.
However, the research participant must be a US citizen or permanent resident to be considered as a potential test subject.