For an out-of-this-world experience, just lie down
12:03 29 March 2006
NewScientist.com news service
Kimm Groshong

Prolonged stays in space have a profound effect on the human body, which is adapted to the Earth's gravitational pull.

In the greatly reduced gravity of space, humans experience bone and muscle loss, decreases in cardiovascular activity and a redistribution of fluids toward the upper body, among other physiological effects.

Now US scientists have confirmed what space researchers have long suspected – people on Earth can experience similar effects simply by lying around for days at a time. For the best simulation of space, they must recline on a bed tilted at a 6° angle with their head at the lower end.

Researchers from Ball State University in Muncie, Indiana, and Marquette University in Milwaukee, Wisconsin, compared records of the exercise performance of four male astronauts on the STS-78 space shuttle mission in 1996 with those of eight men who were confined to inclined beds and instructed to conduct the same activities as the astronauts over a 17-day period.

They found similar declines in both groups in terms of their cardiorespiratory function and their ability to exercise. The amount of oxygen the men's bodies were able to use optimally during cycling tests declined by 10.4% in the astronauts and by 6.6% in the bedrest subjects. Researchers would expect to see a loss of about 10% in this measure as a result of a decade of aging on Earth.

Todd Trappe, an exercise scientist at Ball State, says the finding could be used to help mitigate the effects on inactive people such as bedridden patients and the elderly, as well as ensuring the safety of long-term space travellers.