Space travellers, who stay for longer hours in zero gravity, suffer muscle loss rendering them unable to walk or even sit up on their return to Earth. Now, researchers at the University of Texas Medical Branch at Galveston have conducted the first human experiments by using a device intended to counteract this effect-a NASA centrifuge.
The centrifuge spins a test subject with his or her feet outward 30 times a minute, creating an effect similar to standing against a force two and half times that of gravity.
After working with volunteers kept in bed for three weeks to simulate zero gravity conditions, the researchers found that just one hour a day on the centrifuge was sufficient to restore muscle synthesis.
"This gives us a potential countermeasure that we might be able to use on extended space flights and solve a lot of the problems with muscle wasting. This small amount of loading, one hour a day of essentially standing up, maintained the potential for muscle growth," said UTMB associate professor Douglas Paddon-Jones, senior author of the study on the centrifuge research.
The study was conducted on 15 healthy male volunteers, all of whom spent 21 days lying in a slightly head-down position that previous investigations have shown produces effects on muscles like those of weightlessness. Eight rode the centrifuge daily.
Measurements of protein synthesis and breakdown in thigh and calf muscle were taken at the beginning and end of the investigation, using muscle biopsies and blood samples.
The results showed that members of the centrifuge group continued to make thigh muscle protein at a normal rate, while the control group's muscle synthesis rate dropped by almost half.
"We've studied elderly inpatients here at UTMB - 95 percent of the time they're completely inactive, and in three days they lose more than a kilogram of muscle.
A human centrifuge may not be the answer, but we are interested in seeing if something as simple as increasing the amount of time our patients spend standing and moving can slow down this process," he said.
The study is published in the latest issue of the Journal of Applied Physiology.