As astronaut Garrett Reisman adjusts to Earth's gravity after three months in space, a University of Kentucky physiologist is continuing his tests on a 50-year-old drug used for liver treatments as a means of helping astronauts perform their work during space walks.

Michael Reid, chair of UK's Department of Physiology and a founding member of the National Space Biomedical Research Institute, is researching the value of N-acetylcysteine (NAC) to limit the effect of free radicals made by muscle during heavy exercise.

His research, funded by the National Space Biomedical Research Institute, has particular value for astronauts who work in bulky space suits. "Astronauts report that six to eight hours of extra-vehicular activity is as exhausting as running a marathon. The muscle groups most affected are the hands and arms," he said.

NAC was developed in the late 1950s and has become a frontline drug in protecting the liver against drug overdose by scavenging free radicals. "Free radicals also contribute to muscle fatigue," Reid said. His research has found that NAC "will improve endurance. Now we're trying to determine the right dose and formulation" for space-travel purposes, he said.

Reid and his team also are concerned about muscle wasting that occurs during deep-space exploration, such as long-term stays on the moon and extended flights to Mars.

Astronaut Reisman knows first-hand the wasting effects of extended periods in low- or no-gravity situations, having just returned to earth from three months in the International Space Station.

"We've seen the muscles that astronauts use to stand and walk begin to waste away after a few weeks in Earth orbit. So we know nine months of travel to Mars poses a real risk," Reid said.

"At UK, we're seeking nutritional or drug-based therapies to help the astronauts maintain muscle mass and strength," he said.

The research has potential ripples beyond space travel.

"If these nutritional strategies help astronauts, they'll also help the elderly who suffer broken hips. We're also working with heart-failure patients to determine possible benefits of NAC for them," Reid said.

The research also could benefit cancer patients who undergo chemotherapy, which has been found to have a direct impact on muscles, Reid said.