Liver Drug May Help Exhausted Spacewalkers

Future astronauts might better endure exhausting spacewalks with the help of a handy liver drug.

The drug captures free radical molecules produced during heavy exercise that could damage muscle tissue and cause fatigue for spacewalkers already facing the muscle-wasting effect of weightlessness.

"Astronauts report that six to eight hours of extra-vehicular activity is as exhausting as running a marathon,? said Michael Reid, head physiologist at the University of Kentucky who leads an ongoing study. ?The muscle groups most affected are the hands and arms."

NASA tries to limit the duration of its spacewalks to about 6 1/2 hours on average because astronauts become tired working in their bulky spacesuits. Future astronauts may have more flexible spacesuits to work with, but researchers still look to counteract the muscle fatigue in the shoulders, arms, wrists and hands.

For example, NASA?s newest spacesuit glove modification wraps areas prone to potentially dangerous scratches and tears with a tough material dubbed ?turtleskin.? The change did away with cumbersome, mitten-like glove covers that, despite protecting against tears, enhanced hand fatigue during tasks requiring fine manipulation.

Reid first thought of using N-acetylcysteine (NAC) for spacewalkers after investigating the 50-year-old drug to treat patients on Earth. NAC is already approved for use in humans to protect the liver against drug overdose, but several studies have shown that the antioxidant drug can also increase muscle endurance by an average of 15-20 percent.

?We?re studying NAC because it?s the only game in town,? Reid told SPACE.com, noting that the drug?s safety record meant it should not hurt volunteers or patients in studies. His research group still hopes to find a similar drug to NAC with even fewer side effects for astronauts.

As a member of the National Space Biomedical Research Institute (NSBRI), Reid received $1.2 million in funding for his study through August 2009. Successful results from the study could lead to use in spaceflight within two to four years, depending on NASA approval.

However, treatment for Earth patients suffering from muscle fatigue could theoretically go into effect tomorrow if studies proved positive, Reid said. He credits NSBRI with backing research that can improve human health on Earth as well as in space.

?I?m looking out my office window at three different hospitals, each with patients suffering from premature muscle fatigue and weakness,? Reid said. He added that the NAC study stands as an example of ?space research that?s driving the medical spinoffs? assuming that the drug proves beneficial, he added.

Reid?s lab also has a longer-term focus on slowing muscle atrophy for astronauts during long space missions. Astronauts currently use a combination of strength training and aerobic exercise to keep fit in zero-G, but researchers may eventually give antioxidant or other drug treatments to help supplement the exercise.

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