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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