Astronauts returning from a bout of weightlessness experience painful tearing of muscle cells when they set foot on earth.
But much like a punctured tire is patched, muscles cells literally ripped apart by use after even a week of disuse appear to patch themselves in a matter of seconds, according to researchers at the Medical College of Georgia.
"Nature has retained the economy of the patch," said Dr. Paul L. McNeil, cell biologist. "In nature, cells repair surface tears much like a mechanic used to repair a flat, by applying a membrane patch to the torn spot."
Dr. McNeil first identified this patching process in some of life's simplest forms: sea urchin eggs and fibroblasts. Now, with funding from the National Aeronautics and Space Administration, he's determining if the process holds up in more complex life forms.
"In space, none of the major muscle groups, the legs, hips and back, are loaded under gravity," Dr. McNeil said. "You can move yourself from one end of the spaceship to the other by just pushing on something with your little finger."
But soft muscle tissue adapts to its environment; rather than increasing in number, these cells increase in size in response to mechanical load. "You remove load from the muscle and it shrinks," Dr. McNeil said. "That's an unfortunate fact of life. None of us is going to look like Arnold Schwartznegger unless we exercise like him."
Weightless life in space is more akin to time spent as a couch potato. When astronauts return and reload muscles B particularly with activities, such as walking down stairs or down a hill, that simultaneously stretch and contract muscles, the result is microscopic tears in the membrane of the muscle cells.
Dr. McNeil suspects that the muscle soreness athletes experience is probably a consequence of this tearing; that tearing triggers an inflammatory response directly responsible for the pain. Excessive cell tearing also is a factor in the progressiv
Contact: Toni Baker
Medical College of Georgia