JOIN USMarquette University biologist Robert Fitts, who led the study, stresses the accelerated space ageing is temporary, Astronauts' muscles recover after a few months back on earth.
But what if a crew needed to make an emergency landing here on the home planet and rush from a burning spacecraft? What if after arriving at Mars, an urgent spacewalk was needed for repairs? Would the Mars men and women even be able to muster the strength for routine work?
"I'd be concerned," Fitts said in an interview with The Associated Press.
Astronauts can avoid becoming weaklings, however, with more research and the right equipment for hitting the space gym, Fitts observed. "I really think this is all preventable," he said.
Fitts bases his findings on calf muscle biopsies that his team collected on nine US and Russian space station residents from 2002 to 2005. It's the first muscle study of long-flying astronauts that gets down to the cellular level, with actual biopsies conducted.
Each astronaut spent six months aboard the orbiting lab, and submitted to a biopsy before rocketing away and immediately upon returning to earth.
The researchers discovered that the astronauts had lost more than 40 percent of the power in the slow-twitch fibres of their calf muscles. Those are the muscles so crucial for balance and posture, and seem to take more of a space-beating than other parts of the body.
Fitts said the muscle decline in the 40-something space station astronauts was equivalent to that of a person twice as old.
It didn't matter how musclebound someone was going into the mission. Fitts said the strongest weightlifting astronauts suffered the greatest muscle atrophy in orbit.
This considerable deterioration of the calf muscles occurred even though the astronauts devoted one to two hours a day to exercise. NASA has long realised the importance of weightless workouts, and the space station is equipped with treadmills, stationary cycles, and resistive-exercise machines for leg squats and calf raises.