Astronauts on a mission to Mars could losenearly half their muscle strength during the long trip, giving them thephysiques of senior citizens by the time they arrived, according to a newstudy.
Prolonged exposureto weightlessness could cause astronauts to lose more than 40percent of their muscle strength even with regular exercise, researchers said.On a long voyage, a healthy 30- to 50-year-old astronaut could end up with thestrength of an 80-year-old.
A 10-month tripto Mars would cause such extreme muscle deterioration thatastronauts would find it difficult to perform even routine tasks, let alonemove around the Martian surface in spacesuits, according to the study, whichwas led by Robert Fitts of Marquette University.
Returning to Earth could be even moreperilous, the researchers found: The astronauts could be too weak to evacuatetheir spacecraft if they needed to make an emergency landing.
The research is detailed in the Aug. 17edition of the Journal of Physiology.
The need for better exercise
Fitts, a biological science professor at theuniversity in Milwaukee, and his team concluded the development of better, moreeffective spaceexercise regimes would be vital for any manned spaceflight toMars or another planet.
Fitts and his team studied the effects oflong-duration space missions on astronaut muscles by taking samples from nine InternationalSpace Station astronauts and cosmonauts. The samples were takenbefore and after the astronauts and cosmonauts' 180-day missions aboard thespace station.
Just being strong was no defense, theresearchers found. In fact, the astronaut with the biggest muscles experiencedthe most severe deterioration.
The drill in orbit
The physicaltoll of space missions is no surprise to NASA. The space agencyhas long known about the problem, and astronauts routinely train hard to staveoff the worst effects of muscle-wasting in space.
During their six-month stints aboard theInternational Space Station, astronauts exercise about 2.5 hours per day, sixdays a week, said Lori Ploutz-Snyder, an exercise physiologist at NASA'sJohnson Space Center.
"Exercise is a big part of theirday," she told SPACE.com. "It's a big part of our program."
The training regimen aboard the space stationinvolves three components: a stationary bike, a treadmill and a fancy machinecalled the Advanced Resistive Exercise Device. Installed in November 2008, theARED allows astronauts to perform a variety of weight-training exercises, suchas squats and bench presses, with loads of up to 600 pounds.
How do astronauts weight-train in zerogravity? Ploutz-Snyder said the ARED generates loads using vacuum cylinders. Italso has flywheels to generate the inertia needed to get the load off the rack.
Running in weightlessness
Trotting on a treadmill in space isn't soeasy, either.
"If you weren't strapped in when youpushed off, you'd just float away," Ploutz-Snyder said. So astronautsusing the space station treadmill wear a special harness tethering them to themachine. Bungee cords provide adjustable loading, simulating walking in anon-weightless environment.
And the training doesn't stop when themission ends. After they return to Earth, NASA puts its astronauts through acustomized exercise program that emphasizes strength and aerobic fitness.
"They essentially have their ownpersonal trainer," Ploutz-Snyder said.
Most astronauts stay in this personalizedfitness program for a month or so, but some keep at it for 90 days. It alldepends on how they feel when they land, and what a team of doctors andexercise physiologists thinks is best.
The new Journal of Physiology studyrecommends that astronauts in zero gravity focus on high-resistance exercise tokeep their muscles from wasting away. Ploutz-Snyder says that's just what thespace station's ARED machine will deliver.
"We're just getting started on our newresearch program with higher-intensity exercise," she said. "In acouple of years we'll start to get an idea of how it's working."
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