Image: Astronaut
Japan Aerospace Exploration Agency (JAXA) astronaut Koichi Wakata, Expedition 18 flight engineer, uses the short bar for the advanced Resistive Exercise Device (aRED) equipment to perform upper body strengthening pull-ups in space station.
updated 4/7/2009 2:51:04 PM ET 2009-04-07T18:51:04

Astronauts may need to boost their Bowflex-like resistance training to stave off muscle loss during long space missions, a new study says.

The NASA-sponsored research found that crewmembers of the international space station lost roughly 15 percent of muscle mass and 20 to 30 percent of muscle performance during the average six-month stay at the orbital lab. The solution: Push more resistance training instead of aerobic exercise.

"Intensity wins, hands down," said Scott Trappe, director of Ball State University's Human Performance Laboratory.

Space station residents currently exercise at least two hours each day to prevent their muscles and bones from wasting away in the weightless microgravity environment. The recent study showed a range of astronaut exercise regimens, including five hours per week spent on aerobics, and anywhere from three to six days per week spent on resistance training.

Trappe assessed muscle loss based on muscle biopsy samples. This represents the first time that the procedure has been allowed for astronauts who completed long-duration missions.

"By clinical standards, this is a massive loss," Trappe said. "This approaches what we see in aging populations in comparisons of a 20-year-old versus an 80-year-old."

Researchers recommended more resistance training to avoid muscle loss, based on ground-based bed rest studies that last anywhere from 60 to 90 days.

Orbiting gym
The space station's gym includes an Advanced Resistance Exercise Device that NASA delivered in November 2008, along with bungee-like resistance bands and an exercise bike. Astronauts recently had to pry open the exercise bike and clear a strap that had jammed the pedals.

Given the new findings, detailed in the Journal of Applied Physiology, space denizens may want to work out with than just an exercise bike, anyway.

"From our bed rest studies, we found that when high-intensity resistance and aerobic exercise are balanced correctly, this is an effective prescription that is quite therapeutic in protecting skeletal muscles in a simulated microgravity environment," Trappe noted.

An earlier survey of 13 space station residents found that three had lost as much as 30 percent of bone strength, making them as frail as older women on Earth who suffer from osteoporosis.

NASA is carrying out more studies to continue improving exercise regimens, and hopefully help astronauts avoid the worst of such health problems, said Judith Hayes, a NASA deputy chief of human adaptation and countermeasures at the Johnson Space Center in Houston.

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