How Astronauts Exercise

CNN has an interesting article about how astronauts try to stay in shape.

But floating around in zero-G can have some serious consequences for the human body, NASA's experts have learned, including the weakening of bones. In fact, studies have shown that space travelers can lose 1 to 2 percent of their bone mass each month on average, according to NASA.

One way that astronauts have been fighting bone loss is through strength training. And they're getting some help with a new machine delivered this week by the shuttle Endeavour, which docked with the international space station on Sunday.

The advanced Resistive Exercise Device, aRED for short, functions like a weight machine in a gym on Earth, except it has no conventional weights. Instead, it has vacuum cylinders -- canisters with air that have had a vacuum applied -- that provide concentric workloads up to 600 pounds, NASA says.

The device works somewhat like a bicycle pump, only in reverse, said Mark Guilliams, a NASA trainer. For example, if you are squatting, the vacuum gets pulled out as you stand up, and when you squat back down, the vacuum pulls the bar back to the normal position.

Between the vacuum cans and the bar, there are small flywheels that spin in opposite directions, creating an artificial gravity when someone lifts the bar.

Astronauts can do upper and lower-body exercises, such as squats, dead lift, heel raises, bicep curls and bench press on the device, NASA said.

"In the movie, the 'Transformers,' it looks like one of those things that unfolds into some kind of big monster," Anderson said. "It's huge."

The existing exercise device on the space station has a mechanism that more closely resembles a rubber band. The farther you pull the rubber band, the more force you generate, Guilliams said. The limitations of this device made it somewhat boring, Anderson said.

The new device will allow astronauts do many more kinds of exercises than the old one. The tradeoff is its larger size, Anderson said. It will be in use almost constantly during the day, assuming astronauts work out about two hours a day each, he said.

The international space station also is equipped with a treadmill and a bicycle, Guilliams said.

Of course in space you have to wear a harness so that you don't go floating off of the treadmill. I really want to experience that weightlessness feeling. I wonder what sleep would be like.