NASA ISS Astronauts' Health: Journal of Bone and Mineral Research

NASA astronaut Jeffrey Williams, Expedition 22 commander, exercises using the Advanced Resistive Exercise Device (ARED) in the Tranquility node of the International Space Station. 

Image Credit: NASA.

A new study, published in the September 2012 issue of the Journal of Bone and Mineral Research, looked at the mineral density of specific bones as well as the entire skeleton of astronauts who used a new, stronger “weight lifting” machine.

Of course, weights don’t really “weigh” anything on the space station but resistance machines allow astronauts to get the same kind of workout.

The new Advanced Resistive Exercise Device (ARED), installed in 2008, doubles the maximum simulated weight to as much as 600 pounds.

Researchers compared measurements from 2006 until 2008, when astronauts used a less capable workout machine.

They found that astronauts using the advanced system came home with more lean muscle and less fat, and kept more of their whole body and regional bone mineral density.

Those same astronauts also consumed sufficient calories and vitamin D, among other nutrients. These factors are known to support bone health and likely played a contributing role.

"After 51 years of human spaceflight, these data mark the first significant progress in protecting bone through diet and exercise," said Dr. Scott M. Smith, NASA nutritionist at the agency's Johnson Space Center in Houston and lead author of the publication.

Since the 1990s, resistance exercise has been thought to be a key method of protecting astronauts' bones.

Normal, healthy bone constantly breaks down and renews itself, a process called remodeling. As long as these processes are in balance, bone mass and density stay the same.

Earlier studies of Russian Mir space station residents found an increased rate of breakdown, but little change in the rate of regrowth, resulting in an overall loss in bone density.

In the new study, astronauts who used the ARED device still had increased bone breakdown, but their bone renewal tended to increase, likely resulting in a better balance in whole bone mineral density.

"The increase in both bone breakdown and formation suggests that the bone is being remodeled, but a key question remains as to whether this remodeled bone is as strong as the bone before flight," said Dr. Jean Sibonga, NASA bone discipline lead at Johnson and coauthor of the study.