Short but intense sessions of exercise may help women on bed rest stay strong and recuperate more quickly, according to a NASA funded study by researchers at Ball State University, Muncie, Ind. The findings of the first comprehensive bed rest study focusing exclusively on women will help NASA develop more effective countermeasures to mitigate strength and muscle loss in female astronauts on long-duration missions to the International Space Station and, perhaps, someday to Mars.
It also may have implications for women on Earth confined to bed rest because of illness, injury or pregnancy.
"With NASA astronaut Peggy Whitson commanding the International Space Station now and astronaut Pam Melroy commanding the last space shuttle mission, we're reminded daily that women make up an important segment of our astronaut corps and are taking on more and more leadership roles," said Carl Walz, a former long-duration astronaut and head of NASA's advanced capabilities division in the agency's Exploration Systems Mission Directorate, Washington. "It's important that we look at how space travel -- microgravity, radiation, and other factors -- affects women and men differently."
Ball State's Human Performance Lab has been working with NASA for more than a decade to examine the impact spaceflight has on humans, according to Scott Trappe, the lab's director. He co-authored the study with fellow lab researcher Todd Trappe, his brother.
"Until we completed this study, we had no solid research on how women would adapt to long durations in space," Trappe said. "This information should have a dramatic impact for NASA in the coming years."
Conducted in Toulouse, France, the study was sponsored jointly by the European Space Agency, the Canadian Space Agency, the French space agency CNES, and NASA. Results were published recently in the Journal of Applied Physiology and Acta Physiologica.
The study examined 24 female participants to determine whether specific exercise regimens or nutritional supplements could prevent the loss of lower body muscle mass and strength.
The women spent 60 days on bed rest. They lay with their heads pointing downward at a 6-degree angle, which researchers believe most accurately simulates the weightless conditions of space. One group was put on an exercise regimen. A second group was put on a high-protein diet rich with leucine, an amino acid. The control group did not take part in any exercise or dietary protocols.
"When we looked at these women after two months, the difference in the physical condition among the three groups was undeniable," Trappe said. "The women who did not exercise lost nearly half their strength in some cases. What's more, the group who ate a high-protein diet but did not exercise lost even more muscle mass than the control group."
The exercise regimen included a 40 to 50 minute aerobic workout two or three times a week and 20-minute strength training sessions two or three days a week. While lying on their backs, the women did multiple sets of thigh and calf exercises using a flywheel device similar to a typical leg press machine at a gym. They also worked out on a vertical treadmill.
"The message for women and their doctors is that it really took very little exercise to make an impact," said Trappe. "The total time spent exercising was less than two percent of the time they spent in bed during the entire 60-day period. In the end, a little bit of intense exercise goes a long way."
Using a magnetic resonance imaging device, or MRI, researchers measured muscle mass in all of the study subjects after the 60-day period. They found that women in the control group lost 21 percent of the muscle mass in their quadriceps, and the nutrition group lost more than 24 percent, but the exercise group lost none. Results were similar for MRI scans of the calf muscle.
The loss of muscle strength was even more significant. Researchers tested strength using the flywheel device. Women who did not exercise during the study lost as much as 33 percent of their strength in squat exercises and 46 percent in calf press exercises. But the women who exercised maintained their strength.
NASA's Human Research Program is working to understand the health effects of spaceflight on astronauts in preparation for long-duration missions. "It could take six months to reach the surface of Mars, and we have to make sure our astronauts are healthy when they get there," Walz said.