New Delhi: Astronauts those who are on long space flights or part of deep space missions have lower exercise capacity, says a new study.
This happens because their heart and muscles lose the efficacy of transporting oxygen to the muscles.
Researchers set out to find why astronauts' exercise capacity decreases between 30 and 50 per cent in long-duration spaceflight.
"It is a dramatic decrease," said Carl Ade, assistant professor at Kansas State University in the US.
"When your cardiovascular function decreases, your aerobic exercise capacity goes down. You can't perform physically challenging activities anymore," said Ade.
"While earlier studies suggest that this happens because of changes in heart function, our data suggests that there are some things happening at the level of the heart, but also at the level of the microcirculation within capillaries," he said.
In addition to improving astronaut health and providing valuable information for future long-duration spaceflights, the research also can help Earth-bound clinical patients with heart failure, Ade said.
While in outer space or on the ISS, astronauts have to perform many physically demanding tasks, from the simpler task of opening a capsule door to potentially more intense future planetary tasks such as helping a fallen crew member.
Just as important is making sure astronauts can perform life-saving tasks when they return to gravity - tasks that could include an emergency landing on Earth or performing extravehicular activities on the surface of Mars, Ade said.
For the study, researchers used data from NASA's Johnson Space Centre on nine astronauts who spent about six months aboard the ISS.
The data included exercise measurements before and after their time in outer space.
The astronauts performed a stationary bike exercise test several months before they launched to the ISS.
(With PTI inputs)