Living in Space

Living in space is not the same as living on Earth. In space,

astronauts' bodies change. On Earth, our lower body and legs carry our

weight. This helps keep our bones and muscles strong. In space,

astronauts float. They do not use their legs much. Their lower backs

begin to lose strength. Their leg muscles do too. The bones begin to get

weak and thin. This is very bad for astronauts' bodies. So, how do

astronauts help their muscles and bones? They must exercise in space

every day.

The heart and blood change in space, too. When we stand up on Earth,

blood goes to our legs. The heart has to work extra hard against gravity

to move the blood all around the body. In space, without the pull of

gravity, the blood moves to the upper body and head. Water in the body

also does the same thing. It makes the astronauts' faces look puffy. The

blood and water are fluids in the body. These fluids move from the

bottom of the body to the top. The brain thinks that there are too many

fluids. It will tell the body to make less. When the astronauts come

back to Earth, they do not have enough fluids in their systems. It takes

their bodies a few days to make more blood and water. The astronauts

have to rest so their bodies have time to make new blood and water. If

they don't, they can feel very weak. They might even faint!