The International Space Station environment is not exactly what you might think is right for the human body. Thanks to its micro-gravity, astronauts experience a series of changes in their physique and health while living in space – and some of these changes can be countered through daily exercise and similar activities. But the space environment also confronts astronauts with other situations that cannot necessarily be mitigated.
Our bodies were not made to live in space, to live on a planet like our own planet. Humans have evolved over the centuries and millennia, and so our bodies have become accustomed to living under gravity and under the Earth’s atmosphere. But in the lower orbits of the earth, there is no mention of the elements to which the various systems of our body are accustomed.
Probably the biggest challenge astronauts face is losing muscle and bone. Humans on Earth contribute to the daily functioning of these systems simply by walking and standing in the opposite direction of gravity. But without gravity, the bones lose their mineral density and the muscles weaken. This is something that astronauts are constantly trying to prevent.
“We’re trying to minimize these changes as much as possible,” said Bob Tweedy, a counterterrorism trainer at NASA’s Johnson Space Center. To accomplish this, astronauts stationed on the space station exercise for two and a half hours six days a week.
The International Space Station is equipped with three devices designed to make exercise possible for astronauts’ entire bodies: a bicycle, a treadmill and a weightlifting device called the ARED. Each device is specifically designed for space, as it is obvious that the normal equipment of sports clubs will be inefficient in its microcosms. For example, weightlifting in space is not very efficient, because dumbbells will have no weight. So instead, the ARED device uses two cans with the ability to slow down, and astronauts can exercise by placing a bar on the shoulder.
Likewise, a station treadmill is not a normal machine. Astronauts must be connected to the device with bungee cables, otherwise they will be floating between the ground and the air and will not be able to exercise at all. There is also a stationary bike that helps stretch movements for astronauts’ feet but does not have a saddle, as it is not possible to sit on the saddle at all. When training with this equipment on the ground, it will be difficult to fully understand the conditions in space because gravity is always present on the ground.
But bones and muscles are not the only concerns of astronauts. People in space experience what is called fluid transfer. Without gravity, which pulls body fluids down, fluids will move to the chest and head, causing problems with the circulatory system and even vision. Of course, most of these changes are temporary and usually go away when the astronaut returns to Earth.
In addition, the mere presence of astronauts in outer space means that they will be exposed to other dangers. One of those dangers is space radiation. The energetic particles of the sun and the particles that come from outside the solar system are able to pass through the skin and flesh and damage the body over time.
Fortunately, the astronauts on the International Space Station are still somewhat safe from space radiation thanks to the Earth’s magnetic field, which stretches like a protective layer around our planet. However, NASA sets a specific level of radiation for astronauts, and the extent to which they are exposed to space radiation is constantly monitored to ensure that it does not exceed a certain level.
Space radiation will be a bigger concern for astronauts on missions deeper into space, as it no longer has the Earth’s magnetic field. “Peter Biida, a biologist at NASA’s Space Radiation Laboratory, says:
If you spend most of your time on the space station, you will be exposed to different levels and quality of radiation than deep space. You may be able to perform an estimated 10 space station missions for each deep space mission. The subject is quite relative, but we measure such things very carefully.
NASA is studying the effects of space radiation in a special laboratory at the Brooklyn National Observatory. There, people like Gida and other scientists use particle accelerators to simulate spatial radiation and observe what effect it has on biological samples. “Instead of looking at the samples, we bring the radiation to the samples,” says Gida. The lab’s research will help NASA create better protective layers against space radiation, so astronauts will be able to discover deeper parts of space.