Space and the human body

Eeerm, Philip, why are you doing a headstand? It’s part of my do-it-yourself astronaut preparation program. I need to make sure my body is ready for space! Why does Philip think he needs preparation? The environment in space is very different from the one on Earth.

On Earth, there is a gravitational force acting on your body all the time, pulling you down towards the centre of the planet. The human body has evolved to overcome this force. The heart pumps blood to distribute oxygen and nutrients, bones carry all the weight, and muscles constantly work against gravity. But during space missions, astronauts often spend prolonged periods of time in an environment where gravity is very low. When gravity is low, the human body feels weightless — it “floats.” This weightlessness affects the bodies of astronauts in several ways.

When there is no gravity pulling your body down, bones don’t need to carry as much weight. If there isn’t enough pressure on the bones, they start to release the minerals they are made of, such as calcium. The bones lose their mass and density, bones become weaker and more brittle. This is known as disuse osteoporosis. There is no need for muscles to support the body against gravity either, so they become weaker too.

Even the heart doesn’t have to pump blood as much as on Earth, so the heart weakens over time. This increases the risk of heart issues, such as stroke, upon return to Earth. Astronauts on long space missions need to keep a strict exercise routine and maintain a proper diet, so that their body can function well, both in space and when they come back to Earth. Weightlessness also causes fluids in the body to move up into the head. This makes the face look puffy but might also have more serious consequences.

It can affect vision, or other important brain functions. Another problem in space is radiation. On Earth, the planet’s atmosphere and magnetic field protect us from cosmic radiation. But in space, astronauts are exposed to much higher levels of harmful radiation. This can, for example, lead to an increased risk of cancer.

Monitoring and protective shielding play an important role in keeping radiation levels within safe limits for astronauts. Physical health issues are not the only problems astronauts face in space. Imagine spending a year stuck in a room with a handful of strangers, away from your family, and with nowhere else to go. After a while, it would get rather stressful, upsetting, and at times even boring! So it’s not unusual for astronauts to struggle emotionally and experience changes in their own behaviour.

This is why an astronaut requires a lot of training. Space travel puts a lot of strain on body and mind, so one needs to be well-prepared to cope with the challenges. Despite preparation and training, astronauts still experience some problems upon their return after a long mission. It often takes months of rehabilitation to restore their muscle strength, bone mass, and mental health. In the long run, however, studying the effects space flight has on the human body, might help doctors better understand diseases such as cancer or osteoporosis.

And maybe come up with new treatments. At the same time, scientists are developing technologies and methods that could help reduce the negative effects of space travel on the human body. This will make longer space missions more possible and safer. - Philip, you look like you’ve been in space for months now. Your face is all red and puffy. Maybe that’s enough training for today?