If you’ve been in space for a year, adjusting to life on Earth can be a painful, slow, and difficult process. Microgravity (meaning very little gravity) on the International Space Station means that the human body goes through changes that can be arduous to recover from. We evolved on Earth, not in space, so our bodies don’t enjoy being in space for long periods of time.
Muscles: Use Them or Lose Them
When you’re floating around, weightless, your muscles and bones no longer hold up your weight. This causes several things to happen. First, lack of use means that your muscles atrophy. You see this on Earth with coma patients whose muscles atrophy from lying in bed all the time and not moving. When the bones no longer need to support the weight of the astronaut, they also lose density. This condition is called spaceflight osteopenia and it is sort of like osteoporosis, a disease where bones lose calcium. Except in this case, instead of a disease, it’s the lack of gravity that’s damaging the bones.
Learning to Walk
Once astronauts are back on Earth, the pull of gravity makes it difficult for them to walk. In fact, many astronauts must learn to walk all over again like a baby. They are often disoriented as well because their brain, inner ear, and fluids must all adjust to fighting gravity once again. This means it’s difficult for astronauts to stand up, walk, and keep their balance.
The Price of Going into Space
Even after learning to walk (this takes a few days), astronauts can experience back, abdominal, and foot pain for months after their return. Stabilizer muscles also atrophy as well, so walking can become a painful thing. Not to mention, calluses must grow back on the bottom of the feet! It’s not easy being an astronaut and the price they pay to go to space is their health.