an astronaut being carried after landing

3 reasons why astronauts can't walk after landing on earth

Last Updated: June 16, 2022

The human body is not built to withstand the extreme conditions of space. The lack of gravity can have a serious impact on astronauts’ health, and one of the most noticeable effects is on their bones and muscles. It is not uncommon for astronauts to be carried off the spacecraft on a stretcher or a chair after landing on earth.

There are three main reasons why astronauts may have difficulty walking on land after spending so much time in a microgravity environment.

Reason #1: Living in a microgravity environment causes bone and muscle loss

In a microgravity environment, astronauts are not subject to the same level of gravity that they experience on Earth. Onboard the international space station, the astronauts experience about 89% of the gravity we experience on Earth. 

So it’s not a massive difference but the main issue comes from the state of weightlessness they experience 24/7. Since the ISS, and everything that is inside of it is in a constant state of free fall, the astronauts can float around.

Now, this sounds like a lot of fun, floating around the ISS, but without the force of gravity pulling down on their bodies, astronauts’ muscles and bones are not required to work as hard. Over time, this can lead to a significant loss of muscle and bone mass over time.

  1. The bones break down in the legs, hips, and spines. The loss of calcium renders them weaker, and more prone to injuries once the astronauts are back on Earth.
  2. Over time, the muscles in the legs and back atrophies and weaken too. This will result in a loss of mobility after landing on earth.

To reduce this loss of muscle and bone, astronauts are required to exercise every day for about 2.5 hours.

astronaut exercising onboard the ISS

Reason #2: The cardiovascular system is also affected by microgravity

The heart is a muscle that pumps blood throughout the body. In a microgravity environment, the heart does not have to work as hard to pump blood since there is no gravity pulling down on the body. Over time, this can lead to a decrease in the size and strength of the heart muscle.

After spending 340 days on the ISS, Astronaut Scott Kelly’s heart shrunk by 27% despite doing low-intensity exercises 6 days a week for two hours.

Whilst onboard the ISS, it’s actually not that much of a problem, Dr. Benjamin Levine said “The heart gets smaller and shrinks and atrophies, but it doesn’t become weaker — it’s just fine. The function is normal, but because the body is used to pumping blood uphill against gravity in the upright position when you remove that gravitational stimulus, particularly in someone who is pretty active and fit beforehand, the heart adapts to that new load.”

However, when astronauts return to Earth, their hearts are not as efficient at pumping blood throughout their bodies. This can cause them to feel dizzy or lightheaded and can make it difficult to walk for a few days after landing.

Reason #3: Microgravity also causes balance issues

The inner ear is an important part of our vestibular system, which helps us to maintain balance. The otolith organs, in particular, are affected by the microgravity environment. The otolith organs no longer experience the force of gravity, which is usually used as a reliable reference for movement and maintaining balance and spatial orientation.

This lack of sensory input causes astronauts to experience a form of motion sickness called space motion sickness. During the first few days in space, many astronauts experience increased body warmth, cold sweating, malaise, loss of appetite, nausea, fatigue, vomiting, and headaches, as their bodies adapt to the microgravity environment.

When astronauts return to Earth, their otolith organs must readjust to the planet’s gravitational pull, which can take a few days. They may experience balance issues and coordination difficulties during this time

When astronauts come back to earth, their otolith organs need to readjust to the force of gravity, which can take a few days. In the meantime, they may experience balance issues and problems with coordination.

How long does it take for astronauts to recover from their time in space?

The human body is designed to work in Earth’s gravity, which means that when astronauts return to Earth, their bodies have to readjust to the planet’s gravitational force. Astronauts may experience a reduced sense of balance, mobility, and coordination after landing on earth. It usually takes a few days to a few weeks for astronauts to recover from their time in space and feel back to normal.

However, for some astronauts who have spent extended periods of time in space, it can take months to recover from the effects of microgravity. In the case of Canadian astronaut Chris Hadfield, it took him five months to re-adjust to Earth’s gravity after spending five months on the ISS.

During a press conference shortly after his return to earth, the astronaut described what it felt like: “It feels like I played a hard game of rugby yesterday or played full-contact hockey yesterday and I haven’t played in a while,”.

He was not allowed to drive a car for 21 days after landing.

In the below video, you can see astronaut Drew Feustel attempt to walk on the day after he landed on Earth. He had spent 197 days in the International Space Station. As you can see, it’s not easy.

Now you know why!

Tom Urbain

Space exploration has been a fascinating subject for me since a very young age. As a child, astronauts were my heroes, so it was inevitable that a part of my website would be dedicated to astronauts and their space missions.

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