7 Ways Bodies Change in Space

What happens to your body when you live and work in space? A zero-G environment has a crazy effect on our fragile human bodies.

Space Walk

Hikers and climbers know the effects of altitude on the body – the dangers of altitude sickness above 2,400 metres (8000 feet) are well documented. Astronauts, however, have to deal with a whole other set of issues. At 400km (aprox. 225 miles) above the Earth, the altitude of the International Space Station, the body goes through significant changes.

Beyond skill sets and education, NASA Mission Specialists have many strict physical requirements. Why? Our bodies are linked to our habitat – remove the specific conditions of our planet from our environment and the body undergoes serious changes to function and health, the effects of which NASA is continually discovering as we spend more time up in orbit than ever before.

Here are just 7 things NASA has learned about these biological changes from more than a half-century of space exploration.

Vast Space

1. Our Fluids Shift

Gravity does a lot to help draw the  fluids from our torso and upper body down into the trunk and legs. Remove gravity, and fluid remains in the torso and head causing headaches and congestion. During their time in a zero-g environment, many astronauts experience swollen faces and upper bodies while their legs lose circumference.

Over time, astronauts lose fluids – over 20% of their blood volume! This can cause heart complications like lowered blood pressure and cardiac atrophy.

New Zealand from Space

2. Our Bones Weaken…

Without weight bearing down on the skeletal structure, our  bones begin to weaken and become brittle, releasing calcium into the body and causing  calcification of soft tissues and even kidney stones.   The rate of loss is so great that it poses a significant hurdle in prolonged human space exploration, proving once again our connection to this planet is inherent and essential to our survival and health.

3. … So Do Our Muscles

Bones are not the only thing to weaken and dissolve when in space.  Our muscles begin to deteriorate at a very rapid rate – in just 10 days, some astronauts will experience a 20% loss in muscle mass, which will not only affect their physical appearance but also profoundly affect their lives following their return to terra firma. Replacing the lost bone and muscle can take years after just a few months away from our little blue home.

Shuttle in Orbit
photo via PixaBay

4. Some of Our Senses Change

With all those fluids now amassing in the upper body, there is increase in pressure behind the eyes which, beyond  headaches, can lead to clinically sufficient visual impermanent, especially in male astronauts.
With this effect being noticed after only a month outside the bonds of our planet,  this significant visual impairment remains a concern to NASA in regards to prolonged flights, like those to Mars and beyond.

5. We Lose Our Balance

You don’t have to be into yoga to know the importance balance plays into our lives. Balance is largely responsible for our visual stability, mobility, and body orientation.

With the loss of gravity, so comes the loss of direction. The mind is  unconditioned to receiving sensory input in  a zero-g environment, so motion sickness and ‘space nausea’ are common to astronauts.

With this loss of direction and other sensory input increasing over a prolonged period, NASA has noticed reduced alertness and operational effectiveness in both common and emergency procedures.

Luckily, astronauts are highly trained and conditioned, which allows them to do the best job they can in such a hostile environment.

Lunar Vehicle

6. Even Our Sense of Taste Can Change

In her interview with Wired Magazine, Astronaut Marsha Ivins talks about her experiences with fluid shifts, and their effects on taste, notably chocolate.

This experience in taste shift is not uncommon and perhaps explains why, with so much of the food being eaten pre-packaged, freeze-dried and/or MREs, the quality of space-friendly cuisine is not known to be spectacular.

7. We Sleep Less

Most astronauts sleep significantly less in orbit than on Earth.

The effects of the day-night cycle or circadian rhythm on Earth’s organisms is well known. Human beings are affected by the change in light and season just like any other animal. At 400km above the Earth, the mission specialists aboard the ISS see over a dozen sunrises and sunsets per day. The light of the sun we experience down here is replaced by artificial lighting and radiation protected screens up there.

While the day-night cycle is largely responsible for the disruption in sleep patterns, TMS believes it may also be linked to adrenaline, after all…

Looking Down at Earth

400km Up Has Many Benefits…

Observing the Earth from 225 miles above it’s surface has lead to leaps in our understanding of the planet, thus aiding in natural disaster prevention, natural resource management, communication systems, and much more.

The half-century of work by international specialists and explorers has brought humanity one step closer to learning more about our role in this massive, amazing universe.

Starry Night



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