Kelly McSweeney

Dec 4th 2018

Effects of Space Travel on the Human Body: Before, During and After


Today’s astronauts are going deeper into space on longer missions, and space tourism could soon allow regular vacationers to experience microgravity. The future of space travel is bright. Before we get too comfortable in orbit, though, we have to ask: what are the effects of space travel on the human body?

How Is an Astronaut’s Body Affected in Space?

Astronauts face many hazards in space that can do strange things to the human body. Gravity changes, exposure to radiation and confinement all take a toll on bodies that are used to being protected by Earth’s atmosphere. That’s why, according to ThoughtCo., astronauts have to be in top physical condition and must meet specific health requirements, such as having good vision and normal blood pressure.

An aspiring astronaut, just like an aspiring athlete, should focus on nutrition and fitness. The lack of gravity in space makes astronauts lose muscle mass and bone density, so people who are preparing for space travel should make sure their bodies are as strong as possible. According to Smithsonian, after just six months in space, astronauts can lose up to 10 percent of their bone mass, which can take up to four years to build back up on Earth. Astronauts compensate for this by exercising vigorously two hours each day while in space.

Gravity Affects Body Functions

NASA offers several warnings for people who are preparing for space travel, based on what researchers know about the human body in space. A lack of gravity doesn’t only cause bone and muscle loss, but transitioning to different gravity fields can also affect spatial orientation, head-eye and hand-eye coordination, balance and locomotion. It can even cause motion sickness.

As NASA cautions, if you don’t exercise and eat right, you will lose muscle strength, endurance, and experience cardiovascular deconditioning since it does not take effort to float through space. Fluids are another tricky factor, since bodily fluids shift upwards in space, which can make your legs temporarily skinny and put pressure on your eyes that cause vision problems.

Exercise Is Crucial

All of these complications (and more) will be compounded when humans travel to Mars. Astronauts preparing for Mars missions will practice experiencing weightlessness to see how the body responds. Functional task testing (such as ladder drills) and fine motor skills testing will detect any changes so that astronauts can plan and train accordingly. Wearing compression cuffs on the thighs can help keep blood from traveling up the body. Medication can help prevent bone loss, and astronauts will take vitamin D supplements since they won’t be exposed to the sun.

Put simply, NASA advises, “Good old regular exercise has been shown to keep your heart healthy, your bones and muscles strong, your mind alert, [and] your outlook more positive, and may even help with your balance and coordination.”

Exposure to Radiation in Space

One hazard even the healthiest human body can’t avoid is cosmic radiation. Even with shielding built into the walls on the space station, NASA says astronauts receive 10 times more radiation than naturally occurs on Earth. Without Earth’s magnetic field and atmosphere to protect them from radiation, astronauts face radiation sickness, with symptoms such as nausea, vomiting, anorexia, and fatigue. Space radiation also increases the risks of cancer, damage to the central nervous system, and degenerative tissue diseases (such as cataracts and cardiac and circulatory diseases).

What Happens to Your Body Once You Return to Earth?

NASA’s Twin Study took a deep look at the effects of space travel on the human body, even at the smallest levels. When astronaut Scott Kelly returned from a year in space, NASA compared his body to his twin brother’s. NASA found that space affects an aspect of DNA that is related to aging and cancer. Scott’s telomeres (endcaps of chromosomes that shorten as one ages) grew significantly longer in space.

It turned out that 93 percent of Scott’s genes returned to normal after landing, but according to NASA’s researchers, the remaining seven percent could indicate “longer term changes in genes related to his immune system, DNA repair, bone formation networks, hypoxia, and hypercapnia.”

When you return from space, your body will have to readjust to gravity. When Scott Kelly first returned, he stumbled and had to relearn how to walk. According to the Verge, this is because zero gravity messes with our sense of orientation and throws off our vestibular system (the balance sensors inside our ears). Two months after landing back on Earth, Kelly’s feet still hurt.

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