Bone, Muscle Deterioration, Vision Impairment: Read How Human Body Is Affected In Deep Space

Astronauts returning from the ISS face health risks including muscle and bone loss, balance disruption, and fluid shifts.

File photo of International Space Station (ISS).

Source : NASA

As US astronauts Butch Wilmore and Sunita Williams prepare to return home after nine months aboard the International Space Station (ISS), some of the health risks they have faced are well-documented and managed, while others remain a mystery.

If you stay for a long time in space, your muscles and bones will weaken, primarily in the legs and lower back.

Gravity always acts on you while you are on the earth, so even if you are not really conscious of resisting gravity, you are always using the muscles of your lower body. In space, where gravity is very weak, posture can be maintained without standing on your legs, and there is no need to use your legs to move about. Muscles weaken and bone mass decreases if you stay for a long time in space.

Two-hour daily workout

According to AFP, Rihana Bokhari, an assistant professor at the Center for Space Medicine at Baylor College said that Wilmore and Williams' nine-month stay is "par for the course".

As we know that lifting weights builds muscle and strengthens bones, but even basic movement on Earth resists gravity, an element missing in orbit.

To counteract this, astronauts use three exercise machines on the ISS, including a 2009-installed resistance device that simulates free weights using vacuum tubes and flywheel cables.

A two-hour daily workout keeps them in shape. Bokhari told AFP, "The best results that we have to show that we're being very effective is that we don't really have a fracture problem in astronauts when they return to the ground," though bone loss is still detectable on scans.

Balance Disruption

Balance disruption is another issue which astronauts face. Emmanuel Urquieta, vice chair of Aerospace Medicine at the University of Central Florida, told AFP, "This happens to every single astronaut, even those who go into space just for a few days."

Fluid Shift

Fluid shifts might also add to increased intracranial pressure, altering the shape of the eyeball and causing spaceflight-associated neuro-ocular syndrome (SANS), causing mild-to-moderate vision impairment.

NASA astronaut Jessica Meir said, "I had a pretty severe case of SANS." "When I launched, I wore glasses and contacts, but due to globe flattening, I now have 20/15 vision -- most expensive corrective surgery possible."

Managing radiation

Radiation levels aboard the ISS are higher than on the ground, as it passes through through the Van Allen radiation belt, but Earth's magnetic field still provides significant protection.

The shielding is crucial, as NASA aims to limit astronauts' increased lifetime cancer risk to within three percent.

"Shielding is best done with heavy materials like lead or water, but you need vast quantities of it," said Eggl, of University of Illinois Urbana-Champaign.