What does spending more than a year in space do to the human body?

What does spending more than a year in space do to the human body? Nasa/Getty Images Frank Rubio has set the US record for the longest single trip into space at 371 days, but it will have taken a toll on his body The record for a single trip into space currently stands at 437 days, but prolonged periods in orbit can alter an astronaut's body in some surprising ways, changing their muscles, brains and even their gut bacteria. Even so, he was still around two months short of the record for the longest ever spaceflight by a human – Russian cosmonaut Valeri Polyakov spent 437 days onboard the Mir Space Station in the mid 1990s. Scott Kelly, a Nasa astronaut who took part in the most extensive study of the effects of long-term spaceflight after staying onboard the ISS for 340 days while his twin brother stayed back on Earth, lost 7% of his body mass while in orbit. Nasa/Getty Images Scott Kelly's 340 day trip to the ISS allowed researchers to study how space affected him compared to his twin brother back on Earth A more recent study has raised concerns about other changes in brain structure that can occur during long-term space missions.