NASA astronaut Scott Kelly grew nearly two inches after spending a year in space, but the 52-year-old lost the sudden growth spurt after just two days back on Earth.
The increased height is not uncommon among astronauts who spend a long time in space, where the low-gravity environment decreases pressure on their spines, Dr. John Charles, a Johnson Space Center physiologist said during a press conference with the astronaut Friday.
"He's been squished back to his normal height," Kelly's brother, Mark Kelly, said.
Extended stays in space can mean a grueling adjustment for astronauts returning to the Earth and its gravity.
"Adjusting to space is easier than adjusting to Earth for me," Scott Kelly said during the press conference.
Gravity on Earth compresses human spines, but after spending a record-breaking 340 days on the International Space Station, Kelly was measured roughly 1-and-a-half inches taller upon landing.
Weightlessness has other effects on people, such as allowing liquids to drifts from the lower half of the body to the top, and changing the shape of astronauts' eyeballs, for example.
NASA is well aware of the change in height for its astronauts, and has built their space suits and seats slightly larger for that growth spurt, Charles said.
"Unfortunately that height goes away when they get back to earth and stand up," he said.
NASA officials are still studying Kelly's adjustment after returning home to learn more about the effects of space.
Kelly said his muscles and joints ache, his skin burns when he sits or walks, and he hasn't been able to make a basketball shot, yet.
The extended stay in outer space is part of NASA's ongoing effort and study to reach Mars.
Kelly's identical twin brother, Mark, was also consistently studied on Earth during the year-long trip so scientist could look at the physical and genetic effects of extended space travel on the body.
Kelly has spent 520 days in space during a course of four missions, said he will likely not fly for NASA any more.
Mark Kelly said his brother is likely at his life-time limit of radiation exposure after his long trips in outer space.
But the 52-year-old astronaut said perhaps some time soon anyone will be able to buy a ticket and go into outer space.
"I'll never be done with space," he said.