The 41-year-old lieutenant said he experienced the height growth since arriving from space three weeks ago, and said that he was anxious whether he will fit into the seat of the Russian Soyuz vehicle that will transport him back to Earth.
"My height's been measured here in space and somehow, somehow, I've grown 9 cm!"
He said he had grown the remarkable amount since arriving there just over three weeks ago. Nothing like this since high school. On the Russian Soyuz TMA spacecraft, the vehicle used to get astronauts to and from the ISS, personnel are limited to 6 feet 3 inches so they can fit inside the seats.
A Japanese Astronaut has gained more than a few centimeters while spending time on the International Space Station, and is now anxious he might not be able to return home due to his growth in space. Upon returning to earth and its gravitational pull, astronauts return to their usual height.
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A withdrawal by the U.S. will lead to an "appropriate and heavy response", added foreign ministry spokesman Bahram Ghasemi. These woes persist despite the end of crippling sanctions under the 2015 deal to curb its atomic programme.
Some growth in space is normal, but the extent to which Kanai grew - an astonishing 9cm - is unprecedented.
While height differences are fleeting, NASA scientists and researchers have yet to understand some of the longer-term effects of zero gravity on the human body, a vital lesson if humans reach beyond the moon and colonise Mars and other planets. She told BBC News.
"You do get taller in space as your spine drifts apart", Jackson continued.
The Soyuz spacecraft which transport astronauts from Earth to the ISS and back again have a limit on seating height, so it could pose a problem if crew members become too tall.