However, Japanese astronaut Norishige Kanai wrote on his Twitter account that he grew an incredible 3.5 inches within only three weeks of space travel. "In only three weeks I've really shot up, something I haven't seen since high school", he tweeted.
He said he had grown "like some plant" and was anxious about whether he would fit in the Soyuz spacecraft seat when he returned. As to whether or not he'll fit into the seat of the Soyuz return vehicle, he's probably going to be just fine.
Standing 1.80m tall on Earth, Kanai is already considerably taller than the average Japanese man, who is 1.71m in height according to the latest official statistics. He is well versed in medical research on how extreme environments affect the human body.
Nevertheless, Kanai still has enough time to grow and stretch out while in space.
What's rare is the rate and amount Lt Kanai has grown in three weeks of living on the space lab.
This is because of the absence of gravity which allows the vertebrae in their spines to spread apart.
It's not a long-term effect of space exploration.
Nevertheless, their height returns back to normal when they return back to Earth, due to the increased force of gravity again.
Members of the International Space Station expedition 53/54, NASA astronaut Scott Tingle, Roscosmos cosmonaut Anton Shkaplerov and Norishige Kanai of the Japan Aerospace Exploration Agency.
Astronauts growing onboard the International Space Station is nothing new.
"Nine centimetres is a lot, but it is possible, knowing that every human body is different".
A Japanese astronaut has sparked hilarity back on Earth after he claimed to have grown nine centimetres in space, making him anxious he would not squeeze into the capsule home.
But it's a good thing the crew isn't using the old Soyuz descent capsule, the one used from 1986 to 2002 - a module that was only able to accommodate astronauts with a maximum height of 183cm. He'd have to grow more than another 9cm for his height to become a problem. He will be aboard the station for just under six months. Time in which he could grow even taller.