Astronauts have been losing bone mass for decades in space, many of which are not recovering even a year ago on Earth, researchers have found, warning that this could be a “major concern” for future missions to Mars.
Previous research has shown that astronauts lose between 1% and 2% of bone density for each month spent in space, as the lack of gravity reduces the pressure on their legs when it comes to standing and walking.
To find out how astronauts are recovering after their feet are back on the ground, a new study scans the wrists and ankles of 17 astronauts before, during and after a stay on the International Space Station (ISS).
The bone density lost by astronauts is equivalent to how much they would lose in a few decades if they returned to Earth, said study co-author Dr. Stephen Boyd of the University of Canada in Calgary and director of the McCaig Institute for Bone and Joint Health.
Researchers have found that the shin density of nine of the astronauts has not fully recovered after a year on Earth – and they still lack bone mass for about a decade.
The slowest recovering astronauts, who took part in the longest missions, which ranged from four to seven months on the ISS. “The longer you spend in space, the more bone you lose,” Boyd said.
Boyd said this was a “major concern” for planned future missions to Mars that could cause astronauts to spend years in space.
“Will it continue to deteriorate over time or not? We don’t know, “he said.
“It is possible to reach a stable state after some time or it is possible to continue to lose bone. But I can’t imagine that we will continue to lose him until there is nothing left. “
A 2020 modeling study predicts that in a three-year space flight to Mars, 33% of astronauts will be at risk for osteoporosis.
Boyd said some of the answers could come from research currently being conducted on astronauts who have spent at least a year aboard the ISS.
Guillemette Gauquelin-Koch, head of medical research at the French space agency CNES, said the weightlessness experienced in space was “the most drastic physical inactivity that exists.”
“Even with two hours of exercise a day, it’s like being bedridden for the other 22 hours,” said the doctor, who was not involved in the study. “It won’t be easy for the crew to set foot on Martian land when they arrive – it’s very disabling.”
A new study published in Scientific Reports also showed how space flight changes the structure of the bones themselves.
Boyd said that if you think of body bones like the Eiffel Tower, it would be as if some of the connecting metal rods that hold the structure were lost. “And when we get back to Earth, we thicken what’s left, but we don’t really create new sticks,” he said.
Some exercises are better for maintaining bone mass than others, the study found. Deadlifts have proven to be significantly more effective than running or cycling, it says, suggesting heavier lower body exercises in the future.
But astronauts – who were mostly in shape in their 40s – were reluctant to notice the drastic bone loss, Boyd said, noting that the Earth’s equivalent, osteoporosis, is known as “silent disease.”
Canadian astronaut Robert Thirsk, who has spent the most time in space, said that for him, his bones and muscles recover the most after a space flight.
“But within a day of landing, I felt comfortable as an earthling again,” he said in a statement accompanying the study.
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