(ORDO NEWS) — Astronauts lose bone mass in space over decades, which many do not recover even a year after returning to Earth, researchers said on Thursday, warning that this could be a “big problem” for future flights to Mars.
Previous research has shown that astronauts lose 1 to 2 percent of bone density for every month they spend in space as the lack of gravity takes the strain off their legs when they need to stand and walk.
To find out how astronauts recover after their feet return to earth, a new study scanned the wrists and ankles of 17 astronauts before, during and after their stay on the International Space Station.
According to study co-author Stephen Boyd of the University of Calgary in Canada and director of the McCaig Institute for Bone and Joint Health, the bone density lost by the astronauts was equivalent to what they would lose in a few decades if they returned to Earth.
The researchers found that nine astronauts’ lower leg bone density had not fully recovered after a year on Earth – they still lacked bone mass for about a decade.
The slowest bone recovery was in astronauts who made the longest flights, from four to seven months on the ISS.
“The longer you spend in space, the more bone mass you lose,” Boyd told AFP.
Boyd said it was a “big problem” for future missions to Mars, which could see astronauts spend years in space.
“Will it get worse over time or not? We don’t know,” he said.
“Perhaps after a while we will reach a stable state, and perhaps we will continue to lose bone. But I can not imagine that we will continue to lose it until there is nothing left.”
In a 2020 simulation study, it was predicted that over a three-year mission to Mars, 33 percent of astronauts would be at risk of developing osteoporosis.
Boyd said research currently being done on astronauts who have spent at least a year aboard the ISS may provide some answers.
Guillemette Gauquelin-Koch, head of medical research at the French space agency CNES, said the weightlessness experienced in space is “the most dramatic lack of physical activity that can be.”
“Even if you exercise for two hours a day, it’s like being bedridden for the other 22 hours,” said the doctor, who was not involved in the study.
“It will not be easy for the crew to set foot on Martian soil when they arrive at the site – this is very disturbing.”
The new study, published in the journal Scientific Reports, also showed how spaceflight changes the structure of the bones themselves.
Boyd said that if you imagine the bones of the body as the Eiffel Tower, you would think that some of the metal rods holding the structure were lost.
“And when we return to Earth, we condense what’s left, but we’re not actually creating new rods,” he said.
Research has shown that some exercises are better than others for maintaining bone mass.
Deadlifting has proven to be significantly more effective than running or cycling, the study says, leading to more heavy lower-body exercises being recommended in the future.
But the astronauts, who are mostly fit and in their 40s, didn’t notice the drastic bone loss, Boyd said, noting that the Earth’s equivalent of osteoporosis is known as a “silent disease.”
Canadian astronaut Robert Thirsk, who has spent the longest time in space, said he had the longest time to regenerate bones and muscles after spaceflight.
“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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