Washington on July 2nd
A study of bone loss in 17 astronauts who flew aboard the International Space Station provides a better understanding of the effects of space travel on the human body and steps that can mitigate it, crucial knowledge for potentially ambitious future missions.
The research collected new data on bone loss in astronauts caused by the microgravity conditions in space and the extent to which bone mineral density can be recovered on Earth. It involved 14 male and three female astronauts, middle-aged 47, whose missions ranged from four to seven months in space, with an average of about 5-1 / 2 months.
One year after returning to Earth, astronauts showed an average of 2.1% reduced bone mineral density at the tibia – one of the bones in the lower leg – and 1.3% reduced bone strength.
Nine did not restore bone mineral density after space travel, and experienced permanent loss.
“We know that astronauts lose bones on long-distance space travel. The new thing about this study is that we followed astronauts for a year after their space journey to understand if and how bones recover,” said Professor Leigh Gabel of the University of Calgary, an exercise researcher. who was the lead author of the research published this week in the journal Scientific Reports https://www.nature.com/articles/s41598-022-13461-1.
“Astronauts experienced significant bone loss during six months of space travel – a loss we would expect to see in older adults over two decades on Earth, and they recovered only about half of that loss after a year back on Earth,” Gabel said.
Bone loss occurs because bones that would normally be weight-bearing on Earth do not carry weight in space. Space organizations will need to improve countermeasures – exercise regimes and nutrition – to prevent bone loss, Gabel said.
“During space travel, fine bone structures are thinned out, and eventually some of the bone rods are disconnected from each other.
Once the astronaut returns to Earth, the remaining bone connections can thicken and strengthen, but those that are disconnected in space cannot be rebuilt, so the astronaut’s overall bone structure changes permanently, says Gabel.
The astronauts of the study flew in space for the past seven years. The study did not give their nationalities but they were from the US space agency NASA, Canadian Space Agency, European Space Agency and Japan Aerospace Exploration Agency.
Space travel poses various challenges to the human body – important concerns for space organizations when planning new explorations.
For example, NASA aims to send astronauts back to the moon, a mission that is now planned for 2025 at the earliest. It could be a prelude to future astronaut missions to Mars or a long-term presence on the moon’s surface.
“Microgravity affects many body systems, muscles and bones are among them,” said Gabel.
“The cardiovascular system is also experiencing many changes.
Without gravity drawing blood to our feet, astronauts experience a change in fluid that causes more blood to collect in the upper body. This can affect the cardiovascular system and vision.
“Radiation is also a major health problem for astronauts because the farther they travel from Earth, the greater the exposure to solar radiation and the increased risk of cancer,” said Gabel.
The study showed that longer space missions resulted in both more bone loss and a lower probability of recovering bones afterwards. In-flight training – resistance training on the space station – proved to be important in preventing muscle and bone loss.
Astronauts who performed more ground lifts compared to what they usually did on earth were found to be more likely to recover bones after the mission.
“There’s a lot we still do not know about how microgravity affects human health, especially in space missions longer than six months, and about the long-term health consequences,” Gabel said. “We really hope that bone loss will eventually plateau on longer missions, that people will stop losing bones, but we do not know.” Reuters
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