Staying in weightlessness messes up a lot in the human body. Many astronauts suffer from bone loss even months after their work in space. But this can be counteracted.
For many astronauts, bone loss during a longer stay in space is not compensated for even a year after the return flight. This is the result of a study that measured the properties of the leg bones of 17 astronauts. However, certain sports exercises can counteract bone loss, writes a research group led by Leigh Gabel and Steven Boyd from the University of Calgary in the journal “Scientific Reports”. The findings are important for longer space missions, such as a flight to Mars.
First of all, the scientists noticed that there were large individual differences between the astronauts examined. “We’ve seen astronauts struggling to walk after returning from space due to weakness and balance issues, and others happily riding their bikes around the Johnson Space Center campus to meet us for a study visit,” Boyd is quoted as saying in a statement from his university. In their study, the researchers tried to find reasons for these differences.
The 17 astronauts studied, including three women, were on average 47 years old when they took off and had been in space for four to seven months. They came from North America, Europe and Asia. Measurements on the tibia were taken prior to departure, immediately after return to Earth, and six and twelve months after return. Boyd and colleagues used high-resolution peripheral quantitative computed tomography (HR-pQCT) for the first time in an astronaut study. This imaging technology has a resolution of 61 micrometers (thousandths of a millimeter) and makes it possible to distinguish different bone structures during measurements.
The researchers used this to investigate changes in the bone trabeculae inside the bone for the first time. The bone trabeculae, also known as trabeculae in technical jargon, belong to a spongy structure that is surrounded by bone marrow. The measurements showed that the changes depended to a large extent on the length of time they were in space: in astronauts who had been in space for six months or longer, the bone mineral density of the trabeculae was on average 2.6 percent lower after twelve months than before departure , with the other astronauts only 0.9 percent.
“We found that the weight-bearing bones in most astronauts recovered only partially a year after spaceflight,” says Gabel. The permanent bone loss from space flight is about as great as the age-related bone loss on Earth in a decade. It can also be seen from other measurement data that bone loss is greater the longer people have been exposed to weightlessness.
But the authors of the study also give hope: Those astronauts who had regularly braced their legs against a great force in space had fully regained their bone mineral density in the tibia after twelve months. In this case, the crucial exercise was the so-called deadlift, which is a type of weightlifting.
