The study, the results of which were published in the British Journal of Sports Medicine (New window) (in English), lasted seven years and involved 17 astronauts followed before and after their stay in space.
The researchers went to Johnson Space Center from Houston, the NASA space center located in Texas, to scan the wrists and ankles of astronauts before they depart for space. The same operation is repeated as soon as they return to earth, then after six months, and again after a year.
The bone loss of space travelers is explained by the fact that in weightlessness, the effects of gravity disappear. In other words, it occurs because bones that would normally bear weight on land, such as those in the legs, do not have to bear weight in a weightless environment, the study authors say.
We found that weight-bearing bones only partially recovered in most astronauts one year after spaceflightsays Dr. Leigh Gabel, assistant professor in the School of Kinesiology and lead author of the study.
This suggests that permanent bone loss from spaceflight is about the same as a decade of age-related bone loss on earth.he adds.
The process differs from one astronaut to another
However, the effects of weightlessness and bone loss can vary from astronaut to astronaut. So says Dr. Steven Boyd, director of the McCaig Institute for Bone and Joint Health and professor at the Cumming School of Medicine.
There is a wide variety of reactions among astronauts when they return to earthhe says, citing the example of
astronauts who struggled to walk due to weakness and lack of balance after returning from spaceflightand that of their colleagues being able to cycle to the center of Houston for a study visit.
Former chancellor and astronaut of the University of Calgary, Robert Thirsk, testifies in this regard.
Fatigue, dizziness and imbalance were my first challenges when I returned to earth. Bones and muscles take the longest to recover after spaceflight, he notes. But one day, after landing, I felt comfortable again as an earthling.
He also notes that, for him, the
immediate challenges on his return to earth were
fatigue, dizziness and imbalance.
The study also reveals that some astronauts, who carried out missions of less than six months, recovered the strength and density of their bones in the lower body, unlike those who stayed longer in space.
The next iteration of the study also plans to look at long-duration and longer-range space missions, in order to further highlight the effects of these on bone loss.
The study was funded by the Canadian Space Agency, in partnership with the European Space Agency, NASA and astronauts from North America, Europe and Asia.
With information from The Canadian Press