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Ever wondered if you have anything in common with an astronaut? Turns out there are 206 things — your bones. It’s these parts of our body that are the focus of a research study on bone loss in astronauts, and the important question of whether bone can be re-gained after returning to Earth.

The TBone study was started in 2015 by Dr. Steven Boyd, PhD, director of the McCaig Institute for Bone and Joint Health and professor in the Cumming School of Medicine. The study has followed 17 astronauts before and after spaceflight over the last seven years to understand whether bone recovers after ‘long-duration’ spaceflight. Findings are , and while it might not seem like it matters to you here on Earth, the research is important to better understand bone health generally.

“Bone loss happens in humans — as we age, get injured, or any scenario where we can’t move the body, we lose bone,” says Dr. Leigh Gabel, PhD, assistant professor in kinesiology, and lead author of the study.

“Understanding what happens to astronauts and how they recover is incredibly rare. It lets us look at the processes happening in the body in such a short time frame. We would have to follow someone for decades on Earth to see the same amount of bone loss,” Gabel says.

The researchers travelled to to scan the wrists and ankles of the astronauts before they left for space, on their return to Earth, and then at  six and 12 months post-return.

"We found that weight-bearing bones only partially recovered in most astronauts one year after spaceflight," says Gabel. "This suggests the permanent bone loss due to spaceflight is about the same as a decade worth of age-related bone loss on Earth."

This loss happens because bones that would normally be weight-bearing on Earth, like your legs, don’t have to carry weight in microgravity — you just float.

“We’ve seen astronauts who had trouble walking due to weakness and lack of balance after returning from spaceflight, to others who cheerfully rode their bike on Johnson Space Center campus to meet us for a study visit. There is quite a variety of response among astronauts when they return to Earth," says Boyd.

Former ��ݮ����Ƶ���� chancellor and astronaut Dr. Robert Thirsk, BSc (Eng)'76, Hon. LLD'09, MD, knows firsthand how bizarre the return to Earth can be. “Just as the body must adapt to spaceflight at the start of a mission, it must also readapt back to Earth’s gravity field at the end,” says Thirsk.

“Fatigue, light-headedness, and imbalance were immediate challenges for me on my return. Bones and muscles take the longest to recover following spaceflight. But within a day of landing, I felt comfortable again as an Earthling.”

Some astronauts who flew on shorter missions, under six months, recovered bone strength and density in the lower body, compared to those who flew for longer durations.

Access to astronauts is rare — the study team includes two members from the European Space Agency (ESA), Dr. Anna-Maria Liphardt, PhD, and Martina Heer, PhD, as well as two from NASA, Dr. Scott Smith, PhD, and Dr. Jean Sibonga, PhD. The study was funded by the Canadian Space Agency and conducted in partnership with ESA, NASA and astronauts from North America, Europe, and Asia.

As future space missions are exploring travel to more distant locations, the study’s next iteration will explore the effects of even longer trips, to support astronauts who may one day travel beyond the International Space Station.

As Thirsk says, “Astronauts will venture to deep space this decade and, in the coming centuries, humanity will populate other star systems. Let’s push back the frontiers of space exploration now to make this vision possible.”