Astronomical Bone Loss Recorded From Space Travel

UCalgary TBone study reveals impacts of pre-flight and in-flight exercise on bone loss.

by Kirstyn MacGillivary
McCaig Institute for Bone and Joint Health
University of Calgary

CALGARY, Alb. — Escaping the Earth’s orbit and floating through space for a six-month mission results in an average bone loss equating to nearly two decades of bone loss on earth. That means a 40-year old astronaut returns to Earth with a 60-year old skeleton.

Findings from the TBone study, published in the British Journal of Sports Medicine, reveal that bone loss progresses with the length of a space mission despite daily exercise programs designed to prevent bone loss.

“With astronauts on missions of varying space flight durations, we were able to analyze the trajectory of bone loss and confirm that bone loss progresses with the length of the mission and does not stabilize for up to seven months in-flight,” says lead author Dr. Leigh Gabel, PhD, a postdoctoral fellow at the Cumming School of Medicine (CSM).

Even though many of us may never step foot on the moon, the study findings are relevant to understanding bone loss on Earth and the impact of decreasing use of weight-bearing bones due to injury or immobilization. Space travel research on bone loss shows changes in bone that would typically take decades to study.

Using 3D imaging from a high-resolution peripheral quantitative CT, which can measure bone on a scale finer than human hair, bone structure of an arm (radius) and leg (tibia) bone were recorded pre-flight and after returning from space. Blood and urine samples were also taken in-flight to measure biomarkers of bone turnover and astronauts’ exercise was recorded pre-flight and in-flight. During space flight, astronauts participated in extensive in-flight training that included cardio and resistance training at the International Space Station (ISS).

Findings reveal the astronauts who trained heavily before space flight reduced their training volume in-flight and witnessed greater bone loss in the weight-bearing tibia with little change to the radius. Similar findings were seen for resistance training, although astronauts who increased resistance training during space flight protected some of their bone strength.

“Increasing exercise training before space flight is counterintuitive since it’s hard to maintain the level in space. Bone changes due to microgravity plus the reduction in exercise levels can result in further bone loss,” says Dr. Steven Boyd, PhD, principal investigator and director of the McCaig Institute for Bone and Joint Health at the CSM.

The impacts pre-flight and in-flight training levels on bone loss suggest that astronauts who frequently trained before space flight may require different in-flight training. “The findings of the study relay the importance of noting pre-flight exercise when designing in-flight exercise programs so astronauts can try to maintain the level of training on-orbit to preserve their bone strength,” says Gabel.

Long-term impacts of bone loss from space are still unknown and there is little research on whether bone loss is reversible. “Future research needs to look at whether bone can recover and if the changes in bone microarchitecture are permanent,” says Boyd, professor at the Schulich School of Engineering, the Faculty of Kinesiology and the CSM. “Upcoming TBone studies will look at what happens after a year of space flight and whether bone loss stabilizes in orbit.”

The TBone study is a Canadian research project, funded by the Canadian Space Agency (CSA) in partnership with National Aeronautics and Space Administration (NASA) and crew members around the world. The study team also includes two members from the European Space Agency (Drs. Anna-Maria Liphardt, PhD, Martina Heer, PhD) as well as two from NASA (Drs. Scott Smith, PhD, Jean Sibonga, PhD).

Steven Boyd is a professor at the Cumming School of Medicine (CSM) in the Department of Radiology at the University of Calgary, and holds a joint position at the Schulich School of Engineering and the Faculty of Kinesiology. He is the Bob and Nola Rintoul Chair in Bone and Joint Research and the McCaig Chair in Bone and Joint Health. He is also the director of the McCaig Institute for Bone and Joint Health.

Leigh Gabel is a postdoctoral fellow in the Department of Radiology at the Cumming School of Medicine with the McCaig Institute for Bone and Joint Health.

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