TBone: How does space affect the strength of our bones?

Credits: Canadian Space Agency (CSA), NASA, European Space Agency

Physical activity is vital to our bones. When we walk, dance, play hockey and enjoy other forms of exercise, the force required for us to work against gravity in order to carry our own body weight regenerates our bone tissue, and makes our skeletal system stronger. When we are less mobile, our bones lose density and strength. This can be a problem for the elderly if they are less active, for patients confined to their bed for long periods, and also for astronauts in space, who spend much of their time floating in weightlessness.

Bone loss in space

While we typically lose about 1% of our bone mass each year, astronauts in space can lose up to 1.5% of their bone mass each month. Much of this loss is reversed when astronauts return to Earth. However, scientists do not really know how this may have affected the strength and quality of their bones, which could be a significant issue for future long-term missions to more distant destinations, like Mars. This is the subject of a Canadian study called TBone, which is currently underway with crew members of the International Space Station (ISS).

Astronauts in space get about 2 hours of exercise each day

Astronauts in space get about 2 hours of exercise each day, which helps maintain their bone mass. (Credit: NASA)

TBone: Do astronauts regain lost bone?

With funding and support from the CSA, Dr. Steven Boyd of the University of Calgary has designed an experiment called TBone that uses new 3D imaging technology to study changes in bone mass, structure and density in high resolution. The 10 astronauts taking part in TBone undergo bone scans on their leg and forearm before and after space flight to measure bone density and architecture to see if and how astronauts regain bone structure after their missions. The study also uses blood and urine samples, as well as in-flight food intake, medication, supplements and exercise for a full range of the many factors that can impact bone loss. Dr. Boyd will also compare his results with bone density tests regularly performed by NASA on all astronauts as part of medical monitoring.

Helping people on Earth

Since bone loss in space occurs much more quickly than on Earth, the ISS can help accelerate research.

"What we can learn in 6 months of space flight would take us a decade on Earth," says Dr. Boyd. Studying bone loss during space flight is a useful model for bone loss due to reduced mobility, ageing and even menopause. Dr. Boyd explains that "with age, we all lose bone. But the hormone changes during menopause can even further accelerate that loss."

The outcomes of TBone could be used to better understand bone loss, identify those who are predisposed to bone loss, and lead to individualized treatment strategies.

The TBone team began collecting data for the experiment in 2015. Dr. Steven K. Boyd of the University of Calgary is the principal investigator for TBone. Dr. Paul Hulme is the scientific coordinator of the project, and the co-investigators are Dr. Anna-Maria Liphardt, German Sport University Cologne, Germany; and Dr. Martina A. Heer, University of Bonn, Germany. Two of the team members, Dr. Jean Sibonga and Dr. Scott M. Smith, are NASA scientists at the Johnson Space Center.

The researchers will scan both legs and forearms of a total of 10 astronauts for the study, which is expected to be complete in 2020.

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