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TBone: Effects of microgravity on bones

Health science

The Canadian TBone experiment used 3D imaging technology to study changes in astronauts' bone health caused by the time they spend in space.


Our bones constantly undergo a reshaping process in response to everyday use. On Earth, bones are optimized for working in gravity, the force they must work against to support our body weight.

Due to weightlessness and reduced exercise, more bone is lost than replaced during extended space flight.

While adults past age 50 typically lose about 1% of their bone mass each year (a process that can eventually lead to osteoporosis), astronauts in space can lose up to 1.5% each month. Fortunately, much of this loss is reversed when astronauts return to Earth. TBone's scientists wanted to determine how this cycle of loss and regain affects the long-term strength and quality of bones.

Studies like TBone and the upcoming TBone2 could:

TBone - Effects of microgravity on bones with astronaut Tim Peake

Credits: Canadian Space Agency, NASA, European Space Agency


Using high-resolution imagery, TBone's researchers:

 Impacts on Earth

"What we can learn in six months of space flight would take us a decade on Earth," said Dr. Steven Boyd, TBone's Principal Investigator.

TBone offered researchers a better understanding of diseases like osteoporosis, a bone loss disorder that affects approximately 10% of the Canadian population aged 40 and over. Further research could help identify those who are prone to bone loss, and design individualized treatment strategies to predict and prevent fractures caused by low bone density.

How it works

Seventeen astronauts participated in this study.

  1. Participants underwent high-resolution 3D imaging of their wrists and ankles before and after their missions. This created a comparative picture of the microscopic shapes and structures inside the bones.
  2. Throughout their mission, astronauts provided blood and urine samples for many studies. The data from these samples was shared under an international agreement, and was used for TBone to understand the factors involved in bone adaptation.
  3. Scientists also kept careful records about factors that could affect the results, such as food intake, medication, supplements, and exercise routine.


The TBone experiment confirmed that although astronauts on the International Space Station (ISS) follow daily exercise programs, bone loss progresses proportionally to the length of their missions. An astronaut's skeleton, floating in microgravity, appears to age at an accelerated rate during a six- or seven-month stay in space – the equivalent of almost 20 years of bone loss on Earth. The study's findings also suggest that increasing exercise during their mission as compared to pre-flight was more likely to preserve bone strength while spending time away from Earth's gravity.

These findings have important implications for future space travellers headed to distant destinations like Mars, and for patients on Earth who are immobilized or injured for long periods of time. A follow-on study, TBone2, will continue to investigate the mechanisms of bone loss and regain in astronauts for missions of up to one year on the ISS.

Human bones contain a honeycomb-like structure that helps give support and strength. 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.


The TBone team began collecting data in . The research concluded in .

Astronauts in space get about 2 hours of exercise each day

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

Research team

Principal investigator


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