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The TBone studies: Effects of microgravity on astronauts' bones

Health science

The Canadian TBone and TBone2 experiments use 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.

Researchers want to know whether bone loss might reach its highest levels during the first six months of space flight and continue afterward, as astronauts remain in space.

The objective of the TBone investigation was to determine how this cycle of loss and regain affects the long-term strength and quality of bones. TBone2 will continue to investigate the mechanisms of bone loss and regain in astronauts undertaking missions of up to one year on the International Space Station (ISS).

Studies like TBone and TBone2 could:

European Space Agency (ESA) astronaut Tim Peake explains the Canadian experiment TBone. (Credits: Canadian Space Agency [CSA], NASA, ESA)

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.



Using high-resolution imagery, TBone's researchers:


Researchers will:

 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. According to Osteoporosis Canada, at least 1 in 3 women and 1 in 5 men will break a bone due to osteoporosis in their lifetime. 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.


Thirty astronauts will take part in this study.

  1. Participants will undergo high-resolution 3D imaging of their wrists and ankles before and after their missions.
  2. Data will be gathered from the same group of astronauts during other CIPHER experiments – such as ones that examine the effects of space flight on blood, the cardiovascular system, and stress. This will add knowledge to the TBone2 findings.

As part of NASA's CIPHER program, TBone2 will examine subjects who take part in space flights of six weeks, six months, and one year – longer than the original TBone study. Comparing how astronauts' bodies react to different lengths of time exposed to microgravity will help researchers test a hypothesis: that bone loss happens most during the first six months of space flight and then stabilizes within one year in space.

TBone2 is one of two CSA studies that are part of NASA's CIPHER program. The other is Vascular Calcium.

CIPHER, which stands for Complement of Integrated Protocols for Human Exploration Research, brings together specially selected studies to be conducted on the ISS. CIPHER is designed to help better understand the impact of long-duration space flight by comparing the effects of different mission lengths: short stays, standard six-month missions, and long-duration (one-year) space flights.


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-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.


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

The TBone2 team expects to begin its data collection 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 prevent some of the bone loss that occurs in microgravity. (Credit:  NASA)

Research team

Dr. Steven Boyd of the University of Calgary is principal investigator for the TBone series.

His co-investigators for TBone were:

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