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Rocket science: what spaceflight can tell us about skeletal health on Earth
  1. Kathryn E Ackerman1,2,3,
  2. Kristin L Popp2,3,4,
  3. Mary L Bouxsein2,3,5
  1. 1 Division of Sports Medicine, Boston Children's Hospital, Boston, Massachusetts, USA
  2. 2 Endocrine Division, Massachusetts General Hospital, Boston, Massachusetts, USA
  3. 3 Harvard Medical School, Boston, Massachusetts, USA
  4. 4 United States Army Research Institute of Environmental Medicine, Natick, Massachusetts, USA
  5. 5 Center for Advanced Orthopedic Studies, Beth Israel Deaconess Medical Center, Boston, Massachusetts, USA
  1. Correspondence to Dr Kathryn E Ackerman, Sports Medicine, Boston Children's Hospital, Boston, MA 02115, USA; kathryn.ackerman{at}

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In BJSM, Gabel and colleagues in their paper ‘Pre-flight Exercise and Bone Metabolism Predict Unloading-Induced Bone Loss due to Spaceflight’ study skeletal health in a unique population of ‘occupational athletes’: astronauts.1 Astronauts frequently experience cardiovascular deconditioning, immune suppression, balance disorders, strength deficits and bone loss as a result of space travel.2 After more than 50 years of space missions, various contributors to bone loss in astronauts have been postulated—microgravity, radiation, stress, metabolic disruption and altered calcium homeostasis all likely play a role.3 Using high-resolution three-dimensional imaging (HR-pQCT), Gabel et al report declines in bone mineral density (BMD), bone microstructure and strength at the distal tibia, although minimal changes at the distal radius.1 Their findings are broadly similar to prior reports, revealing an average rate of bone decline nearly 10-fold higher than that seen in postmenopausal women, although with remarkable interindividual variability seen in these astronauts.4 Notably, their analyses bring several new insights to our understanding of unloading-induced bone loss.


For spaceflight of 3.5–7 months, mission time predicted tibial BMD loss linearly, with accelerated trabecular bone loss in longer flights.1 A …

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  • Contributors KEA, KLP and MLB conceived of, wrote and edited the manuscript.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.