Maintaining Crew Bone Health

Abstract

Bone loss continues to be a concern in spaceflight, with some crew members depicting local losses of up to 25% within a 6-month mission. Possible causes are direct or indirect effects by microgravity, radiation, dietary restriction, and atmospheric challenges. Despite their magnitude, bone losses have not yet led to increased fracture rates in astronauts returning from low-Earth orbit (LEO) missions. This could change for deep space missions, in particular to planets where falls and trauma will occur. Physical countermeasures, meant to provide musculoskeletal loading forces in the body’s lower half, are an important contribution to crew bone health. This requirement becomes an increasing imperative with prolonged missions. Forces and moments transmitted from exercise devices should therefore be considered at an early stage of the planning of space habitats. In addition, appropriate shielding against ionizing radiation, avoidance of exaggerated accumulation of CO2, and provision of a balanced diet will all contribute to bone health in astronaut crews.