Pathophysiological Spine Adaptations and Countermeasures for Prolonged Spaceflight: Part II-Space Radiation.

The future of space exploration will include a prolonged presence on the Moon, commercial low-orbit spaceflight, and long-range missions to Deep Space, including a prolonged Martian presence. Understanding the effects the space environment will have on astronauts' musculoskeletal system is mission critical and include both microgravity and space radiation. In spaceflight, crewmembers are exposed to a vast mixture of radiation species and energies including cosmic rays (CR) from galactic cosmic radiation (GCR), solar ejections, and neutrons. Any trip beyond the protection of the Earth's electromagnetic field will expose astronauts to the near-maximum levels of lifetime allowable radiation exposure. We have previously reviewed how microgravity induces pathophysiological adaptations in the spine and how countermeasure strategies can play a role in minimizing astronaut morbidity. Now, through the National Aeronautics and Space Administration's (NASA) Human Research Roadmap (HRR), there is a renewed interest in characterizing and mitigating the effects of radiation as astronauts prepare for the Artemis missions and beyond. Thus, our aim in this critical narrative review is to focus on how the second greatest challenge to crewmembers' health, radiation, and identify how potential countermeasures will affect the spine.