MICROGRAVITY AND SKELETAL DECONDITIONING: A NARRATIVE REVIEW OF BONE DENSITY LOSS AND EXERCISE COUNTERMEASURES IN ASTRONAUTS

Izabela Matuszek; Natalia Badowska; Bartosz Wiśniewski; Dominika Pachnowska; Natalia Pluta; Katarzyna Aleksandra Nowak; Alicja Rutkowska-Nowosielska; Oliwia Nikola Czekanow; Zofia Kania-Bonicka; Jerzy Demkow

doi:10.31435/ijitss.2(50).2026.5793

Authors

Izabela Matuszek Medical University of Warsaw, ul. Żwirki i Wigury 61, 02-091 Warszawa, Poland https://orcid.org/0009-0008-4002-2868
Natalia Badowska Medical University of Warsaw, ul. Żwirki i Wigury 61, 02-091 Warszawa, Poland https://orcid.org/0009-0003-9767-334X
Bartosz Wiśniewski Medical University of Warsaw, ul. Żwirki i Wigury 61, 02-091 Warszawa, Poland https://orcid.org/0009-0004-1025-5573
Dominika Pachnowska Medical University of Warsaw, ul. Żwirki i Wigury 61, 02-091 Warszawa, Poland https://orcid.org/0009-0000-6326-655X
Natalia Pluta Medical University of Warsaw, ul. Żwirki i Wigury 61, 02-091 Warszawa, Poland https://orcid.org/0009-0006-9108-8993
Katarzyna Aleksandra Nowak Medical University of Warsaw, ul. Żwirki i Wigury 61, 02-091 Warszawa, Poland https://orcid.org/0009-0002-2324-3219
Alicja Rutkowska-Nowosielska Medical University of Warsaw, ul. Żwirki i Wigury 61, 02-091 Warszawa, Poland https://orcid.org/0009-0008-4018-7179
Oliwia Nikola Czekanow Medical University of Warsaw, ul. Żwirki i Wigury 61, 02-091 Warszawa, Poland https://orcid.org/0009-0008-4813-7862
Zofia Kania-Bonicka Medical University of Warsaw, ul. Żwirki i Wigury 61, 02-091 Warszawa, Poland https://orcid.org/0009-0007-5511-133X
Jerzy Demkow Medical University of Warsaw, ul. Żwirki i Wigury 61, 02-091 Warszawa, Poland https://orcid.org/0009-0009-8637-9181

DOI:

https://doi.org/10.31435/ijitss.2(50).2026.5793

Keywords:

Microgravity, Bone Mineral Density, Spaceflight Osteoporosis, Skeletal Deconditioning, Exercise Countermeasures, ARED, HR-pQCT, QCT, Sclerostin, Bisphosphonates, Long-Duration Spaceflight

Abstract

Background: Microgravity uncouples skeletal remodelling — accelerating resorption and suppressing formation — causing BMD losses of 0.5–2%/month at weight-bearing sites, six-month ISS deficits are comparable to a decade of postmenopausal bone loss.

Objective: To synthesise evidence on mechanisms, countermeasure efficacy, recovery, and gaps for exploration.

Methods: Narrative review. PubMed/MEDLINE, Scopus, and NASA Technical Reports Server searched 1990–2025, 82 of 312 records included: spaceflight studies with DXA, QCT, or HR-pQCT, bed-rest RCTs, systematic reviews.

Results: ARED reduced hip BMD loss by ~40% versus aerobic-only protocols, proximal femur deficits persist. HR-pQCT confirmed resorption exceeded formation threefold in-flight, bone repair concentrated within 6 months. QCT revealed trabecular deficits at 24 months despite DXA normalisation. Alendronate preserved BMD in the only spaceflight RCT (n=28).

Conclusions: Available evidence suggests current exercise countermeasures may be insufficient for missions beyond six months. Bisphosphonate therapy alongside ARED may be considered for high-risk crewmembers, though evidence is limited to a single small trial. Longer missions will likely require multimodal strategies. Pre-flight risk stratification and anti-sclerostin trials are priority research needs.

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