The Weight of Lightness: The Role of Physical Exercise in Musculoskeletal Deconditioning in Space

Abstract

Prolonged exposure to microgravity causes severe musculoskeletal deconditioning, including a monthly loss of 1–2% in bone mineral density and a 20–30% reduction in muscle strength, particularly in antigravity muscles. These alterations compromise astronauts’ functional capacity and mission safety. This work examines physical exercise as the primary countermeasure against microgravity-induced deconditioning and proposes a three-phase rehabilitation model applicable to pre-flight, in-flight, and post-flight stages. A systematic literature review (2015–2025) was conducted using PubMed and Google Scholar, selecting 15 relevant studies from NASA, ESA, and Roscosmos programs. Results show that resistive and combined aerobic-resistive training (e.g., flywheel systems, ARED, NASA SPRINT) effectively mitigate bone and muscle loss, though full recovery after spaceflight remains incomplete. The study highlights the physiotherapist’s pivotal role in designing and monitoring multimodal, individualized exercise protocols that bridge aerospace medicine and terrestrial rehabilitation.