Musculoskeletal Responses to Microgravity Environments

Exposure to microgravity rapidly disrupts the normal loading patterns that maintain musculoskeletal integrity on Earth. Within days, skeletal muscle mass declines, particularly in antigravity and postural muscle groups, while intervertebral discs absorb excess fluid and swell in the absence of axial compression. The spinal column lengthens, lumbar curvature flattens and trunk stability diminishes, contributing to back pain and an elevated risk of disc herniation. Concurrently, changes in spinal motor control strategies emerge, with altered recruitment of deep paraspinal stabilisers and increased reliance on abdominal musculature. Bone mineral density also decreases at weight-bearing sites, compounding the risk of fracture. Ground-based analogues such as bed rest and dry immersion reproduce key features of unloading, enabling investigation of cell-level mechanisms in muscle and cartilage, and assessment of countermeasures. Current efforts focus on optimising in-flight exercise protocols, resistive devices and intermittent artificial loading to preserve muscle volume, bone strength and spinal health, with potential terrestrial applications for patients who experience prolonged inactivity.

Research from Nature Portfolio

Recent studies have investigated how reduced gravity levels affect muscle contractile behaviour during locomotion. Simulated Lunar and Martian gravities were shown to alter joint kinematics and force production in the calf muscle, with gastrocnemius medialis activation reaching a plateau below Earth gravity. These findings challenge the assumption of a simple linear scaling of muscle demand and highlight the need to tailor exercise prescriptions for different planetary environments. The work emphasises that hypogravity locomotion practice on the Moon may not directly translate to Mars, underlining the importance of gravity-specific training regimens for long-duration missions.

Musculoskeletal Responses to Microgravity Environments publication trend

The graph below shows the total number of articles in musculoskeletal responses to microgravity environments across all publications each year (not limited to Nature Index journals).

Technical terms

Microgravity: A near-weightless environment in which gravitational forces are greatly reduced compared with Earth’s gravity.

Muscle atrophy: Loss of muscle mass and strength resulting from decreased mechanical loading or neural activation.

Intervertebral disc (IVD): Fibrocartilaginous structure between vertebrae that absorbs shock and allows spinal flexibility; susceptible to swelling under unloading.

Dry immersion: A ground-based analogue of microgravity in which subjects are immersed in water while remaining dry, leading to fluid shifts and musculoskeletal unloading.

Parabolic flight: An aerial manoeuvre creating brief periods of microgravity or partial gravity to study physiological responses in real time.

Axial loading: Compression force along the spine or limb axis that maintains bone and muscle health under normal gravity.

References

1. DI-5-Cuffs: Lumbar Intervertebral Disc Proteoglycan and Water Content Changes in Humans after Five Days of Dry Immersion to Simulate Microgravity. International Journal of Molecular Sciences (2020).
2. Intervertebral Disc Swelling Demonstrated by 3D and Water Content Magnetic Resonance Analyses after a 3-Day Dry Immersion Simulating Microgravity. Frontiers in Physiology (2016).
3. Spinal Health during Unloading and Reloading Associated with Spaceflight. Frontiers in Physiology (2018).
4. Gastrocnemius medialis contractile behavior during running differs between simulated Lunar and Martian gravities. Scientific Reports (2021).
5. Lunar and mars gravity induce similar changes in spinal motor control as microgravity. Frontiers in Physiology (2023).
6. Lumbopelvic Muscle Changes Following Long-Duration Spaceflight. Frontiers in Physiology (2019).
7. Crew-Friendly Countermeasures Against Musculoskeletal Injuries in Aviation and Spaceflight. Frontiers in Physiology (2020).