Changes in intervertebral disc morphology persist 5 mo after 21-day bed rest

Area of Science:

• Space Physiology
• Musculoskeletal Research
• Biomedical Imaging

Background:

• Head-down tilt bed rest simulates microgravity effects on the human body.
• Understanding lumbar spine recovery post-bed rest is crucial for astronaut health and terrestrial populations.
• Previous studies highlight muscle atrophy and disc degeneration, but recovery dynamics remain unclear.

Purpose of the Study:

• To assess the recovery of lumbar intervertebral discs and paraspinal muscle cross-sectional area (CSA) after prolonged bed rest.
• To investigate changes in lumbar muscle activation patterns post-bed rest using T2-weighted MRI.
• To explore the relationship between muscle changes, activation, and low back pain incidence.

Main Methods:

• Utilized magnetic resonance imaging (MRI) to measure intervertebral disc dimensions and muscle CSA.
• Employed a standardized isometric spinal extension loading task to assess muscle activation via T2-weighted signal intensity.
• Monitored seven healthy males undergoing two 21-day head-down tilt bed rest periods with a 153-day recovery interval.

Main Results:

• Intervertebral disc volume, height, and length changes did not revert to pre-bed rest values after 153 days.
• Muscle CSA, including multifidus, psoas, and quadratus lumborum, recovered and showed significant increases post-recovery.
• A trend for increased erector spinae and multifidus activation was observed post-bed rest; reduced muscle CSA and increased signal intensity correlated with low back pain.

Conclusions:

• While spinal extensor muscle CSA recovers within 5 months post-bed rest, intervertebral disc changes persist.
• These findings suggest potential long-term structural implications of bed rest on the lumbar spine.
• The study provides insights into recovery mechanisms and identifies potential biomarkers for low back pain risk.