Prospective case series
Determine the extent of paraspinal muscle cross-sectional area (CSA) and attenuation change after long-duration spaceflight and recovery on-Earth. Determine association between in-flight exercise and muscle atrophy.
Long-duration spaceflight leads to marked muscle atrophy. However, another negative consequence of disuse is intramuscular fatty infiltration. Notably, few studies have investigated the effects of spaceflight on intramuscular fatty infiltration, or how muscle atrophy is associated with in-flight exercise.
We analyzed CT scans of the lumbar spine (L1/L2) from 17 long-duration astronauts and cosmonauts to determine paraspinal muscle CSA and attenuation. CT scans were collected pre-flight, post-flight, 1-year post-flight, and, in a subset, 2–4 years post-flight. We measured CSA (mm2) and attenuation (Hounsfield Units, HU) of the erector spinae (ES), multifidus (MF), psoas (PS) and quadratus lumborum (QL) muscles. We used paired t-tests to compare muscle morphology at each post-flight time point to pre-flight values and Pearson correlation coefficients to determine the association between muscle changes and in-flight exercise.
ES, MF, and QL CSA and attenuation were significantly decreased post-flight compared to pre-flight (−4.6% to −8.4% and −5.9% to −8.8%, respectively, p < 0.05 for all). CSA of these muscles equaled or exceeded pre-flight values upon Earth recovery, however QL and PS attenuation remained below pre-flight values at 2–4 years post-flight. More resistance exercise was associated with less decline in ES and MF CSA, but greater decline in PS CSA. Increased cycle ergometer exercise was associated with less decline of QL CSA. There were no associations between in-flight exercise and muscle attenuation.
Both CSA and attenuation of paraspinal muscles decline after long-duration spaceflight, but while CSA returns to pre-flight values within 1 year of recovery, PS and QL muscle attenuation remain reduced even 2–4 years post-flight. Spaceflight-induced changes in paraspinal muscle morphology may contribute to back pain commonly reported in astronauts.
Level of Evidence: 4
*Harvard-MIT Health Sciences and Technology Program, Massachusetts Institute of Technology, Cambridge 02139, Massachusetts
†Center for Advanced Orthopaedic Studies, Beth Israel Deaconess Medical Center, 330 Brookline Ave., Boston 02215, Massachusetts
‡Department of Orthopaedic Surgery, Harvard Medical School, Boston 02115, Massachusetts.
Address correspondence and reprint requests to Katelyn Burkhart, MS, Harvard-MIT Health Sciences and Technology, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139; E-mail: firstname.lastname@example.org
Received 21 August, 2018
Revised 1 November, 2018
Accepted 21 November, 2018
The manuscript submitted does not contain information about medical device(s)/drug(s).
National Aeronautics and Space Administration (NASA) grant NNX16AC15G and by the National Space Biomedical Research Institute through NASA NCC 9-58 funds were received in support of this work.
No relevant financial activities outside the submitted work.
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