UCSD Study Finds Astronauts' Spinal Muscles Weaken While in Space

A study done by researchers at the University of California San Diego (UCSD) School of Medicine has found that the spinal muscles of astronauts weaken while in space and do not return to normal strength until months after their return to earth.

The study, published in the research journal Spine, also found that astronauts do not experience a change in spinal disc height, contrary to popular scientific belief.

Astronauts often report spinal pain during prolonged missions in space and are about four times more likely to suffer spinal disc herniation in immediate months after returning to earth. This was thought to be the result of a near two-inch increase in body height believed to stem from the lack of gravitational force on the lower back, allowing the spine to expand.

UCSD researchers studied six NASA astronauts before and after four to seven months in microgravity at the international space station. Crew members were given spinal MRI scans prior to departure from earth, immediately upon their return and once more four to eight weeks after.

MRI scans revealed “significant” atrophy of paraspinal lean muscle mass, or a decrease in size of the small muscles that connect to the vertebrae which move individual bones of the spine and prevent misalignment.

The functional, cross-sectional area of the paraspinal muscles decreased by an average of 19 percent from pre-launch to immediate return scans, according to the study, and only recovered about two thirds of its reduction a month or two later.

Also, the ratio of lean muscle to non-lean muscle decreased from 86 percent prelaunch to 72 percent immediately upon return to earth, and no consistent change in the height of the spinal intervertebral discs was seen.

The data suggests that some of the core-strengthening exercises recommended for patients on earth with back pain could be a useful addition to the astronaut exercise training program.

Douglas Chang, MD, PhD, associate professor of orthopedic surgery and chief of physical medicine and rehabilitation service at UC San Diego Health, and first author of the study, said that yoga could also be another “promising” technique to address spinal stiffness and reduced mobility issues.

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