Spending six months in space and coming home two inches taller may sound great to the vertically challenged, but the added height comes with a price – an increased risk of herniated discs and back pain.
A recent study found that with microgravity exposure in space, crewmembers experience spine-related issues, including a torso lengthening of 4 to 6 cm, two to three times the normal diurnal increase on Earth.
“This reportedly occurs because of spinal unloading, flattening of spinal curvature, loss of paravertebral muscle tone, and vertebral disc degeneration,” wrote the authors of “Lumbar Spine Paraspinal Muscle and Intervertebral Disc Height Changes in Astronauts After Long-Duration Spaceflight on the International Space Station,” recently published in the journal Spine from Wolters Kluwer Health.
“Flight medical data indicate that more than half of the U.S. astronauts report spine pain during their mission. Although in space, astronauts report that a lumbar flexed, “fetal tuck” position to stretch is the most effective way of alleviating back pain. The back pain is described with a moderate to severe level of intensity for 14 percent to 28 percent of U.S. astronauts. Shuttle crewmembers described pain lasting for 15 percent to 100 percent of their mission. The location of pain is reported most frequently in the following anatomic regions: 50 percent low back, 11 percent mid-back, 11 percent neck, and 1 percent chest.”
Six NASA crewmembers were imaged supine with a 3 Tesla MRI preflight. The crewmembers were also imaged immediately post-flight and again 33 and 67 days after landing. The research was conducted by scientists from the University of California’s Department of Orthopedic Surgery; the Ola Grimsby Institute of Bellevue, Wash.; KBRwyle of Houston; and the School of Biological and Health Systems Engineering at Arizona State University in Tempe.
Functional cross-sectional measurements of the paraspinal muscles were performed at the L3-4 level and was measured by grayscale thresholding within the posterior sections of all lumbar levels.
The images revealed that paraspinal lean muscle mass from the functional cross-sectional area decreased from 86 percent of the total PSM cross-sectional area to 72 percent right after the missions. A 68 percent post-flight recovery occurred over the next six weeks, leaving a significantly lower lean muscle fractional content compared with preflight values.
By contrast, lumbar intervertebral disc heights were not appreciably different at any point in the testing.
“The data reveal lumbar spine PSM atrophy after long-duration spaceflight,” said the paper.
“Some FCSA recovery was seen with 46 days post-flight in a terrestrial environment, but it remained incomplete compared with preflight levels.”
Post-flight, astronauts have a 4.3 times greater risk of herniated intervertebral discs compared to the general and military aviator populations.
Filed Under: Aerospace + defense
