Astronauts are also at increased risk of spinal disc herniation. (File photo)
Yoga may help fight spinal stiffness and reduced mobility suffered by astronauts during prolonged spaceflight, a new study on NASA crew members suggests.
While astronauts on long space missions do not experience a change in spinal disc height, the muscles supporting the spine weaken.
The study by researchers at University of California San Diego School of Medicine in the US provides new insights into the elevated rates of back pain and disc disease associated with prolonged spaceflight.
"These findings run counter to the current scientific thinking about the effects of microgravity on disc swelling," said Douglas Chang, associate professor at UC San Diego Health, and first author of the study.
The findings suggest possible preventive steps to reduce the spinal effects of spaceflight. Core-strengthening exercises, like those recommended for patients with back pain on Earth, might be a useful addition to the astronaut exercise training programme, Chang said.
He also said yoga might be another promising approach, especially for addressing spinal stiffness and reduced mobility.
"It is information like this that could provide helpful information needed to support longer space missions, such as a manned mission to Mars," said Chang.
Six NASA crew members were studied before and after spending four to seven months in microgravity on the International Space Station (ISS).
Each astronaut had magnetic resonance imaging (MRI) scans of their spines before their mission, immediately after their return to Earth and again one to two months later.
The researchers' goal was to understand factors affecting lumbar spine strength and low back pain during long-duration spaceflight, as well as the spine's response after returning to Earth gravity.
Back pain is common during prolonged missions, with more than half of crew members reporting spinal pain.
Astronauts are also at increased risk of spinal disc herniation in the months after returning from spaceflight - about four times higher than in matched controls.
Back issues in astronauts are accompanied by a roughly two-inch increase in body height, thought to result from spinal unloading (lack of weight carried by the lower back) and other body changes related to microgravity.
The MRI scans showed significant weakening of paraspinal lean muscle mass during the astronauts' time in space.
The functional cross-sectional area of the paraspinal muscles decreased by an average of 19 per cent from preflight to immediate post-flight scans.
A month or two later, only about two-thirds of the reduction had recovered.
There was an even more dramatic reduction in the functional cross-sectional area of the paraspinal muscles relative to total paraspinal cross-sectional area.
The ratio of lean muscle decreased from 86 per cent preflight to 72 per cent immediately post-flight.
The study was published in the journal Spine.
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