the astronauts who lived in International space station have significant reductions in terms of size and density of paraspinal muscles of the trunk on his return to Earth.
Some changes in the muscular composition they are still present until four years after a long-term space flight, according to new research by Katelyn Burkhart of the Massachusetts Institute of Technology and colleagues.
"The changes induced by the space flights in the morphology of paraspinal muscle it can contribute to backache commonly reported in the astronauts", says the study, published in the magazine spine.
of the trunk show a 'reduced area, increase in adipose tissue, after months in space. The researchers analyzed computed tomography (CT) scans of the lumbar spine (lower) in 17
who flew on a mission in the
International space station
. The scans obtained before and after the missions were analyzed to determine the changes in size and composition of the
. The average time in space was six months.
Acting up and down the spine, the paraspinal muscles They play a key role in the movement and posture of the spine. Previous studies have found a reduction in paraspinal muscle mass after a prolonged time in space, suggesting that muscle atrophy can occur without the resistance provided by gravity.
The CT scans showed reductions in the size of the paraspinal muscles after traveling to space. For individual muscles, muscle mass decreased from 4.6 to 8.8%. In the follow-up scans performed one year later, the size returned at least normal for all the muscles.
The scans also showed significant increases in the amount of adipose tissue present in the spinal muscles. As a result, the muscle density of the astronauts, which is inversely related to fat content, decreased from 5.9% to 8.8%. For most muscles, the composition is back to normal within a year.
However, for two muscles, -il lumbar square and the iliopsoas– the fat content has remained above the pre-flight values, even two to four years after astronaut come back from space travel. these muscles, which connect the vertebral column with the pelvis, are located laterally (along) the vertebral column. Compared, paraspinal muscles located behind the spine has recovered the normal size and density.
Changes in muscle size and composition varied among individuals. For some muscles, size changes were related, at least in part, to the amount and type of exercise astronauts performed while they were at zero gravity: resistance exercise or cycling. In-flight exercise does not seem to influence changes in muscle density.
Previous studies of the astronauts have connected the space travel with the muscle atrophy, especially the muscles that maintain posture and stability in a vertical position on the Earth in normal gravity. lot of astronauts they experience lumbar pain during and immediately after space missions and appear to have an increased risk of spinal disc herniation.
The new study is the first to measure changes in size and density of individual paraspinal muscles. The results show that muscle size returns to normal after recovery from the Earth, but that some changes in muscle composition, particularly the increase in fat infiltration, may persist for at least a few years.
Some of the changes in the spinal muscle appear to be influenced by the exercise, suggesting possible approaches to prevent the adverse effects of prolonged space flight on the health and functioning of the spine. Burkhart and his co-authors conclude: "Like the NASA plans future missions to Mars and beyond, these results can be used to guide future countermeasures to mitigate the decline in trunk morphology and associated functional deficits ".