Highlights of the story
Astronauts can temporarily grow 2 inches in height, but suffer from muscle loss and back pain
More countermeasures involving exercise can help mitigate pain and muscle wasting
A six-month stay on the International Space Station can be back-breaking for astronauts. While they may gain up to 2 inches in height temporarily, this effect is accompanied by a weakening of the muscles that support the spine, according to a new study.
Astronauts have been reporting back pain since the late 1980s, when space missions became longer. Their flight medical records show that more than half of American astronauts have reported back pain, particularly in the lower back. Up to 28% reported moderate to severe pain, sometimes lasting the duration of their mission.
Things don’t improve when they return to Earth’s gravity. In the first year after their mission, astronauts have a 4.3 times greater risk of suffering from a herniated disc.
“It’s kind of an ongoing problem that has been a major cause for concern,” said Dr. Douglas Chang, first author of the new study and associate professor of orthopedic surgery and chief of physical medicine and rehabilitation at University of California San Diego Health. “So this study is the first to take it from just an epidemiological description and look at the possible mechanisms of what’s happening with astronauts’ backs.”
A lot of attention has been focused on the intervertebral discs, the spongy shock absorbers that sit between our vertebrae, as the culprit for the back problems astronauts face. But the new study goes against that thinking. In this research, funded by NASA, Chang’s team observed little or no change in the discs, their height or swelling.
What they observed in six astronauts who spent four to seven months on the ISS was tremendous degeneration and atrophy of the supporting musculature in the lumbar (lower) spine, Chang said. These muscles are what help us stand upright, walk, and move our upper limbs in an environment like Earth, while protecting our discs and ligaments from strain or injury.
In microgravity, the torso elongates, most likely due to spinal unloading, in which the curvature of the spine flattens. Astronauts also don’t use muscle tone in their lower back because they don’t bend over or use their lower back to move, like they do on Earth, Chang said. This is where pain and stiffness occur, as if astronauts were in one body for six months.
MRI scans before and after the missions revealed that the astronauts experienced a 19% decrease in these muscles during their flight. “Even after six weeks of training and reconditioning here on Earth, they’re only recovering about 68 percent of their losses,” Chang explained.
Chang and his team see this as a serious problem for long-term manned missions, especially when considering a trip to Mars that could take eight to nine months just to reach the Red Planet. This journey, and the astronauts’ potential time spent in Martian gravity, 38% of Earth’s surface gravity, creates the potential for muscle atrophy and deconditioning.
The team’s future research will also look at reported neck problems, where there may be even more cases of muscle atrophy and a slower recovery period. They also hope to partner with another university on in-flight spine ultrasounds, to see what happens to astronauts while on the space station.
Since no one likes back pain and muscle wasting, Chang suggested countermeasures that should be added to the two to three hours of training astronauts get each day on the space station. While their exercise machines focus on a range of issues, including cardiovascular and skeletal health, the team believes space travelers should also include a core strengthening program that focuses on the spine .
In addition to the “fetal tuck” position that astronauts in microgravity use to stretch their lower backs or relieve back pain, Chang suggested yoga. But he knows that’s easier said than done.
“So much of yoga relies on the effects of gravity, such as downward dog, where a stretch through the hamstrings, calf muscles, back of the neck and shoulders is possible because of gravity. When you remove this, you may not get the same benefit.”
Any machine on the space station must also be designed for weight, size, and even the reverberations it might produce on the station.
Chang and the other researchers brainstormed with a virtual reality team about different exercise programs that would allow astronauts to invite friends, family or even Twitter followers to join them in a virtual workout, making the daily repetition of your workouts more fun and competitive.
One of Chang’s colleagues has felt this pain personally. Dr. Scott Parazynski is the only astronaut to have climbed the summit of Everest. He suffered a herniated disc after returning from the ISS to Earth. Less than a year later, when he tried to climb Everest for the first time, he had to be airlifted. After a rehabilitation process, he finally reached the top. Now, he’s talking to current astronauts about ways they can contribute to studies of their health in microgravity.
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Keeping astronauts healthy and fit is the least they can do, Chang said.
“When a crew comes back, they say that on one side of the space station, they see this beautiful blue planet,” he said. “All they love is on this fragile little planet. And they look out the other window and see infinity stretching into the darkness, and they come back with a different sense of themselves and their place in the universe
“All of them are committed to advancing space knowledge and making incremental steps in whatever way they can for the next crew.”