Space travel: Going into space is a real pain in the back

CNN
—

A six-month stay on the International Space Station can be a pain in the back for astronauts. While they can gain up to 2 inches in height temporarily, that 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 got longer. Their flight medical data shows that more than half of US astronauts have reported back pain, especially in the lower back. Up to 28% indicated that it was moderate to severe pain, sometimes prolonged for the duration of their mission.

Things don’t get better when they return to Earth’s gravity. In the first year after their mission, astronauts have a 4.3 times higher risk of suffering a herniated disc.

“It’s kind of an ongoing problem that has been significant and a cause for concern,” said Dr. Douglas Chang, first author of the new study and associate professor of orthopedic surgery and chief of the physical medicine and rehabilitation service at the University of California San Cheers Diego. “So this study is the first to take it just from an epidemiological overview and look at the possible mechanisms of what is happening to the backs of astronauts.”

A lot of attention has focused on intervertebral discs, the spongy cushions that sit between our vertebrae, as the culprits behind back problems astronauts face. But the new study goes against that thinking. In this NASA-funded research, Chang’s team observed little to no change in the disks, their height, or swelling.

What they did see 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 extremities in an Earth-like environment, while protecting discs and ligaments from strains or injury.

In microgravity, the torso elongates, most likely due to spinal unloading, in which the curvature of the spine flattens out. Astronauts also don’t use muscle tone in their lower backs because they don’t bend over or use their lower backs to move, like on Earth, Chang said. This is where the pain and stiffness occurs, as if astronauts had a body cast for six months.

MRIs 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, an Earth, they are only recovering about 68% of their losses,” Chang explained.

Chang and his team see this as a serious problem for long-term crewed missions, especially when considering a trip to Mars that could take eight or nine months just to reach the Red Planet. That travel, and the potential time astronauts spend in Martian gravity (38% of Earth’s surface gravity) creates the potential for muscle atrophy and wasting.

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 spinal ultrasounds, to see what happens to astronauts while on the space station.

Because no one likes back pain and loss of muscle mass, Chang suggested countermeasures that should be added to the two to three-hour training that astronauts have on the space station every day. Although their exercise machines target a variety of issues, including cardiovascular and skeletal health, the team believes space travelers should also include a spinal-focused core-strengthening program.

In addition to the “fetal fold” position that astronauts use in microgravity to stretch the lower back or relieve back pain, Chang suggested yoga. But he knows that is easier said than done.

“A lot of yoga relies on the effects of gravity, like downward-facing dog, where you can stretch your hamstrings, calf muscles, back of the neck, and shoulders due to gravity. When you remove that, you may not have the same benefit.”

Any machines on the space station must also be designed with respect to weight, size, and even the reverberations they might produce on the station.

Chang and the other researchers brainstormed with virtual reality equipment about different exercise programs that would allow astronauts to invite friends, family, or even Twitter followers to join them in a virtual workout, making daily repetition of their workouts be more fun and competitive.

One of Chang’s teammates has felt this pain personally. Dr. Scott Parazynski is the only astronaut to reach the top of Mount Everest. He experienced a herniated disc after returning from the ISS to Earth. Less than a year later, when he attempted to climb Everest for the first time, he had to be airlifted. After a rehabilitation process, he finally made it to the summit. Now, he talks to current astronauts about ways they can contribute to studies of their health in microgravity.

Keeping astronauts healthy and fit is the least they can do, Chang said.

“When a crew comes back, they say that on the side of the space station they see this beautiful blue planet,” he said. “Everything they hold dear is on this fragile little planet. And they look out the other window and see infinity stretching out 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 furthering space awareness and taking incremental steps in any way they can for the next crew.”