ISS - International Space Station logo.
May 17, 2021
Astronauts rocket off Earth to spend months isolated in orbit some 250 miles overhead. By any measure, they have fortitude and backbone in spades.
Image above: NASA astronaut Kate Rubins adjusts research hardware aboard the International Space Station. Her feet are strapped to the floor to give her leverage as she works in the station’s low gravity. The longer she stays in this low gravity, the more her bone density and muscle mass will change. Image Credit: NASA.
Backbone, however, is exactly what’s at risk as astronauts float in low gravity aboard the International Space Station. For every month in space, astronauts’ weight-bearing bones become roughly 1% less dense if they don’t take precautions to counter this loss. What could be happening?
Without the continuous load of Earth’s gravity, the living tissues of bone reshape themselves. Freed from pressures of Earth’s surface, cells that build new bone slow down their work. Cells that remove old bone keep chugging along. Removal outpaces growth, producing weaker, more brittle bones. Simultaneously, muscles usually activated by simply standing on Earth start to atrophy because they no longer need to work as hard.
To learn more, NASA turns to researchers like Dr. Ashley Weaver, a biomedical engineer in the Center for Injury Biomechanics at Wake Forest University in Winston-Salem, North Carolina. Weaver and her team study how spaceflight affects the network of bones and muscles in the spinal column. This network provides structural support for vital organs, including the brain, heart, and lungs.
“Spinal health is integral to postural control and facilitating the core trunk movements required for all activities on mission,” explains Weaver. “So, it’s crucial that we understand how these muscle changes are influenced by long-duration exposure to microgravity.”
Weaver’s team compares detailed scans of astronauts’ spines immediately before and after spaceflight. Techniques such as quantitative computed tomography, or “qCT,” and magnetic resonance imaging, or MRI, allow researchers to pinpoint subtle shifts in bone density and muscle size upon return to Earth.
Changes in an astronaut’s qCT scans, for example, reveal the degree to which spaceflight hollows out bones. Changes in MRI scans reveal how much spaceflight causes muscles to atrophy, seen through the accumulation of fat tissue in the muscle and shifts in muscle size. By studying muscle and bone together, Weaver hopes to tease out their “cross-talk”— how loss of bone density affects muscles, as well as how changes in muscle function and strength influence bone density.
International Space Station (ISS). Image Credit: NASA
After scrutinizing trends found through these scans, scientists and engineers will brainstorm strategies — such as specific resistive exercises — to counter bone and muscle loss in space. These strategies may prove useful as missions stretch longer, to the Moon and Mars. On Earth, similar strategies could help people with bone diseases such as osteoporosis to strengthen their weakened spines.
Nine astronauts who each lived on the space station for more than six months have been scanned. Expedition 64 crew were among the last examined for this study. "Now that all scanning is complete, we' re looking forward to learning what bone and muscle changes occur during space missions and how these relate to injury risk," said Weaver.
NASA's Human Research Program, or HRP, is dedicated to discovering the best methods and technologies to support safe, productive human space travel. HRP enables space exploration by reducing the risks to astronaut health and performance using ground research facilities, the International Space Station and analog environments. This leads to the development and delivery of an exploration biomedical program focused on several goals: informing human health, performance, and habitability standards; developing countermeasures and risk-mitigation solutions; and advancing habitability and medical-support technologies. HRP supports innovative, scientific human research by funding more than 300 research grants to respected universities, hospitals and NASA centers to over 200 researchers in more than 30 states.
Related links:
Human Research Program (HRP): https://www.nasa.gov/hrp/
Studying muscle and bone: https://www.nasa.gov/mission_pages/station/research/station-science-101/bone-muscle-loss-in-microgravity/
Space Station Research and Technology: https://www.nasa.gov/mission_pages/station/research/overview.html
International Space Station (ISS): https://www.nasa.gov/mission_pages/station/main/index.html
Images (mentioned), Text, Credits: NASA/Kelli Mars/Human Research Program Strategic Communications/Mohi Kumar/Jennifer L. Turner.
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