How does spaceflight influence sarcopenia, which is a common age-related muscle decline, specifically for elder adults? This is what a recent study published in Stem Cell Reports hopes to address as a team of researchers investigated how microgravity influences muscle cell function. This study has the potential to help scientists, mission planners, astronauts, and the public better understand the long-term health impacts of microgravity on muscle decline and the steps that can be taken to mitigate it.
For the study, the researchers launched skeletal muscle microtissues obtained from both young and old adult donors aboard the SpaceX CRS-25 mission to the International Space Station (ISS), which occurred between July and August 2022. The goal of the study was to ascertain how muscles atrophy during prolonged periods of microgravity and how electrical stimulation can be used to reverse this trend. This study comes as scientists estimate that astronauts lose approximately 30 percent of their skeletal muscle mass while being exposed to microgravity for only one month.
In the end, the researchers identified that microgravity changed 86 muscle-specific age-associated genes while noting that the younger muscle fibers responded more positively to electrical stimulation than the older muscle fibers. It is this latter finding that enables the researchers to offer positive words for addressing the issue for spaceflight in the long-term.
“Using electrical pulses to trigger real-time muscle contractions in space, we can simulate exercise and observe how it helps protect against rapid muscle weakening in microgravity,” said Dr. Siobhan Malany, who is an associate professor in the College of Pharmacy at the University of Florida and a co-author on the study. “This technology advancement offers insight into how we might preserve muscle health during long-duration space missions and ultimately, how to combat age-related muscle loss here on Earth.”
The history of muscle loss from microgravity is well-documented and has been examined since the dawn of human spaceflight. It is estimated that astronauts can lose approximately 20 percent of their muscle mass during missions spanning only 5-11 days, while losing up to 30 percent of their muscle mass on longer missions. This has been determined to result from the lack of lower back and leg muscles needed since astronauts don’t stand up in space. To combat this, ISS astronauts conduct a daily exercise regimen for two hours involving a treadmill, bike, and specialized equipment designed to simulate weightlifting on Earth.
Recent studies discussing sarcopenia and spaceflight include a 2023 study published in Ageing Research Reviews that explored how spaceflight increased ageing while a 2024 study published in Scientific Reports discussed how spaceflight altered biological markers. Examples of how long-term spaceflight can impact muscle loss includes the one-year mission on the ISS with NASA astronaut Scott Kelly and Russian cosmonaut Mikhail Kornienko, who lived onboard the ISS from March 2015 to March 2016. Upon returning to Earth, both astronauts were found to have lost bone and muscle mass during their journey, highlighting the importance of better understand the physiological impacts of long-term spaceflight.
This most recent study and past research highlight the importance of raising awareness and addressing muscle loss during spaceflight, specifically as governments like the United States and China plan to send their own astronauts to the lunar surface within the next few years, and Mars sometime next decade. While future astronauts on the Moon and Mars won’t experience full microgravity, as both planetary bodies exhibit one-sixth and one-third gravity, respectively, protocols like electric stimulation to counteract muscle loss could prove beneficial for long-term astronaut health.
What new connections between spaceflight and sarcopenia will researchers make in the coming years and decades? Only time will tell, and this is why we science!
As always, keep doing science & keep looking up!