As humans prepare to return to the moon after an absence of more than half a century, researchers have taken a radical approach to keeping astronauts fit as they potter around the orb of rock.
To prevent lunar explorers from becoming weak and weak in the low gravity environment, scientists suggest that astronauts go for a run. But this being space, it’s not just any kind of running – researchers have advised astronauts to run around a “lunar wall of death” several times a day.
Using a rented Wall of Death – a giant wooden cylinder used by motorcycle stunt performers in their gravity-defying fairground act – a 36m-tall telescopic crane, and some bungee cords, researchers showed it was possible for a human to run fast enough in the moon gravity not only to stay on the wall, but to generate sufficient lateral force to combat bone and muscle wasting.
“I’m amazed that no one had the idea before,” said Alberto Minetti, professor of physiology at the University of Milan. “It could be a convenient way to exercise on the moon.” And easier than building a spinning moon base that generates the power, like the giant wheel of Space Station One in 2001: A Space Odyssey.
Humans have not set foot on the moon since the end of the Apollo program in 1972, but Nasa and other space agencies are preparing for a return, with long-term missions in permanent habitats. Nasa’s Artemis astronauts will fly around the moon next year with a follow-up mission to the surface as early as 2026.
The hostile lunar environment presents several challenges, from ensuring that astronauts have air, food and water to being well protected from space radiation. But without normal gravity to counteract, astronauts lose bone and muscle mass, along with the fine nervous system control needed for coordinated movements, making measures to combat “deconditioning” a priority.
Calculations by Minetti and his colleagues show that humans would find it extremely difficult to run around a Wall of Death on Earth without falling down. But in lunar gravity, which is one sixth of that on Earth, the achievement is much easier. According to his calculations, running at more than 8mph should be enough.
To test the idea, two researchers ran around a 10m-wide Wall of Death while attached to a bungee cord suspended from the crane. The setup mimicked lunar gravity by taking five-sixths of their body weight. Combined with treadmill data, the scientists conclude that running for a few minutes at the beginning and end of each day should generate enough lateral force, or “artificial gravity,” to keep bones and muscles strong and maintain good nervous system control.
Rather than transporting an actual Wall of Death to the moon, astronauts could be housed in circular habitats, allowing them to run around the walls of their off-world homes, the team writes Royal Society Open Science.
“A horizontal walking cylinder certainly promises to be a useful countermeasure to help prevent deconditioning in reduced gravity on the moon,” says Maria Stokes, professor of neuromusculoskeletal rehabilitation at the University of Southampton. But specific training for everyday life and work activities will still be needed, she added, to maintain specific skills and ensure astronauts work safely on the surface.
Nick Caplan, professor of aerospace medicine and rehabilitation at Northumbria University, Newcastle, said the proposal was “certainly novel” but questioned whether early lunar habitats would be large enough to accommodate such runways. With colleagues, he is working on new approaches to exercise in space and on the moon, including inflatable cuffs to compress limbs and restrict blood flow.
“Blood flow restriction exercise has been shown in studies on Earth to provide similar muscle, bone and cardiorespiratory training benefits normally seen during higher intensity exercise, at much lower exercise intensities and durations,” Caplan said. “So it could make existing exercise countermeasures more effective at keeping astronauts healthy without the need for a lunar wall of death.”
