We can't all be astronauts, but the Artemis II crew has fitness lessons for everyone

The Artemis II astronauts don't have a lot of space to exercise. That's why they've got the flywheel — a small device that can be used for strength and cardio workouts.

Even a few days away from Earth can alter the human body. Without the constant pull of gravity on the skeleton, muscle and bone can quickly atrophy. To combat this immediate physical decline, the four astronauts aboard Orion on the Artemis II mission are using a specially designed machine known as the flywheel.

In a video blog posted before the crew launched, Canadian astronaut Jeremy Hansen compared the flywheel to a rowing machine. Astronauts strap their feet onto a small platform and pull on a handle connected to a cable. Pulling spins a flywheel, which works like a yo-yo — astronauts get as much resistance as they put into it. The device is small, not unlike an extra large shoebox, and can provide both cardiovascular workouts and resistance exercises up to 400 pounds. Astronauts can use it to do weightlifting moves like squats, deadlifts and curls.

The flywheel has been years in the making. Jessica Scott, an exercise physiologist at Memorial Sloan Kettering Cancer Center, worked on early prototypes for NASA, anticipating that astronauts would be vulnerable to rapid muscle atrophy without physical exertion. Scott compares ten days in space to ten days in bed. During that timeframe, muscles start to lose size quickly, and the heart is especially vulnerable with this decline in strength.

Researchers recruited 30 subjects willing to lie in bed for 70 days to study the early flywheel prototypes. More than 10,000 people applied for those 30 positions, calling themselves the "pillownauts." Participants were divided into different groups. Some stayed in bed all day. Others broke their bed rest to work out on traditional exercise equipment or used the flywheel. The goal was not to improve fitness but to prevent declines. The flywheel delivered the results researchers were hoping for — the small device could prevent declines at the same level that a full gym could achieve.

Context

The Artemis II crew — Christina Koch, Jeremy Hansen, Victor Glover and Reid Wiseman — share tight quarters aboard the Orion spacecraft on their way home. Orion's interior measures only 316 cubic feet, about the size of a small bedroom. Other missions aboard the International Space Station have full suites of exercise equipment. The flywheel has not yet been tested for longer durations, but researchers are hopeful it could provide fitness benefits for astronauts during extended periods of gravity deprivation.

What's Next

The research has implications beyond space exploration. Thomas Lang, a radiologist who studies bone and muscle loss and has worked with NASA on exercise science for previous missions, notes that bone density and mass reach a peak in late twenties or early thirties. Over time, hormonal changes lead to bone loss, particularly affecting older adults and women.