How do astronauts maintain their shape in space without gyms?

After years of studying on the International Space Station (ISS) and other spacecraft circling Low Earth Orbit (LEO), it’s clear that spending a long time in microgravity isn’t great for the human body. We’ve seen things like muscle shrinkage, weaker bones, and problems with eyesight, blood flow, and heart health. But, as NASA’s Twin Study revealed, these effects go beyond the obvious—they mess with our organs, mess with our heads, and even mess with our genes. Figuring out how to deal with these issues is super important for future trips to the Moon, Mars, and wherever else we might be heading in deep space.

To tackle the effects of microgravity, astronauts on the ISS stick to a tight routine of resistance training, good eating, and cardio to keep their muscles, bones, and other body parts in check. The problem is the workout gear on the ISS is too big and heavy to lug around on smaller spacecraft for those lengthy space journeys where space and weight are at a premium. So, NASA’s looking into whether simpler exercise plans that need little or no equipment can still keep astronauts in good shape.

Being in space for a month means astronauts could see a 1% drop in the density of their weight-bearing bones and serious muscle loss if they don’t do something about it. Back on Earth, these issues are usually linked to getting older, not moving around much, or dealing with degenerative diseases. The problem is, for deep space missions, astronauts have to endure months of microgravity, and when they finally land, they need to be in top shape for demanding tasks. If not, they risk some pretty nasty injuries.

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A long-standing tradition

Astronauts have been hitting stationary bikes and treadmills for ages to stay fit. Back in the day, during the Soviet Salyut program from ’71 to ’86, they did a bunch of studies on astronaut health. To try out different ways to counter the effects of space, they equipped these stations with a treadmill, a suit that mimics gravity (worn for a long time), a bike with a fancy ergometer, some medications, and a suit that fights gravity worn right after the flight. They split up the exercise routine into two one-hour sessions in the morning and afternoon, sandwiched between work cycles.

On the Soviet/Russian space station Mir, they had two treadmills (with bungee cords to keep the cosmonauts in place) and a stationary bicycle. Every cosmonaut had to cover 10 kilometers (6.2 mi) on the bike and run the equivalent of 5 kilometers (3.1 mi) each day. NASA did something similar, with Skylab astronauts needing to clock in 90 minutes of exercise daily. They used gear like a stationary bicycle and a treadmill-like device, and some clever astronauts even figured out they could jog around the water tank.

Once the ISS kicked off in 2001, they shipped in the Treadmill with Vibration Isolation Stabilization System (TVIS) as one of the first exercise setups. It hooks users up with a harness to the machine and cranks up the resistance. Then there’s the Cycle Ergometer with Vibration Isolation and Stabilization System (CERVIS), a workout bike from Danish Aerospace. And let’s not forget the Advanced Resistive Exercise Device (ARED), which uses vacuum cylinders and pistons to give astronauts resistance, kind of like doing weightlifting in microgravity.

Figuring out the right diet, exercises and medicines

Medical experts get the general idea of why atrophy happens, but researchers are still digging into the nitty-gritty details and factors that contribute to atrophy in microgravity. They’re on the hunt for solutions. A big chunk of this research is all about figuring out the perfect mix of diet, exercise, and meds to keep astronauts in good shape while they’re up in space, doing missions on the Moon or Mars, and when they come back to Earth. Take the Zero T2 experiment, for instance; it’s about astronauts skipping the treadmill and doing more aerobic and resistance exercises.

After the experiment wraps up, the research crews will check out how well the participants’ muscles perform and recover compared to their buddies who stuck to the treadmill. In another experiment called VR for Exercise, they’re trying to whip up a cool virtual reality world for astronauts to dive into while pedaling away on the station’s exercise bike. And then there’s the research with “tissue chips,” these little devices that mimic the complex functions of certain tissues and organs.

In this cool experiment called Human Muscle-on-Chip, they built a 3D model of muscle fibers using cells from both younger and older adults. They zapped the tissues with electrical pulses to make them contract and checked for any changes due to microgravity. Turns out, for muscle cells in microgravity, there was a drop in the expression of genes linked to muscle growth and age-related metabolism.

What happens to the musculoskeletal system in microgravity

Apart from trying out various exercise routines, researchers are also diving into how the whole musculoskeletal system deals with working out in microgravity. That’s the goal of the ARED Kinematics human physiology experiment, with backing from the Italian Space Agency (ASI) and the ESA. The idea is to measure the joint torque, muscle forces, and bone stresses when astronauts exercise in microgravity. Plus, they want to figure out how performance adapts over time.

To tackle the issue of bone density loss, they’re running the Vertebral Strength experiment. They took close-up scans of astronauts’ bones before and after their space trip, focusing on the ones supporting the spine. This helps researchers understand how spaceflight messes with the overall strength of muscles and bones. What’s interesting is that this research, along with other studies on bone density loss and musculoskeletal health in space, connects with what we’re learning about osteoporosis on Earth. It’s like a two-for-one deal with potential applications benefiting both space and Earth.

Likewise, there are these drugs, myostatin inhibitors, that have already shown their worth on Earth, especially in treating osteoporosis. These medications put the brakes on myostatin, a human growth factor that keeps muscles from growing too much. By doing that, they help cut down on bone density loss and lower the risk of fractures. In a recent experiment called Rodent Research 19 (RR-19), they tried out this drug on a bunch of mice in space, and it seems like it could be a solid treatment not just for astronauts but also for folks dealing with degenerative diseases back on Earth.

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Taking mental health into account

Obviously, when looking into how microgravity messes with human health, you can’t ignore the mental toll that comes with long stints in space. That’s where the Complement of Integrated Protocols for Human Exploration Research (CIPHER) comes in. It’s this all-in-one experiment that made its way to the ISS not too long ago.

In this setup, astronauts are part of 14 studies backed by NASA and pals from around the globe. These studies are all about checking out the physical and mental changes in the crew during missions that last a few weeks, stretch between 3.5 to 8 months, or even go on for a full year in space.

These studies will keep tabs on the astronauts’ health from start to finish—before, during, and after their missions. By doing the same research across missions of various lengths, scientists can use the data to make educated guesses about what might go down during longer missions, like a three-year round trip to Mars.