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Physical fitness is an important part of being an astronaut. Astronauts must be healthy enough to conduct experiments, such as measuring the impact of long-term stays in microgravity on the human body. They must also maintain the technology of the International Space Station (ISS), satellites, or other equipment. This can mean fine-tuning electronic devices inside a rocket or the ISS. It can also mean taking a “space walk” to repair or enhance an external piece of equipment.
Most importantly, working out helps to keep astronauts healthy and able to adjust to life when they’re back on Earth. In space, muscles don’t have to interact with gravity—because there is (almost) no gravity! Muscles, including the heart, can lose strength and endurance.
Astronauts maintain their physical fitness using athletic equipment modified for the restraints and rigors of a microgravity environment. 
This NASA video shows real astronauts using exercise equipment both in space and on the ground. Watch the video to learn how astronauts work out, and how you can exercise like an astronaut using equipment in your school, gym, or home.
  • Astronauts ride a CVIS (Cycle-Ergometer Vibration Isolation System), an unusual stationary bicycle, to help improve their cardio (heart) health. On Earth, we can go for a bike ride or use a regular stationary bike. Astronauts have to “strap in” to a CVIS, because a lack of gravity prevents them from sitting down and staying put. Special shoes also snap into CVIS’ pedals to make sure astronauts don’t just float away.
  • Astronauts use an ARED (Advanced Resistive Exercise Device) to build strong muscles. Back on Earth, we can lift weights or use weightlifting machines. ARED uses air, not weights, to create resistance. (In microgravity, “weights” don’t actually weigh much of anything!) Astronauts pull against vacuum cylinders, which lack air, to create resistance and work their muscles.
  • Astronauts use a TVIS (Treadmill Vibration Isolation System) to increase their endurance, so they can work for longer periods of time without getting tired. On Earth, we can go running or use a treadmill. Astronauts “strap in” to a TVIS using a series of flexible bungees. This keeps them on the treadmill. TVIS also has strong steel “treads” that won’t break and float away, putting astronauts and equipment in danger.

person who takes part in space flights.


ability to accept and deal with hardship.


physical force by which objects attract, or pull toward, each other.

International Space Station (ISS)

satellite in low-Earth orbit that houses several astronauts for months at a time.


object that orbits around something else. Satellites can be natural, like moons, or artificial.

space walk

physical activity outside a spacecraft in orbit.


the science of using tools and complex machines to make human life easier or more profitable.