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Physical activity in space

Everyone knows that it's important to exercise to stay in shape—on Earth, that is. But when you're in orbit, exercise is absolutely vital!

Physical activity is the most effective way to counteract the adverse effects of weightlessness on the human body. Exercise is therefore a crucial part of the daily routine on board the International Space Station (ISS). Over the course of a long-duration mission, astronauts must exercise approximately two hours per day!

Canadian astronaut Bob Thirsk

Former Canadian astronaut Robert Thirsk enjoys cycling on board the ISS! (Credit: NASA)

The importance of physical activity in orbit

On Earth, each time we move, gravity provides resistance to the muscles and bones of our body. It's like we're exercising without even realizing it! That way, our body stays strong enough to support our weight.

In microgravity, however, bones and muscles no longer have to support the weight of astronauts' bodies. What's more, the cardiovascular system becomes lazy because the heart doesn't have to work as hard as it does on Earth to counteract gravity and pump blood up to the head.

That means that without exercise, the astronauts' bones would be more fragile and their muscles weaker after time spent in space.

If astronauts didn't exercise while they were in space, their bodies would experience major loss in:

In other words, astronauts need to stay in shape in order to:

Space gym

Exercising looks a bit different in microgravity. Exercise machines have been modified to simulate a gravitational pull being exerted on the astronauts' bodies.

The team members on the ISS use three cardiovascular and muscular exercise machines to stay in shape.

Canadian Space Agency (CSA) astronaut David Saint-Jacques talks about working out on the ISS and explains the unique exercise equipment he uses in space: the stationary bicycle, the treadmill and the Advanced Resistive Exercise Device (ARED). (Credits: CSA, NASA)


ARED: Advanced Resistive Exercise Device

Robert Thirsk - ARED


Robert Thirsk - TVIS

During his six-month mission on the ISS, Robert Thirsk ran "alongside" his son!

He used videos filmed by the Canadian Space Agency (CSA) that showed his son running. Robert watched the videos on the treadmill's screen, and the illusion was complete!

Stationary bike

Robert Thirsk - CVIS

Side effects of weightlessness on the human body

Flying in space is a bit like aging prematurely.

Chris Hadfield undergoes CT scan

Chris Hadfield undergoes a quantitative CT scan to obtain detailed images of the bones in his ankle, shortly after his return to Earth in 2013. (Credit: CSA)

Despite a rigorous exercise regime, astronauts lose an average of 1% of their bone density per month in space. On Earth, an average elderly person loses 1% of his or her bone density per year.

The physical consequences of a prolonged journey in weightlessness are similar to those caused by osteoporosis, which affects elderly people. However, these consequences aren't as serious because astronauts' bone density gradually returns to normal after they return to Earth.

That is why scientists use astronauts as subjects in their scientific experiments. This research allows us to gain a better understanding of the effects of weightlessness and how to mitigate them, for the purposes of future long-duration space missions but also for people with various health problems on Earth.

Thanks to the current protocol of two hours of exercise per day, astronauts return to Earth with more muscle mass than when they blasted off!

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