Audio from 2009 NASA video: You can see the parachute coming down

Vik Adhopia / CBC News:It was a landing that felt like a crash, but for Canadian astronaut Bob Thirsk, that wasn't the worst part.

Robert Thirsk / Former Canadian astronaut: I felt like a wet dishrag on landing day.

Vik Adhopia: In space, astronauts' bodies go through an unearthly ordeal. They work out daily to counter the effects of low gravity on their muscles, but it's never enough.

Robert Thirsk: They wanted exercise, do thatlittle bit of extra exercise, so that I wasI was theIronmanon landing day. Didn't happen. Weightlessness takes a toll on the human body.

Vik Adhopia: Researchers are getting a better idea of how much of a toll. This lab works with volunteers and astronauts, developing new technologies, measuring the damage caused by weightlessness, pushing blood upwards to the head.

Richard Hughson / University of Waterloo: And we found that arteries get stiffer by quite a bit while they're in space. In fact, in six months in space, the arteries get stiffer by the equivalent of about 20 years of aging.

Vik Adhopia: With the muscle and artery damage in space also comes changes to bone marrow, which is being studied by another Canadian team.

Dr. Guy Trudel / University of Ottawa: So, it kind of reverses your normal forces of gravity. It's not like being in space, but it's a good model for it.

Vik Adhopia: This doctor is trying to counteract that effect by working with German researchers on this: a centrifuge that spins test subjects. It creates a pole, similar to gravity, and exercising while spinning counteracts the effects of low gravity. You may have seen the concept before, in the movies, which is not far off from what might be our reality.

Dr. Guy Trudel: So, if the studies that we're carrying (out) in Germany now are conclusive, that could well be part of the design of the future spacecraft to Mars.

Vik Adhopia: Artificial gravity won't solve all the problems of longer space travel. There's still the extended exposure to solar radiation and also the unknown cognitive and psychological effects of spending more time in space. Astronauts' bodies will have to endure a lot.

Dr. Guy Trudel: We need to build up a bit more knowledge before we can send people to Mars. We do not know if the damage will continue to progress at the same rate, or if there's gonna be a plateau at one point.

Vik Adhopia: As space exploration takes astronauts deeper into the galaxy, it'll open up new frontiers, not just for human travel, but for human health.

Vik Adhopia, CBC News Toronto.

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Effects of space on the body: Level 2 transcript - CBC.ca