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    Tim Peake Ran The London Marathon In Space – Here's Why That's Hard

    It's pretty hard running marathons normally, but it's even worse when you're strapped to a treadmill 250 miles above the ground and your bones have wasted away. Update: The British astronaut finished the race in three hours, 35 minutes, and 21 seconds.

    Tim Peake, the British astronaut, is going to run the London marathon on the International Space Station (ISS).

    ESA / Via

    He'll be running it on a treadmill. But he'll set off at 10am on Sunday at the same time as the other 30,000 runners, and will do the full 26.2 miles.

    He's on the ISS as part of the European Space Agency's (ESA) Principia mission, doing scientific experiments and helping maintain the space station. He went up in December and is coming back in June.

    The lack of gravity will make things more difficult, obviously.

    Astronaut Frank de Winne on the ISS treadmill. NASA / Via

    Since the ISS is in orbit, there's no sensation of gravity, so Peake has to have elasticated straps over his shoulders holding him on to the treadmill. That, apparently, is the most uncomfortable bit.

    He told the ESA blog: "I have to wear a harness system that's a bit similar to a rucksack. It has a waistbelt and shoulder straps.

    "That has to provide quite a bit of downforce to get my body onto the treadmill, so, after about 40 minutes, that gets very uncomfortable. I don't think I'll be setting any personal bests. I've set myself a goal of anywhere between 3:30 to 4 hours."

    That's not the only problem he faces. Keeping fit in space is extremely difficult.

    "Keeping healthy in space is non-trivial," Kevin Fong, an astrophysicist and medical doctor, told BuzzFeed last year. "It's not just a case of eat your fruit and veg and do a bit of exercise."

    ISS astronauts have to exercise for two hours a day to counteract the effects of microgravity.

    For one thing, Peake's muscles will be steadily wasting.

    NASA / ESA / Via

    Weightlessness "looks like fun, but it has a lot of quite profound effects on your body", said Fong.

    Peake's muscles have grown weaker through lack of exercise, because they're not working against gravity. "This is an environment that is basically eroding your physiology for every moment that you're up there," said Fong

    Peake's been there four months already, which is plenty of time for muscles to start to deteriorate.

    And his bones are getting thinner.

    "Your bones also have a job to support your body against gravity, and they also reduce," says Fong. "It leaves you much more prone to fracture when you return to Earth." The long bones of your legs, and your spine and pelvis – the bits that carry the bulk of your weight – suffer particularly badly. They become less dense – like older people, astronauts develop osteoporosis.

    They also often get kidney stones, because their body is trying to pee out so much calcium from their disappearing bones.

    His heart and blood vessels probably aren't working as well, either.

    Ben Hoskins / Getty Images

    Gravity provides a good workout for your cardiovascular system as well, said Fong. "When you go from lying on the sofa to standing upright, it has to enact a set of reflexes that cope with that change in posture and pressure in the system."

    In microgravity, those reflexes rust up with lack of use. That's not so disastrous in space, but it becomes a problem when astronauts return to Earth – you rely on them to keep blood flowing to your brain properly when you sit down or stand up.

    And there's no St John Ambulance by the side of the ISS.

    Daniel Berehulak / Getty Images

    So if he hurts or overexerts himself, medical attention is a bit harder to come by.

    Although it's not as bad as it could be. His fellow astronauts are trained in first aid. Also, if he has a severe medical problem, "you bundle into the Soyuz capsule and you come home", said Fong. "And depending on where you are in the orbit, you could be home in hours."

    Unfortunately, at the time of the start of the marathon, it looks as though the ISS will be flying over sparsely populated areas of North Africa and Central Asia. So people running the marathon the usual way will definitely have the advantage.

    Still, he'll probably run it in a pretty good time.

    Peake ran the London Marathon in 1999 in a seriously impressive 3hrs 18mins 50sec. He's not expecting to run it that fast again, but he's physically extremely fit (he's an astronaut) and is hoping to keep it below four hours – a thoroughly respectable time.

    He'll be monitored throughout the run by the ESA medical team on the ground in Cologne, Germany, and will have an iPad in front of him that will show the route as though he's actually running in London.

    Peake said: "The thing I'm most looking forward to is that I can still interact with everybody down on Earth.

    "I'll be running it with the iPad and watching myself running through the streets of London whilst orbiting the Earth at 400km."


    Peake completed the marathon in a time of three hours, 35 minutes and 21 seconds. Not bad, all things considered...

    .@astro_timpeake has finished his #LondonMarathon in space! Estimated time 3:35:21. @Astro_Jeff comes to applaud Tim