On Sunday, April 24, 38,000 descended upon the streets of London to take part in the annual London Marathon. This year, though, they were joined by a rather unusual participant – an astronaut orbiting 410 kilometers (255 miles) above their heads.

Yes, British European Space Agency (ESA) astronaut Tim Peake, who launched to space in December 2015, took part in the London Marathon by completing the 42.2 kilometers (26.2 miles) while on the International Space Station (ISS), beginning at the same time as his Earth-based counterparts at 10 a.m. BST (5 a.m. EDT). He didn't run around the station, though; he used a treadmill to complete the full distance. His final time was 3 hours and 35 minutes.

To run in space, Peake wore a backpack-like harness, which holds him in place in the microgravity environment of the ISS. Two chains attach to bungee cords, which keep him pulled onto the surface of the treadmill so he doesn’t float off. To keep himself occupied, he used an app called RunSocial to show him the streets of London as he ran.

“The thing I’m most looking forward to is that I can still interact with everybody down on Earth,” Peake said before the event in an interview on Wednesday. “I’ll be running it with the iPad and watching myself running through the streets of London whilst orbiting the Earth at 400km.”

Aside from, you know, being in space, one major difference between Peake and the runners on the ground was that most of Peake’s own body weight was channelled through his shoulders. To account for the weightless environment on the station, the straps mimicked up to 80 percent of his weight. However, there are plans for better treadmills to go to space in future that spread the weight more evenly, such as the design from QinetiQ below.

 

 

Peake, like people on Earth, had been training hard to get himself ready to run the full distance. But while marathon runners on Earth will take a deserved rest of at least a few days after they finish the race, for Peake it was back to business as usual the following day, which means he will immediately go back into his daily exercise regime. He'll still have to do the required daily 2.5 hours of exercise, to limit the loss of bone and muscle mass caused by prolonged stays on the ISS. Ouch.

He was not the first to run a marathon in space; NASA's Sunita Williams completed the Boston Marathon in 2007 in 4 hours and 23 minutes, but Peake's time does make him the fastest marathon-runner in space. And he's got some experience, having run the actual London Marathon before in 1999, with an impressive time of 3 hours and 18 minutes.

 

42 km, while @Space_Station flew almost 100000 km. Congratulations to everyone in #LondonMarathon & #teamastronaut…gonna sleep well tonight!

— Tim Peake (@astro_timpeake) April 24, 2016

 

This isn’t all just for fun, though. Medical experts from ESA monitored Peake’s physiology and progress, and importantly, they’ll also be keen to see how he recovers from this strenuous activity. It’s thought that the reduced load on the human body from floating in microgravity could help him recover more quickly.

Technically, owing to the speed of the station, 27,600 kilometers per hour (17,100 miles per hour), he finished the marathon in 5.5 seconds – but hey, that's cheating, right?

^{Main image via @PrincesTrust/Twitter}