Astronaut to run marathon on ISS

An International Space Station (ISS) astronaut is taking part in a US marathon in an attempt to become the first person to run the race in space.

Sunita Williams will run 26.2 miles on a treadmill 210 miles above ground while 24,000 other competitors pound the streets of Boston back on Earth.

She'll be tied to the treadmill using an elasticated harness to cancel out effect of being weightless in space.

Sunita qualified for the marathon before she was sent into space.

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Space race

Sunita Williams in training

During the race the US Navy Commander will circle the Earth at least two times, running about eight miles per hour while flying more than five miles per second, according to NASA.

Sunita, who has been training aboard the ISS every day, told Nasa she wanted to run the race to encourage children to make fitness part of their daily lives.

The astronaut, who has been stationed in space since December 2006, has already completed lots of marathons back on Earth.