Boston marathon

For one participant, the Boston marathon will not only be 26.2 miles long. It will also be 210 miles above the surface of the earth.

Sunita Williams, an American Astronaut, is to run the marathon on board the International Space Station.

The 41-year-old secured a place in the normally terrestrial endurance test by completing the qualifying marathon in Houston last year in three hours 29 minutes.

But her plans to take part in Boston ran into difficulty after she rocketed from earth in the Discovery space shuttle last December.

Thankfully Boston marathon's organisers permit participants who are unable to run in the Massachusetts town itself.

Williams will be tied to a treadmill to combat the effect of weightlessness.

According to the BBC, BAA spokesman Jack Fleming said: "The Boston Marathon is the pinnacle of achievement for most runners.

"For Suni to choose to run the 26.2 miles (42.2km) in space on Patriots Day is really a tribute to the thousands of marathoners who are running here on Earth," he added.