Sebastian Coe has spoken of the biggest challenge facing athletes taking part in the marathon in Doha as the World Athletics Championships start on Friday.

As president of the IAAF, Coe has said that while the heat is not an issue, the humidity will be.

He said: "I don't want to speculate, but I want as many people to finish as possible.

"Heat is not the big issue, the issue is humidity which is a real challenge.

"We have extra precautions, extra things out on the course. We have more medical supervision, more water available. But it is going to be tough."

Emergency safety measures have been put in place in order to protect athletes during the women's marathon on Friday.

It is set to be 32 degrees with 81 percent humidity. 

The race has been pushed back to 11.59 am local time. Other measures put in place include extra officials on the course, more water for athletes and a bigger recovery area with more ice baths made available.

The IAAF have said that there are no plans to cancel any events despite the extreme weather.

Great Britain's Tish Jones and Charlotte Purdue are among those  competing in Friday's race.