TOMORROW, March Athletic Club runner Sean Brown will take on the biggest challenge of his life. Fifteen years ago, 37-year-old Brown was told that he would never run again after sustaining an ankle injury while playing football. Since then however, Brown

TOMORROW, March Athletic Club runner Sean Brown will take on the biggest challenge of his life.

Fifteen years ago, 37-year-old Brown was told that he would never run again after sustaining an ankle injury while playing football.

Since then however, Brown has run marathons and ultras (races in excess of marathon distance) across the world.

At 10.30am local time tomorrow, Brown will set off from Whitehorse, Canada to compete in the fourth Yukon Arctic Ultra - the world's toughest and coldest race.

This year's race has attracted a record number of entries for the marathon, 100-mile and 320-mile races but each athlete will have to face the Yukon wilderness alone as they attempt to reach the finish line.

Brown will attempt the gruelling 320-mile unstaged course, which entrants must complete within eight days, and he is hoping to improve on his performance last year.

In his first attempt at the race last February, injury forced Brown to withdraw from the race at the 100-mile Braeburn checkpoint.

Each athlete must carry all the equipment they need to survive eight days in the Arctic wilderness where temperatures often drop to -40 degrees C.

Event organiser Robert Pollhammer said: "People need to be prepared very well and you need excellent equipment and perfect training."

Brown will need to carefully prepare his sled, his only companion on the course, which will carry all the food, water, cooking equipment and clothing he will need.

Last year, his lack of experience in packing a sled led to problems finding essential items quickly but this time, Brown will have a much greater appreciation of the demands placed upon the entrants.

There are checkpoints along the 320-mile course where athletes can shelter and eat but the relentless nature of the race means that more often than not, participants are forced to bed down in the open.

Pollhammer said: "The participants are on their feet an average of 20 hours a day. That is not only difficult physically but psychologically."

Of the 17 competitors in last year's 320-mile race, only seven completed the course. Italy's Stefano Miglietti won in a time of six days, two hours and 35 minutes.