A wild ride as athletes take sport to extremes

RUNNING the distance of Sydney to Katoomba in under 12 hours, cycling up rocky mountainsides and plunging through mud-filled assault courses is increasingly being regarded as a good time by a growing group of extreme sport nuts.

A new breed of ultra-tough weekend athletes are testing their bodies to the limit with 100-kilometre races through the bush and 24-hour mountain-biking marathons in dozens of events that have sprung up across the country.

Organisers report they can scarcely keep up with demand, with entries to the gruelling races often selling out within hours.

The North Face 100 is a 100-kilometre race where competitors run through the night for up to 27 hours in the Blue Mountains in NSW. It started three years ago and this year's event is expected to draw 600 competitors - triple the number in 2008.

''Interest is huge,'' said organiser Steve Winnacott. ''It gives people the chance to get away from the boredom and have fun, as well as test themselves physically. A lot of people who enter have never done anything like this before, which is amazing.''

Ross Marceau, 29, from Mona Vale, will be among the pack setting out from Leura on May 15. He was introduced to the concept of ultra-marathon trail running by a friend over dinner one night and got hooked on the idea.

''I had thoughts about knocking off a marathon but road running was not really my thing and then I got on to this and it's a real buzz,'' he says. ''I know there will be times in the race when I'm not enjoying it at all but it will be a big post-race enjoyment thing and sense of achievement.''

Also in the Blue Mountains is the Six Foot Track Marathon, an iconic 42-kilometre race that has been staged for 27 years. Race director Kevin Tiller, who also founded the website CoolRunning Australia, says interest has been extraordinary this year, with the event's 1000 places selling out in just 12 hours.

Tiller says many ultra-distance runners want more of a challenge than a road marathon can provide. ''Previously it was, 'Oh my God, you've run a marathon. How awesome!' That was the peak of human achievement,'' he says. ''I guess people are saying now, 'You can do a marathon but what's next?'''

The explosion in popularity can also be partly explained by word of events spreading through the internet and the growth in corporate sports events. It's not just foot races that are attracting attention. Mountain bike events have also become very popular.

This year's Dirtworks 100km Classic mountain bike race - held in the Hawkesbury in May - sold out all 1500 entries within 24 hours, says Gary Farebrother of organisers Maximum Adventure, who run a number of endurance events.

''Growth has just been phenomenal,'' Farebrother says. ''People are wanting to push themselves and challenge themselves much further. You'll also find the people who tend to do better are older because there is more endurance involved. With age you learn to deal with a bit more pain and to pace yourself.''

Michael Farkas took part in last year's event and rides in other mountain bike races most months. ''I love the challenge of the long distance and being fit,'' says the 37-year-old from Wahroonga. ''And I love the feeling of total exhaustion at the end of the race.''

Alongside these longer events, shorter ''adventure races'' are also inspiring a whole new army of weekend athletes. These races usually combine running and cycling legs in the bush with activities such as kayaking, climbing or even archery. Robyn Lazenby of race organiser In2Adventure says adventure race numbers have surged over the past three years.