"Ultramarathon Man": From tequila to Olympic torch

So he drunkenly stripped down to his shorts, put on some old sneakers and hit the road -- and has never looked back.

Now 45, Karnazes has run hundreds of marathons -- technically races of 26.2 miles -- and many more unconventional distances. He once ran 350 miles non-stop. It took him just over 80 hours, with no sleep.

"My thing is: What are the limits of human endurance? And I’m just going to push it as far as I can to see," he said in a telephone interview on his return home from Chile to San Francisco, where he was one of a host of runners chosen to carry the Olympic torch this month.

In 2006, Karnazes ran 50 marathons in 50 consecutive days in 50 U.S. states. Once he had completed the last one, he then ran 1,300 miles home over the period of a month. He also ran a marathon at the South Pole in 2002.

He sleeps on average 4 hours a night to fit in fatherhood with his running and business interests, and wears out 30-40 pairs of running shoes each year.

Karnazes won the 135-mile Badwater ultramarathon through Death Valley on the border of California and Nevada in 2004, billed as the toughest race on earth. The first year he ran it he became over-dehydrated, hallucinated vividly and then collapsed on the tarmac.

THRIVING ON THE EXTREME

He says the run across the moon-like Atacama, the world’s driest desert and centre of the global copper-mining industry, was probably the most difficult endeavour he has undertaken.

"It’s one of the most foreboding places on earth ... It’s a combination of the elements, the altitude, the fact that you had to carry all of your supplies with you."

Karnazes’ backpack weighed 13 kilos at the outset.

"It throws your electrolytes out of balance because you become very dehydrated," he added, saying he needed to replace between 5-7 litres of liquids a day. His feet were so badly blistered he eventually gave up trying to tend them with tape.

Karnazes even found time to write a blog at the end of each leg of the race, posted on his Web site www.ultramarathonman.com.

He is also set to run this year in the Gobi Desert in China, Death Valley, the Sahara and Antarctica.

Coincidentally, Forrest Gump, the 1994 blockbuster movie featuring Tom Hanks as a man with a very low IQ but extraordinary running ability, was being filmed around the time Karnazes threw himself into the life of long-distance running.

He sees some similarities.

"Forrest Gump was kind of a simpleton, and that’s pretty much what I’m all about as well -- just a simple guy, honest, straightforward, pretty happy, just trying to enjoy life as I move down the road."

So a Forrest Gump-meets-Lance Armstrong?

"I guess that’s kind of it. The Forrest Gump mentality with the Lance Armstrong drive."

Fellow runners flock to jog with Karnazes, tracking him down by the GPS icon on his Web site. They also look to him for advice, but he’s no agony aunt.

"I don’t know how to deal with it," he said. "I’m not big on dispensing advice."

A second generation American of Greek descent, Karnazes says marathon running is in his genes.

"My ancestors literally did come from the same village that Pheidippides came from," Karnazes said of the legendary Ancient Greek runner tradition says ran 150 miles in two days to seek help from Sparta to fight the Persian Army and then died from exhaustion after another 26 mile run in 490 BC.

Karnazes believes his endurance is improving over time, and says his doctors took X-rays of his knees and say they are like those of an 18-year-old. And for his next challenge, how about running around the world in a year?

"I’m tempted, but I couldn’t leave my family for that long," he said. "When they’re old enough, and if they want to (follow in a vehicle) -- it’s an amazing challenge, I’d love to do it. And I want you to join me."

(Editing by Kieran Murray)