AUBURN – As the world watches Olympic athletes pursue gold and glory in China, Karl Meltzer is deep in the Appalachian wilderness chasing a feat of incredible endurance.

A former Class L cross-country champion at Manchester's Memorial High, Meltzer set out at 7:08 a.m. Tuesday from atop Maine's Mount Katahdin determined to run the famed Appalachian Trail in record time.

To break the unofficial speed mark held by Derry native Andrew Thompson, Meltzer must negotiate 2,174 miles of mountainous terrain from Maine to Georgia in less than 47 days, 13 hours and 31 minutes. That's an average of 46 miles a day, or the length of nearly two marathons every 24 hours for seven weeks.

"It's not like running around Derryfield Park," quipped Meltzer's father, Karl Sr., as he tinkered last Sunday with the 24-foot support RV he's driving the first two weeks of his son's journey. A Utah resident, Meltzer visited his parents' home near Lake Massabesic before departing last Monday for Maine.

Meltzer, 40, has been running ultramarathons -- races that exceed the traditional marathon length of 26.2 miles -- since 1996. He's won 49 of the 92 ultramarathons he's entered, including 23 100-mile races. In 2006 alone, he captured six 100-milers.

"You don't have to run fast, you just have to run all day," Meltzer said.

Despite this simple explanation, it's common for the uninitiated to believe ultra running defies reason.

"I didn't really understand it at first," said Meltzer's wife, Cheryl. "I thought he was a little crazy when he told me he ran 100-mile races."

Meltzer exclusively runs trail-based races. He is a six-time winner of the Wasatch 100, an endurance run through Utah's Wasatch Mountains, and has captured the Hardrock 100 in Colorado's San Juan Mountains four times.

"There's never been a mountain runner in America like him," said Billy Simpson, a fellow ultra runner who will drive Meltzer's RV during the last three weeks of his Appalachian trek. "He's like Lance Armstrong on the Tour de France course."

That Meltzer runs peaks so well doesn't surprise his old cross-country coach at Memorial.

"We used to call him a mountain goat," said Richard Provencher, who follows Meltzer's career closely. "He was great on hills in high school."

The idea for an Appalachian speed assault grew out of Meltzer's lifelong desire to hike the entire trail. "I'd always wanted to do it, even as a kid," he said.

Late last year Meltzer mentioned the idea to representatives of Backcountry.com, an outdoor-gear retailer that had agreed in November to sponsor Meltzer as an ultra runner. In response, the Utah-based company elected to underwrite much of Meltzer's effort and supply him with the RV, which will meet him at road crossings each night during the trip.

Ultramarathoner Karl Meltzer and his dog, Binger, check out the RV that will be his home during his 47-day run on the Appalachian Trail. (JAMES COOK/UNION LEADER)

To promote Meltzer's quest, Backcountry.com launched a Web site, whereskarl.com. Seven company employees will each work a week in the traveling RV to maintain the site, which includes a blog chronicling Meltzer's progress. A satellite tracking device Meltzer wears allows site visitors to pinpoint his location.

Meltzer is tackling some of the trail's toughest terrain early, including New Hampshire's White Mountains. He spent last week traversing Maine with Matt Hart, a friend from Seattle, and anticipates reaching the Granite State by Tuesday.

Last Thursday he provided an update from the Maine woods through an intermediary, Backcountry.com's Marit Fischer.

"My body's holding up well, with the exception of one nasty blister that I'm slightly concerned about," he said. "It's been raining the last few days, so it's extra wet. Running on the wet trail is like running on an ice rink."

In their first three days, Meltzer and Hart completed their goal of 122 miles. They averaged between 3.3 and 4 mph during that time, running about 25 percent of the distance and hiking the rest, Meltzer said.

Although his traveling crew will keep him well fed, Meltzer said he anticipates losing 10-12 pounds from his sinewy 5-foot-10, 142-pound frame during the expedition. On his record pilgrimage in 2005, Thompson dropped more than 30 pounds and experienced low-level hallucinations.

"It messes with you on a molecular level," said Thompson, a 32-year-old Lyme resident who set the mark traveling north to south with a one-man support crew. "You're always operating from a place of deprivation."

Given his ultra running prowess, Meltzer has the physical tools to break the record, Thompson said. Success or failure will depend largely on factors beyond his control, such as weather and trail conditions.

"The difficulty of the terrain is usually underestimated, especially going southbound," said Thompson, who failed to complete the trail in two previous record attempts traveling south to north. Harsh weather in the White Mountains thwarted his second attempt in 2001.

Because of the challenges Meltzer will face, his supporters agree that breaking the record isn't a given. But they remain optimistic about his chances.

"I feel confident about it," said Karl Meltzer Sr., a 65-year-old retiree and outdoors enthusiast. "He always gives 100 percent, but he knows when to back off, too."

"He's strong enough mentally and physically to complete it," added Cheryl Meltzer, who will drive the RV for the two-week middle leg of her husband's odyssey. "And if he breaks the record, that's even better."

"He has what it takes to get the record, and he totally respects this trail," Simpson said. "He's got the heart and the talent, and he's humble enough in his own way to get this done."