Lance Mackey sees no limit to what he and his dogs can do.

"Every year I learn something more about my dogs," said Mackey, one of 67 mushers who will line up Saturday in downtown Anchorage for the ceremonial start of the 1,100-mile Iditarod Trail Sled Dog Race from Anchorage to Nome. "We still don't know their full potential."

The two-time defending Iditarod champion has already redefined what's possible in long-distance sled dog racing as the only musher to win the Iditarod and the nearly as long Yukon Quest International Sled Dog Race in the same year. He did it in 2007 and 2008, taking about two weeks off between races.

"Just a few short years ago people didn't think you could run the Quest and the Iditarod with the same dog team, well I proved that it is capable and possible," Mackey said.

That is about as boastful as Mackey ever gets. Hailed by Alaskans as a humble, one-of-their own hero, the 38-year-old Mackey took a breather from the Quest this year to help train an Alaska Native to run the Iditarod.

Mackey said he prepared Harry Alexie to run what's called "The Last Great Race on Earth" because he wanted to help the people who got dog mushing started _ the Alaska Natives who used dog teams to haul food and supplies in the villages, and held short races before snowmobiles in large part replaced the dogs.

"The Natives have kind of been squeezed out of this sport," Mackey said.

Mackey said he was flattered when Alexie, who is being sponsored by the Alaska National Guard, approached him instead of other former Iditarod champions for help.

"For them to approach me as opposed to somebody like a Rick Swenson, a Martin Buser, a Jeff King, people who have much more experience and bigger kennels, for them to come to me first was a huge honor," he said.

Mackey stands out among those former Iditarod champions because he challenged a cardinal rule of long-distance sled dog racing _ the race/run schedule that says for each hour a dog races, it should get the same amount of rest. It was that type of thinking that prevented mushers from attempting both the Quest and the Iditarod in the same year.

Mackey looked at his own life and thought, why should dogs be any different?

"I kind of compare my dogs to myself. I don't need 12 hours of rest every day to work 12 hours a day. I think the dogs are the same way," said Mackey, who generally needs only five hours of rest a day.

"That theory has gotten the attention of the rest of my competitors," said Mackey, noting that many mushers now are taking longer runs and resting their teams less. The strategy works, Mackey said, as long as the dogs get the proper training, excellent nutrition and enough good rest.

Mushers must still abide by race rules that require one 24-hour stop to rest their dogs, as well as two 8-hour stops. One is taken on the Yukon River and the other at White Mountain, a checkpoint near the finish line in Nome.

Mackey, whose father and brother also won the Iditarod, said his pivotal experience came when he was diagnosed with throat cancer after the 2001 Iditarod. He fought the disease in 2001 and 2002 and now is considered a cancer survivor.

"If it ended tomorrow I would not be disappointed. I have had a second chance," Mackey said. "Doctors told me I would never be able to race again. They told my family to say goodbye."

In 2002, with a feeding tube in his stomach because he couldn't swallow, Mackey was competing in the Iditarod but had to withdraw when he felt too ill to continue. No wonder Sports Illustrated last year named him the second toughest athlete in sports, behind Tiger Woods.

Mackey took second, Sports Illustrated said, for doing the "impossible" in sled dog racing by winning both the Quest and the Iditarod, and exhibiting "caginess and a steadfast refusal to quit" in the face of cancer, hostile terrain and 40-below temperatures.

Even so, Mackey is a realist.

"It won't last forever," he said. "Every champion has had a bad year or two and I don't think I am going to be any exception to that. I hope it is not this year, but that remains to be seen. If it backfires, I won't be disappointed."

For now, Mackey said it is the comments from some of his competitors, including four-time champion King, that fire him up for a third victory.

King appeared to be on his way to a fifth Iditarod win last year when he got snookered by Mackey 123 miles from the finish.

In an old musher's trick, Mackey arrived at the checkpoint 3 minutes ahead of King, drank coffee and acted like he was settling in for a long nap. He told checkpoint volunteers to wake him in an hour. But with King snoring, Mackey sneaked out ahead of his opponent.

"Anyone who can bluntly tell the rest of the world they are the best and continue to get beat is somebody who just needs an attitude adjustment in my opinion," Mackey said. "How can you keep saying you have the best, the strongest, the fastest and all this and not win?"

Mackey said his style has never been to claim he's the best, and that no matter what happens in this year's Iditarod there is one thing his fans can count on.

"I will guarantee I will do my best," he said.

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