updated 2:02 a.m. ET March 9, 2010

ANCHORAGE, Alaska - Both knees are shot, injected with synthetic cartilage until he can have surgery next summer. His right arm is still healing from a major operation to fix a staph infection. He continues to deal with other side effects of cancer.

But Lance Mackey is gunning for his fourth consecutive win in the 1,100-mile Iditarod Trail Sled Dog Race, which started Sunday in Willow.

Paul Gebhardt of Kasilof moved into the lead Monday night, becoming the first musher to leave the Rohn checkpoint, about 272 miles beyond Anchorage. A handful of mushers were reported in Rohn, including Canadian Sebastian Schnuelle, John Baker, Zack Steer, Sven Haltmann, Hugh Neff and four-time champion Jeff King.

Going into the race, Mackey said his 16-dog team looked sharp, consisting of new youngsters and a core of veterans that are capable of beating 70 other teams to the finish line in Nome on Alaska’s western coast. The Fairbanks musher, whose father and brother are past Iditarod winners, said he feels as competitive as he’s been in the past, despite a host of health issues that make you wonder how he can even get to the trail.

“I know. A lot of people say the same thing,” he said. “But I make up mentally what I’m lacking a little bit physically.”

That motto could apply to his entire mushing career since he was diagnosed with throat cancer in 2001 and underwent extensive surgery as well as radiation treatment and the loss of his salivary glands. After returning to the sport he went on to become the only musher ever to win both the Iditarod and the 1,000-mile Yukon Quest International Sled Dog Race in the same year, taking about two weeks off between races. It’s a feat he has accomplished twice.

Mackey speaks openly about using medical marijuana on the trail as a post-cancer painkiller and appetite enhancer. He also talks about facing a misdemeanor count of marijuana possession after being found with a small amount at the Anchorage airport in January, after his medical marijuana card had expired.

For this race, he said he’s staying away from pot. That’s because the Iditarod for the first time is testing mushers for alcohol and illegal drugs, although a provision allowing testing has been on the rule books since 1984. Officials say exemptions include Marinol, a government-approved drug that contains the active ingredient in marijuana, but Mackey said he’s even laying off on his own prescription.

Mackey believes the policy is directed at him. He said other competitors have complained that pot has given him an advantage.

“We’re going to prove some people wrong,” he said. “The dogs are the ones doing all the work, for the most part. I don’t see much of an argument beyond that.”

Stan Hooley, executive director of the Iditarod Trail Committee, said it would be “hard to deny” speculation that the implementation is targeted at Mackey.

“There’s been a lot of rumors, a lot of innuendo over the years and our organizational response to this was, ’Well, you know what? Let’s implement a drug testing program and find out just what is happening or, or hopefully not happening,”’ Hooley said.

Yukon Quest rules don’t specifically address drug use among mushers.

Mackey has won that race four times in a row. In February, he came in second by about an hour. But he considers the winner, 51-year-old Canadian Hans Gatt, a lesser rival in the Iditarod. The one he’s watching for is four-time Iditarod champion Jeff King.

“He’s always the team to beat, in my opinion,” Mackey said.

Gatt, who came in 10th in the Iditarod last year, also considers King a strong contender, noting the Denali Park musher’s outstanding team. There are other veterans to heed as well, he said, including perpetual front-runner John Baker of Kotzebue, who was third last year.

However it turns out, this looks like the last time fans will see Mackey and King squaring off in the Iditarod. King, 54, said he is running his final Iditarod.

Mackey said he’ll never run the Iditarod and Yukon Quest in the same year again. He skipped the 2009 Quest to mentor a musher and felt much better for the Iditarod. He ran both again this year even though he has been coaching a rookie from Jamaica, Newton Marshall.

“My body’s just getting beat up,” he said. “If I’m not having fun and my body’s not holding up, then I don’t see what the point is.”

Mackey plans to skip both the Iditarod and the Quest altogether next year. Instead he hopes to try out the lower 48 mushing circuit, including the 345-mile International Pedigree Stage Stop Sled Dog Race in Wyoming.

“Now, if I go and win the Iditarod this year, it’d be pretty hard not to go back,” he said.

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