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What makes Iditarod dogs perfect endurance athletes?

Ned Rozell
Loren Holmes photo

Mike Davis lives in Oklahoma, but he travels to Alaska all the time to work with our greatest athletes.

“I’m up here about once a month, about half around Anchorage and half around Fairbanks,” the Oklahoma State University veterinarian and exercise physiologist said on the phone from Wasilla. “If I could settle on a single address, I could get a Permanent Fund Dividend.”

Davis was in Wasilla for the start of the Iditarod. There, he cheered on Aliy Zirkle, Martin Buser, Jake Berkowitz, Rick Swenson and other mushers who have over the years entrusted Davis to take blood and muscle samples from their dogs. His goal is to discover the magic within a sled dog that allows it to keep going and going. While humans tend to fade after exercising just a few hours, sled dogs are somehow able to avoid that crash.

“Dogs will go from using their reserves -- to not -- in 48 hours,” Davis said. “They gain fitness that fast. Their response is to change their metabolism so they don’t use up their reserves anymore.”

Finding the trigger to that change is Davis’s big question. He is funded in part by the U.S. Army Research Office Division of Life Sciences, which is interested in improved performance of human beings.

Musher Aliy Zirkle of Two Rivers, runner-up to Dallas Seavey in this year’s Iditarod, again showcased the amazing ability of sled dogs -- most of the dogs that pulled her from Willow to Nome in 2012 were the same dogs that pulled her husband Allen Moore to second place in the Yukon Quest less than three weeks earlier.

“They don’t just continue to perform, they perform a lot better,” Davis said of dogs that run both races. “There’s a good argument that nothing prepares a dog better for a 1,000-mile race than a 1,000-mile race. They can do it indefinitely, as long as you have trail and they’ve got food. They get tired, but they don’t fatigue in the biochemical sense.”

The key to a sled dog’s endurance is its ability to get energy it can use immediately. Davis and others have found that dogs are much quicker than humans at moving energy to their muscles.

“The faster you can get stuff into a muscle cell, the faster you can use it,” Davis said. “They may get better at pulling fat out of the bloodstream on the fly.”

The key to this ability is in a sled dog’s “transporters” -- proteins that allow it to pull carbohydrates and fats through cell membranes and into muscle cells. The proteins we use for that job also exist in dogs, but Davis and other researchers found decreased numbers of the human-style transporters in dogs  when the measurements showed the dogs were moving more fat.

“Something is transporting the fat into dog muscle, but it isn¹t the transporter that we use,” Davis said.

The mystery protein may be so efficient in sled dogs that there are few of them to be found.  It appears sled dogs are pulling Davis and other physiologists into the frontier of animal performance.

“We have to be more creative in our ideas so we don’t miss something,” Davis said. “It’s like a treasure hunt.”

Before this year’s Iditarod ended, Davis was back in Oklahoma, where he was busy with two tasks. One was analyzing sled dog muscle tissue and other samples graciously provided by top dog mushers. The other was following the race the way most people do.

“I’ll have my computer open (to an Iditarod website), hitting refresh every 10 minutes,” he said.

Ned Rozell is a science writer at the University of Alaska Fairbanks Geophysical Institute.  Used with permission.