Iditarod: Can sled dogs’ endurance translate to human athletes?

Q.  What elite athlete has four legs and burns up to 12,000 calories a day?
A.  A sled dog running the Iditarod.

Sled dogs may be the most amazing high-endurance athletes: able to run all day through rough terrain in bitterly cold temperatures and then do it again for days—even weeks—in a row. Such abilities have piqued the interest of researchers looking to unlock that endurance capacity for human athletes and military personnel.

“Athletic dogs in general have four to five times the athletic capacity of the very best human, but they have all the same parts—all the same enzymes and transporters and biochemical pathways—that we do, they just use them a lot better,” explained Michael Davis, DVM, MS, PhD, director, Comparative Exercise Physiology Laboratory, Oklahoma State University, Stillwater, OK.

“And so, what we'd like to know, essentially, is how they do that so much better than what we can do, and is there anything that we can do differently that will get us closer to a dog?” he asked.

‘Working like a dog’

“Right now, most of our funding, and therefore most of our interest, is coming from the Department of Defense, and it's basically to…either learn about how to better produce a working dog for the military or to see how the physiology of a working dog can be adapted to a human to essentially make a human capable of working like a dog,” Dr. Davis said.

This research has led him and his colleagues to Alaska to study the metabolism of dogs that run the 1,100-mile sled race on the Iditarod Trail, which takes place annually in early March amid heavy blizzards, temperatures as low as -40° F, and winds up to 60 mph. The trail stretches from Anchorage to Nome, crossing two mountain ranges and a frozen inlet. The fastest sled dog teams have completed the trek in less than 9 days, but some teams take 2 weeks or more to cross the finish line.

During the race, dogs burn an estimated 10,000 to 12,000 calories a day—the equivalent of 22 McDonald’s Big Macs. By comparison, a cyclist competing in the grueling Tour de France burns half that, averaging about 6,000 calories a day.

Throwing a switch

Unlike competitive cyclists, sled dogs have a metabolic trick up their furry sleeves. As they begin the race, the dogs adapt to strenuous running conditions and somehow downshift their metabolism to accommodate.

On the first day of the race, conditioned dogs undergo most of the same metabolic changes that human endurance athletes experience: muscle energy reserves get depleted, stress hormones increase, and cellular injury (to proteins, lipids, and DNA) and oxidative stress occur.

But as the dogs keep up the pace over consecutive days, their metabolism resets. Within days, the dogs’ metabolic profile returns to where it was before the race, although they’re still performing at a sustained high level of activity.

“Before the race, the dogs’ metabolic makeup is similar to humans. Then suddenly they throw a switch—we don’t know what it is yet—that reverses all of that,” Dr. Davis told The New York Times. “In a 24-hour period, they go back to the same type of metabolic baseline you see in resting subjects. But it’s while they are running 100 miles a day.”

Human athletes can’t do this. When racing, marathon runners and other endurance athletes diminish stores of fat and glycogen, build up lactic acid, and eventually become fatigued. At that point, human athletes must rest and replenish.

But sled dogs don’t. They can keep running for days.

“They have a hidden strategy that they can turn on,” Dr. Davis said. “We are confident that humans have the capacity for that strategy. We have to figure out how dogs are turning it on to turn it on in humans.”

Dr. Davis doesn’t expect that this research will increase human athletic performance five-fold to the level of an athletic dog.

“But if you consider taking the best human athlete and increasing their exercise capacity 20%, that's still a huge increase, and I think it's entirely possible,” he said.