Each March, the Lance Armstrongs of the canine world take to the mountains with their sled drivers, or mushers, in the world's longest sled race.
Called the Iditarod Trail Sled Dog Race, the event begins in Anchorage, Alaska, and ends in Nome on the western Bering Sea coast. Teams of 12 to 16 dogs and their musher cover over 1,150 miles (1,850 km) in about 10 to 17 days. Each dog has a microchip, about the size of a grain of rice, inserted beneath its skin to help race organizers keep track of so many dogs over the lengthy race.
The dogs often trek through heavy blizzards and endure temperatures as low as minus 40 degrees Fahrenheit (minus 40 degrees C).
The treacherous terrain and chill might do in your average pup, but not these sled dogs, which are not all purebred Siberian Huskies, but mutts, with a mix of Husky, Alaskan Malamute, Pointer and other breeds.
The chilly conditions are necessary for the dogs, which would overheat in balmier climes. That's because dogs can't sweat, except through their paws, and they generate a tremendous amount of heat purely from the burning of calories during the race.
Michael Davis of Oklahoma State University's Center for Veterinary Health Sciences has studied the sled dogs for the past 10 years. He runs check-ups on the dogs before and after races as well as during controlled experiments for which he sets up races with groups of sled dogs. The secret to the dogs' feats of day-to-day endurance lies in their ability to "reprogram" their bodies' responses to stress after just one day of competition, something humans can't do.
Davis found that just like human athletes, conditioned sled dogs show body damage during their first day of exercise.
For instance, when any athlete, canine or Homo sapiens, pounds the pavement or icy ground for miles, bits of muscle enzymes and proteins leak out from their cells. Scientists say this is a sign of cell damage. Our cells do recover in a day or so, but as soon as we go for another run, the same damage happens all over again.
For sled dogs, that's not the case. "If you then take them out and do exactly the same exercise the following day and the day after that, and the day after that, you don't continue to get that leakage [of enzymes and proteins]," Davis told LiveScience.
He added, "In the course of just a day or two, they manage to adapt their system so that exercise that was injuring a muscle cell here and there on the first day is no longer injuring muscle cells."
Davis found the sled dogs somehow reprogram their bodies after that first or second day of training with an athletic armor of sorts to prevent other bodily stresses as well.
The four-legged fur-balls also have appetites rivaling any human athlete. During race season, the dogs, which weigh a mere 55 pounds (25 kg), consume 12,000 calories a day, Davis said.
For comparison, Olympic swimmer Michael Phelps reportedly eats some 10,000 to 12,000 calories a day during competitions. But Phelps boasts at least three times the weight of a race dog, Davis said.
"The challenge is getting 12,000 calories into a little dog like that and it has to be very calorie-dense," he said. "While they're racing, they're eating a diet that is pushing between 60 and 70 percent fat."
(Every gram of fat contains nine calories, compared with the 4 calories in a gram of protein or carbohydrate.)
Whatever it is that allows sled dogs to chow down on so much fatty food and stay healthy could be beneficial to humans. And so results of Davis' findings have implications for humans who have become obese or developed Type 2 diabetes.
"If you feed a diet that's very high fat to a human, a lot of humans become obese and they develop type 2 diabetes. And the dogs don't," Davis said. "There is no such thing as an obese Type 2 diabetic sled dog despite the fact that they're eating a diet that should produce that."
The dogs and their drivers have a long history.
The late Dorothy G. Page, then chairman of the Wasilla-Knik Centennial, conceived the idea of having a sled-dog race along the trail in 1967. She had been intrigued that dog teams could travel over land (along this trail) that was inaccessible by automobiles. Two short races were completed along part of the trail in 1967 and 1969. The first complete race to Nome occurred in 1973.
Soon after, the Iditarod Trail became the major thoroughfare through Alaska with dog sleds carrying mail, supplies and just individuals traveling place to place.
Today the trail is made up of a northern and southern route, with races alternating between the two on even- (northern) and odd- (southern) numbered years. In the early years of the race, mushers only traversed the northern trail. But when the board of directors realized the smaller villages were being impacted by the race coming through year after year, they decided to use both sections.
Here are some past records along the trail:
- Musher Rick Swenson is the only five-time winner of race, having won in 1977, 1979, 1981, 1982 and 1991.
- In 2002, Martin Buser broke previous records when he crossed the finish line in 8 days, 22 hours, 46 minutes and 2 seconds. This record has not yet been broken. The closest anyone has gotten to this winning time was in 2000, when Doug Swingley came in at 9 days, 58 minutes and 6 seconds.
- Carl Huntington won the 1974 race with the slowest winning time, 20 days, 15 hours, two minutes and seven seconds.
Sometimes a sled driver can be nipping at the heels of the winner. The closest finish was in 1978 when Dick Mackey finished one second ahead of Rick Swenson. The winner was decided by the nose of the lead dog across the finish line.