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Sled dogs are super athletes

It has been a dark start to the year for man's best friend. On Jan. 31, news broke that up to 100 sled dogs were slaughtered in Whistler last April.

It has been a dark start to the year for man's best friend. On Jan. 31, news broke that up to 100 sled dogs were slaughtered in Whistler last April.

The matter is being investigated by the SPCA, and the provincial government has launched a task force to review both the tragic event and the state of the dogsledding industry.

This drama comes at a time when professional sled dog racing teams are commencing final preparations for the Iditarod - the "Last Great Race on Earth."

Starting March 5, the course covers more than 1,150 miles (1,850 kilometres) from Anchorage to Nome, Alaska. Teams of one musher and 12 to 16 dogs compete in often gruelling conditions - blizzards, high winds and temperatures as low as -40 degrees Celsius. The fastest teams complete the race in less than 10 days, with dogs running more than 100 miles (160 km) a day.

Dr. Michael S. Davis of the Oklahoma State University has been studying sled dogs for more than 10 years in a bid to understand why they are capable of such remarkable feats of endurance.

"These are one-of-a-kind athletes," Davis said. "What we learn from them will undoubtedly tell us a lot about human performance as well."

Davis' work is partly funded by the U.S. Defence Advanced Research Projects Agency. Special operations soldiers are required to be active under stressful conditions for long periods of time and the results of Davis' research could lead to methods of improving troop performance.

The answers lie in the unique physiology of a sled dog's muscle cells. Muscle cells require energy to function which is produced by mitochondria, otherwise known as "cellular power plants." These tiny structures use oxygen to produce chemical energy by breaking down molecules from fats, lipids and carbohydrates.

Researchers have found that the dogs contain large numbers of mitochondria in their muscle cells. Racing sled dogs have up to 70 per cent more mitochondria than human muscle cells.

Racing sled dogs also exhibit high aerobic capacities, meaning their bodies are able to take in and use large amounts of oxygen during times of peak exercise.

One of the most fascinating discoveries of the research is that sled dogs are able to use fats as their main source of energy during the race. Human muscles rely mainly on the carbohydrate glucose to produce energy.

Glucose is stored in muscle cells as glycogen, and reconverted to glucose when needed. These stores quickly deplete during intense exercise, and human athletes need rest to "recharge" their muscles.

Davis and his team of researchers found that racing sled dogs are able to switch their source of fuel from glucose to fat during periods of sustained exercise.

As a result, the dogs are able to restore their glycogen supplies, preventing cellular burnout and build-up of lactic acid. Incredibly, a dog that has been racing for several days will show a similar metabolic profile as before the race - it is able to adapt to the extreme stress.

Research is continuing into the ability of racing sled dogs to use fat for energy in such an efficient manner. It is hoped this research will lead to breakthrough treatments for type 2 diabetes and obesity.

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