When humans engage in highly strenuous exercise day after day, they start to metabolize the body’s reserves, depleting glycogen and fat stores. When cells run out of energy, a result is fatigue, and exercise grinds to a halt until those sources are replenished.

Dogs are different, in particular the sled dogs that run the annual Iditarod Trail Sled Dog Race in Alaska. This is a grueling 1,100-mile race, and studies show that the dogs somehow change their metabolism during the race.

Dr. Davis, who is teaming with researchers at Texas A&M in a $300,000 Darpa grant, awarded last fall, has been traveling to Alaska for years to learn why the sled dogs are “fatigue-proof.”

“They have a hidden strategy that they can turn on,” he 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.”