The popularization of sled racing in the 20th century favored the selection of dogs with qualities of speed and endurance rather than abilities to carry heavy loads. This is the case with the Siberian husky imported from Russia because of its small size and speed. Crossed with other breeds of racing dogs, such as greyhounds, he gave birth to the mixed-breed Alaskan husky. Able to run for several days over long distances, the latter has become the preferred dog for racing.