Not the typical dogsled race, but a dog racing a sled in this case. I don't remember who won, but I don't think the dog had trouble keeping up with the sled.
I was tracking the sled with the center AF point (I didn't know the dog was going to show up). This meant that some cropping was necessary for the final image shown here.
Camera and Lens Settings
400mm f/2.8 1/1000s
3744 x 2516px