(Photo: Kalia Angelo)
It's called skijoring, a Norwegian term that means "ski driving." The video below show the good people of southwestern Montana giving a demonstration. It's not just a pleasant ride through the snow behind a trotting horse. The horses run fast, so the skiers have to maneuver carefully around obstacles and over jumps on the course. In some competitions, the skiers have to grab objects along the way.
Slate has article about it. Historians trace skijoring back to the Nineteenth Century, when good skiing was a military necessity. Skijoring developed out of the skills of a good dispatch rider. Baron Pierre de Coubertin, the founder of the modern Olympics, was a fan of it. Skijoring was a demonstration sport at the 1928 Winter Olympics in St. Moritz, Switzerland.
Skijoring never became a regular sport at the Olympics, but it has fans in Scandinavia, Switzerland and the United States.
-via The Presurfer