1 / 4   A musher competes in the 6th edition of the Baile Tusnad Cup – Sled dog sprint competition – on Jan. 28 in Baile Tusnad, Covasna county, central Romania. /Xinhua photo

2 / 4   Sled dog racing, a popular dog sport popular in the Arctic region, involves a team of sled dogs pulling a sled with a driver standing on it. /Xinhua photo

3 / 4   Races are categorized, not only by the miles .... /Xinhua photo

4 / 4   ... but also by the numbers of dogs. /Xinhua photo