Jan 30 (Reuters) - Factbox on cross country skiing ahead of the Feb 7-23 Sochi Winter Olympics
There will be 12 gold medals up for grabs at the Sochi Olympics - six each for men and women in the individual, mass start, skiathlon, relay, sprint and sprint relay.
In the individual race, the skiers start at 30-second intervals, and the competitor who covers the distance in the shortest time wins. Participants start in reverse order to their ranking for the season, so the competitor ranked highest starts last. Men will race in the classical style for 15km and women 10km.
In the mass start race, all skiers begin at the same time, with 60 to 80 athletes arranged into rows of 7 to 11 people. Men and women race in the free technique events, with men skiing 50km and ladies skiing 30km.
In the skiathlon, skiers race the first half of the course on classic technique skis, then exchange them for skating skis in the stadium and finish the event using the free technique. The timer does not stop while the skiers change skis. The first skier to cross the finish line wins the skiathlon. The men race 15 km in each style (30km total), while the women race 7.5km in each style (15km total).
The individual sprint begins with a qualifying round, in which skiers start at 15-second intervals and race around a 1.2-1.3km loop (for women) or a 1.4-1.6km loop (for men). The top 30 finishers advance to the quarter-final heats. Six people start in each of the quarter-finals, semi-finals, and final races. The two fastest competitors from each heat, plus the two third or fourth-place skiers with the best times advance to the next round. Six skiers compete for the gold medal in the final round.
The team sprint is a relay, where teams of two skiers take turns to complete 1.5km legs three times each, for a total of six legs. The event begins with the semi-final round, in which 10 to 15 teams start in each heat. The top five finishers in each semi advance to the final. The team that crosses the finish line first after six legs wins.
The relay is skied by teams of four athletes. The first and second legs are skied using the classic technique, and the third and fourth using free technique. Women ski 5km legs, while men ski for 10km. The relay begins with a mass start. The team that crosses the finish line first after four legs wins.
Cross country skiing made its Olympic debut at the 1924 Chamonix Games, with two men's races over 18km and 50km. Women were given the chance to compete for the first time at the 1954 Oslo Games, competing over 10km.
Other distances and formats have since been added. The 1988 Calgary Games introduced events using the new free technique. Mass start and the sprint event were introduced in Salt Lake City in 2002.
The first Olympic champion was Thorleif Haug. Almost 100 years later, Norway is still one of the leading nations in the sport, which has also become popular in Central and Eastern Europe as well as North America.
Cross country skiing will be contested from Feb. 8-23 at the 'Laura' complex, which will also be used for biathlon. It is located in the Krasnaya Polyana resort, which is around 90km from the centre of Sochi.
The 'Laura' complex houses two stadiums. There are two separate tracks for cross country skiing and biathlon, with the latter having a separate shooting zone and warm-up zones.
The stands can hold 7,500 spectators.
Petter Northug, 28 is one the favourites for the men's races after the Norwegian won two gold medals in Vancouver four years ago. He had a fantastic season in 2013 - claiming two top of the podium finishes at the world championships.
Northug is likely to face competition from Russia's Nikita Kriukov in the sprint - the home country's main hope of winning a cross country skiing gold. Dario Cologna of Switzerland is likely to be a threat in the longer disciplines.
Three-times Vancouver Olympic champion Marit Bjorgen is one of the favourites in the women's events. The 33-year-old, who has won 12 world championship golds, has qualified for all six disciplines. (Compiled by Dmitriy Rogovitskiy; editing by Pritha Sarkar)