biathlon (bīăth´lŏn), sport in which cross-country skiers race across hilly terrain, occasionally stopping to shoot, prone or standing as required, with rifles at sets of fixed targets. The biathlon features the 10-km (6.2-mi) sprint, in which contestants shoot at two sets of targets; the 12.5-km (7.8-mi) pursuit, in which contestants shoot four times and start at intervals determined by their finish in the sprint; the 20-km (12.5-mi) race with four shooting stops; a 30 contestant, 15-km (9.3-mi) mass start race with four shooting stops; and a relay race with four 7.5-km (4.7-mi) legs and two shooting stops per leg. The women's races are shorter: a 7.5-km (4.7-mi) sprint, a 10-km (6.2-mi) pursuit, a 15-km (9.3-mi) race, a 12.5-km (7.8-mi) mass start race, and a relay with 6-km (3.7-mi) legs. In the mixed relay, two women and then two men ski a leg of the appropriate length. Competitors are penalized for each missed target by having a standard length added to the course distance that they must complete, or by having a minute added to their time. The control of fine motor skills and breathing required to shoot after the skiing segment makes this a demanding sport. Biathlon competition developed from the military training of ski troops. The sport first became an official part of the Winter Olympics in 1960. Biathlon has also recently acquired meaning as applied to a combined two-sport competition, such as running and swimming.