To move when on level ground or uphill whilst using the classical style, cross-country skiers slide one ski forward and reach with the arm on the same side to implant the pole in the snow in front of them, then pull on the pole to accelerate themselves along. They then lift the pole out of the snow and repeat the process with the other side of the body, hopefully maintaining momentum and achieving a smooth, energy-saving rhythm. When reaching a downhill slope, they are able to coast down in a similar manner to downhill skiing.
Cross-country skiing has been practised in Scandinavian countries since prehistoric times, and also possibly by native Americans for similar lengths of time. It has been used by polar explorers as a means of transport, and all Scandinavian armies train their infantry on skis for winter operations.
Today, there are several types of cross-country competitive events, involving races of various types and lengths, as well as the biathalon[?], involving a combination of cross-country skiing and rifle shooting.
As an adventure activity, skiiers tackle trails of various lengths and difficulties. Some skiiers stay out for extended periods using tents and equipment similar to bushwalkers, others take relatively short trips from ski resorts, or use huts provided along some trails.