Freestyle skiing began in the 1930s, when Norwegian skiers began performing acrobatics during alpine and cross-country training. Later, non-competitive professional skiing exhibitions in the United States featured performances of what would later be called freestyle. Aerial skiing was developed in about 1950 by Olympic gold medalist Stein Eriksen.

Freestyle skiing began to develop further throughout the 1960s and into the 1970s, when it was often known as "hot-dogging." The free-form sport had few rules and wasn't without danger. Knee enjuries were also a comon phenomenon with most professional athletes.

The International Ski Federation (FIS) recognised freestyle as a sport in 1979 and brought in new regulations regarding certification of athletes and jump techniques in an effort to curb the dangerous elements of the competitions. The first World Cup series was staged in 1980 and the first World Championships took place in 1986 in Tignes, France. Freestyle skiing was a demonstration event at the Calgary Winter Olympics in 1988. Mogul skiing was added to the official programme of the Albertville Games in 1992, and aerials was added for the Lillehammer Games in 1994.

Currently (2006) there are two main branches of freestyle skiing: one encompassing the more traditional events of moguls and aerials, and a newer branch often refferd to as new school, comprising events such as halfpipe, big air, slopestyle, and skiercross. New school skiing has grown so much that new ski companies were created, companies that strictly make twintip skis (skis that are designed for landing switch (backwards) of rails and jumps). Such companies as the likes of Ninthward, Line, Armada, 4frnt and liberty all specialise in twintip skis. A relativly new aspect to skiing was also born, jibbing, or grinding, this is when the skier leaves the seface of the snow and slides across a metal bar or plastic box with his/her skis perpendicular to the rail/box. there are many different types of rails such as, kink, double kink, etc., rainbow, rollercoaster, wave, S rail/box, C rail/box, the battle ship rail/box and the sexchange rail.

Aerial skiing

Aerialists ski off jumps, usually built of wood and then covered with snow, that propel them up to 40-50 feet in the air. Once in the air, professional aerialists perform multiple flips and twists before landing on a 34- to 39-degree inclined landing hill about 100 feet in length. The top male aerialists can currently perform triple back flips with up to four or five twists. Quadruple back flips have been performed on snow, but currently (2006) they are not legal in competition.

There are two varieties of aerial skiing competitions: upright and inverted. In upright aerials, movements in which a skier's feet come higher than his or her head are illegal. This is the most common type of aerials competition for junior competitors. In inverted aerials, skiers execute elaborate flips and someraults.

Scoring
Aerial skiing is a judged sport, and competitors are judged on jump takeoff (20%), jump form (50%) and landing (30%). A degree of difficulty (DD) is then factored in for a total score.

Summer Training
Aerialists train for their jumping maneuvers during the summer months by skiing off specially constructed water ramps and landing in a large swimming pool. A water ramp consist of a wooden ramp covered with a special plastic mat that when lubricated allows an athlete to ski down the ramp towards a jump. The skier then skis off the wooden jump and lands safely into a large swimming pool. A burst of air is sent up from the bottom of the pool just before landing to break up the surface area of the water, thus softening the landing of the impact. Skiers reinforce the skis that they use for water-ramping with 1/4 inch of fiberglass.

Summer training also includes training on trampolines, diving boards, and other acrobatic or gymnastic training apparatuses.

Mogul skiing

Competitive mogul skiing arose soon after aerials became popular. During a competive mogul run, skiers must turn around large bumps (moguls) and also perform two jumps. The slope is very steep, usually between 22 and 32 degrees, and about 660-890 feet in length. The jumps in a moguls competition are smaller than those in aerials, and until recently inverted maneuvers were banned.

Judging: The skiier is judged on overall form and turns (50%), jumps (25%) and speed(25%).

Ski ballet (Acroski)

No longer a part of competitive freestyle skiing, ski ballet (later renamed acroski) was a third freestyle discipline conducted from the mid-1970s until the mid-1990s. Ballet involved a 90-second choreographed routine of flips and spins, performed to music and scored by a panel of judges. It was a demonstration sport in the 1988 and 1992 Winter Olympics.

Source: Wikipedia