Freestyle Skiing: Twist and shout - how freestyle skiers take to the air and come back to earth

AERIAL sites are built to precise dimensions, writes Julia Snell. They consist of a smooth 55-metre run-in, leading to a flat transition and a wide platform known as the 'knoll', where the jumps or 'kickers' are built. These are carved from solid blocks of snow, up to 3.10m high. The steepest jump is 66 degrees at the top. World Cup sites have three triple kickers, two doubles and a single. A steep 30-degree hill of well-chopped snow drops away from the knoll to ensure a safe landing.

Before going off the jump, skiers perform speed checks to test they have enough speed for their manoeuvre - approximately 24mph for singles, 30mph for doubles and 36mph for triples. Though there are speedometers at most sites, many jumpers judge their speed on feel and experience. Before performing the jump, they rehearse it in their mind and then set off straight down the run-in. As they ski up the jump, they try to stand as tall as possible, locking the body in a tight position at 90 degrees to the kicker. They initiate the somersault by swinging the arms up to just in front of their ears. Once they have started or 'set' the somersault, they then initiate the twist by pulling with the left or right shoulder, depending on which way they twist.

After the first somersault, they see the landing hill and judge whether they need to speed up or slow down their rotation to complete their chosen manoeuvre. If they realise they do not have enough height to complete the somersault in a lay-out (fully stretched) position, they have to 'pull' and complete the manoeuvre in a tucked position. If they have too much air and are in danger of over-rotating and landing on their backs, they stretch the somersault to slow the rotation. A triple somersault takes all of three seconds to complete, so athletes have to be highly concentrated while in the air and make split-second decisions to adjust their technique.

The steep angle of the landing hill and the well-chopped snow means they always land with minimal impact. Judges are looking for a fully stretched body position, controlled movement in the air and a strong, well-balanced landing as they ski down the hill to the finish area.