Question: Which leg muscle do artificial lugers use to steer the luge?
About the article "Luge", section "Artificial tracks".

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A luge is a small one- or two-person sled on which one sleds supine (face up) and feet-first.
Steering is done by flexing the sled's runners with the calf of each leg or exerting opposite shoulder pressure to the seat.
Racing sleds weigh 21–25 kilograms (46–55 lb) for singles and 25–30 kilograms (55–66 lb) for doubles.
Luge is also the name of an Olympic sport.
Lugers can reach speeds of 140 km per hour (87 mph).
Manuel Pfister of Austria, reached a top speed of 154 km per hour (95.69 mph) on the track in Whistler, Canada prior to the 2010 Vancouver Winter Olympics.
Lugers compete against a timer and are timed to a thousandth of a second, making luge one of the most precisely timed sports in the world.
The first recorded use of the term "luge" is 1905, from the Savoy/Swiss dialect of French "luge" meaning "small coasting sled", and is possibly from a Gaulish word with the same root as English sled. 
Hoffman and Pietszch become the first lugers to win three straight World Championship events. 
Artificial luge tracks have specially-designed and -constructed banked curves plus walled-in straights.
Most tracks are artificially refrigerated, but artificial tracks without artificial cooling also exist (for example, in St. Moritz).
Tracks tend to be very smooth.
The athletes ride in a flat, aerodynamic position on the sled, keeping their heads low to minimize air resistance.
They steer the sled mainly with their calves by applying pressure on the runners--right calf to turn left, left calf to turn right.
It takes a precise mix of shifting body weight, applying pressure with calves and rolling the shoulders.
There are also handles for minor adjustments.
A successful luger maintains complete concentration and relaxation on the sled while traveling at high speeds.
Most lugers "visualize" the course in their minds before sliding.
Fastest times result from following the perfect "line" down the track.
Any slight error, such as a brush of the wall, costs time.
Track conditions are also important.
Softer ice tends to slow speeds, while harder ice tends to lead to faster times.
Lugers race at speeds averaging 120–145 km/h (75–90 mph) around high banked curves while experiencing a centripetal acceleration of up to 5g.
Men's Singles have their start locations near where the bobsled and skeleton competitors start at most tracks, while both the Doubles and Women's Singles competition have their starthouse located further down the track.
Artificial track luge is the fastest and most agile sledding sport.
The sport of luge requires an athlete to balance mental and physical fitness.
To become an elite luger, a competitor must begin training at an early age and spend decades honing their skills.
Physically, a luger must have strong neck, upper body, abdominal, and thigh muscles.
Strength training is essential to withstand the extreme G-forces of tight turns at high speeds.
Since lugers have very little protection other than a visor and helmet, they must be able to endure the physical pounding administered by the track when mistakes are made.
Mentally a luger must maintain total focus as they steer their sled through more than a kilometer of curves and straights at high speed.
Dozens of subtle movements and weight shifts are required to find the perfect line down the track.
Consistency is essential for success.
Sled maintenance is also an important element for success.
Serious lugers spend hours meticulously sanding their "steels," and making other important adjustments and repairs to their sleds.
No luger can possibly achieve elite status without working closely with an experienced coaching staff, implementing suggestions and fine tuning technique.
Other lugers will often give tips that can improve a slider's ability to find the "sweet spot" on the track.
Though luge is a winter sport, it requires daily, year-round training. 
Sledding took place in Sigulda as early as 1887.
Several alpine skiing venues were held near the track following World War II.
By the late 1960s, the city government of Sigulda approved construction of a new track, which was finally completed in 1986.
It was built for the needs of Soviet bobsledders and lugers.
Although skeleton wasn't initially in the building plan, Sigulda has hosted World Cup races in skeleton in the 2000s.
Also, luge competitions are hosted in Sigulda each year, however, the track can't host four-man bobsleigh races, therefore there haven't been any Bobsleigh World Cup or World Championship races hosted in Sigulda.
Zintis Ekmanis and the original track designer has designed a new layout which would change two curves and make four-man bobsleigh races possible, though lugers are not happy with this idea because this may render the track unusable for women's singles and men's doubles lugers.
Also, Dainis Dukurs has said in an interview for Sporta Avīze that there was an experiment involving Juris Šics, Andris Šics, Tomass Dukurs and Martins Dukurs, in which the quartet drove with a four-man bobsleigh without crashing.
Dukurs stated that this proves that the track is, in fact, suitable for four-man teams, but to make it perfect for bobsleigh, most of the track should be rebuilt.
Reconstruction was expected to be completed in 2010.
However the idea was abandoned due to costs and uncertainty that such investment would pay off.
The track will undergo major renovation after 2014 season.
Also, an artificial ice start estacade was built in summer of 2008.