The Discus is an athletic throwing event in track and field competition. The discus, the object to be thrown, is a heavy lenticular disc with a diameter of 220 mm (8.66 inches) and a weight of two kilograms (4 lb 7 oz) for the men's event, and one kg (2 lb 3 oz) for the women's, with a smaller diameter of 181 mm (7.17 inches). In U.S. high school track and field, boys typically throw a discus weighing 1.616 kg (3 lb 9 oz) and the girls throw the 1 kg (2.2 lb) women's disc. The discus can be thrown starting at age 11 (midget division). Most children throw the 1 kg discus. The discus usually has sides made of rubber, plastic, wood, or metal with a metal rim and a metal core to attain the weight. A discus with more weight in the rim produces greater angular momentum for any given spin rate, and thus more stability, although it is more difficult to throw. A practice discus made of solid rubber is often used in High School; it is cheaper, more durable, and easier to learn to throw (due to its more equal distribution of weight, as opposed to the heavy rim weight of the metal rim/core discus).
Discus throwing is an ancient sport. In the 5th century BC the sculptor Myron made a statue of a discus thrower (Discobolus), which is world-famous today. To make a throw, the competitor starts in a slightly recessed concrete-surfaced circle of 2.5 meters (8 feet 2½ inches) diameter. The thrower typically takes an initial stance facing away from the direction of the throw. He then spins around one and a half times through the circle to build momentum, then releases his throw. The discus must land within a 40-degree or 60-degree arc marked by lines on the landing zone, and the competitor must not exit the circle until the discus has landed, then must wait for the judge to give clearance to exit the ring from the rear half. The distance from the front edge of the circle to where the discus has landed is measured, and distances are rounded down to the nearest centimeter or half-inch. The competitor's best throw from the allocated number of throws, typically three to six, is recorded, and the competitor who legally throws the discus the farthest is declared the winner. Ties are broken by determining which thrower has the longer second-best throw.
The basic motion is a forehanded sidearm movement. The discus is spun off the index finger or the middle finger of the throwing hand, spinning clockwise when viewed above for a right-handed thrower, and vice-versa. As well as achieving maximum momentum in the discus on throwing, the discus's distance is also determined by the trajectory the thrower imparts, as well as the aerodynamic behaviour of the discus. Generally, one wishes to throw into a moderate headwind to achieve maximum throws. Also, a faster-spinning discus imparts greater gyroscopic stability. The technique of discus throwing is quite difficult to master and needs lots of experience to get right, thus most top throwers are thirty years old or older.
A common technique employed by younger people is to not spin at all, but to jump forward a step to gather momentum. Although it doesn't provide as much power, it is easier to do.
Interestingly, the discus is the only track and field event in which a men's world record has never been set during the Olympic Games.
