Sprints are short running events in athletics and track and field. Races over short distances are among the oldest running competitions. The first 13 editions of the Ancient Olympic Games featured only one event the stadion race, which was a race from one end of the stadium to the other.[36] There are three sprinting events which are currently held at the Olympics and outdoor World Championships: the 100 metres, 200 metres, and 400 metres. These events have their roots in races of imperial measurements which were later altered to metric: the 100 m evolved from the 100 yard dash,[37] the 200 m distances came from the furlong (or 1/8 of a mile),[38] and the 400 m was the successor to the 440 yard dash or quarter-mile race.[39] At the professional level, sprinters begin the race by assuming a crouching position in the starting blocks before leaning forward and gradually moving into an upright position as the race progresses and momentum is gained.[40] Athletes remain in the same lane on the running track throughout all sprinting events,[39] with the sole exception of the 400 m indoors. Races up to 100 m are largely focused upon acceleration to an athlete's maximum speed.[40] All sprints beyond this distance increasingly incorporate an element of endurance.[41] Human physiology dictates that a runner's near-top speed cannot be maintained for more than thirty seconds or so as lactic acid builds up and leg muscles begin to be deprived of oxygen.[39] The 60 metres is a common indoor event and it an indoor world championship event. Other less-common events include the 50 metres, 55 metres, 300 metres and 500 metres which are used in some high and collegiate competitions n the United States. The 150 metres, though rarely competed, has a star-studded history: Pietro Mennea set a world best in 1983,[42] Olympic champions Michael Johnson and Donovan Bailey went head-to-head over the distance in 1997,[43] and Usain Bolt improved Mennea's record in 2009. The Olympic Games (Ancient Greek: - ---? ta Olympia) were a series of athletic competitions among representatives of city-states of Ancient Greece. They were held in honor of Zeus, and the Greeks gave them a mythological origin. Historical records indicate that they began in 776 BC in Olympia. They continued to be celebrated when Greece came under Roman rule, until the emperor Theodosius I suppressed them in 394 AD as part of the campaign to impose Christianity as the state religion of Rome. The games were usually held every four years, or olympiad, which became a unit of time in historical chronologies. During the celebration of the games, an Olympic Truce was enacted so that athletes could travel from their countries to the games in safety. The prizes for the victors were wreaths of laurel leaves. The games became a political tool used by city-states to assert dominance over their rivals. Politicians would announce political alliances at the games, and in times of war, priests would offer sacrifices to the gods for victory. The games were also used to help spread Hellenistic culture throughout the Mediterranean. The Olympics also featured religious celebrations and artistic competitions. The statue of Zeus at Olympia was counted as one of the seven wonders of the ancient world. Sculptors and poets would congregate each olympiad to display their works of art to would-be patrons.