Metrication in the United States traditional mile-based lengths. In the Olympics, athletes run 1500 meters, not 1600 meters. Running races in the U.S. are usually run in metric distances (e.g., the 100 metres dash or the 5K run), although the mile distance remains popular. But even 5 and 10 kilometer races most often have mile markers on the course, and no kilometer markers. Long-distance races are often measured in kilometers, although exceptions exist (generally 10 mile races). The marathon is referred to as a 26.219-mile race (the official marathon standard distance originally being in English units — 26 miles, 385 yards) rather than 42.195 km.
2012 Olympic Marathon Course as 42.195 km and specifically state that the course must not be less than this distance. The rules further state that in Olympic competition the standard distance may not be exceeded by more than 0.1%. In order for a marathon performance to be ratified as a world record by the IAAF, the course must also meet other criteria that rule-out "artificially fast times" produced on courses aided by downhill slope or tailwind: the distance between start and end points when measured in a straight line should not exceed 50% of the length of the course (21.092 km in the case