Ultramarathon
An ultramarathon, also called ultra distance or ultra running, is any footrace longer than the traditional marathon length of 42.195 kilometres. Various distances are raced competitively, from the shortest common ultramarathon of 50 kilometres (31 mi) to over 100 kilometres (62 mi). 50k and 100k are both World Athletics record distances, but some 100 miles (160 km) races are among the oldest and most prestigious events, especially in North America. Around 100 miles is typically the longest course distance raced in under 24 hours but there are also longer multi-day races of 200 miles (320 km) or more, sometimes raced in stages with breaks for sleep. While some ultras are road races, many take place on trails, leading to a large overlap with the sports of trail running and mountain running.