   a half marathon is a road running event of .usatf: course measurement and certification procedures it is half the distance of a marathon and usually run on roads. participation in half marathons has grown steadily. one of the main reasons for this is that it is a challenging distance, but does not require the same level of training that a marathon requires. in 2008, running usa reported that the half marathon is the fastest growing type of race. a 2010 article by universal sports echoed the growing popularity of the distance. it is common for a half marathon event to be held concurrently with a marathon, using almost the same course with a late start, an early finish or shortcuts. the half marathon is also known as a 21k, 21.1k or 13.1 miles, although these values are rounded and not formally correct. ==world record progression== world records in the half marathon are now ratified by the international association of athletics federations, the international governing body for the sport of athletics. the official iaaf world record for men is 58:23, set by zersenay tadese of eritrea on 21 march 2010 in lisbon, portugal, and for women is 1:05:12, set by florence kiplagat of kenya on 16 february 2014, in barcelona, spain. this list is a chronological progression of record times for the half marathon. key:  {{legend2|#87cee
Events_in_athletics_(track_and_field) Half_marathons Long-distance_running Road_running_competitions