FINA amended its regulations governing the recognition of world records in 1956; specifically, FINA mandated that only record times that were contested in 50-metre (or 55-yard) pools were eligible for recognition after that time.
[2] In October 2013 FINA decided to establish "standards" before something can be recognized as the first world record in these events.
[3] But later on March 13, 2014 FINA has officially ratified the eight world records set by Indiana University swimmers at the IU Relay Rally held on September 26, 2013 in Bloomington.
[5] Swimming the other three legs of the medley relay cannot qualify as world records as FINA criteria require a "static start" for world record recognition – swimming relay exchanges are characterized as "dynamic".
FINA recognizes only long-course world records for mixed relays in this event.