On 16/2/2025, Kiplimo became the first person to complete a half marathon (21,0975 km) in under 57 minutes, clocking 56 minutes 42 seconds at the eDreams Mitja Marato in Barcelona. His time was 48 seconds faster than the previous record of 57 minutes 30 seconds, set by Yomif Kejelcha of Ethiopia in 10/2024 in Valencia.

However, on 3/2, almost a year later, World Athletics (WA) confirmed it would not ratify Kiplimo's men's half marathon world record set in Barcelona.

Kiplimo running behind a pace car with a large clock and a person on its roof at the eDreams Mitja Marato in Barcelona on 16/2/2025. Photo: eDreams Mitja Marato 2025

According to Runner’s World, Kiplimo's performance in Barcelona violated WA's competition rules. Specifically, Technical Rule 6.3.1 states that athletes are not permitted to receive pacing assistance from any non-competing individual or from technical devices, excluding personal wearable devices.

Live broadcast footage showed Kiplimo running for most of the race approximately 10-15 meters behind the pace car. WA assessed this as an illegal form of assistance.

WA's current regulations do not specify a minimum distance between a pace car and an athlete. This was reportedly a loophole exploited by the Barcelona event organizers and Kiplimo. The report also suggested that the Ugandan athlete committed other violations, including a clause prohibiting receiving tactical guidance during competition.

Consequently, WA continues to recognize Yomif Kejelcha of Ethiopia's men's half marathon world record, with a time of 57 minutes 30 seconds set at the Valencia Half Marathon 2024.

Kejelcha and Kiplimo are expected to face each other directly at the London Marathon 2026, scheduled for 26/4.

Analysis of Kiplimo's half marathon world record attempt.

Kiplimo's situation mirrors Eliud Kipchoge's attempt to run a full marathon in under two hours at the INEOS 1:59 Challenge in 2019. During that event, the Kenyan legend utilized an electric SUV pace car, maintaining a distance of 6 to 8 meters to reduce wind resistance. This car also projected a laser line onto the road, helping the pacer team maintain a precise arrow formation for further wind resistance reduction. This enabled Kipchoge to become the first person to run a marathon in under two hours.

This achievement was not recognized by World Athletics. Therefore, to date, no athlete has officially achieved a sub-2 marathon. Kelvin Kiptum came closest to this milestone, clocking 2 hours 0 minutes 35 seconds at the Chicago Marathon 2023. However, he passed away in a traffic accident near Kaptagat, Kenya, on 11/2/2024.

By Hong Duy (according to Canadian Running Magazine)