Hamilton runner completes 250 laps in 15:29:01, with Guinness World Records certification pending.
HAMILTON, Ontario — Kat Clewley has set a new, unverified women’s 100-kilometer backward-running record, completing 250 laps of a Hamilton track in 15 hours, 29 minutes and one second on Saturday, Oct. 17. Her result is awaiting certification from Guinness World Records.
After nearly 15 hours of running backward, Clewley still had 10 laps to go. She passed 96 kilometers at 14:54:07, according to the event’s Race Roster leaderboard, then completed the final four kilometers in 34 minutes and 54 seconds. Her 100K finish was more than twice the distance of a marathon.
Clewley averaged 9 minutes, 18 seconds per kilometer at Hamilton’s Ray Lewis Track & Field Centre. Running backward meant negotiating each 400-meter lap while facing away from her direction of travel.
The challenge also supported Good Shepherd’s Steps to Health program, giving the day’s effort a community purpose beyond the record.
A Long Day of Running in Reverse
The race began at 6 a.m. Saturday and continued into the evening. According to the event’s Race Roster listing and the leaderboard supplied to BWF, Clewley reached 20 kilometers in 2:45:32, 40 kilometers in 5:33:55 and 60 kilometers in 8:40:13. By 80 kilometers, her elapsed time was 12:07:30. The publicly linked event page provides event details; the individual splits come from the supplied leaderboard.
She passed the 96-kilometer mark at 14:54:07, covering the final four kilometers in 34 minutes and 54 seconds. Her quickest recorded four-kilometer segment came much earlier: between 24 and 28 kilometers, she took just 30:49, an average of approximately 7:42 per kilometer over that stretch. The leaderboard does not provide individual one-kilometer splits, so her single fastest kilometer cannot be determined from the published data. Her recorded finish time was 15:29:01. The leaderboard was last updated Oct. 17 at 9:29 p.m. EDT.
Those numbers describe more than a long run. Moving backward changes the running stride and makes seeing the direction of travel an additional challenge. Over 250 laps, runners must also manage concentration, pacing and fatigue.
Clewley’s result is the latest chapter in a much longer story. Our history of backwards running traces the pioneers and marathon records that preceded her effort.
An Experienced Retro Runner
Clewley has a history with the sport. She told BWF she first tried backward running about a decade ago while encouraging her aging Giant Schnauzer, Vanilla, to finish a run. She later raced the Road2Hope Marathon backward in both 2015 and 2017. The international backward-running records database lists her 2017 Hamilton backward marathon at 4:26:06. Clewley says she sought Guinness recognition on both occasions but could not supply complete GoPro footage after camera batteries died. Her latest effort covered more than twice the traditional marathon distance of 42.195 kilometers.
Retro running, also called backwards running or backward running, generally involves shorter strides and different lower-body loading than conventional running. For newcomers curious about the activity, our beginner’s guide to retro running explains its history, technique and precautions. Our retro-running shoe guide covers footwear features worth considering, while making clear that no current shoe has been proven best for backward running.
A New Record Awaiting Guinness Certification
The event was billed as the Guinness World Record Fastest Female Retro Running 100km. Race Roster lists Clewley finishing the 100K backward event in 15:29:01 over 250 laps. That is the new unverified record time being reported for the event, while formal recognition from Guinness World Records remains pending.
The time and completed distance are documented in the race results. Guinness certification has not yet been announced.
For other historical performances, including men’s backward 100K and marathon times, visit our backward-running marathon and 100K records guide.
Sources: Race Roster event leaderboard (results supplied Oct. 18, 2026); event listing; CHCH; and historical backward-running records.
